A&P C12 Neural Tissue

Which area of the graph shows when voltage-gated sodium channels are open?

2

Which area of the graph shows when potassium channels open?

3

Which part(s) of the neuron can propagate an action potential?

3

Which point of the graph shows when potassium ion outflow exceeds sodium ion inflow?

3

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

3 intracellular sodium ions for 2 extracellular potassium ions.

When is the neuron in the refractory period?

4

Which area of the graph shows when membrane potential approaches the potassium equilibrium potential?

4

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

Bipolar

The structures labeled "1" are dendrites. Their membranes contain numerous chemically-gated ion channels.

Both statements are true.

________ open or close in response to binding specific molecules.

Chemically gated channels

Which of the following is not true regarding the establishment of a neuron's resting potential?

Electrical forces push sodium ions into the cell.

________ line the brain ventricles and spinal canal.

Ependymal cells

What is occurring at the area labeled #4? Use Figure 12-2 The Nerve Action Potential to answer the following questions:

Excessive potassium has diffused out causing hyperpolarization.

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

Interneurons

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

It is more positive than the resting potential.

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

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

Schwann cells.

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

chemically-regulated potassium channel

A threshold stimulus is the

depolarization necessary to cause an action potential.

Opening of sodium channels in the axon membrane causes

depolarization.

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

direct long-term functions, such as growth

When pressure is applied to neural tissue, all of the following effects are possible except

neurons are triggered to divide

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

neurotransmitter; receptor

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

saltatory propagation.

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

synapse.

Axons terminate in a series of fine extensions known as

telodendria.

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.

When potassium channels open and the ions diffuse through the membrane,

the inside of the membrane will become more negative.

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

A neuron that receives neurotransmitter from another neuron is called

the postsynaptic neuron

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.

Neurotransmitters ready for release are 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 divide to regenerate damaged tissue.

The equilibrium potential for potassium ion occurs at approximately

-90 mV

On which structure do most neuron to neuron communications occur?

1

Which area of the graph shows when chemically gated sodium channels are open?

1

Which area of the graph occurs when there is a sudden rush of sodium ions into the neuron?

2

The following are the main steps in the generation of an action potential. 1. Sodium channels are inactivated. 2. Voltage-gated potassium channels open and potassium moves out of the cell, initiating repolarization. 3. Sodium channels regain their normal properties. 4. A graded depolarization brings an area of an excitable membrane to threshold. 5. A temporary hyperpolarization occurs. 6. Sodium channel activation occurs. 7. Sodium ions enter the cell and depolarization occurs. What is the proper sequence of these events?

4, 6, 7, 1, 2, 3, 5

Type ________ fibers have the largest diameter axons.

A

The axoplasm of the axon contains which of the following?

All of the answers are correct (mitochondria, neurofibrils, vesicles, neurotubules)

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

All of the answers are correct. (adjusting the composition of the interstitial fluid, guiding neuron development, repairing damaged neural tissue, maintaining the blood-brain barrier)

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

All of the answers are correct. (by ATP-dependent ion pumps like the sodium-potassium exchange pump, through chemically gated channels as in neuromuscular transmission, through passive or leak channels, through voltage-gated channels as in the action potential)

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

All of the answers are correct. (chemically gated, voltage-gated, mechanically gated, sodium)

The efferent division of the peripheral nervous system innervates ________ cells

All of the answers are correct. (glandular, heart muscle, smooth muscle, skeletal muscle)

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

Anaxonic

_______ neurons are the most common structural 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.

_______ neurons form the afferent division of the PNS.

Sensory

What is occurring in the area between #2 and #3?

Sodium ions are entering the axon and causing depolarization

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.

How would a chemical that prevents the opening of voltage-regulated Na+ channels affect the function of a neuron?

The neuron will only be capable of producing graded potentials.

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

If the axolemma becomes more permeable to potassium ion,

a stronger stimulus will be required to cause an action potential

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

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

astrocytes

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

astrocytes.

The axon is connected to the soma at the

axon hillock.

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

bipolar.

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

both hyperpolarize it and decrease the magnitude of the potassium equilibrium potential

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

central

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.

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 regrowth.

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

A stimulus that changes a postsynaptic neuron's membrane from resting potential to -85 mV is a(n) ________ stimulus

inhibitory

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

inward movement of sodium will increase and the membrane will depolarize.

Ion channels that are always open are called ________ channels.

leak

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

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

microglia

The sodium-potassium ion exchange pump

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

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

multipolar

Neurons that have several dendrites and a single axon are called

multipolar.

The myelin sheath that covers many CNS axons is formed by

oligodendrocytes.

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

perikaryon.

During repolarization of a neuron

potassium ions move out of the cell.

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

pseudopolar

The rabies virus travels to the CNS via

retrograde axoplasmic transport

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

satellite cells

Glial cells that surround the neurons in ganglia are

satellite cells.

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

sight

The ________ nervous system controls the skeletal muscles.

somatic