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MCAT Bio (Physiology/Genetics)
Terms in this set (164)
Which organelle launches apoptosis?
Mitochondria, which releases enzymes from ETC; lysosomes can as well
What are endosomes?
Transport, package, sort cell material traveling to/from membrane; some can transport trans-golgi or to lysosomes
What are microfilaments?
Solid rods of actin resistant to compression/fracture, providing protection; use ATP to generate force to move with myosin (in muscles)
Play role in cytokinesis, comprising cleavage furrow that forms ring at site of division b/w daughter cells
What are microtubules?
Hollow polymers of tubulin that radiate through cell, serving as primary pathway for kinesin and dynein to carry vesicles
Make up cilia and flagella (which have 9+2 structure)
Centrioles are microtubule organising centers and are found in centrosome. They attach to chromsomes in mitosis via kinetochores
What are intermediate filaments?
Different filamentous proteins, e.g. keratin, desmin, vimentin, lamins; for cell-cell adhesion, cytoskeleton stability (b/c rigid), anchor organelles
What are parenchyma?
Functional cells of most organs, made of epithelial cells
What are examples of connective tissue?
Bone, cartilage, tendons, ligaments, adipose tissue, and blood
What are the basement membrane and extracellular matrix made of?
Basement membrane is connective tissue underlying epithelial cells.
Extracellular matrix is made of collagen/elastin that were secreted from connective tissue.
What is the prokaryotic equivalent of cilia?
What are main differences in cell structure between prokaryotes and eukaryotes?
Prokaryotes are single-celled (but can be in colonies) and lack membrane-bound organelles.
Prokaryotes have smaller ribosomes than eukaryotes' ribosomes.
Cell wall surrounds cell membrane (together, make the envelope) b/c prokaryotic cells have to defend themselves and for controlling solute movement.
Bacteria have 1-many flagella for chemotaxis
They lack nucleus, so DNA concentrated in single circular chromosome as the nucleoid without nuclear envelope with additional plasmids.
Cell membrane is used for ETC/ATP-synthesis
Very simple cytoskeleton
How can bacteria be classified by shape?
Bacteria are either cocci (spherical), bacilli (rod-shaped, e.g. E coli), or spirilli (spiral-shaped)
What effect does oxygen have on obligate anaerobes?
Obligate anaerobes cannot survive in environment with oxygen because O2 leads to production of reactive oxygen-containing radicals, leading to cell death
How do gram positive and gram negative cell walls differ?
When stained with crystal violet, gram positive appears purple and gram negative appears pink-red.
Gram-positive has thick layer of peptidoglycan and aids a pathogen. Also, has lipoteichoic acid (unknown).
Gram-negative are thin and have much less peptidoglycan. Cell wall separated from membrane by periplasmic space. They also have outer membranes with phospholipids and lipopolysaccharides (triggers immune response in humans)
What are the components of a flagellum?
1) Filament- hollow, helical structure made of flagellin
2) Basal body- complex structure anchoring flagellum to membrane; motor of flagellum by rotating
3) Hook- connects filament and basal body so basal body exerts torque on filament
What is binary fission?
Simple form of asexual reproduction in prokaryotes; chromosome attaches to cell wall to replicate while cell grows in size until envelope grows inward along cell midline to produce daughter cells; more rapid than mitosis
What are episomes?
Plasmids that can integrate into genome
What are the four different recombination processes?
Transformation- integrate foreign genetic material into host genome
Conjugation- sexual reproduction; two cells form conjugation bridge (made of sex pili) to transfer genetic material unidirectionally from donor male to recipient female. To form pilus, bacteria must have plasmids called sex factors, e.g. F (fertility) factor; bridge breaks before full genome copied. Cells that underwent change are high frequency of recombination Hfr.
Transduction- vector, or virus carrying genetic material b/w bacteria (specifically bacteriophages), cannot reproduce themselves, so trap a segment of host DNA during assembly and transfer DNA that integrates into host genome
Transposons- genetic elements that can insert/remove themselves from genome
What are different phases of prokaryotic cell growth?
In new environment, bacteria adapt to local conditions (lag phase 1). As they adapt, growth increases (exponential phase or log phase 2). As number of bacteria grow, resources are reduced, slowing reproduction and resulting in (stationary phase 3). Finally, exceed environment ability to support (death phase 4)
What structure does a virus have?
Genetic material (to produce virions/progeny), protein coat (capsid), and it may have an envelope of phospholipids and virus-specific proteins that are sensitive to heat, detergent, dessication.
Bacteriophages also have a tail sheath (syringe to inject material into bacteria) and tail fibers (help recognize/connect the right cell).
Which sort of RNA viruses have an RNA replicase?
Negative-sense RNA need an RNA replicase to make a complementary strand of RNA to its viral RNA that can be translated by host ribosomes. Positive-sense RNA on the other hand already has RNA that can be translated by host ribosomes
Why are retroviruses so difficult to kill?
Retroviruses are enveloped, single-stranded RNA viruses. They use reverse transcriptase to make DNA from its viral RNA, and the DNA injected into the host cell is transcribed/translated as if it was the host's own DNA
What are different ways viruses infect host cells?
As long as host cell has specific receptors for virus, virus can infect it as: enveloped viruses fuse with plasma membrane intact (e.g. HIV), host cell endocytoses it, bacteriophages inject genetic material through tail sheath, tail fibers have enzymatic activity to penetrate/make pores in host envelope
In what ways can viral progeny exit the host cell?
It may initiate cell death and spill virions out.
It may lyse after being filled with tons of virions.
It may fuse with plasma membrane to leave (extrusion), which is most favorable because a virus can continue to use host cell, i.e. remain in the productive cycle.
What are the lytic and lysogenic cycles?
Bacteriophages enter one of two life cycles.
Lytic- bacteriophage uses (virulent) host cell until host is swollen with new virions and lyses
Lysogenic- virus integrated as provirus or prophage and gets replicated as bacterium reproduces and remains until environmental factors cause it to leave and revert to lytic cycle (having one strain of phage makes bacterium less susceptible to superinfection or simultaneous infection by other phages)
What are prions and viroids?
Prions are infectious proteins that cause disease by triggering other proteins to misfold, usually converting alpha helices to beta-pleated sheets.
Viroids are pathogens of short/circular/single-stranded RNA that infect plants usually and bind to RNA to silence genes. Necessary proteins do not get synthesized.
When are individual chromosomes visible?
During interphase (at least 90% of the time), chromosomes are not visible with light microscopy, but in less condensed chromatin so that they're available to RNA polymerase. During mitosis, DNA are condensed into tightly coiled chromosomes to retain genetic material, making them visible.
What occurs during each step of the cell cycle?
G1 (Presynthetic Gap): cells create organelles for energy/protein synthesis, increase in size, and must get proper complement of DNA to pass restriction point onto ...
S (Synthesis of DNA): cell replicates genetic material so that each chromosome has two identical chromatids bound together at centromere (ploidy does not change even though # of chromatids double)
G2 (Postsynthetic Gap): Cell checks to ensure enough organelles/cytoplasm to divide and replication proceeded right before ...
M (Mitosis): mitosis and cytokinesis
What is the difference between autosomal and germ cells?
Autosomal cells are diploid while germ cells are haploid, i.e. one copy of each chromosome. Autosomal (somatic) cell division yields two genetically identical daughters, unlike germ cells that produces four nonidentical daughters (sex cells/gametes).
How do the G1/S and G2/M checkpoints differ?
G1/S checks if DNA is in good enough condition for synthesis, i.e. repair any DNA damage.
G2/M checkpoint ensures cell achieved adequate size and organelles have been replicated
How do cyclin and cyclin-dependent kinase concentrations differ over time?
CDKs require presence of the right cyclins to process cell cycle. Various cyclin concentrations increase/decrease during specific stages to bind to CDKs that phosphorylate transcription factors
What is the most common mutation in cancer?
Mutation of gene that produces p53, called TP53, because p53 is the main protein in both G1/S and G2/M checkpoints. This, cell cycle is not stopped at checkpoints when gene mutated, and cell divides continuously, making tumors and possibly metastasizing (if proteases to digest basement membranes or factors to form blood vesesls are produced)
What occurs in each stage of mitosis?
