Anatomy and Physiology Ch.12

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Test#3

Opioids relieve pain by blocking the release of

Substance P

The afferent division of the PNS _____________.

carries sensory information

Neuroglia perform all of these functions except __________.

release neurotransmitters

If a nerve cell receives many IPSPs at the same time, __________.

it will show spatial summation

The neuroglial cells that participate in maintaining the blood-brain barrier are the

astrocytes

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

central

The ________ nervous system controls the skeletal muscles.

somatic

The efferent division of the peripheral nervous system innervates: smooth muscle cells
skeletal muscle cells
heart muscle cells
glandular cells
All of the answers are correct.

All of the answers are correct

The axon hillock connects the axon with the __________.

cell body (soma)

Most CNS neurons fall into which structural category?

multipolar

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

multipolar

Clusters of RER and free ribosomes in neurons are called

Nissl bodies

Branches that may occur along an axon are called

collaterals

Axons terminate in a series of fine extensions known as

telodendria

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

bipolar

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

Anaxonic

Most CNS neurons lack centrioles. This observation explains

why CNS neurons cannot divide to regenerate damaged tissue

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

astrocytes

Functions of astrocytes include all of the following, except
maintaining the blood-brain barrier.
forming a three-dimensional framework for the CNS.
conducting action potentials.
responding to neural tissue damage.
guiding neuron development.

conducting action potentials

What are the functions of astrocytes in the CNS?

Guiding neuron development
repairing damaged neural tissue
adjusting the composition of the interstitial fluid
maintaining the blood brain- barrier

________ line the brain ventricles and spinal canal.

Ependymal cells

The site of intercellular communication between a neuron and another cell is the

synapse

Sensory neurons of the PNS are

unipolar

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

microglia

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

Schwann cells

Glial cells that surround the neurons in ganglia are

satellite cells

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

Extensive damage to oligodendrocytes in the CNS could result in

loss of sensation and motor control

Damage to ependymal cells would most likely affect the

formation of cerebrospinal fluid

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

forming a cellular cord that directs axonal re-growth

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

microglia

Which type of ion channel is always open?

passive

At the normal resting potential of a typical neuron, its sodium-potassium exchange pump transports

3 intracellular sodium ions for 2 extracellular potassium ions.

Opening of sodium channels in the axon membrane causes

depolarization

Voltage-gated channels are present

in the membrane that covers axons

Voltage-gated channels are present

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

________ open or close in response to binding specific molecules.

Chemically gated channels

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

Mechanically gated

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

Graded potentials

may be either a depolarization or hyper-polarization

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

inactivation

If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind?

chemically-regulated potassium channel

If the axolemma becomes more permeable to potassium ion:

a stronger stimulus will be required to cause an action potential

In what part of the neuron does the action potential typically initiate?

initial segment of the axon

During an action potential of a neuron, what directly causes the different channels to open and close?

the transmembrane potential (voltage)

What is the typical duration of a nerve action potential?

2 ms

Around what transmembrane potential does threshold commonly occur?

-60 mV

What ion is responsible for the depolarization of the neuron during an action potential?

Na+ (sodium)

What type of membrane transport causes the depolarization phase of the action potential in neurons?

diffusion

Where are action potentials regenerated as they propagate along an unmyelinated axon?

at every segment of the axon

The movement of what ion is responsible for the local currents that depolarize other regions of the axon to threshold?

sodium (, sodium (Na+)

Approximately how fast do action potentials propagate in unmyelinated axons in humans?

1 meter per second

In contrast to the internodes of a myelinated axon, the nodes __________.

have lower membrane resistance to ion movement.

Where are action potentials regenerated as they propagate along a myelinated axon?

at the nodes

The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.

saltatory propagation

How do action potential propagation speeds in myelinated and unmyelinated axons compare?

Propagation is faster in myelinated axons.

What happens just after an axon is depolarized to threshold?

Some sodium channels are open

The all-or-none principle states that

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

During repolarization of a neuron

potassium ions move out of the cell.

A threshold stimulus is the

depolarization necessary to cause an action potential.

Rapid impulse conduction from "node" to "node" is called

Saltatory propagation

Which of the following is an example of a presynaptic cell?

neuron

What separates the presynaptic and postsynaptic cells at a chemical synapse?

synaptic cleft

What mechanism releases neurotransmitter from presynaptic neurons?

exocytosis

What type of channel in the postsynaptic membrane binds neurotransmitter?

chemically gated

What separates the presynaptic and postsynaptic cells at a chemical synapse?

synaptic cleft

A neuron that receives neurotransmitter from another neuron is called

the post-synaptic neuron

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

chemical

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

Calcium

Cholinergic synapses release the neurotransmitter

Acetylcholine

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

Synaptic transmission would fail

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

change the type or receptor found in the postsynaptic membrane

Presynaptic facilitation by serotonin is caused by

calcium channels in the presynaptic membrane remaining open longer

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