ch 12

________ open or close in response to binding specific molecules.

Chemically gated channels

The part of the peripheral nervous system that carries sensory information to the CNS is designated

afferent.

The all-or-none principle states that

all stimuli great enough to bring the membrane to threshold will produce identical action potentials.

Neurons that are rare, small, and lack features that distinguish dendrites from axons are called

anaxonic.

Axons terminate in a series of fine extensions known as

telodendria.

The axon is connected to the soma at the

axon hillock.

The site in the neuron where EPSPs and IPSPs are integrated is the

axon hillock.

When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what occurs?

temporal summation

Which type of synapse is most common in the nervous system?

chemical

In the peripheral nervous system, Schwann cells participate in the repair of damaged nerves by

forming a cellular cord that directs axonal regrowth.

Small, wandering cells that engulf cell debris and pathogens in the CNS are called

microglia.

The smallest neuroglia of the CNS are the

microglia.

The sodium-potassium ion exchange pump

moves sodium and potassium opposite to the direction of their electrochemical gradients.

The myelin sheath that covers many CNS axons is formed by

oligodendrocytes.

When pressure is applied to neural tissue, all these effects are possible, except

neurons are triggered to divide.

The same ________ can have different effects depending on the properties of the ________.

neurotransmitter; receptor

Which of the following activities or sensations is not monitored by interoceptors?

sight

Adrenergic synapses release the neurotransmitter

norepinephrine.

When cholinergic receptors are stimulated,

sodium ions enter the postsynaptic neuron.

The ________ nervous system controls the skeletal muscles.

somatic

If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur, except

the intracellular concentration of potassium ions will increase.

If the axon terminal of a motor neuron suddenly became permeable to calcium ion,

the motor end plate will be depolarized.

Sensory information from skeletal muscles travels over ________ fibers.

type A

Which of the following types of nerve fiber possesses the fastest speed of impulse propagation?

type A

In a(n) ________ neuron, the dendrites and axon are continuous or fused.

unipolar

Neurons in which dendritic and axonal processes are continuous and the soma lies off to one side are called

unipolar.

Sensory neurons of the PNS are

unipolar.

Neurotransmitter for release is stored in synaptic

vesicles.

Which of the following does not influence the time necessary for a nerve impulse to be transmitted?

whether or not the impulse begins in the CNS

Most CNS neurons lack centrioles. This observation explains

why CNS neurons cannot regenerate.

The equilibrium potential for potassium ion occurs at approximately

—90 mV.

Many medications introduced into the bloodstream cannot directly affect the neurons of the CNS because

the endothelium of CNS capillaries forms a blood-brain barrier.

At the normal resting potential of a typical neuron, its Na-K ion exchange pump transports

3 intracellular sodium ions for 2 extracellular potassium ions.

Type ________ fibers have the largest diameter axons.

A

Which of the following is true about threshold for an action potential

A) It is more positive than the resting potential. C) Voltage-gated sodium channels begin to open. D) A and C only

Any stimulus that opens ________ ion channel will produce a graded potential.

A) a voltage-gated B) a chemically gated C) a sodium D) a mechanically gated E) any of the above

The function of the astrocytes in the CNS includes which of the following?

A) adjusting the composition of the interstitial fluid B) guiding neuron development C) maintaining the blood-brain barrier D) repairing damaged neural tissue E) all of the above

Opening of sodium channels in the axon membrane causes

A) depolarization. D) increased positive charge inside the membrane. E) both A and D

Raising the potassium ion concentration in the extracellular fluid surrounding a nerve cell will have which effect?

A) depolarize it D) decrease the magnitude of the potassium equilibrium potential E) both A and D

Which of the following is a recognized class of opioid neuromodulators?

A) endorphins B) enkephalins C) endomorphins D) dynorphins E) all of the above

Which of the following are types of neuroglia?

A) ependymal cells B) microglia C) astrocytes D) oligodendrocytes E) all of the above

The cytoskeleton of the perikaryon contains which of the following?

A) neurofilaments B) neurofibrils C) neurotubules Answer is E

The axoplasm of the axon contains which of the following?

A) neurotubules B) mitochondria C) vesicles D) neurofibrils E) all of the above

Which of the following is a function of neuroglia?

A) regulate the composition of interstitial fluid B) provide a supportive framework C) produce cerebrospinal fluid D) act as phagocytes E) all of the above

The efferent division of the peripheral nervous system innervates:

A) skeletal muscle cells B) smooth muscle cells C) heart muscle cells D) glandular cells E) all of the above

Which of the following are properties of cerebrospinal fluid?

A) surrounds the brain and spinal cord B) fills the brain ventricles C) transports nutrients D) circulates continuously E) all of the above

For which of the following functions do active neurons require a supply of ATP?

A) synthesis and reuptake of neurotransmitters B) axoplasmic transport C) powering the sodium-potassium exchange pump D) all of the above

In the process of continuous action potential propagation,

A) the action potential is triggered by graded depolarization of the initial segment. B) at threshold, sodium channels begin to open rapidly. C) local currents depolarize the region just adjacent to the active zone. Answer is E

In the process of saltatory action potential propagation,

A) the action potential is triggered by graded depolarization of the initial segment. B) at threshold, sodium channels begin to open rapidly. D) local currents depolarize a sensitive spot distant from the active zone. E) A, B, and D

The effect that a neurotransmitter has on the postsynaptic membrane depends on

A) the frequency of neurotransmitter release. B) the nature of the neurotransmitter. C) the characteristics of the receptors. D) the quantity of neurotransmitters released. E) all of the above

If the permeability of a resting axon to sodium ion increases,

A) the membrane potential will depolarize. C) inward movement of sodium ion will increase. both A and C

Active neurons need ATP to support which of the following?