Prophase: chromatin condenses into chromsomes, centriole pairs move to opposite ends, centrioles form spindle fibers made of radiating microtubules (some of which form asters to anchor centriole to membrane), nuclear membrane dissolves, nucleolus becomes less distinct/disappears, kinetochores appear at centromere (for attachment points of spindle apparatus' fibers)
Metaphase: centriole pairs at opposite ends have kinetochore fibers interact with spindle apparatus' fibers to align chromosomes at metaphase/equatorial plate
Anaphase: centromeres split so each chromatid has its own distinct centromere, so sister chromatids separate via shortening of kinetochore fibers
Telophase: spindle apparatus disappears, nuclear membrane forms, nucleoli reappear, chromosomes uncoil (ends with cytokinesis)
What are the two microtubule organizing centers of the cell?
Centrosome (i.e. centrioles) and basal body of a flagellum/cilium
What are differences between meiosis and mitosis?
Meiosis produces four nonidentical sex cells, and mitosis produces two identical somatic cells.
Mitosis has one round of replication and division while meiosis has one round of replication and two rounds of division. Meiosis I has homologous chromosomes separated into haploid daughter cells (reductional division), and meiosis II has sister chromatids separate (equational division).
What occurs in each stage of meiosis I?
Prophase I: chromatin condenses into chromosomes, spindle apparatus forms, nucleoli and nuclear membrane disappear, homologous chromosomes come together and intertwine (synapsis) into tetrad held together by synaptonemal complex, chromatids of homologous chromosomes may break at chiasma/ta and exchange equivalent DNA pieces or cross over (does NOT happen b/w sister chromatids which are identical b/c both come from one parent)
Metaphase I: tetrads align at metaphase plate, each homologous pair attaches to a distinct spindle fiber by kinetochore where homologous chromosmes are lined up across from each other
Anaphase I: homologous pairs separate (disjunction) randomly i.e. either chromosome ends up in either daughter cell regardless of parent origin
Telophase I: nuclear membrane forms, cytokinesis, cell is now haploid, short rest b/w meiosis parts called interkinesis for chromosomes to partially uncoil
What is linkage?
Tendency for genes to be inherited together, which increases if genes are closer together physically; physically explained by crossovers during Prophase I in meiosis
What are Mendel's two laws? And what are they explained by biologically?
First law of segregation is explained by disjunction or alleles/homologous pairs separating into each gamete.
Second law of independent assortment (inheriting one allele does not determine which allele of another gene is inherited) explained by crossover
What are hemizygous genes?
Genes on males' X chromosome because they only have one copy unlike females with two X chromosomes, as Y chromosome has little genetic info other than SRY (sex-determining region Y) for testis differentiation and male gonad formation
Do males or females express X-linked disorders more?
Because most X-linked disorders are recessive, females express them less than males, and females that carry a diseased allele without expressing it are carriers
What are testes?
Primitive gonad in males with two functional components:
1) Seminiferous tubules- highly coiled tubules where sperm are produced and nourished by Sertoli cells
2) Interstitial cells (of Leydig)- secrete testosterone and other male sex hormones, i.e. androgens
Where do sperm travel through the male reproductive system?
Seminiferous tubules produce sperm
Epididymis are where flagella gain motility and are stored until ejaculation
Vas deferens is where sperm travel through during ejaculation (And has a muscle that can raise and lower testis to maintain temperature for sperm development)
Ejaculatory ducts are where sperm travel to during ejaculation; at posterior edge of prostate gland
Urethra is where two ejaculatory ducts fuse; carries sperm through penis as they exit the body
Penis is where sperm leaves (same pathway for urinary system for males, not for females)
What is seminal fluid and how is it produced?
Seminal fluid is what sperm mixes with to become semen, and it's produced by 3 glands
1) Seminal vesicles- contribute fructose to nourish sperm and give fluid mildly alkaline property to survive acidity of female reproductive tract
2) Prostate gland- gives fluid milky alkaline property to survive acidity of female reproductive tract
3) Bulbourethal (Cowper's) glands- produces clear viscous fluid to clear remnants of urine and lubricate urethra during sexual arousal
What are sperm called throughout spermatogenesis?
Diploid stem cells are spermatogonia.
After replicating genes (S stage), they become diploid primary spermatocytes.
After first meiotic division, they become haploid secondary spermatocytes.
After second meiotic division, they become haploid spermatids
After maturation, they become spermatozoa
How are sperm structured?
They have a head with genetic material, a midpiece filled with mitochondria for energy to swim, a cap (called acrosome) to cover head that is derived from Gogli apparatus and necessary to penetrate ovum
What consists of the female reproductive system?
Ovaries are gonads that produce estrogen and progesterone; located in pelvic cavity, each with thousands of follicles (multilayered sacs that contain, nourish, protect immature ova or eggs).
Peritoneal sac is where one egg per month is ovulated b/w puberty and menopause; lines abdominal cavity
Fallopian tube or oviduct- lined with cilia to propel egg forward; connected to muscular uterus (site of fetal development)
Cervix- lower end of uterus that connects to caginal cord and where sperm are deposited during intercourse
Vagina- passageway for sperm to deposit and for childbirth
Vulva- external female anatomy as a whole
How is oogenesis different from spermatogenesis?
All oogenia a woman will ever have are formed during fetal development, not unending supply. These cells are primary oocytes by birth and arrested in prophase I. Once menarche reached, one primary oocyte per month completes meiosis, producing secondary oocyte and a polar body, an unequal cytokinesis. The secondary oocyte is arrested in metaphase II until/if fertilization occurs. Sperm coming in triggers meiosis II into a mature ovum and another polar body to be broken down
What layers surround oocytes?
Zone pellucida- surrounds oocyte, acellular membrane of glycoproteins for protection and providing compounds for sperm cell binding
Corona radiata- lies outside zona pellucida, layer of cells adhered to oocyte during ovulation
What hormones become activated at puberty?
At puberty, the hypothalamus releases its restriction on producing gonadotropin-releasing hormone (GnRH), which triggers the anterior pituitary gland to synthesize/release follicle-stimulating hormone (FSH, which stimulates Sertoli cells) and luteinizing hormone (LH, which causes interstitial cells to produce testosterone)
What is involved in female sexual development?
Anterior pituitary -> FSH + LH -> ovaries -> estrogens and progesterone
Estrogens- made in reseponse to FSH, result in developing/maintaining female reproductive system and secondary sexual characteristics; stimulate embryo development. In adults, it thickens uterus lining (endometrum) each month to prepare zygote implantation
Progesteron- secreted by corpus luteum, remnant follicle that remains after ovulation; in response to LH; develops/maintains endometrum (not its thickening); supplied by placenta during pregnancy as corpus luteum atrophies
*Ovaries less sensitive to both and atrophies along with endometrium and FSH/LH levels rise at menopause
What are the stages of the menstrual cycle?
Menstrual cycle = rise and fall of estrogen and progesterone to grow/shed endometrial lining
1) Follicular phase- when menstrual flow begins (i.e. uterine lining of previous cycle sheds). As progesterone/estrogen levels decrease at end of cycle, hypothalamus secretes more GnRH -> more secretion of FSH and LH -> ovarian follices develop to produce estrogen, which levels off GnRH/LH/FSH and stimualtes vascularization and glandularization of the decidua
2) Ovulation- estrogen concentrations reach a threshold that results in positive (over negative) feedback, so GnRH/LH/FSH spikes. Surge in LH induces ovulation, or release of ovum from ovary into abdominal cavity
3) Luteal Phase- LH causes ruptured follicle to form corpus luteum to secrete progesterone. Estrogen remains high while progesterone rises, causing negative feedback on GnRH/FSH/LH, preventing ovulation of multiple eggs
4A) Menstruation- if implantation does not occur, corpus luteum loses LH stimulation, progesterone decreases, uterine lining comes off, estrogen decreases, GnRH can increase again
4B) Pregnancy- if fertilization occurs, zygote -> blastocyst that implants in uterine lining and secretes human chorionic gonadotropin (hCG), analog of LH that maintains corpus luteum. It is critical in first trimester b/c estrogen/progesterone secretion keeps uterine lining in place until placenta grows enough. Negative feedback of GnRH continues throughout thisq
What occurs during fertilization?
