ch 12 nervous system
The part of the peripheral nervous system that carries sensory information to the CNS is designated autonomic. motor. afferent. efferent. somatic.
afferent
The efferent division of the peripheral nervous system innervates: glandular cells heart muscle cells smooth muscle cells skeletal muscle cells All of the answers are correct.
all
The function of the astrocytes in the CNS includes which of the following? guiding neuron development adjusting the composition of the interstitial fluid maintaining the blood-brain barrier repairing damaged neural tissue All of the answers are correct.
all
The neuroglial cells that participate in maintaining the blood-brain barrier are the astrocytes. oligodendrocytes. microglia. ependymal cells. Schwann cells.
astrocytes
Where in the neuron is an action potential initially generated? anywhere on the axon soma and dendrites axon hillock
axon hillock
vThe axon is connected to the soma at the telodendria. synaptic terminal. axon hillock. synapse. collaterals
axon hillock
A myosin head binds to which molecule to form a cross bridge? troponin actin tropomyosin a-c
b
________ open or close in response to binding specific molecules. Voltage-gated and chemically-gated channels Activated channels Chemically-gated channels Voltage-gated channels Leak channels
chemically gated
If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind? voltage-regulated sodium channel chemically-regulated sodium channel mechanically-regulated channel voltage-regulated calcium channel chemically-regulated potassium channe
chemically regulated potassium channel
Branches that may occur along an axon are called synapses. hillocks. telodendria. synaptic terminals. collaterals
collaterals
Functions of astrocytes include all of the following, except forming a three-dimensional framework for the CNS. guiding neuron development. responding to neural tissue damage. conducting action potentials. maintaining the blood-brain barrier.
conducting action potentials
A threshold stimulus is the peak of an action potential. hyperpolarization of an axon. resting potential. depolarization necessary to cause an action potential. electrical current that crosses the synaptic cleft a b c or d
d
Approximately how fast do action potentials propagate in unmyelinated axons in humans? 0.1 meters per second 120 meters per second 12 meters per second 1 meter per second a-d
d
Curare is a drug that prevents ACh from binding to ACh receptors. How would you expect curare to affect events at a cholinergic synapse? Calcium would not diffuse into the presynaptic neuron. Vesicles would not release ACh. Acetylcholinesterase (AChE) would not break down ACh. The postsynaptic cell would not depolarize. a-d
d
During an action potential of a neuron, what directly causes the different channels to open and close? neurotransmitter binding to chemically gated channels calcium ions Sodium and potassium ions the transmembrane potential (voltage) a-d
d
In what part of the neuron does the action potential typically initiate? axon terminals dendrites soma (cell body) initial segment of the axon a-d
d
T tubules and the terminal cisternae are clustered into structures called __________. myofibrils fascicles sarcomeres triade a -d
d
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell? T tubule cytosol sarcolemma terminal cisternae of the sarcoplasmic reticulum a-d
d
The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________. local propagation continuous propagation myelinated propagation saltatory propagation a-d
d
What causes repolarization of the membrane potential during the action potential of a neuron? potassium influx (entering the cell) sodium efflux (leaving the cell) sodium influx (entering the cell) potassium efflux (leaving the cell) a-d
d
What ion causes repolarization of the neuron during an action potential? Ca2+ (calcium) Mg2+ (magnesium) Na+ (sodium) K+ (potassium) a-d
d
What type of membrane transport causes the depolarization phase of the action potential in neurons? active transport facilitated diffusion filtration diffusion a-d
d
A stimulus that changes a postsynaptic neuron's membrane from resting potential to -85 mV is: a temporal stimulus an excitatory stimulus a saltatory stimulus an inhibitory stimulus a depolarizing stimulus
inhibitory stimulus
the ________ system controls brain and spinal cord
central
Clusters of RER and free ribosomes in neurons are called perikaryon. neurofilaments. microglia. neurofibrils. Nissl bodies
nissl bodies
The tiny gaps between adjacent Schwann cells are called ________
nodes of ranvier
cThe myelin sheath that covers many CNS axons is formed by oligodendrocytes. astrocytes. ependymal cells. satellite cells. microglia.
