Chapter 8 Review Questions from book

Question 1

List the three functional classes of neurons, and explain how they differ structurally and functionally.

Answer 1

sensory neurons: carry messages from sensory receptors to CNS. Their cell bodies are located close to the CNS.

motor neurons: carry information away from the CNS back to various parts of the body

Interneurons: neurons that lie entirely within the CNS

Question 2

Somatic motor neurons control _____, and ____ neurons control smooth and cardiac muscles, glands, and some adipose tissue.

Answer 2

skeletal muscle, autonomic

Question 3

Autonomic neurons are classified as either ____ or ______ neurons.

Answer 3

sympathetic or parasympathetic

Question 4

Match each term with its description

Answer 4

(a) axon: long process that transmits information to the CNS.
(b) dendrite: process of a neuron that receives incoming signals.
(c) afferent: sensory neuron, transmits information to CNS.
(d) efferent: neuron that transmit signals to the target cell.
(e) trigger zone: region of neuron where action potential begins.

Question 5

Name the two primary cell types found in the nervous system.

Answer 5

neurons and glia cells

Question 6

Draw a typical neuron and label the cell body, axon, dendrites, nucleus, trigger zone, axon hillock, collaterals, and axon terminals.

Answer 6

See fig 8.2 and 8.3

Question 7

Axonal transport refers to the

Answer 7

movement of organelles and cytoplasm up and down the axon

Question 8

Match the numbers of the appropriate characteristics with the two types of potentials. Characteristics may apply to one or both types:

Answer 8

(a) action potential: all-or-none, exhibits a refractory period

(b) graded potential: can be summed, amplitude decreases with distance, amplitude depends on strength of stimulus, has no threshold

Question 9

Arrange the following events in the proper sequence:
A. Efferent neuron reaches threshold and fires an action potential.
B. Afferent neuron reaches threshold and fires an action potential.
C. Effector organ responds by performing output.
D. Integrating center reaches a decision about the response.
E. Sensory organ detects change in the environment.

Answer 9

E B D A C
1. Sensory organ detects change in the environment.
2. Afferent neuron reaches threshold and fires an action potential.
3. Integrating center reaches a decision about response.
4. Efferent neuron reaches threshold and fires an action potential.
5. The effector organ responds by performing output.

Question 10

List the four major types of ion channels found in neurons. Are they chemically gated, mechanically gated, or voltage-gated.

Answer 10

Na+ channels (voltage-gated along axon; any type of gating on dendrites); voltage-gated K+ channels along axon; voltage-gated Ca2+ channels in axon terminal; chemically gated Cl− channels

Question 11

function of astrocytes

Answer 11

help form the blood-brain barrier

Question 12

function of ependymal cells

Answer 12

separate CNS fluid compartments

Question 13

function of microglia

Answer 13

modified immune cells

Question 14

function of oligodendrocytes

Answer 14

form myelin

Question 15

function of satellite cells

Answer 15

found in the peripheral nervous system
found in ganglia

Question 16

function of Schwann cells

Answer 16

form myelin found in the peripheral nervous system

Question 17

An action potential is (circle all the correct answers)

Answer 17

The same size and shape at the beginning and end of the axon.

Transmitted to the distal end of a neuron and causes release of neurotransmitter

Question 18

Arrange the following events in the proper sequence:

Answer 18

1. sensory organ detects change in the environment
2. afferent neuron reaches threshold and fires action potential
3. integrating center reaches decision about response
4. efferent neuron reaches threshold and fires an action potential
5. effector organ responds by performing output

Question 19

Choose from the following ions to fill in the blanks correctly: Na+ , K+ , Ca2+ , Cl-

a) the resting cell membrane is more permeable to ___________ than to ___________. Although ________ contribute little to the resting membrane potential, they play a key role in the generating of electrical signals in excitable tissues.

b) the concentration of ___________ is 12 times greater outside the cell than inside.

c) the concentration of ________ is 30 times greater inside the cell than outside.

d) an action potential occurs when _____ enters the cell.

e) the resting membrane potential is due to the high ___________ permeability of the cell.

Answer 19

a) K+ , Na+ , Na+

b) Na+

c) K+

d) Na+

e) K+

Question 20

Match the glial cell(s) on the right to the functions on the left. There may be more than one correct answer for each function.

Answer 20

a. modified immune cells: microglia
b. help form the blood-brain barrier: astrocytes
c. form myelin: oligodendrocytes and schwann cells
d. seperate CNS fluid compartments: ependymal cells
e. found in peripheral nervous system: satellite cells and schwann cells
f. found in ganglia: satellite cells

Question 21

The resting cell membrane is more permeable to _______ than to ______. Although ______ contribute little to the resting membrane potential, they play a key role in generating electrical signals in excitable tissues.