In widest part of fallopian tube (ampulla), sperm meets secondary oocyte and releases acrosomal enzymes so sperm penetrates its layers, forming the tube-like acrosomal apparatus to transfer its pronucleus.
After this, a cortical reaction (release of Ca2+) allows Ca2+ to depolarize fertilization membrane, so 1) prevent fertilization with multiple sperm, and 2) increases metabolic rate of new zygote
*Dizygotic twins is when two eggs are fertilized by two sperm. Monozygotic is when zygote splits
What occurs during cleavage?
Zygote must be implanted in endometrium before too late, so rapid mitosis occurs (becoming an embryo). Embryo size doesn't change, but each cell becomes smaller, making nuclear-to-cytoplasmic ratio and surface area-to-volume ratio increase. Thus, cells have increased gas and nutrient exchange.
Two types of cleavage:
1) Indeterminate- cells still develop into complete organisms, i.e. monozygotic twins
2) Determine cleavage- cells with determined fates, i.e. differentiating types
What occurs during blastulation?
After morula (when embryo becomes solid mass of cells) forms, it forms blastula that moves through fallopian tube to uterus and burrows into endometrium.
Trophoblast give rise to chorion (extraembryonic membrane that develops into placenta), and forms chorionic villi (little projections into endometrium) to connect embryo to maternal blood supply. Embryo is connected to placenta by umbilical cord (two arteries and a vein in gelatinous substance) which carries freshly oxygenated blood with nutrients.
The yolk sac supports embryo until placenta is functional; site of early blood cell development.
Allantois is for early fluid exchange between embryo and yolk sac until umbilical cord forms from it.
Amnion surrounds allantois as a membrane filled with amniotic fluid - a shock absorber.
What is a blastula?
Hollow ball of cells with fluid-filled inner cavity called bastocoel; called blastocyst in mammals.
Blastula have two important cell groups
1) Trophoblast cells- surround blastocoel and lead to chorion and later, placenta
2) Inner cell mass- protrudes into boastocoel and gives rise to organism itself
What occurs during gastrulation?
A blastula gains additional layers until deflating its hollow interior to create a grastula. Membrane hole is archenteron and develops into gut. Blastopore is the opening of the archenteron, which develops into anus in deuterostomes or mouth in protostomes.
Primary germ layers (rest of blastocoel and other cells coming in) include:
Ectoderm- outermost, leads to integument or skin, hair, nails, epithelia of nose, mouth, lower anus, eye lens, nervous system, and inner ear.
Mesoderm- middle layer, develops into musculoskeletal, circulatory, excretory systems, gonads, muscle/connective tissue in digestive and respiratory systems and adrenal cortex.
Endoderm- innermost, forms digestive and respiratory tracts, e.g. pancreas, thyroid, bladder, lungs, liver
How does selective transcription of genome occur?
(Induction) or ability of one group of cells (organizing cells) to influence or use chemical substances (inducers) on other group of cells (responsive cells) that must be able to respond (competent). This allows for highly specialized functions of different cell types
How does neurulation, which originates from ectoderm, develop nervous system inside embryo?
Rod of mesodermal cells called notochord forms along long axis of organism like a primitive spine. It induces overlying ectodermal cells to slide in (migrate) to form neural folds, which surrounds a neural groove, and neural folds fuse into a neural tube that becomes CNS. At tip of each neural fold are neural crest cells that become PNS
What are the three steps of cell specialization?
1) Specification- cell is reversibly designated to a specific cell type
2) Determination- irreversible commitment of a cell to having a particular function either by asymmetric distribution in cleavage/mitosis or secretion of morphogens (causes nearby cells to follow a certain developmental pathway)
3) Differentiation- cell changes to cause cell to develop into determined cell type, changing structure, function, biochemistry
What are stem cells?
Cells that have not yet differentiated, exist in embryonic and adult tissues, and differentiates into tissue depending on potency.
- Cells with greatest potency and totipotent, including emborynic stem cells), i.e. any cell type.
- Cells that differentiate into any cell type but those in placental structure are pluripotent, i.e. either inner cell mass or trophoblast
- As cells become more specialized, they become multipotent, choosing multiple cell types within a certain group
What is reciprocal development?
When cell differentiation allows not only inducers to induce responders, but also the other way around, e.g. growth factors between lens and optic vesicle form optic cup and eventually retina
How do apoptosis and necrosis differ?
Both are cell death. Apoptosis is programmed, so cell undergoes changes in morphology and divides into self-contained protrusions (apoptotic blebs), which are broken apart as (apoptotic bodies) digested by other cells.
Necrosis is when a cell dies due to injury. Internal substances can leak and cause nearby tissues to irritate or even an immune response.
What is senescence?
Biological aging or changes in molecular and cellular structure over time that causes disruption of metabolism and eventually organism death. At cellular level, cells fail to divide (after about 50 times, possibly due to telomeres)
What functions does the placental barrier serve?
1) serves as a gradient, oxygen and nutrients diffuse down to fetus while waste and CO2 diffuse in opposite direction
2) immune protection because fetus has not been exposed to pathogens (unless accidental), so antibodies cross placenta
3) endocrine organ b/c it produces progesterone, estrogen, and hCG to maintain pregnancy
How does fetal circulation differ from that of adults?
Because they are not yet developed and sensitive to high blood pressure of postnatal life,
1) Lungs: oxygenation occurs at placenta, and umbilical arteries carry deoxygenated blood while umbilical veins carries oxygenated blood.
2) Liver: Mother's liver controls detoxification and metabolism, and nutrient and waste exchange occurs at placenta
Fetus has three shunts to actively direct blood away from lungs and liver as they develop:
1) Foramen ovale- one-way valve that reroutes blood from lungs, flowing blood from right atrium to left atrium instead of right ventricle (no vascular circulation, only systemic). [This is why blood pressure is higher at right side than left in fetus, not adult].
2) Ductus arteriosus- shunts leftover blood from pulmonary artery to the aorta
3) Ductus venosus- shunts blood returning from placenta to inferior vena cava so that liver only receives little blood from smaller hepatic arties in systemic circulation
What hormones assist and stages consist of pregnancy?
Vaginal childbirth = parturition is accomplished by rhythmic contraction of smooth muscle by prostaglandins and oxytocin (peptide hormone).
Birth occurs in three phases 1) cervix thins and amniotic sac ruptures 2) strong uterine contractions result in birth 3) placenta and umbilical cord are expelled, or afterbirth
What are the four glial cells?
Astrocytes- nourish neurons and form blood-brain barrier, which controls solute transmission
Ependymal cells- line ventricles and produces CSF, which supports brain and absorbs shock
Microglia- phagocytic cells that ingest and degrade waste and pathogens in CNS
Oligodendrocytes/Schwann cells- produce myelin around axons
What is a collection of cell bodies in CNS vs. PNS?
In CNS, it's a nucleus. In PNS, it's a ganglion.
What are the equilibrium potentials of potassium and sodium?
Because K concentration outside cell is 4 mM and inside is 140 mM, deltaV for K = -90 mV.
Because Na concentration outside cell is 145 mM and inside is 12 mM, deltaV for Na = 60 mV.
Resting membrane potential is -70, closer to potassium's because membrane is more permeable to K.
What is temporal and spatial summation?
Summation is additive effect of multiple excitatory and/or inhibitory signals to a postsynaptic neuron from different presynaptic neuron(s).
Temporal- multiple signals are integrated in short period of time
Spatial- multiple signals firing closer to the axon hillock than dendritic ends
What are the three states of a sodium channel?
Closed- before the cell reaches threshold and after inactivation has been reversed
Open- from threshold -55 to 40 mV until approximately +35 mV
Inactive- after reaching +35, sodium channels cannot be active and wait until resting potential to be deinactivated
What are the two refractory periods?
Absolute refractory period- no amounth of stimulation can cause another action potential to occur (before returning to resting potential)
Relative refractory period- there must be greater than normal stimulation to cause an action potential (after returning to resting potential)
*Presence of absolute refractory period allows impulse to propagate in one way, i.e. down an axon
What are factors of speed and intensity of an action potential?