oligodentrocytes
What is the value for the resting membrane potential for most neurons? +30 mV -90 mV -70 mV
-70
What is the magnitude (amplitude) of an action potential? 70 mV 30 mV 100 mV
100 mv
What energizes the power stroke? hydrolysis of ATP calcium binding of ATP a-c
a
Where are action potentials regenerated as they propagate along an unmyelinated axon? at every segment of the axon at myelin at the nodes at the internodes a-d
a
Why does the action potential only move away from the cell body? The areas that have had the action potential are refractory to a new action potential. The flow of the sodium ions only goes in one direction—away from the cell body a or b
a
Around what transmembrane potential does threshold commonly occur? -60 mV -60 V -70 mV +60 mV a-d
a
Binding of the neurotransmitter to its receptor causes the membrane to __________. either depolarize or hyperpolarize depolarize hyperpolarize a b or c
a
During repolarization of a neuron potassium ions move out of the cell. potassium ions move into the cell. sodium ions move out of the cell. sodium ions move into the cell. both sodium and potassium ions move into the cell a b c or d
a
In a synapse, neurotransmitters are stored in vesicles located in the __________. presynaptic neuron synaptic cleft postsynaptic neuron a b or c
a
Malignant hyperthermia (MH) is a rare genetic disease in which the sarcoplasmic reticulum leaks calcium when the patient is put under general anesthesia. Which of the following best describes how anesthesia would affect the skeletal muscles of a patient with MH? The muscles would contract because of calcium binding to troponin. The muscles would contract because of increased action potential generation in the sarcolemma. The muscles would contract because of increased nerve stimulation. The muscles would relax because of calcium being pumped back into the sarcoplasmic reticulum a-d
a
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. Binding causes potassium voltage-gated channels to open in the motor endplate. Binding causes chemically gated potassium channels to open in the motor end plate. Binding causes voltage-gated sodium channels to open in the motor endplate. a-d
a
Multiple sclerosis (MS) is a disease that stops action potential propagation by destroying the myelin around (normally) myelinated axons. Which of the following best describes how MS stops action potential propagation? Without myelin, the internode membrane is depolarized more easily. Without myelin, the internode membrane resistance decreases, preventing local currents from reaching adjacent nodes. Without myelin, the node membrane more easily becomes refractory. Without myelin, the internode membrane resistance increases, preventing local currents from reaching adjacent nodes. a-d
b
Opioids relieve pain by blocking the release of substance X. substance P. substance Q. substance O. None of the answers are correct. a b c d e
b
The acetylcholine receptor is an example of what type of channel? a voltage-gated channel a chemically gated channel a leak channel a mechanically gated channe a-d
b
The binding of calcium to which molecule causes the myosin binding sites to be exposed? actin troponin tropomyosin a-c
b
The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned? glutamate acetylcholine a or b
b
What is primarily responsible for the brief hyperpolarization near the end of the action potential? the sodium/potassium exchange pump taking some time to restore the normal ion concentrations voltage-gated potassium channels taking some time to close in response to the negative membrane potential voltage-gated potassium channels opening as the membrane potential becomes more negative (repolarized) voltage-gated sodium channels taking some time to recover from inactivation a-d
b
What is the typical duration of a nerve action potential? 20 ms 2 ms 200 ms 0.2 ms a-d
b
Which of the following causes the active site on actin to be exposed or uncovered? cross-bridge formation tropomyosin shifting position calcium entering the sarcoplasmic reticulum troponin releasing calcium a-d
b
After acetylcholinesterase acts, the synaptic terminal reabsorbs axoplasm. pinches off and a new terminal grows. reabsorbs the choline. reabsorbs the acetylcholine. reabsorbs the acetate. a b c d or e
c
An action potential releases neurotransmitter from a neuron by opening which of the following channels? chemically gated Ca2+ channels voltage-gated Na+ channels voltage-gated Ca2+ channels voltage-gated K+ channels a b c or d
c
Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane. voltage-gated; postsynaptic voltage-gated; presynaptic chemically gated; postsynaptic chemically gated; presynaptic a b c or d
c
During an action potential, after the membrane potential reaches +30 mV, which event(s) primarily affect(s) the membrane potential? Voltage-gated sodium channels begin to inactivate (close). Voltage-gated sodium channels begin to inactivate (close) and the sodium-potassium exchange pump begins removing the excess sodium ions from the inside of the cell. Voltage-gated sodium channels begin to inactivate (close) and voltage-gated potassium channels begin to open. Voltage-gated potassium channels begin to open and the sodium-potassium exchange pump begins removing the excess Na+ ions from the inside of the cell. a-d
c
