25 terms

AP Biology Chapter 32


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Hierarchical organization
cell → tissue (group of similar cells with common a function) → organ (tissues organized into functional units) → organ system (groups of organs that work together)
Organ System in mammals
• Digestive - The digestive system contains mouth, pharynx, esophagus, stomach, intestines (small and large), liver, pancreas, gall bladder, and anus. The function of the digestive system is in food processing (ingestion, digestion, absorption, and elimination).
• Circulatory - The circulatory system contains hear, blood vessels (arteries, veins, arterioles, venuoles, capillaries), and blood. The function of the circulatory system is gas exchange with the cells, as well as the distribution of hormones and other materials.
• Respiratory - The respiratory system consists of the trachea, larynx, bronchi, bronchioles, and lungs. The function of the respiratory system is gas exchange.
• Immune and lymphatic - The immune and lymphatic systems include bone marrow, lymph nodes, thymus, spleen, lymph vessels, and lymphocytes (white blood cells). The function of the immune system is to defend the body from foreign invaders and cancer.
• Excretory - The excretory system is composed of kidneys, ureters, urinary bladder, and urethra. The function of the excretory system is to dispose of metabolic waste and osmotic balance of the blood.
• Endocrine - The endocrine system consists of the pituitary, thyroid, pancreas, adrenal glands, and all other hormone secreting glands. The endocrine system coordinates the body's activities (metabolism, digestion, growth, reproduction, etc.)
• Reproductive - The reproductive system contains the ovaries, uterine tubes, uterus, cervix, vagina, testicles, epididymis, vas deferens, seminal vesicles, prostate gland, bulbourethral glands, penis, and scrotum. The reproductive system has one function, reproduction.
• Nervous - The nervous system contains the brain, spinal cord, nerves, and sensory organs (ears, eyes, nose, skin, tongue). The nervous system coordinates the body's activities, detection of stimuli, and responses to stimuli.
• Integumentary - The integumentary system consists of the skin and its derivatives (hair, nails, skin glands). The function of the integumentary system is protection from mechanical injury, infection, dehydration, and thermo regulation.
• Skeletal - The skeletal system is composed of bones, cartilage, ligaments, and tendons. The function of the skeletal system is support, protection, and movement.
• Muscular - The muscular system is composed of the skeletal, smooth, and cardiac muscles. The function of the muscles is locomotion and other movements.
When is an organism a regulator?
An organism is a regulator if it uses internal mechanisms to control internal changes when confronted by external stimuli. Humans can regulate their body temperature making them regulators.
When is an organism a conformer?
An organism a conformer if it allowed its internal conditions to change as its external environment changes. A bass is a conformer because its body temperature changes with the external temperature.
Tissue types found in animals
• Epithelial tissue covers the outside of the body and lines the internal organs and cavities. Its function is protection from mechanical injury, fluid loss, and protection from pathogens. Epithelial cells are closely packed and the tissue has two sides: apical surface that faces the lumen (cavity) or outside the organ and basal surface that separates the epithelium from the underlying tissue.
• Muscle cells consist of filaments composed of actin and myosin. Muscle tissue comes in three types: smooth, cardiac, and skeletal. Smooth muscle lacks striations, is responsible for involuntary actions, and is found in many internal organs. Skeletal (striated/voluntary) muscle appears striated (striped) due to the arrangement of the contractile units. It is responsible for voluntary movements. Cardiac muscle is striated, forms the contractile wall of the heart, and is involuntary.
• Nervous tissue functions by receiving, processing, and transmitting information. The basic unit of the nervous system is the neuron (consisting of dendrites, cell body, and axon). Neurons receive impulses from the dendrites of other neurons (or cell receptor or glands) and transmits information from its axon to other neurons, glands, and muscles. Axons can be bundled together into nerves. Nervous tissue is supported (nourished, insulated, replenished) by glial cells.
• Connective tissue is composed of cells scattered throughout an extra cellular matric (often a web of fibers in a liquid, jellylike, or solid substance). In this matrix are fibroblasts that secrete fiber proteins, and macrophages that engulf cell debris and foreign particles. Vertebrates have the following types of connective tissue:
− Loose connective tissue - Loose connective tissue holds skin and organs in place
− Fibrious connective tissue - Fibrious connective tissue is found in tendons and ligaments
− Adipose tissue - Adipose tissue stores fat
− Blood - Blood contains lymphocytes, erythrocytes, platelets, and plasma
− Cartilage - Cartilage provides flexible support and cushioning
− Bone - Bone is a hard tissue composed of calcium, magnesium, and phosphate ions in a collagen matrix.
• Homeostasis is a steady state, or maintaining an internal balance. Animals preform homeostasis for many physical and chemical properties like temperatures, blood pH, blood glucose levels, solute concentrations, and fluid levels (to name a few).