Length and cross-sectional area of axon
Increased length means greater resistance and slower movement. Increased cross-sectional area means less resistance and faster propagation. Cross-sectional area has a more significant effect than length. To maximize speed, myelin prevents dissipation of electric signal, so signal hopes frmo node to node (saltatory conduction)
Intensity of a stimulus does NOT depend on potential difference because the same type of neuron has action potentials of the same potential difference, but rather increased frequency of firing leads to increased intensity.
What is an effector?
Postsynaptic cell that is not another neuron, e.g. a gland or a muscle
What are different sorts of neurotransmitter receptors?
Neurotransmitter receptors are either ligand gated ion channels (hyperpolarize or depolarize) or they are a G protein-coupled receptor (change cAMP levels or influx Ca2+)
What are three mechanisms to regulate neurotransmission?
1) Neurotransmitters are broken down by enzymes, e.g. ACh by AChE
2) Neurotransmitters are brought back to presynaptic neuron by reuptake carriers, e.g. those of serotonin, dopamine, and norepinephrine
3) Neurotransmitters diffuse out of the synaptic cleft, e.g. Nitric Oxide
Does white matter envelop gray matter or the other way around?
In the brain, grey matter (cell bodies + dendrites) envelop white matter (axons + myelin sheaths) but in the spinal cord, the opposite is true.
What is the vertebral column? What are the spine divisions?
Between adjacent vertebrae are a space where nerves come out of, and this protects the spinal cord at all divisions (cervical, thoracic, lumbar, and sacral i.e. Cerve Thor Lumber in a Sac)
Do sensory/motor neurons enter/exit from the ventral or dorsal side of the spinal cord?
Sensory neurons are found in the dorsal root ganglia while motor neurons exit the spinal cord ventrally. (my MoVie is in an SD card)
What is the difference between the STRUCTURE of autonomic and somatic nervous systems?
A motor neuron in somatic nervous system directly innervates spinal cord without synapsing to release (nicotinic) acetylcholine while two neurons work in series to transmit messages in autonomic nervous system (preganglionic neuron in the CNS and postganglionic neuron in PNS). Also, the preganglionic neuron secretes (nicotinic) acetylcholine while the postganglionic neuron in sympathetic NS releases norepinephrine and the postganglionic neuron in parasympathetic NS releases (muscarinic) acetylcholine.
What is the vagus nerve?
Cranial nerve X that innervates most of parasympathetic neurons in the thoracic and the abdominal cavity
What is the difference between monosynaptic and polysynaptic reflex arcs?
Monosynaptic reflex arc- a single synapse between sensory neuron receiving stimulus and motor neuron responding to it; e.g. knee-jerk reflex (feedback loop to respond to potential injury of knee muscles)
Polysynaptic reflex arc- at least one interneuon between sensory and motor neuron; e.g. stepping on a nail involves withdrawal reflex (not only do hip and hamstring muscles have to pull foot upwards, but also quadriceps in opposing limb must extend)
What are the three types of hormone structures?
Peptide: derived from precursors (from Golgi before exocytosed), charged and cannot pass through plasma membrane, bind to extracellular receptor and use 2nd messengers like cAMP/IP3/Ca2+, effect is rapid but short-lived (b/c 2nd messenger system is quicker to turn off), travel freely through blood stream, e.g. ADH, insulin
Steroids: derived from cholesterol, produced by gonads and adrenal cortex mostly, nonpolar and can cross cell membrane, receptors are intracellular or intranuclear and (when bound to steroid, i.e. change conformation, e.g. dimerization) binds directly to DNA to increase/decrease transcription of certain genes, slower but longer lived effect, must be carried by protein in bloodstream (either specific or not like albumin; inactive when bound to these proteins), e.g. estrogen, testosterone, T3/T4
Amino acid derivatives: derived from 1-2 a.a. with few modifications, less predictable like catecholamines (nor/epinephrine binds to G protein-coupled receptors, fast onset but short-lived) and thyroid hormones (T3/T4 bind intracellularly, slower onset but longer duration b/c they are also steroid hormones)
What happens when a G protein-coupled receptor is activated?
Binding a peptide hormone triggers activating or inactivating enzyme called adenylate cyclase, which raises or lowers cAMP. cAMP binds to intracellular targets like protein kinase A which can phosphorylate different transcription factors.
What are different input to the hypothalamus?
Input may be sourced from light from retinae to regulate sleep/wake, blood osmolarity to regulate appetite and satiety, etc.
How does the hypothalamus communicate with the anterior pituitary?
The hypothalamus connects to a blood vessel system called hypophyseal portal system to secrete hormones. This travels directly to anterior pituitary down the pituitary stalk and is not really found in rest of circulation. They bind to anterior pituitary receptors and stimulate release of other hormones as only tropic hormones go to anterior pituitary. These resultant hormones have negative feedback effects. The result of these hormones as well can negative feedback either the anterior pituitary or hypothalamus, e.g. CRF -> ACTH -> cortisol (an axis, specifically HPA axis)
How are hormones from the posterior pituitary released?
Hypothalamuis sends axons down pituitary, not through hypophyseal portal system, but directly into posterior pituitary to release two hormones. 1) Oxytocin stimulates uterine contraction during labor and milk letdown in lactation (involved in bonding); uses positive feedback loop for stronger uterine contractions. 2) Antidiuretic hormone or vasopressin increases water reabsorption in collecting ducts of kidneys; secreted in response to increased plasma molarity or low blood volume
What are the products of the anterior pituitary?
GnRH -> FSH (follicle stimulating hormone) -> gonads
GnRH -> LH (luteinizing hormone) -> gonads
CRF -> ACTH (adrenocorticotropic hormone) -> adrenal cortex -> cortisol
TRH -> RSH -> thyroid
Nipple stimulation -> Prolactin -> mammary glands -> milk (*Dopamine inhibits Prolactin release)
Endorphins -| perception of pain
GHRH -> GH (growth hormone) -> bone/muscle -> glucose uptake in tissues not growing and breakdown of fatty acids to make glucose
What are the functions of the thyroid?
1) Setting basal metabolic rate by releasing T3 and T4 (iodination of tyrosine in follicular cells) which increases cellular respiration
2) Calcium homeostasis/control by calcitonin (produced in C-cells or parafollicular cells), which decreases plasma Ca2+ levels by: a) increasing Ca2+ secretion in kidneys, b) decreasing Ca2+ absorption in gut, and 3) increased storage of Ca2+ in gut
What does parathyroid hormone do?
1) PTH antagonizes calcitonin by raising Ca2+ levels by a) decreasing Ca2+ excretion by kidneys, b) increases Ca2+ absorption in gut by Vitamin D, and c) increases bone resorption to free up Ca2+. It is subject to negative feedback by Ca2+ concentration rising.
2) PTH affects phosphorus homeostasis by resorbing phosphate from bone and reducing reabsorption of phosphate in kidney
3) PTH activates vitamin D, which absorbs Ca2+ and phoshpate in gut
What roles does calcium play in the body?
- Bone strength and structure
- Release of neurotransmitters from neurons
- Regulation of muscle contraction
- Blood clotting (cofactor)
- Cell movement and exocytosis
What corticosteroids does the adrenal cortex secrete?
1) Glucocorticoids: steroid hormones that regulate glucose levels and affect protein metabolism, e.g. cortisol and cortisone increase gluconeogenesis and decreases protein synthesis and decrease inflammation/immune response (related to stress); regulated by ACTH <- CRF
2) Mineralcorticoids: steroid hormones in salt and water homeostasis, mostly working on kidney, e.g. aldosterone increases Na+ reabsorption in distal convoluted tubule and collecting duct of nephron, which also increases water reabsorption (and blood volume and pressure) and decreases K+/H+ reabsorption (i.e. promote excretion in urine) [*Plasma osmolarity is unchanged unlike ADH]; aldosterone <- angiotensin II converted by ACE from angiotensin I <- angiotensinogen cleaved to angiotensin I <- renin <- decreased blood pressure
3) Cortical sex hormones: make androgens (though small because made mostly in testes) and estrogens (females are more sensitive to disorders of cortical sex hormone production b/c tendency to produce excess androgen affects females)
What are the products of adrenal medulla?