How do action potential propagation speeds in myelinated and unmyelinated axons compare? Propagation is faster in unmyelinated axons. Propagation speeds are similar in both axon types. Propagation is faster in myelinated axons. Propagation in myelinated axons is faster over short distances, but slower over long distance a-d
c
How is an action potential propagated along an axon? Stimuli from the graded (local) potentials from the soma and dendrites depolarize the entire axon. An efflux of potassium from the current action potential depolarizes the adjacent area. An influx of sodium ions from the current action potential depolarizes the adjacent area. a b or c
c
In contrast to the internodes of a myelinated axon, the nodes __________. are wrapped in myelin have higher membrane resistance to ion movement have lower membrane resistance to ion movement only occur at the beginning and end of the axon a-d
c
Presynaptic facilitation by serotonin is caused by temporal summation. increased extracellular concentration of potassium ion. calcium channels in the presynaptic membrane remaining open longer. increased extracellular concentration of sodium ion. blockage of calcium channels in the presynaptic membrane. a-e
c
Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons? Neurons would depolarize more rapidly. None, because the chemically-gated sodium channels would still function. The axon would be unable to generate action potentials. Action potentials would lack a repolarization phase. The absolute refractory period would be shorter than normal. a b c d e
c
The movement of what ion is responsible for the local currents that depolarize other regions of the axon to threshold? voltage-gated sodium (Na+) channels Potassium (K+) sodium (Na+) calcium (Ca2+) a-d
c
The velocity of the action potential is fastest in which of the following axons? a large unmyelinated axon a small unmyelinated axon a small myelinated axon a b or c
c
To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers? actin tropomyosin troponin myosin a-d
c
What causes the myosin head to disconnect from actin? binding of calcium hydrolysis of ATP binding of ATP binding of troponi a=d
c
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell? ATP calcium ion pump arrival of an action potential troponin a-d
c
What ion is responsible for the depolarization of the neuron during an action potential? K+ (potassium) Cl- (chloride) Na+ (sodium) Ca2+ (calcium) a-d
c
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open? voltage-gated sodium channels chemically gated calcium channels voltage-gated calcium channels voltage-gated potassium channels a-d
c
When cholinergic receptors are stimulated, norepinephrine deactivates acetylcholine. chloride ions leave the postsynaptic neuron. sodium ions enter the postsynaptic neuron. chloride ions enter the postsynaptic neuron. sodium ions leave the postsynaptic neuro a b c d e
c
Where are action potentials regenerated as they propagate along a myelinated axon? at every segment of the axon at the internodes at the nodes at myelin a-d
c
Which of the following best describes how ACh causes depolarization of the postsynaptic membrane? ACh activates acetylcholinesterase (AChE). ACh opens voltage-gated calcium channels. ACh opens ACh receptors. ACh causes vesicles to fuse, releasing neurotransmitter into the synaptic cleft. a-d
c
Which of the following best describes the role of calcium in synaptic activity? Calcium diffuses across the synaptic cleft to bind with receptors on the postsynaptic cell. Calcium enters the postsynaptic cell and causes depolarization. Calcium enters the presynaptic cell and causes the release of ACh. Calcium breaks down acetylcholine. a-d
c
Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers? through T tubules through cross-bridge formation through calcium release from the sarcoplasmic reticulum through electrical impulses travelling along the sarcolemm a-d
c
Which of the following most correctly describes excitation in the context of excitation-contraction coupling in skeletal muscle? the formation of cross-bridges the binding of calcium to troponin the release of calcium by the sarcoplasmic reticulum the generation of an action potential in the sarcolemma a-d
d
A shift of the resting transmembrane potential toward 0 mV is called ________
depolarization
During depolarization, which gradient(s) move(s) Na+ into the cell? Na+ does not move into the cell. Na+ moves out of the cell. only the electrical gradient both the electrical and chemical gradients only the chemical gradient
electrical and chemical gradients
The sum of the electrical and chemical forces acting on an ion is known as its ________.
electrochemical gradient
Many medications introduced into the bloodstream cannot directly affect the neurons of the CNS because the neurolemma is impermeable to most molecules. astrocytes form a capsule around neurons. ependymal cells restrict the flow of interstitial fluid between the capillaries and the neurons. oligodendrocytes form a continuous myelin sheath around the axons. the endothelium of CNS capillaries forms a blood-brain barrier.
endothelium of CNH capillaries forms a blood-brain barrier
Damage to ependymal cells would most likely affect the formation of myelin sheaths. formation of cerebrospinal fluid. transport of neurotransmitters within axons. formation of ganglia. repair of axons.