Answer 21

K+, Na+, Na+

Question 22

The concentration of ______ is 12 times greater outside the cell than inside.

Answer 22

Na+

Question 23

The concentration of ______ is 30 times greater inside the cell than outside.

Answer 23

K+

Question 24

An action potential occurs when _______ enter the cell.

Answer 24

Na+

Question 25

The resting membrane potential is due to the high ______ permeability of the cell.

Answer 25

K+

Question 26

What is the myelin sheath?

Answer 26

Acts as a insulating layer, preventing leakage of electrical current

Question 27

List two factors that enhance conduction speed:

Answer 27

Conduction velocity is influenced by myelin sheath thickness and internode distance.

Question 28

List three ways neurotransmitters are removed from the synapse.

Answer 28

enzymatic degradation, reabsorption, and diffusion

Question 29

Draw and label a graph of an action potential. Below the graph, draw the positioning of the K+ and Na+ channel gates during each phase.

Question 30

What causes the depolarization phase of an action potential? (Circle all that apply.)

Answer 30

Na+ entering the cell through voltage-gated channels

Question 31

Name any four neurotransmitters, their receptor(s), and tell whether the receptor is an ion channel or a GPCR.

Question 32

Create a map showing the organization of the nervous system using the following terms, plus any terms you choose to add:

afferent signals
astrocyte
autonomic division
brain
CNS
efferent neuron
ependymal cell
glands
glial cells
integration
interneuron
microglia
muscles
neuron
neurotransmitter
oligodendrocyte
parasympathetic division
peripheral division
satellite cell
Schwann cell
sensory division
somatic motor division
spinal cord
stimulus
sympathetic division
target

Question 33

Arrange the following terms to describe the sequence of events after a neurotransmitter binds to a receptor on a postsynaptic neuron. Terms may be used more than once or not at all.

a. action potential fires at axon hillock
b. trigger zone reaches threshold
c. cell depolarizes
d. exocytosis
e. graded potential occurs
f. ligand-gated ion channel opens
g. local current flow occurs
h. saltatory conduction occurs
i. voltage-gated Ca2+ channels open
j. voltage-gated K+ channels open
k. voltage-gated Na+ channels open

Answer 33

(f) - (c) - (g) - (e) - (b) - (k) - (c) - (a) - (h) - (j) - (i) - (d)

Question 34

Match the best term (hyperpolarize, depolarize, repolarize) to the following events. The cell in question has a resting membrane potential of −70 mV.

Answer 34

A. membrane potential changes from −70 mV to −50 mV. Depolarize
B. membrane potential changes from −70 mV to −90 mV. Hyperpolarize
C. membrane potential changes from +20 mV to −60 mV. Repolarize
D. membrane potential changes from −80 mV to −70 mV. depolarize

Question 35

A neuron has a resting membrane potential of −70 mV. Will the neuron hyperpolarize or depolarize when each of the following events occurs? (More than one answer may apply; list all those that are correct.)
A. Na+ enters the cell
B. K+ leaves the cell
C. Cl- enters the cell
D. Ca2+ enters the cell

Answer 35

A. Depolarize
B. Hyperpolarize
C. Hyperpolarize
D. Depolarize

Question 36

If all action potentials within a given neuron are identical, how does the neuron transmit information about the strength and duration of the stimulus?

Answer 36

Strength is coded by the frequency of action potentials, duration is coded by the duration of a train of repeated action potentials

Question 37

The presence of myelin allows an axon to

Answer 37

conduct impulses more rapidly

Question 38

Define, compare, and contrast the following concepts:
a. threshold, subthreshold, suprathreshold, all-or-none, overshoot, undershoot
b. graded potential, EPSP, IPSP
c. absolute refractory period, relative refractory period
d. afferent neuron, efferent neuron, interneuron
e. sensory neuron, somatic motor neuron, sympathetic neuron, autonomic neuron, parasympathetic neuron
f. fast synaptic potential, slow synaptic potential
g. temporal summation, spatial summation
convergence, divergence

Question 39

If human babies’ muscles and neurons are fully developed and functional at birth, why can’t they focus on their eyes, sit up, or learn to crawl within hours of being born? (Hint: Muscle strength is not the problem)

Answer 39

All the necessary synapses have not yet been made between neurons or between neurons and effectors

Question 40

The voltage-gated Na+ channels of a neuron open when the neuron depolarizes. If depolarization opens the channels, what makes them close when the neuron is maximally depolarized?

