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129 terms

Mastering Anatomy Review

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Why was the hypophysectomized rat's metabolic rate lower after hypophysectomy?
The thyroid gland in this rat wasn't being stimulated by TSH, therefore it wasn't making enough thyroxine.
Which of the following hormones has intracellular receptors?
cortisol (steroid-based)
What is the mechanism of action of lipid-soluble hormones?
activation of mRNA, which increases protein synthesis in the cell
After a lipid-soluble hormone is bound to its intracellular receptor, what does the hormone complex do?
acts as a transcription factor and binds to DNA, activating a gene
Which hormone's receptor is always bound to DNA, even when the receptor is empty?
Thyroid hormone (lipid soluble)
What keeps intracellular receptors from binding to DNA before a hormone binds to the receptor?
chaperone proteins (chaperonins)
What type of hormones bind to receptors located on the cell membrane?
water-soluble hormones, such as insulin and epinephrine
Which intracellular substance degrades cAMP, thus inactivating the response to a hormone?
Phosphoidesterase
Growth factor hormones, such as insulin, bind to which type of receptor?
Tyrosine Kinase receptors
Which is the correct order of events for hormones activating G proteins?
activation of G protein, binding of GTP, activation of adenylate cyclase, conversion of ATP to cAMP
Which second messenger causes the release of calcium from the endoplasmic reticulum?
IP3
Which of the following adrenergic receptors increase cAMP levels?
beta receptors
Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?
Resting Membrane Potential
Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?
Leak channels
On average, the resting membrane potential is -70mV. What does the sign and magnitude of this value tell you?
The inside surface of the plasma is much more negatively charged than the outside surface.
The plasma membrane is much more permeable to K than to Na. Why?
There are many more K leak channels than Na leak channels in the plasma membrane
The resting membrane potential depends on two factors that influence the magnitude and direction on the Na and K diffusion across the plasma membrane. Identify these two factors.
The presence of concentration gradient and leak channels.
What prevents the Na and K gradients from dissipating?
Na-K ATPase
Where do most action potentials originate?
Initial segment (axon hillock)
What opens first in response to a threshold stimulus?
Voltage-gated channels
What characterizes depolarization, the first phase of the action potential?
The membrane potential changes from a negative value to a positive value.
What characterizes repolarization, the second phase of the action potential?
Once the membrane depolarizes to a peak value of +30mV, it depolarizes to its negative resting value of -70mV.
What event triggers the generation of an action potential?
The membrane potential must depolarize from the resting voltage of -70mV to a threshold value of -55mV.
What is the first change to occur in response to a threshold stimulus?
Voltage-gated Na channels change shape, and their activation gates open.
What type of conduction takes place in unmyelinated axons?
Continuous conduction.
An action potential is self-regenerating because-
depolarizing currents established by the influx of Na flow down the axon and trigger an action potential at the next segment.
Why does regeneration of the action potential occur in one direction, rather than in two directions?
The inactivation gates of voltage-gated Na channels close in the node, or segment, that has just fired an action potential.
What is the function of the myelin sheath?
The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
What changes occur to voltage-gated Na and K channels at the peak of depolarization?
Inactivation gates of voltage-gated Na channels close, while activation gates of voltage-gated K channels open.
In which type of axon will velocity of action potential conduction be fastest?
Myelinated axons with the largest diameter.
In a synapse, neurotransmitters are stored in vesicles located in the-
presynaptic neuron
An action potential releases neurotransmitter from a neuron by opening which of the following channels?
Voltage-gated Ca channels
Binding of a neurotransmitter to its receptors opens --- channels on the --- membrane
chemically gated, postsynaptic
Binding of the neurotransmitter to its receptor causes the membrane to
either depolarize or hyperpolarize
The mechanism by which the neurotransmitter is returned to the presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?
Acetylcholine
Which type of white matter tract connects the two cerebral hemispheres?
Commissures
Which of the following best describes the hypothalamus?