Adrenal medulla (inside adrenal cortex, made of nerve cells) produces sympathetic hormones, epinephrine and norepinephrine (catecholamines, amino acid derivatives); wide variety of effects regarding fight-or-flight, e.g. epinephrine causes glycogenolysis in liver/muscle, increased basal metabolic rate; both increase heart rate, etc. [Note: cortisol is for long-term/slow stress responses while catecholamines are for short-term/fast stress responses]
Which pancreatic cells have which function?
1) Alpha cells secrete glucagon. During fasting, stimulated by low glucose levels and certain hormones (e.g. cholecystokinin, gastrin), stimulates degradation of protein/fat, glycogenolysis, gluconeogenesis
2) Beta cells secrete insulin. Secreted when blood glucose levels are high, induces muscle/liver to take up glucose for glycogen store, stimulates fat and protein synthesis
3) Delta cells secrete somatostatin, which inhibits both insulin and glucagon secretion. It's stimulated by high blood glucose and amino acid concentration; produced by hypothalamus, decreases GH secretion as well
What causes/results from different types of diabetes?
Diabetes mellitus or hyperglycemia is insensitivity to glucose while hypoglycemia is oversensitivity to glucose in excess. Glucose in excess can lead to excess excretion of water and increase in urine.
Type I diabetes (insulin-dependent) is caused by autoimmune destruction of beta-cells, so must take insulin injection to prevent hyperglycemia.
Type II diabetes (non-insulin-dependent) is caused by receptor resistance to effects of insulin; partially inherited and partially due to high-carb diet and obesity. These individuals require insulin only when bodies can no longer control glucose levels
What is the pineal gland?
Gland deep in brain that secretes hormone melatonin which is involved in circadian rhythms; receives projections from retina, but not involved in vision (maybe light intensity affects it)
What is erythropoietin?
Hormone produced by kidneys; stimulates bone marrow to increase erythrocyte production in response to low oxygen levels in blood
What is atrial natriuretic peptide?
Hormone released by the heart to regulate salt and water balance; when atria cells are stretched from excess blood volume, this is relased; promotes Na+ excretion (and thus water), antagonizing aldosterone
What is thymosin?
Hormone released by thymus (behind sternum) that is important for proper T-cell development; atrophies by adulthood
What is the difference between larynx and pharynx?
Pharynx is a common pathway for air for lungs and food for esophagus, but larynx lies below it and is only a pathway for air. Also, the larynx opening (glottis) is covered by the epiglottis.
What is the function of surfactant on alveoli?
Lowers surface tension and prevents alveolus from collapsing on itself, especially with its large surface area for a small size
How do the pleura drive breathing?
The area between the visceral pleura (close to lungs) and parietal pleura (outer layer) is the intrapleural space, which has a thin layer of fluid between the sacs that lubricates the two pleural surfaces when breathing in and out. The pressure differentials drive breathing (pressure -> work).
Not only do skeletal muscle e.g. the diaphragm (muscle dividing thoracic and abdominal cavity), generate negative pressure for expansion by somatic control, but other muscles like the chest wall, back, and neck may also participate in breathing, especially when labored
What forces are involved in inhalation?
Inhalation is active. The diaphragm flattening and external intercostal muscles (b/w ribs) constricting expand the thoracic cavity (i.e. increases intrathoracic volume, specifically intrapleural first). By Boyle's law, increase in volume leads to decrease in intrapleural pressure, relative to 1 atm. Thus, lungs expand into intrapleural space, and pressure in lungs drop so that air is sucked in from higher pressure environment. This mechanism is negative-pressure breathing (driving force is lower pressure)
What forces are involved in exhalation?
Exhalation does not have to be active.
External intercostal muscles relax, as does the diaphragm, so chest cavity decreases in volume. Intrapleural space increases in pressure relative to 1 atm, so air is pushed out.
The process can be sped by internal intercostal muscles and abdominal muscles, which oppose external intercostals and pull ribcage down, actively decreasing thoracic cavity volume.
What are different lung volumes?
Total Lung Capacity TLC- maximum volume of air in lungs in a complete inhalation, 6-7 L
Residual Volume RV- minimum volume of air in lungs when one exhales completely
Vital Capacity VC- differences between min. and max. volume of air in lungs
Tidal Volume (TV)- volume of air inhaled/exhaled in normal breath
Expiratory Reserve Volume (ERV)- volume of additional air that can be forcibly exhaled after a normal exhalation
Inspiratory Reserve Volume (IRV)- volume of additional air that can be forcibly inhaled after normal inhalation
VC = IRV + TV + ERV = TLC - RV
How is breathing regulated?
Primarily, a collection of neurons in medulla oblongata called ventillation center fire rhythmically to cause regular contraction of respiratory muscles.
These neurons have chemoreceptors sensitive to [CO2]. As PCO2 rises (hypercarbia/hypercapnia), respiratory rate increases to exhale more CO2.
They also respond to changes in [O2], but only during significant hypoxemia (very low [O])
Breathing can also be controlled by cerebrum, i.e. voluntarily, but extended hypoventilation would be overrided by medulla oblongata
How would respiratory systems adjust to higher altitudes?
Less O2 available would lead us to avoid hypoxia by breathing more rapidly.
Also, hemoglobin binding would be affected to alter O2 unloading.
We could also make more red cells to carry O2 and, long-term, more blood vessels (vascularization)
How can lungs be used for thermoregulation?
Because entire respiratory tract is vascular, body heat can be regulated through its large surface area by vasodilation and vasoconstriction.
As capillaries expand, more blood goes through, and more thermal energy is dissipated.
As capillaries contract, less blood passes, conserving thermal energy.
^Mostly applies to nasal/tracheal capillary beds (however, humans mostly do this with capillaries and sweat glands in skin or rapid muscle contraction)
Heat can also be transferred to environment by water evaporation in mucous secretion (panting in dogs)
How are lungs involved in the immune system?
Lungs' interaction with outside world means they must be able to fight off potential invaders.
1) Nasal cavity has small hairs to trap particles that may be infectious. It has an enzyme called lysozyme (also in tears/saliva) to attack peptidoglycan walls of gram + bacteria.
2) Internal airways are lined with mucus to trap particles and larger invaders. Underlying cilia propel mucus up respiratory tract to mouth to expel/swallow (mucociliary escalator)
3) Lungs have immune cells, including macrophages (engulf/digest pathogens and signal invader to rest of immune system) and IgA antibodies (protect against pathogens contacting mucous membranes
4) Mast cells on lungs have preformed antibodies on their surfaces. When right substance attaches, they release inflammatory chemicals to surrounding and promote immune response (also reactive to pollen/mold for allergies)
How do the lungs control blood pH?
It contributes to the bicarbonate buffer, i.e. [CO2(g) + H2O(l) <=> H2CO3(aq) <=> H+(aq) + HCO3-(aq)]. Body wants to maintain pH between 7.35-7.45.
When pH is low, [H+] is high (acidemia); acid-sensing chemoreceptors outside blood-brain barrier signals brain to increase respiratory rate and shifting buffer to create more CO2 also has a similar effect. Breathing increasing levels off CO2 and brings back equilibrium.
When pH is high, too basic (alkalemia), body increases acidity by slowing respiratory rate with too much CO2, shifting buffer to the right and producing more H+ and bicarbonate.
*Much faster control than kidney
What are differences between atria and ventricles?
Atria are more thin than the more muscular ventricles (and the left heart is more muscular than the right).
Atria receives blood from venae cavae (right) or pulmonary vein (left) to push into the ventricles while ventricles fill until contracting and sending blood to lungs (right) or system circulation (left)
Where is each valve in the heart and what is it called?
Atrioventricular valves connect atria and ventricles. Semilunar valves connect ventricles to vasculature.
Atrioventricular valves: LAB RAT
-Bicuspid (mitral) valve for left atrium
-Tricuspid valve for right atrium
Semilunar valves: (Rat on the Moon)
-Aortic valve for left atrium/aorta
-Pulmonary valve for right atrium/pulmonary circulation
How is electricity conducted throughout the heart?
Path: SA node -> AV node -> bundle of His -> Purkinje fibers
1) The SA (sinoatrial) node generates 60-100 signals/min without neurological input; located in wall of right atrium, causing two atria to contract simultaneously.