Answer 40

Inactivation gates also respond to depolarization, but they close more slowly than the activation gates open, allowing ions to flow for a short period of time

Question 41

One of the pills that Jim takes for high blood pressure caused his blood K+ levels to decrease from 4.5 mM to 2.5 mM. What happens to the resting membrane potential of his liver cells
a. decreases
b. increases
c. does not change
d. becomes more negative
e. becomes less negative
f. fires an action potential
g. depolarizes
h. hyperpolarizes
i. repolarizes

Answer 41

b, d, h

Question 42

Characterize each of the following stimuli as being mechanical, chemical, or thermal:
a. bath water at 106 F
b. acetylcholine
c. a hint of perfume
d. epinephrine
e. lemon juice
f. a punch on the arm

Answer 42

a. thermal
b. chemical
c. chemical
d. chemical
e. chemical
f. mechanical

Question 43

An unmyelinated axon has a much greater requirement for ATP than a myelinated axon of the same diameter and length. Can you explain why?

Answer 43

Unmyelinated axons have many ion channels, so more ions cross during an action potential and must be returned to their original compartments by the Na+-K+-ATPase, using energy from ATP

Question 44

The GHK equation is sometimes abbreviated to exclude chloride, which plays a minimal role in membrane potential for most cells. In addition, because it is difficult to determine absolute membrane permeability values for Na+ and K+, the equation is revised to use the ratio of the two ion permeabilities, expressed as

Thus, if you know the relative membrane permeabilities of the two ions and their intracellular (ICF) and extracellular (ECF) concentrations, you can predict the membrane potential for a cell.

A.) A resting cell has an alpha value of 0.025 and the following ion concentrations

What is the cell’s membrane potential?
B.) The Na+ permeability of the cell in (a) suddenly increases so that alpha= 20. Now what is the cell’s membrane potential?
C.) Mrs. Nguyen has high blood pressure, and her physician puts her on a drug whose side effect decreases her plasma (ECF) K+ from 4 mM to 2.5 mM. Using the other values in (a), now what is the membrane potential?
D.) The physician prescribes a potassium supplement for Mrs. Hguyen, who decides that if two pills are good, four must be better. Her plasma (ECF) K+ now goes to 6 mM. What happens to the membrane potential?

Answer 44

A.) -80 mV
B.) 63 mV
C.) -86 mV
D.) -73 mV

Question 45

A resting cell has an alpha (α) value of 0.025 and the following ion concentrations:

Na+:ICF=5 mM, ECF=135 mM

K+:ICF=150 mM, ECF=4 mM

What is the cell’s membrane potential?

Question 46

The central nervous system (CNS) consists of:

Answer 46

Brain and spinal cord

Question 47

The peripheral nervous system (PNS) consists:

Answer 47

Sensory (afferent) neurons and motor efferent neurons. Information flow through the nervous system follows the basic pattern of a reflex

Question 48

What causes the depolarization phase of AP?

Answer 48

The depolarization phase is caused by the opening of voltage-gated sodium channels and the influx of sodium ions into the cell.

Increased permeability of Na+

Question 49

Why does the peak of AP reach a positive potential?

Answer 49

The system generates positive feedback as depolarization further engages additional channels.

The rush of Na+ ions depolarizes the cell (+).

Question 50

Why does the AP terminate?

Answer 50

The inactivation of the Na+ channels and the opening of K+ channels.

K+ hyperpolarizes the cell by leaving (bc of increased K+ membrane permeability)

Question 51

What will TEA (a voltage-gated K+ channel blocker) do to the AP?

Answer 51

Blocks voltage-gated K+ channels and K+ cannot pass even when the channels are open. Will not allow cell to hyperpolarize.

Question 52

What is the refractory period?

Answer 52

The refractory period is a period of time during which a cell is incapable of repeating an action potential. Another AP cannot be easily produced.

Question 53

What effect would blocking Na+ channel inactivation have on a cell’s response to repeated synaptic input?

Answer 53

No AP

Question 54

What happens after an AP invades a presynaptic terminal?

Answer 54

When an action potential reaches the presynaptic terminal, it causes neurotransmitter to be released from the neuron into the synaptic cleft

Question 55

Describe the cellular machinery that underlies exocytosis?

Answer 55

Vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell

Question 56

How would TEA (voltage-gated K+ channel blocker) affect synaptic release?

Answer 56

TEA is a voltage-gated K+ blocker responsible for repolarizing the membrane potential during an action potential. It can affect synaptic release by increasing neurotransmitter release.