• Homeostasis in animals relies mainly on a negative feedback system (reducing the stimulus). Organisms have a set point (like body temperature at roughly 37°C or 98.6°F) and any fluctuations above or below the set point create a stimulus. The stimulus is detected by receptors/sensors, and the receptor sends a signal to a control center. The control center interprets the signal and triggers a response to help return the organism to the set point. Ex. Thermostat in your home
Thermoregulation and homeostasis
• Thermoregulation is the process by which animals maintain a normal body temperature within a range.
• Thermoregulation can come from an animal's internal metabolism or external environment. Humans, other mammals, and birds are endothermic (warmed by heat generated by their metabolism). Amphibians, most fish, nonavian reptiles, and most invertebrates are ectothermic (gain most of their body heat externally).
• Endotherms can maintain their body temperature even when there are large fluctuations in the external temperatures. Ectotherms don't generate enough heat for thermoregulation and adjust their body temperature by basking in the sun or hiding in the shade. Ectotherms don't need to consume as much food as endotherms because much of their thermoregulation is controlled by their environment.
• There are four ways heat can be exchanged between an organism and its environment:
− Radiation - Emission of electromagnetic waves by all objects warmer than absolute zero.
− Evaporation - The removal of heat from the surface of a liquid as it loses some of its molecules as gas.
− Convection - The transfer of heat by the movement of hair or liquid past a surface.
− Conduction - the direct transfer of heat between molecules in contact with one another. Heat is always transferred from warmer to cooler.
• Animals have many adaptations to help with thermoregulation:
− Fur, hair, feathers, or fat for insulation
− Circulatory system - changing the amounts of blood flowing to the core or skin to regulate heat through vasodilation and vasoconstriction of superficial (surface level) vessels, or reducing heat loss through countercurrent exchange (arteries and veins are adjacent to each other by running in opposite directions and the warm core blood in the arteries transfers heat to the cooler blood returning from the extremities in the veins).
− Acclimatization - Physiological adjustments to environmental changes (increasing layers of insulations, fish that can produce antifreeze proteins in their cells).
The regulation of body temperature in humans
• The regulation of body temperature is regulated on a negative feedback loop. The body's control center/thermostat is the hypothalamus, which receives signals from receptors indicating if the body's temperature is outside of the set point (approx. 36°C).
• If the body temperature increases above the set point, the hypothalamus signals for the following to occur (lowering the temperature):
− Vasodilation (releasing heat through peripheral vessels)
− Secretin of sweat (evaporative cooling)
− Some animals may pant
• If the body temperature decreases below the set point, the hypothalamus signals for the following to occur (raising the temperature):
− Vasoconstriction
− Involuntary shivering
• Many organisms can increase their biological temperature set point when infected by bacteria or viruses, producing what we know as a fever.
The coordination and control of the endocrine and nervous system
• The endocrine system produced hormones (signaling compounds) that are release into the blood stream and carried throughout the body. Hormones may travel throughout the body but only affect particular cells known as receptor cells. An example of this happens in the small intestine to control pH. The pH level of chime entering the duodenum (1st part of the small intestine) is low (acidic), which stimulates cells to release for more secretin. Secretin travels through the blood stream to the pancreas and stimulates target cells to release bicarbonate (a base) into the duodenum to neutralize the stomach acid.
• The nervous system sends nerve impulses to target cells through axons. There are four types of cells that can receive nerve signals: neurons, muscle cells, endocrine cells, and exocrine cells. Transmission of nerve impulses is extremely fast (just a fraction of a second) and last only a fraction of a second.
• Hormone signals take seconds to be released and travel through the body, and hormones can remain in effect for minutes to hours.
• The endocrine system is adept at gradual changes (growth, development, metabolic processes, digestion, and reproduction), whereas the nervous system is adept at immediate, rapid responses (behavior or quick locomotion).
• The two systems must work hand in hand.
• The hypothalamus plays the central role in integrating the endocrine and nervous system.
• The hypothalamus receives signals from throughout the body and routes the signals to the pituitary gland. The pituitary glans has two parts: the anterior pituitary gland and the posterior pituitary gland.
• Hormones from the anterior pituitary regulate other glands in the endocrine system. The posterior pituitary gland is an extension of the hypothalamus and stores and releases two hormones produced by the neurosecretory cells of the hypothalamus: oxytocin (regulates milk production and contractions during childbirth) and antidiuretic hormone (ADH).
• Hormones produced by they hypothalamus regulate the anterior pituitary causing it to stimulate or inhibit production of one or more specific hormones like the following
− Follicle stimulating hormone or leutenizing hormone targets the ovaries or testicles.
− Thyroid stimulating hormone targets the thyroid gland.
− Adrenocorticotropic hormone targets the adrenal cortex.
− Prolactin targets mammary glands.
− Melanocyte stimulating hormone target melanocytes.
− Growth hormone stimulates the liver, bones, and other tissues.
Pineal gland
(brain) Produces melatonin and plays a role in the regulation of biological rhythms.
