ch 12 nervous system

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the ________ system controls brain and spinal cord

central

The ________ nervous system controls the skeletal muscles.
autonomic
parasympathetic
afferent
sympathetic
somatic

somatic

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 most abundant class of neuron in the central nervous system is
bipolar.
unipolar.
multipolar.
pseudopolar.
anaxonic

multipolar

The cytoplasm that surrounds the nucleus of a neuron is called the
neuroplasm.
sarcoplasm.
nucleoplasm.
perikaryon.
protoplasm.

perikaryon

Clusters of RER and free ribosomes in neurons are called
perikaryon.
neurofilaments.
microglia.
neurofibrils.
Nissl bodies

nissl bodies

vThe axon is connected to the soma at the
telodendria.
synaptic terminal.
axon hillock.
synapse.
collaterals

axon hillock

Branches that may occur along an axon are called
synapses.
hillocks.
telodendria.
synaptic terminals.
collaterals

collaterals

Axons terminate in a series of fine extensions known as
dendrites.
terminals.
synapses.
collaterals.
telodendria

telodendria

The site of intercellular communication between a neuron and another cell is the
collateral.
telodendria.
synapse.
hillock.
synaptic terminals.

synapse

Neurotransmitters ready for release are stored in synaptic
telodendria.
terminals.
mitochondria.
neurosomes.
vesicles.

vesicles

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

The basic functional unit of the nervous system is the ________.

neuron

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

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

________ account for roughly half of the volume of the nervous system.
Dendrites
Efferent fibers
Axons
Synapses
Neuroglia

neuroglia

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

cThe myelin sheath that covers many CNS axons is formed by
oligodendrocytes.
astrocytes.
ependymal cells.
satellite cells.
microglia.

oligodentrocytes

Small, wandering cells that engulf cell debris and pathogens in the CNS are called
satellite cells.
ependymal cells.
oligodendrocytes.
microglia.
astrocytes

microglia

The neurilemma of axons in the peripheral nervous system is formed by
oligodendrocytes.
astrocytes.
microglia.
Schwann cells.
satellite cells.

schwann cells

Glial cells that surround the neurons in ganglia are
ependymal cells.
satellite cells.
astrocytes.
oligodendrocytes.
microgli

satellite cells

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

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

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

The tiny gaps between adjacent Schwann cells are called ________

nodes of ranvier

Regions of the CNS with an abundance of myelinated axons constitute the ________ matter.

white

After a stroke, what type of glial cell accumulates within the affected brain region?
satellite cells
oligodendrocytes
microglia
ependymal cells
Schwann cells

microglia

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

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

What is the value for the resting membrane potential for most neurons?
+30 mV
-90 mV
-70 mV

-70

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

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

Ion channels that are always open are called ________ channels.
active
leak
local
regulated
gated

leak

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

________ channels open or close in response to physical distortion of the membrane surface.
Mechanically-gated
Active
Voltage-gated
Leak
Chemically-gated

mechanically gated

________ 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 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

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

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

A shift of the resting transmembrane potential toward 0 mV is called ________

depolarization

The sum of the electrical and chemical forces acting on an ion is known as its ________.

electrochemical gradient

Where in the neuron is an action potential initially generated?
anywhere on the axon
soma and dendrites
axon hillock

axon hillock

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

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

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

What is the magnitude (amplitude) of an action potential?
70 mV
30 mV
100 mV

100 mv

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

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

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

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

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

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

In a synapse, neurotransmitters are stored in vesicles located in the __________.
presynaptic neuron
synaptic cleft
postsynaptic neuron

a b or c

a

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

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 the neurotransmitter to its receptor causes the membrane to __________.
either depolarize or hyperpolarize
depolarize
hyperpolarize
a b or c

a

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

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

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

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

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

The buildup of depolarization when EPSPs arrive in rapid succession is called ________ summation.

temporal

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

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

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

T tubules and the terminal cisternae are clustered into structures called __________.
myofibrils
fascicles
sarcomeres
triade
a -d

d

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

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

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

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

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

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

The binding of calcium to which molecule causes the myosin binding sites to be exposed?
actin
troponin
tropomyosin
a-c

b

A myosin head binds to which molecule to form a cross bridge?
troponin
actin
tropomyosin
a-c

b

What energizes the power stroke?
hydrolysis of ATP
calcium
binding of ATP
a-c

a

What causes the myosin head to disconnect from actin?
binding of calcium
hydrolysis of ATP
binding of ATP
binding of troponi

a=d

c

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

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

What is the typical duration of a nerve action potential?
20 ms
2 ms
200 ms
0.2 ms
a-d

b

Around what transmembrane potential does threshold commonly occur?
-60 mV
-60 V
-70 mV
+60 mV
a-d

a

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

What type of membrane transport causes the depolarization phase of the action potential in neurons?
active transport
facilitated diffusion
filtration
diffusion
a-d

d

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

What ion causes repolarization of the neuron during an action potential?
Ca2+ (calcium)
Mg2+ (magnesium)
Na+ (sodium)
K+ (potassium)
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 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

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

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

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

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

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

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

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

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

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

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 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

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

What is the primary role of acetylcholinesterase (AChE) at a cholinergic synapse?
AChE binds to ACh receptors, causing them to open.
AChE degrades acetylcholine in the synaptic cleft.
AChE releases acetylcholine into the synaptic cleft.
AChE depolarizes the postsynaptic cell.
a-d

b

Which of the following best describes the order of events in synaptic activity?
Extracellular calcium enters the synaptic knob, triggering exocytosis of ACh. An action potential arrives and depolarizes the synaptic knob. ACh binds to receptors and depolarizes postsynaptic membrane. ACh is removed by AChE.
ACh is removed by AChE. ACh binds to receptors and depolarizes postsynaptic membrane. An action potential arrives and depolarizes the synaptic knob. Extracellular calcium enters the synaptic knob, triggering exocytosis of ACh.
An action potential arrives and depolarizes the synaptic knob. Extracellular calcium enters the synaptic knob, triggering exocytosis of ACh. ACh is removed by AChE. ACh binds to receptors and depolarizes postsynaptic membrane.
An action potential arrives and depolarizes the synaptic knob. Extracellular calcium enters the synaptic knob, triggering exocytosis of ACh. ACh binds to receptors and depolarizes postsynaptic membrane. ACh is removed by AChE.

d

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