Visceral control center of the body
Which part of the brain stem houses the reflex centers for respiration and cardiovascular functioning?
Medulla Oblongata
Spinal nerves are all classified as
mixed nerves
Nerves that only carry impulses away from the central nervous system (CNS) are called
motor nerves
The majority of the cranial nerves attach to the
brain stem
Select the statement that is the most correct
Ganglia associated with afferent nerve fibers contain cell bodies of sensory neurons.
Transduction refers to conversion of
stimulus information to nerve impulses
Which of the following is not an aspect of sensory perception?
quality estimation
Which receptors adapt most slowly?
nociceptors
---- are receptors that can respond to changes in pressure
Mechanoreceptors
Feeling a gentle caress on your arm would likely involve all of the following except
Pacinian corpuscles
The synapse of the olfactory nerves with the mitral cells is called a
glomerulus
Most taste buds are located
on the tongue
Which of the following is not a requirement for something to be tasted?
The tastant must contact the basal cells of the taste buds.
Which of the following is true about gustatory receptors?
Complete adaptation occurs in about one to five minutes.
Which of the following types of neurons are replaced throughout adult life?
Olfactory receptor cells
The cells of the retina in which action potentials are generated are the
ganglion cells
During accommodation,
the ciliary muscle contracts, causing the lens to bulge
In the visual transduction pathway of the retina,
neurotransmitter from the photoreceptor causes IPSPs in the bipolar cell.
Which of the following is NOT a possible cause of conduction deafness?
death/damage to hair cells of the organ of Corti.
Some people get motion sickness because of mismatched sensory information sent to the ----- center of the ----
vestibular, medulla oblongata
The two types of receptors that bind acetylcholine are --- and --- receptors
Nicotinic, muscarinic
Which division of the nervous system has short preganglionic neurons?
sympathetic
Once a preganglionic axon reaches a trunk ganglion, one of three things can happen to the axon. Which of the following is not one of these things?
The axon can emerge from the sympathetic trunk to synapse in another axon.
The parasympathetic division uses only --- as a neurotransmitter in the ganglionic neurons
acetylcholine
Sweat glands are innervated by the --- fibers alone
sympathetic
When the vagus nerve was stimulated, what happened to the heart rate?
heart rate decreased
What do you think would happen to heart rate if the vagus nerve was severed?
heart rate would increase
Atropine is an antagonist on which of the following receptors?
muscarinic-AChR
Epinephrine potentiates which division of the autonomic nervous system?
sympathetic nervous system
Which of the following would increase heart rate?
administering epinephrine, administering atropine
The notable hardness of bone is attributed to
the presence of inorganic hydroxyapatites
The osteon is
the structural unit of compact bone
What is an osteoid?
the organic part of the matrix of bone
Osteoblasts
from new bone
Bones are constantly undergoing resorption for various reasons. Which of the following cells accomplishes this process?
osteoclast
Wolff's las is concerned with
the thickness and shape of a bone being dependent on stresses placed upon it
The correct order (from start to finish) of fracture repair is
Hematoma formation, fibrocartilaginous callus formation, bony callus formation, bone remodeling
A long bone forms by a process known as ---- ossification
endochondral
Ossification of the ends of long bones
is produced by secondary ossification centers.
In some cases the epiphyseal plate of the long bones of children closes too early. What might be the cause?
elevated levels of sex hormones.
Which hormone increases osteoclast activity to release more calcium ions into the bloodstream?
parathyroid hormone
Why should people who live in the north take supplemental calcium with vitamin D?
People who live in the north have decreased amount of sunlight exposure. Vitamin D is manufactured by skin cells when exposed to sunlight, and is needed for absorption of dietary calcium.
Mrs. Sanchez makes an appointment to see her doctor for pain in her abdominal area. Tests and X rays reveal kidney stones as well as bones with a moth-eaten appearance. Further questioning reveals a medical history of abnormal reflexes and weakness. What is the problem and what treatment would be recommended?