(brain) Regulates the anterior pituitary and releases oxytocin and antidiuretic hormone (also known as vasopressin) from the posterior pituitary.
(brain) Regulated by the hypothalamus, releases hormones that regulate many other endocrine glands
(front of neck) Produces thyroid hormones T3 and T4 to maintain metabolic processes and calcitonin to lower blood calcium levels
(front of neck) Produces parathyroid hormone to raise blood calcium levels
(top of each kidney) Produces epinephrine and norepinephrine to increase metabolic activities and constrict some blood vessels, glucocorticoids to raise glucose levels, and mineralocorticoids to reabsorb sodium and excrete potassium in the kidneys.
(abdomen) Produces insulin to lower blood glucose levels and glucagon to increase blood glucose levels.
(pelvis) Produces estrogen to promote and maintain secondary sex characteristics and stimulate uterine lining growth, and progesterone to cause uterine lining growth.
(scrotum) Produces androgens to promote and maintain secondary sex characteristics and sperm formation.
Positive feedback
• Positive feedback reinforces a stimulus and leads to an even greater response. Positive feedback isn't common in animal homeostasis, and mainly works to drive a process to completion. Oxytocin plays a role in two positive feedback situations: milk production and childbirth.
Multiple effects of epinephrine
• A single hormone can create multiple effects in the body because of the following:
− Target cells having different receptor sites
− Different molecules produced in response to the hormone
• Epinephrine (adrenalin) is an example of a hormone that can produce many effects. Epinephrine is produced by the kidneys in response to a stressful situation. It causes the release of glucose (extra energy), increased blood flow to the muscles, and decreased blood flow to the digestive system.
• Osmoregulation involves controlling solute concentrations in interstitial fluid and balancing water loss and gain.
• As animals breakdown proteins and nucleic acids, ammonia is released (which is the toxic byproduct nitrogen containing molecules). The body has developed different mechanisms for dealing with excreting this waste.
• Flushing out ammonia takes large amounts of water, so only aquatic animals can excrete ammonia. Most terrestrial (and some marine species) convert ammonia to urea for excretion.
• Animals must balance water intake and loss (if they gain too much water their cells will rupture, and if they loose too much water their cells will shrivel).
• If two solutions (separated by a selectively permeable membrane) are equal in osmomolarity they are considered isosmotic.
• When two solutions differ in osmomolarity, the one with the greater concentration is hyperosmotic, and the one with lesser concentration is hypoosmotic.
• Animals can maintain fluid balance in two ways:
− Osmoconformer (marine animals) are isosmotic with their surroundings.
− Osmoregulators control internal ismolarity independently of their environment
The kidney and excretion
• The kidney plays a role in both osmoreglation and excretion.
• Most excretory systems carry out the following:
− Filtration - Filtrate (water and small solutes - salts, sugars, amino acids, and nitrogenous waters) in body fluids cross a selectively permeable membrane forming a solution called filtrate.
− Reabsorption - Recovers needed molecules (glucose, certain salts, amino acids, hormones, and vitamins) and water and concentrate the filtrate into waste products.
− Secretion - Processed, concentrate filtrate (containing nitrogenous wastes) is released from the body as urine.
• The functional unit of the kidney is the nephron. The nephron is made up of a long tubule and a ball of capillaries called the glomerulus. The glomerulus sits a cup shaped capsule called Bowman's capsule (it is one end of the tubule of the nephron). Figure 32.19
• Filtrate is formed in the following steps:
− Blood pressure forces fluid from the blood in the glomerulus into Bowman's capsule. The filtrate is further processed as it passed through the proximal tubule, loop of Henle and the distal tubule.
− In the proximal tubule reabsorption of water, ions (sodium, potassium), nutrients (glucose), and amino acids takes place. Toxic substances filtered by the liver are secreted into the filtrate at this point.
− In the descending loop on Henle water absorption continues and the filtrate becomes more concentrated (salt cant penetrate and be reabsorbed).
− In the ascending loop of Henle salt is reabsorbed, but not water (water cant penetrate).
− In the distal tubule regulates potassium and solid levels in body fluids. The amounts of potassium secreted into the filtrate and the remaining amounts of sodium absorbed are regulated here to ensure the body has the needed concentrations.
− The colleting duct plays a role in the final processing of the filtrate and the formation of urine.
• 1600 L of blood pass though each kidney a day. The nephrons process this blood creating 180 L of initial filtrate. Only 1.5 L of urine are transported to the bladder because 99% of the water and most all of the sugars, amino acids, vitamins, and other nutrients are reabsorbed.
Homeostasis regulation of the kidney
Antidiuretic hormone (ADH or vasopressin) regulates fluid retention by the kidney. If filtrate concentrations rise in the blood (too much water has been lost or too little water has been consumed) the hypothalamus is triggered to release antidiuretic hormone making you thirsty and causing water reabsorption (less urine production and urination). If levels of filtrate concentration become too low in the blood, ADH production drops drastically, much less water is absorbed, and diluted urine is excreted.