formation of cerebrospinal fluid
Voltage-gated channels are present along the perikaryon of neurons. on the surface of dendrites. on the soma of neurons. at the motor end plate. in the membrane that covers axons
in the membrane that covers axons
The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____. Na+; K+ Na+; Cl- K+; Na+ K+; Cl
k, na
Ion channels that are always open are called ________ channels. active leak local regulated gated
leak
Extensive damage to oligodendrocytes in the CNS could result in loss of sensation and motor control. loss of the structural framework of the brain. inability to produce scar tissue at the site of an injury. decreased production of cerebrospinal fluid. a breakdown of the blood-brain barrier.
loss of sensation and motor control
________ channels open or close in response to physical distortion of the membrane surface. Mechanically-gated Active Voltage-gated Leak Chemically-gated
mechanically gated
After a stroke, what type of glial cell accumulates within the affected brain region? satellite cells oligodendrocytes microglia ependymal cells Schwann cells
microglia
Small, wandering cells that engulf cell debris and pathogens in the CNS are called satellite cells. ependymal cells. oligodendrocytes. microglia. astrocytes
microglia
The most abundant class of neuron in the central nervous system is bipolar. unipolar. multipolar. pseudopolar. anaxonic
multipolar
The concentrations of which two ions are highest outside the cell. Na+ and A- (negatively charged proteins) K+ and Cl- K+ and A- (negatively charged proteins) Na+ and Cl-
na and cl
The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped? Both Na+ and K+ are pumped out of the cell. Both Na+ and K+ are pumped into the cell. K+ is pumped out of the cell and Na+ is pumped into the cell. Na+ is pumped out of the cell and K+ is pumped into the cell
na out k in
________ account for roughly half of the volume of the nervous system. Dendrites Efferent fibers Axons Synapses Neuroglia
neuroglia
The basic functional unit of the nervous system is the ________.
neuron
The repolarization phase of an action potential results from __________. the opening of voltage-gated K+ channels the opening of voltage-gated Na+ channels the closing of voltage-gated Na+ channels the closing of voltage-gated K+ channels
opening of voltage gated k channels
The cytoplasm that surrounds the nucleus of a neuron is called the neuroplasm. sarcoplasm. nucleoplasm. perikaryon. protoplasm.
perikaryon
Glial cells that surround the neurons in ganglia are ependymal cells. satellite cells. astrocytes. oligodendrocytes. microgli
satellite cells
Which of the following is a type of glial cell found in the peripheral nervous system? astrocytes ependymal cells microglia oligodendrocytes satellite cells
satellite cells
The neurilemma of axons in the peripheral nervous system is formed by oligodendrocytes. astrocytes. microglia. Schwann cells. satellite cells.
schwann cells
Hyperpolarization results from __________. slow closing of voltage-gated Na+ channels fast closing of voltage-gated K+ channels slow closing of voltage-gated K+ channels
slow closing of voltage gated k channels
The ________ nervous system controls the skeletal muscles. autonomic parasympathetic afferent sympathetic somatic
somatic
The site of intercellular communication between a neuron and another cell is the collateral. telodendria. synapse. hillock. synaptic terminals.
synapse
Axons terminate in a series of fine extensions known as dendrites. terminals. synapses. collaterals. telodendria
telodendria
The buildup of depolarization when EPSPs arrive in rapid succession is called ________ summation.
temporal
If the potassium permeability of a resting neuron increases above the resting permeability, what effect will this have on the transmembrane potential? There will be almost no effect on transmembrane potential. The membrane will depolarize to threshold. The inside of the membrane will become more negative. The inside of the membrane will become more positive. The membrane will become depolarized.
the inside of the membrane will become more negative
Neurotransmitters ready for release are stored in synaptic telodendria. terminals. mitochondria. neurosomes. vesicles.
vesicles
The depolarization phase of an action potential results from the opening of which channels? chemically gated Na+ channels chemically gated K+ channels voltage-gated K+ channels voltage-gated Na+ channels
voltage gated na channels
Regions of the CNS with an abundance of myelinated axons constitute the ________ matter.
white
Most CNS neurons lack centrioles. This observation explains the ability of neurons to produce a resting potential. the ability of neurons to communicate with each other. why CNS neurons grow such long axons. the ability of neurons to generate an action potential. why CNS neurons cannot divide to regenerate damaged tissue.
why CNS neurons cannot divide to regenerate damaged tissue