*Ventricular filling is passive, but contraction (atrial systole) results in increased atrial pressure by additional blood called atrial kick (5-30% CO), i.e. Die Passively or Act Systematically
2) Signal reaches AV (atrioventricular) node, sitting at atria/ventricles junction. The signal is delayed here to allow ventricles to fill completely (diastole) before contracting.
3) Signal travels to bundle of His (AV bundle) and its branches, embedded in the interventricular septum (wall)
4) Signal travels to Purkinje fibers, which distribute electrical signal through ventricular muscle which are connected by intercalated discs (have many gap junctions for coordinated contraction)
*60 beats/minute or signals/minute can be decreased with exercise and fluctuate with arousal, like parasympathetic signals from vagus nerve
How does the heart contract?
Systole: ventricular contraction, close AV valves, blood pumped out of ventricles
Diastole: relaxed heart, semilunar valves closed, blood from atria fills ventricles
Contraction creates pressure in systole, but relaxation causes it to decrease,
How is cardiac output calculated?
Cardiac output- total blood volume pumped by ventricle per minute (usually 5L/min, increasing in sympathetic and decreasing in parasympathetic)
Heart rate- beats per minute
Stroke volume- volume of blood per beat
CO = HR*SV
What are important features of arteries?
-Elastic walls allow for pressure in left ventricle to lower/blood flow; which is why left ventricle must generate enough pressure to overcome artery resistance
-Blood travels away from the heart
-Mostly oxygenated blood except umbilical and pulmonary
-Largest is aorta, and other common ones are coronary, common carotid, subclavian, renal arteries
-Lined with endothelial cells
-Have more smooth muscle than veins
-Branches into smaller/muscular arterioles
What are capillaries?
-Vessels that permeate tissues, linking arterioles and venules
-Single epithelial cell layer, thin enough for diffusing gas, nutrients, hormones, wastes
-Easy to damage, leaking blood into interstitial space or bruising if closed
What are important features of veins?
-Lined with endothelial cells; thin
-Empties blood into superior and inferior venae cavae at right side of the heart
-Inelastic; have less smooth muscle than arteries, giving less recoil than arteries, but skeletal muscles are able to squeeze veins to propel blood forward
-Veins can stretch to hold more blood (up to 3/4 of total blood), holding more blood because blood is moving at same rate as in arteries
-Carry blood to heart; deoxygenated except pulmonary and umbilical veins
-Goes against gravity sometimes, letting pressure even exceed systolic; larger veins have valves that open with forward flow and that close to prevent backward flow; failure of these vains -> varicose veins (distended where blood has pooled)
-Blood pools in lwoer extremities; clot in deep veins of leg = deep vein thrombosis
What are the function of endothelial cells in the cardiovascular system?
They line all blood vessels and maintain the vessel by releasing chemicals to aid in vasodilation and vasoconstriction.
They also allow white blood cells to pass through the vessel wall into tissue during inflammatory response.
They release chemicals when damaged to form blood clots and repair vessel/stop bleeding
What is the difference between the superiro vena cava and inferior vena cava?
Superior vena cava returns blood from body above heart; inferior vena from body below heart
What are the three portal systems?
Portal- blood passing through two capillary beds in series
1) Hepatic portal system- blood leaving capillary beds in walls of gut passes through hepatic portal vein before reaching capillary beds in liver
2) Hypophyseal portal system- blood leaving capillary beds in hypothalamus travels to capillary bed in anterior pituitary
3) Retal portal system- blood leaving glomerulus travels through an efferent arteriole before surrounding the nephron in capillary network called vasa recta
What is blood plasma made of?
It makes up 55% of blood; has nutrients, salts, respiratory gases, hormones, blood proteins
What are the features of erythrocytes?
-red blood cells
-allow O2 to travel in blood, as well as CO2/waste, via hemoglobin
-biconcave, i.e. indented on both side so 1) shape assists traveling through tiny capillaries, 2) increases cell's surface area for greater gas exchange
-when mature, loses nuclei, mitochondria, membrane-bound organelles to make space for hemoglobin and to avoid metabolizing O2 (relies on lactic acid fermentation)
-measured as hemoglobin count (grams/dL, usually 13.5-17.5 in M and 12-16 in F) or hemotacrit (how much of blood is red blood cells, usually 41=53% in M and 36-46% in F)
What are the features of leukocytes?
-white blood cells, <1% blood volume
-increases concentration during infection
-defenders against pathogens, foreign cells, cancer
-granulocytes (neutrophils, eosinophils, basophils) have cytoplasmic granules that have compounds toxic to microbes; involved in inflammatory reactions, allergies, pus formation, destroying bacteria/parasites
-agranulocytes (lymphocytes, monocytes)
*lymphocytes- for specific immune response (targeted fight against paricular pathogen; help body learn and prepare fast response from repeated exposure to familiar pathogens (vaccines train these by giving weakened pathogen or antigenic protein of pathogen) (maturation takes place in bone marrow as B-cells to make antibodies, thymus as T-cells to kill virally infected cells/active other cells)
*monocytes- phagocytize foreign matter; most organs have a collection of these called macrophages (e.g. microglia, osteoclasts)
What are thrombocytes?
-platelets, cell fragments/shards released from cell in marrow konwn as megakaryocytes
-assist blood clotting, in high concentration
What are the two major products of hematopoiesis?
1) erythropoietin- secreted by kidney and stimulates red blood cell development
2) thrombopoietin- secreted by liver/kidney, stimulates platelet development
Why is blood type matching critical to transfusions?
If donor blood antigen is recognized as foreign by recipient's immune system, severe hemolysis can occur (but type O blood cells express neither A or B antigen variant) (and those with AB blood can receive any A or B antigen variant)
When are antibodies made?
They are only made in response to/target an antigen and are not made prior to exposure to antigen
What is the Rh factor?
Several variants of an antigen (+ or -)
If mom is Rh- and first fetus is Rh+, mom will make Rh+ antibodies after child is born. However, if mom has second fetus with Rh+, anti-Rh molecules attack fetal blood cells (erythroblastosis fetalis). [Less concern for ABO b/c maternal antibodies IgM cannot cross placenta]
How is blood pressure measured/interpreted?
Blood pressure propels blood forward, so kept high, but high blood pressure or hypertension may damage blood vessels/organs.
It is measured as unit force per area with a sphygmomanometer; it is expressed as ratio of systolic to diastolic pressure (normally b/w 90/60 and 120/80) with the largest drop across arterioles.
It can be compared to Ohm's Law (delta P = CO x TPR) (With resistance coming from blood vessels' length and cross-sectional area). Longer vessel, more resistance. Larger cvross sectional area, less resistance. Arteries can expand/contract via its elasticity. All capillary beds (except portals) are parallel, so capillary beds decrease vascular resistance.
How is blood pressure regulated?
Baroreceptors in walls of vasculature, i.e. special neurons to detect mechanical forces on vessel walls; stimulate sympathetic nervous system when blood pressure is low for vasoconstriction; senses high blood osmolarity (dehydration) to release ADH.
If blood pressure is high, sympathetic control inhibited; atrial cells secrete atrial natriuretic peptide (ANP), which helps lose salt within nephron as a natural diuretic to lose fluid
How does partial pressure of oxygen fluctuate throughout rest and exercise?
A normal partial pressure of oxygen in the blood is 70-100 mmHg (e.g. oxygen saturation from a finger probe is normally 97%). If blood is 100% saturated at 100 mmHg, when oxygen partial pressure reduces to 40 mmHg at rest, hemoglobin saturation only decreases to 80% (due to sigmoidal curve). When oxygen partial pressure reduces to 20 mmHg at rest, hemoglobin saturation decreases to 70%. The oxygen that unbound from hemoglobin went into the tissues.
How does carbon dioxide's interaction with hemoglobin differ from oxygen?
How does pH affect hemoglobin?
Hemoglobin carries CO2, but it has lower affinity for it than for O2. Most exists in blood as HCO3-.
Carbonic anhydrase (reversibly catalyzes CO2 + H2O -> H2CO3) is in red blood cell, and H2CO3's dissociation into H+ and HCO3- makes it more soluble in water.
This allows pH to allosterically affect oxyhemoglobin dissociation curve because protons can bind to hemoglobin and reduce hemoglobin's affinity for oxygen (Bohr effect). Thus, more catabolic metabolism leads to more CO2 (and H+ in water) and lactic acid production, decreasing pH.