A) the movement of materials to the soma by axoplasmic transport B) the synthesis of neurotransmitter molecules C) the movement of materials from the soma by axoplasmic transport D) the recovery from action potentials E) all of the above

Ions can move across the plasma membrane in which of the following ways?

A) through voltage-gated channels as in the action potential B) through passive or leak channels C) by ATP-dependent ion pumps like the sodium-potassium exchange pump D) through chemically-gated channels as in neuromuscular transmission E) all of the above

Which of the following comparisons between neurons and muscle tissue is false?

Action potentials are briefer in muscle fibers.

________ neurons are small and have no anatomical features that distinguish dendrites from axons.

Anaxonic

________ neurons are short, with a cell body between dendrite and axon, and occur in special sense organs.

Bipolar

Which of the following interactions between electrical and chemical gradients does not lead to the establishment of a neuronʹs resting potential?

Electrical forces push sodium ions out of the cell.

________ line the brain ventricles and spinal canal.

Ependymal cells

________ are the most numerous type of neuron in the CNS.

Interneurons

How would the absolute refractory period be affected if voltage-regulated sodium channels failed to inactivate?

It would last indefinitely.

________ channels open or close in response to physical distortion of the membrane surface.

Mechanically gated

________ neurons are the most common class in the CNS.

Multipolar

________ account for roughly half of the volume of the nervous system.

Neuroglia

Clusters of RER and free ribosomes in neurons are called

Nissl bodies.

The neurilemma of axons in the peripheral nervous system is formed by

Schwann cells.

________ neurons form the afferent division of the PNS.

Sensory

Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons?

The axon would be unable to generate action potentials.

If the potassium permeability of a resting neuron increases above the resting permeability, what effect will this have on the transmembrane potential?

The inside of the membrane will become more negative.

Which of the following statements about the action potential is false?

The rapid depolarization phase is caused by the entry of potassium ions.

How does blocking retrograde axoplasmic transport in an axon affect the activity of a neuron?

The soma becomes unable to respond to changes in the distal end of the axon.

Deteriorating changes in the distal segment of an axon as a result of a break between it and the soma is called ________ degeneration.

Wallerian

In which of the following would the rate of impulse conduction be the greatest?

a myelinated fiber of 10-μm diameter

Cholinergic synapses release the neurotransmitter

acetylcholine.

IPSPs (inhibitory postsynaptic potentials)

are local hyperpolarizations.

The largest and most numerous neuroglia in the CNS are the

astrocytes.

The largest and most numerous of the glial cells in the central nervous system are the

astrocytes.

Neurons that have one axon and one dendrite, with the soma in between, are called

bipolar.

Presynaptic facilitation by serotonin is caused by

calcium channels in the presynaptic membrane remaining open longer.

The ion that triggers the release of acetylcholine into the synaptic cleft is

calcium.

The ________ nervous system is composed of the brain and spinal cord.

central

Which of the following is not a possible drug effect on synaptic function?

change the type of receptor found in the postsynaptic membrane

Branches that may occur along an axon are called

collaterals.

Functions of astrocytes include all of the following, except

conducting action potentials.

Integral membrane proteins that connect electrical synapses are called

connexons.

Which of the following is not a function of the nervous system?

direct long-term functions, such as growth

EPSPs (excitatory postsynaptic potentials) occur when

extra sodium ions enter a cell.

Damage to ependymal cells would most likely affect the

formation of cerebrospinal fluid.

Which of the following is the most important excitatory neurotransmitter in the brain?

glutamate

Voltage-gated channels are present

in the membrane that covers axons.

Voltage-gated sodium channels have both an activation gate and a(n) ________ gate.

inactivation

Ion channels that are always open are called ________ channels.

leak

Ion channels that are always open are known as

leak channels.

Extensive damage to oligodendrocytes in the CNS could result in

loss of sensation and motor control.

Graded potentials

may be either a depolarization or a hyperpolarization.

Which of the following is not involved in creating the resting potential of a neuron?

membrane permeability for sodium ions greater than potassium ions

Which of the following is not a function of the neuroglia?

memory

After a stroke, what type of glial cell accumulates within the affected brain region?

microglia

Neurons that have several dendrites and a single axon are called

multipolar.

The most abundant class of neuron in the central nervous system is

multipolar.

Each of the following is an example of a neuroeffector junction, except the junction between a neuron and a(n)

nerve cell.

The cytoplasm that surrounds the nucleus of a neuron is called the

perikaryon.

Which of the following is not a recognized structural classification for neurons?

pseudopolar

After acetylcholinesterase acts, the synaptic knob

reabsorbs the choline.

The rabies virus travels to the CNS via

retrograde axoplasmic transport.

Which of the following are a type of glial cell found in the peripheral nervous system?

satellite cells

Glial cells that surround the neurons in ganglia are

satellite cells.

Summation that results from the cumulative effect of multiple synapses at multiple places on the neuron is designated

spatial summation.

Opioids relieve pain by blocking the release of

substance P.

The site of intercellular communication between neurons is the

synapse.

If the chemically gated sodium channels in the postsynaptic membrane were completely blocked,

synaptic transmission would fail.