Hyperparathyroidism resulting from a parathyroid gland tumor, the treatment is removal of the tumor
Which of the following is true about calcium homeostasis?
Parathyroid hormone is the single more important regulator of calcium levels in the blood
John is a 26-year-old man who begins to notice a progressive enlargement of feet, hands, cranium, nose, and lower jaw bone. His doctor recommends irradiation of the pituitary gland. What is the most likely diagnosis, and what caused this condition?
The diagnosis is acromegaly. The condition results from excess secretion of growth hormone from the pituitary gland post puberty and after the epiphyseal plates of the long bones has fused.
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
Voltage-gated calcium channels
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
How is acetylcholine (ACh) removed from the synaptic cleft?
Acetylcholinesterase (AChE, an enzyme)
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ion stored in the muscle cell?
Terminal cisternae of the sarcoplasmic reticulum
Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
Calcium release from the sarcoplasmic reticulum initiates the contraction
One component of the triad is a t-tubule. How does activity in the T tubule impact the other two components?
The T tubule is linked to tow adjacent terminal cistern of the sarcoplasmic reticulum by a series of proteins
What is the name given to the regularly spaced infoldings of the sarcolemma?
transverse or T tubules
A triad is one portion of a T tubule plus two adjacent terminal cisternae of the sarcoplasmic reticulum. What is the significance of this arrangement?
Action potentials propagating down the t tubule trigger the release of calcium ions by the terminal cisternae
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
Arrival of an action potential
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
Troponin
A myosin head binds to which molecule to form a cross bridge?
Actin
What causes the myosin head to disconnect from actin?
binding of ATP
What energizes the power stroke?
hydrolysis of ATP
Opening and then closing of the Na channels
Depolarization phase in the generation of an action potential
All voltage-gated Na and K channels are closed
The resting state of a neuron
Opening of potassium gates and the rushing out of K
The repolarization phase in an action potential
The sodium channels remain opened
The absolute refractory period
Increased potassium efflux as a result of sluggish closure of the potassium gates
The phase in action potential known as the "after hyper polarization"
Reflexes
Rapid automatic responses to a stimulus in which the particular stimulus always produces the same motor response
Numerous nerve impulses arriving at a synapse at closely timed intervals exert a cumulative effect
Temporal summation
Simultaneous stimulation of many terminals, distributed widely over the surface of a postsynaptic neuron
Spatial summation
An insufficient stimulus
Subthreshold stimulus
Any stimulus above this intensity will result in an action potential in a neuron
Threshold stimulus
Somatic nervous system
Conducts impulses from CNS to skeletal muscles
Autonomic nervous system
Conducts impulses from CNS to internal organ muscles
Central nervous system
Consists of brain and spinal cord
Peripheral nervous system
Consists of nerves carrying impulses to and from brain and spinal cord
Presynaptic calcium influx
Triggers neurotransmitter release
Synaptic cleft
Separates presynaptic terminal from postsynaptic membrane
Receptor/Channel
Triggers voltage change in postsynaptic neuron
Neurotransmitter
Binds to a postsynaptic receptor/channel
Acetylcholine
Excites skeletal muscle
Norepinephrine
Main neurotransmitter of sympathetic nervous system
Dopamine
"Feel Good" transmitter, deficient in parkinson's disease
Serotonin
"Mood" transmitter, target of Prozac to relieve depression
GABA
generally inhibitory, found throughout CNS
Endorphins
Peptides with inhibitory, opiate-like actions
Somatic afferent fibers
skin, skeletal muscles, and joints to CNS
Visceral afferent fibers
organs in the ventral body cavity to CNS
Somatic motor fibers
CNS to skeletal muscles
Visceral motor fibers
CNS to smooth muscles, cardiac muscles, and glands
Which of the following statements concerning inhibitory synapses (IPSPs) is correct?
Postsynaptic membrane becomes more permeable to potassium and chloride
The sodium-potassium ion pump will
pump three sodium ions out of the cell for every two ions of potassium it brings into the cell