When exercising, partial pressure of CO2 increases, pH decreases, and temperature increase, all shifting the oxyhemoglobin dissociation curve right (reducing affinity for O2). Other causes of a right shift are increased 2,3-bisphosphoglycerate, side product of glycolysis in red blood cells.
A left shift occurs due to decreased PCO2, decrease [H+]/increased pH, decreased temperature, and decreased 2,3-BPG. Fetal hemoglobin also has higher affinity than adult.
What are two forms of pressure gradients in the blood?
Hydrostatic pressure- force per unit area blood exerts against vessel walls; comes from heart contractions and artery elasticity, measured in large arteries as blood pressure; pushes out of bloodstream into interstitium through capillaries.
Osmotic pressure- sucking pressure by solutes as they draw water into the bloodstream; also called oncotic pressure b/c attributable to plasma proteins
*Hydrostatic is greater than osmotic right before capillary, but right after, it drops to below osmotic; this draws water in
*Their balance is called Starling forces
*Accumulation of excess fluid in insterstitum leads to edema, also caused by blockage of lymph (fluid) through thoracic duct
How does clotting occur in the blood?
Clots/thrombus (coagulation factors/proteins + platelets) prevent blood loss by sensing exposing underlying connective tissue (collagen + tissue factor) as damaged blood vessel endothelium. In response to this, they begin to aggregate as coagulation factors secreted by the liver sense tissue factor and initiate activation cascade.
At endpoint of cascade, prothrombin activates to form thrombin by thromboplastin, and thrombin converts fibrinogen into fibrin, which forms fibers that aggregate and cross link to pcature red blood cells/platelets and form stable clot.
Clot is eventually broken down by plasmin, generated from plasminogen
What is the difference between red and white fibers?
Red fibers (slow-twitch fibers) have high myoglobin content and primary drive energy aerobically; have lots of mitochondria. Used for muscles that contract slowly, but can sustain activity.
White fibers (fast-twitch fibers) have much less myoglobin/iron/red color. Used for muscles that contract rapidly but fatigue quickly
What causes smooth muscle to contract?
Smooth muscle has more sustained contractions than skeletal, i.e. constant, low-level contraction called tonus. It contracts without nervous system input, i.e. myogeniac activity, where they contract in response to stretch and other stimuli. Like cardiac and unlike skeletal, it thus has autonomic innervation
How do muscle cells differ by muscle tissue type?
Skeletal muscle cells are multinucleated, having fused in development. Arrangement of actin and myosin into repeating units (sarcomeres) lead to striated appearance.
Smooth muscle has a single nucleus. Unorganized actin/myosin makes it not striated.
Cardiac muscle is uninucleated but cells may contain two nuclei. Looks striated. Cardiac muscle cells are connected by intercalated discs, which contain many gap junctions to exchange ions between cells' cytoplasm
What is the sarcomere composed of?
Sarcomere is the basic contractile unit of skeletal muscle.
Made of thick and thin filaments. Thick are organized bundles of myosin and thin are made of actin with troponin and tropomyosin, which regulate interaction b/w actin and myosin filaments. Also, titin acts like spring and anchors actin and myosin to prevent excessive stretch.
Sarcomere divided into lines/zones/bands. Z-line defines boundaries of sarcomere. M-line runs down center of sarcomere, through middle of myosin filaments. I-band has only thin filaments. H-zone has only thick filaments. A-band has the entirety of thick filaments, including overlap with thin. During contraction, H-zone, I-band, distance between Z-lines, and distance between M-lines become smaller whereas A-band remains constant
What is a muscle cell composed of?
Each myocyte/muscle fiber/muscle cell has many myofibrils in parallel and many nuclei at cell periphery. Myocytes in parallel form muscle.
Sarcomeres are attached end-to-end to form myofibrils. (Sarcomere, Myofibril, Myocyte/Muscle Cell/Muscle Fiber, Muscle)
Myofibrils are surrounded by covering of sarcoplasmic reticulum (special ER) with high concentration of Ca2+.
Sarcoplasm is modified cytoplasm just outside SR.
Cell membrane of a myocyte is a sarcolemma, which can propagate action potential to all sarcomeres in a muscle via T-tubules (Transverse tubules) oriented perpindicularly to myofibrils.
How does muscle contraction proceed?
- Nervous system innervates muscles via efferent neurons at neuromuscular junction. Signal reaches motor end plate (the nerve terminal) to release acetylcholine, which binds to receptors of sarcolemma and depolarizes it. Within a motor unit, a nerve terminal can innervate multiple myocytes.
- Depolarization launches action potential down sarcolemma to T-tubules, which travel into muscle tissues to sarcoplasmic reticulum.
- At sarcoplasmic reticulum, Ca2+ is released, which binds to regulatory subunit in troponin
- Bound tropomin causes conformation change in tropomyosin, exposing myosin-binding sites on actin thin filament
2) Shortening of Sarcomere
- Free globular heads of myosin move toward/bind with exposed actin; myosin carries ADP and Pi
- New actin-myosin cross bridges allow myosin to pull actin, drawing thin filaments to M and shortening sarcomere. Release of ADP and Pi together provides energy for power stroke so that actin thin filament slides over myosin
- ATP is hydrolyzed to ADP/Pi, which recocks myosin head so that it is in position to initiate another cross-bridge cycle.
*Repetitive binding/release of myosing -> sarcomere shortening [sliding filament model]
- Acetylcholine is degraded in synapse by enzyme, acetylcholinesterase, terminating signal at NMJ
- Sarcolemma repolarizes when signal ends so that Ca2+ release ends/is taken up by SR
- ATP binds to myosin heads, freeing them from actin (end of cross-bridge cycle)
- With actin/myosin disconnected, sarcomere returns to original width
- Without Ca2+, myosin-binding sites covered by tropomyosin
How do muscle signals fire?
Muscle cells have all-or-nothing response / must reach threshold.
Reaching threshold as a result of a brief stimulus -> a simple twitch. It is followed by a latent period (time b/w threshold and onset of contraction), allowing time for AP to spread and Ca+ to release.
However, a muscle fiber exposed to frequent and prolonged stimulation will not have time to relax (tetanus). Contractions combine to become stronger, more prolonged (frequency summation). Prolonged tetanus -> muscle fatigue
How can the muscle access O2 and ATP quickly?
Creatine phosphate- made by transferring phosphate from ATP to creatine during rest. This allows muscle to quickly generate ATP from ADP.
Myoglobin- binds O2 with high affinity; used when muscles run out of oxygen to keep metabolism going. Fast-twitch/white muscle (and after a while, red too) relies on glycolysis and fermentation
Heart rate and respiratory rate- increase to omve O2 to actively respiring muscles; oxyhemoglobin dissociation curve has right shift, decreased pH, increased temperature
*Oxygen debt- different b/w amount of O2 needed by muscles and the actual amount present
*After exercise, lactic acid -> pyruvate -> TCA (requires O2)
What are axial and appendicular skeletons?
Axial skeleton- skull, vertebral column, ribcage, hoid bone (for swallowing); provides central framework for body
Appendicular skeleton- bones of limbs (humerus, radius, ulna, carpals, metacarpals, phalanges; femur, tibia/fibula, tasrsals, metatarsals, phalanges), pectoral girdle (scapula, clavicle), and pelvis
What is bone composed of, macroscopically?
Compact bone- gives bone its strength, though same material as cartilage; dense, strong, lightweight; outer bone
Spongy or cancellous bone- lattice structure, made of bony spicules (points) called trabeculae
Bone marrow- fills cavities between trabeculae; either red (hematopoietic stem cells) or yellow (fat, inactive); inner bone
Diaphyses- long bones in appendicular skeleton with cylindrical shafts that swell at each end; filled with bone marrow
Metaphyses- swell at end of diaphyses; filled with bone marrow
Epiphyses- where diaphyses terminate; filled with spongy cores to disperse force/pressure at joints
Epiphyseal (growth) plate- cartilaginous structure, site of longitudinal growth; filled with mitotic cells prior to adulthood; in puberty, plates close and vertical growth is halted
Periosteum- fibrous sheath surrounding long bone to protect it and attach muscle
What is bone composed of, microscopically?
Bone matrix- gives compact bone strength; has organic (collagen, glycoproteins, other peptides) and inorganic (Ca2+, PO43-, OH-, which make hydroxyapatite crystals) components
Osteons/Haversian systems- structural unit of bony matrix; uniform distribution of organic/inorganic provides strength
Lamellae- concentric circle of bony matrix in osteons, surrounding central microscopic channel filled with blood vessels, nerve fibers, lymph vessels to maintain bone health
Harvesian canals- longitudinal channels (parallel to bone)
Volkmann's canals- transverse channels (perpendicular to bone)
Lacunae- between lamellar rings, house mature bone cells called osteocytes
Canaliculi- tiny channels interconnecting lacunae; allow nutrient/waste exchange between osteocytes and canals
How do bones remodel?
Osteoblasts- build bone; along with osteoclasts, make bone constantly turnover; takes up PO43- and Ca2+ from blood
Osteoclasts- reabsorb bone; polynucleated resident marcophages of bone; release ion back to blood
*Remodeling is in response to stress to accomodate repetitive stresses faced by body
Parathyroid hormone- peptide hormone released by parathyroid in response to low blood calcium, promotes bone resorption
Vitamin D- activated by parathyroid hormone; also promotes bone resportion
Calcitonin- peptide hormone released by parafollicular cells of thyroid in response to high Ca2+ in blood, promotes bone formation
What is cartilage made of?
Softer, more flexible than bone; makes up fetal skeleton; in adults, only in body parts needing extra flexibility/cushion
Made of firm but elastic matrix (chondrin) secreted by cells called (chondrocytes); avascular (without blood and lymphatic vessels) and is not innervated
Most bones made from hardening cartilage into bone (Endochondral ossification); responsible for long bones in body. Also, in (intramembranous ossification), undifferentiated embryonic connective tissued called mesenchymal tissue transforms into/replaced by bone, in skull
How do joints move?
-Joints made of connective tissue
-Immovable joints are made of bone fused together to form sutures or similar fibrous joints; in the head to anchor skull together
-Movable joints include hinge joints (elbow, knee), ball and socket joints (shoulder, hip), etc. Permit bones to shift relative to each other
-Ligaments strengthen movable joints; pieces of fibrous tissue that connect bones together; consist of synovial capsule that encloses actual joint/articular cavity
-Synovium or layer of soft tissue secretes synovial fluid, which lubricates moving structures in joint
-Articular cartilage contributes to joint by coating articular surfaces of bone so impact restricted to lubricated joint cartilage instead of bone
Origin- end of muscle with larger attachment to bone; proximal connection
Insertion- end of muscle with smaller attachment of bone; distal connection
Antagonist pairs- what muscles work in; one relaxes while other contracts; muscles also work synergistically
Extensor- increases/strengths angle across joint, e.g. triceps
Flexor- decreases angle across joint, e.g. biceps
Abductor- moves part of body away from midline, e.g. deltoid
Adductor- moves part of body toward midline, e.g. pectoralis major
Medial and lateral rotation- motions in limbs; medial rotator rotates limb toward midline, lateral rotator rotates limb away from midline
What is penetrance?
A population measure for alleles; proportion of individuals in the population carrying the allele who actually express the phenotype; can have full, high, reduced, low, or non penentrance
What is expressivity?
Varying phenotypes despite identical genotypes; if expressivity is constant, all individuals within a given genotype express same phenotype; if variable, individuals with same genotype may have different phenotypes; individual measure for alleles
What are Mendel's laws?
1) Genes exist in alternate forms or alleles; an organism has 2 alleles for each gene, one from each parent; two alleles segregate in meiosis resulting in gametes carrying only one allele for an inherited trait; if two alleles of an organism are different, one will be fully expressed and the other silent (exceptions: codominance, incomplete dominance)
2) inheritance of one gene does not affect inheritance of another gene (crossover between homologous chromosomes in prophase I, recombination) (exceptions: linked genes)
What is a gene pool?
All alleles that exist within a species
What is a transposon?
Element that can insert and remove themselves from a genome; disrupts gene if in middle of coding sequence
What are types of chromosomal mutations?
1) Deletion mutation- large segment of DNA is lost from a chromosome; on a small scale, like frameshift mutation
2) Duplication mutation- segment of DNA is copied multiple times in the genome
3) Inversion mutation- a segment of DNA is reversed within the chromosome
4) Insertion mutation- a segment of DNA moved from one chromosome to another; on a small scale, like frameshift mutation
5) Translocation mutation- a segment of DNA from one chromosome is swapped with a segment of DNA from another chromosome
What is leakage?
Flow of genes between species, e.g. hybrid or offspring from different but closely related species
What is genetic drift? What is founder effect?
Change s in composition of gene pool due to change
Founder effect- extreme case of genetic drift where small population in reproductive isolation due to natural barriers, catastrophic events, or other bottlenecks that drastically and suddenly reduce population size for breeding, leading to inbreeding in later generations, which encourages homozygosity, increasing genetic drift/founder effect (inbreeding depression or reduced fitness of the population)
*Outbreeding/outcrossing- introduction of unrelated individuals into breeding group to increase variety in gene pool and increased fitness theoretically
What is recombination frequency?
Probability two alleles separated from each other during crossing over; proportional to distance between genes on genome; further apart two genes are, more likely there will be a point of cross over or chiasma between them.
Tightly linked genes have 0% recomb. frequency; weakly linked approach 50% as expected from independent assortment
On a genetic map, one map unit or one centimorgan = 1% chance of recomb. occurring b/w two genes
What is the Hardy-Weinberg equilibrium?
Gene pool is not changing, specifically allele frequency (how often an allele appears in a population) is stable. Evolution causes changes over time.
To meet equilibrium, must meet five criteria:
1) Population is very large (no genetic drift)
2) There are no mutations that affect the gene pool
3) Mating b/w individuals is random (no sexual selection)
4) No migration of individuals in/out of population
5) Genes in population are equally successful at reproducing
Large, no mutations, random mating, no migration, reproduction equal
If equilibrium, can use these equations: if p = frequency of dominant and q = frequency of recessive,
p^2 + 2pq + q^2 = 1, where p^2 = frequency of homozygous dominant, 2pq = frequency of heterozygous dominant, q^2 = frequency of homozygous recessive
What is inclusive fitness?
Measure of an organism's success in the population based on number of offspring, success in supporting offspring, and ability of those offspring to then support others.
Different from Darwin's fitness of an individual organism by defending altruism to promote reproduction/survival of individuals who share same genes and defending sacrificing self to protect young to ensure passing of shared genes to future generations
What is punctuated equilibrium?
Unlike Darwin, this theory suggests changes in some species occur in random bursts rather than evenly over time
What are modes of natural selection?
Stabilizing Selection- keeps phenotypes within a specific range by selecting against extremes
Directional Selection- emergence and dominance of an initially extreme phenotype due to adaptive pressure
Disruptive Selection- two extreme phenotypes are selected over the norm; leads to polymorphisms- naturally occurring differences in form b/w members of the same population; adaptive radiation is when there's rapid rise of # of different species from a common ancestor; niche- specific environment for which a species can be specifically adapted, e.g. habitat, resources, predators
What is speciation and isolation?
Speciation- forming new species (largest group of organisms capable of breeding to form fertile offspring) through evolution
Isolation- progeny of populations are no longer free to interbreed
Prezygotic mechanisms- isolation preventing formation of zygote completely
Postzygotic mechanisms- isolation that allows gamete fusion but yields either nonviable or sterile offspring
Examples of isolation: pre (temporal, ecological, behavioral, reproductive, gametic), post (hybrid inviability, hybrid sterility, hybrid breakdown (2nd generate is infertile))
What are different patterns of evolution?
Divergent- independent development of dissimilar characteristics in 2+ lineages sharing a common ancestor, like due to adapting to different environments and selection pressures
Parallel- related species evolve in similar ways for a long time in response to analogous environmental selection pressures
Convergent- independent development of similar characteristics in 2+ lineages not sharing a recent common ancestor, like due to adapting to similar environments and selection pressures
What is molecular clock model?
Idea that degree of genomic similarity is correlated with the amount of time since two species split off from the same common ancestor; i.e. more similar the genome, more recent the common ancestor
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