module 2.2

Question 1

The membrane of a neuron is specialized to:

keep all types of intercellular chemicals from moving out of the neuron.
keep all types of extracellular chemicals from moving into the neuron.
control the exchange of chemicals between the inside and outside of the cell.
produce chains of fatty acids and proteins.

Answer 1

control the exchange of chemicals between the inside and outside of the cell.

Question 2

The membrane of a neuron is composed of ___ with ___ embedded in them.

carbohydrates; purines
fat molecules; proteins
proteins; neurotransmitters
benzene molecules; carbohydrates

Answer 2

fat molecules; proteins

Question 3

What is the difference in voltage called that typically exists between the inside and the outside of a neuron?

concentration gradient
generator potential
resting potential
shock value

Answer 3

resting potential

Question 4

The resting potential is mainly the result of:

negatively charged proteins inside the cell
positively charged proteins inside the cell
negatively charged proteins outside the cell
positively charged proteins outside the cell

Answer 4

negatively charged proteins inside the cell

Question 5

What is the approximate resting potential of the inside of a neuron’s membrane, relative to the outside?

-70 millivolts
+10 millivolts
0 millivolts
+90 millivolts

Answer 5

-70 millivolts

Question 6

The selectivity of a neuron membrane is analogous to:

the blood-brain barrier
the action potential
the resting potential
myelin

Answer 6

the blood-brain barrier

Question 7

When the neuronal membrane is at rest, the potassium channels:

permit potassium ions to pass quickly and easily.
permit potassium ions to pass slowly.
prohibit any movement of potassium ions.
help to open up the sodium channels.

Answer 7

permit potassium ions to pass slowly.

Question 8

When the neuronal membrane is at rest, the sodium channels:

permit sodium ions to pass quickly and easily
permit potassium ions to cross instead of sodium
are closed
fluctuate rapidly between open and closed

Answer 8

are closed

Question 9

Which of the following describes selective permeability?

Ions can only travel in certain directions across the membrane.
Only certain molecules are allowed to cross the membrane freely.
Only certain types of stimulation will result in an action potential.
All molecules must pass through designated channels.

Answer 9

Only certain molecules are allowed to cross the membrane freely.

Question 10

When a neuron’s membrane is at rest, the concentration gradient tends to move sodium ____ the cell and the electrical gradient tends to move it ___ the cell.

into, into
into, out of
out of, into
out of, out of

Answer 10

into, into

Question 11

When a neuron’s membrane is at rest, the concentration gradient tends to move potassium ___ the cell and the electrical gradient tends to move it ___ the cell.

into, into
into, out of
out of, into
out of, out of

Answer 11

out of, into

Question 12

The sodium-potassium pump repeatedly transports ___ sodium ions out of the cell while drawing ___ potassium ions into it.

three; two
two; three
one; three
one; two

Answer 12

three; two

Question 13

Electrical gradients lead to what kind of movements?

the general movement of ions into the neuron
the general movement of ions out of the neuron
the movement of ions to areas having the same electrical charges
the movement of ions to areas having the opposite electrical charges

Answer 13

the movement of ions to areas having the opposite electrical charges

Question 14

What is meant by the term “concentration gradient” with respect to neurons?

Sodium is more concentrated in the dendrites and potassium in the axon.
Negative charges are more concentrated outside the cell.
Sodium and potassium ions are more concentrated on opposite sides of the membrane.
Potassium is more concentrated in the dendrites and sodium in the axon.

Answer 14

Sodium and potassium ions are more concentrated on opposite sides of the membrane.

Question 15

Concentration gradients lead to what kind of movements?

the general movement of ions into the neuron
the general movement of ions out of the neuron
the movement of ions to areas of their highest concentrations
the movement of ions to areas of their lowest concentrations

Answer 15

the movement of ions to areas of their lowest concentrations

Question 16

The concentration gradient for potassium tends to:

draw potassium into the cell.
push chloride out of the cell.
push sodium out of the cell.
push potassium out of the cell.

Answer 16

push potassium out of the cell.

Question 17

When the neuron is at rest, what is responsible for moving potassium ions OUT of the cell?

a concentration gradient
an electrical gradient
both a concentration gradient and an electrical gradient
the sodium-potassium pump

Answer 17

a concentration gradient

Question 18

When the neuron is at rest, what is responsible for moving potassium ions into the cell?

concentration gradient
an electrical gradient
the sodium-potassium pump
both the sodium-potassium pump and electrical gradient

Answer 18

both the sodium-potassium pump and electrical gradient

Question 19

When a membrane is at rest, what attracts sodium ions to the inside of the cell?

an electrical gradient
a concentration gradient
both an electrical gradient and a concentration gradient
neither an electrical gradient nor a concentration gradient

Answer 19

both an electrical gradient and a concentration gradient

Question 20

When the neuron is at rest, what is responsible for moving sodium ions out of the cell?

a concentration gradient
an electrical gradient
both a concentration gradient and an electrical gradient
the sodium-potassium pump

Answer 20

the sodium-potassium pump

Question 21

Which of the following is an advantage of having a resting potential?

The toxic effects of sodium are minimized inside the cell.
No energy is required to maintain it.
The cell is prepared to respond quickly to a stimulus.
All of the ions are maintained in equal concentrations throughout the cytoplasm.

Answer 21

The cell is prepared to respond quickly to a stimulus.

Question 22

Ordinarily, stimulation of a neuron takes place:

through hyper polarization.
at the synapse.
in the mitochondria.
in the endoplasmic reticulum.

Answer 22

at the synapse.

Question 23

What is the result if a stimulus shifts the potential inside a neuron from the resting potential to a more negative potential?

Hyperpolarization
Depolarization
an action potential
a threshold

Answer 23

Hyperpolarization

Question 24

What is the result if a stimulus shifts the potential inside a neuron from the resting potential to a potential slightly closer to zero?

hyperpolarization
depolarization
selective permeability
a refractory period

Answer 24

depolarization

Question 25

The neuron will produce an action potential only if the depolarization exceeds what level? the threshold of excitation the resting potential hyperpolarization the refractory period

Answer 25

the threshold of excitation

Question 26

What tends to open the sodium gates across a neuron's membrane? hyperpolarization of the membrane depolarization of the membrane increase in the sodium concentration outside the neuron passing the peak of the action potential and entering the refractory period

Answer 26

depolarization of the membrane

Question 27

Stimulus A depolarizes a neuron just barely above the threshold. Stimulus B depolarizes a neuron to 10 mV beyond threshold. What can we expect to happen? Stimulus B will produce an action potential that is conducted at a faster speed than A. Stimulus B will produce an action potential of greater magnitude than stimulus A. Stimulus B will produce an action potential but stimulus A will not. Stimulus A and stimulus B will produce the same response in the neurons.

Answer 27

Stimulus A and stimulus B will produce the same response in the neurons.

Question 28

Which of the following actions would depolarize a neuron? decreasing membrane permeability to calcium increasing membrane permeability to potassium decreasing membrane permeability to sodium increasing membrane permeability to sodium

Answer 28

increasing membrane permeability to sodium

Question 29

The action potential of a neuron depends mostly on what movement of ions? sodium ions entering the cell sodium ions leaving the cell potassium ions entering the cell potassium ions leaving the cell

Answer 29

sodium ions entering the cell

Question 30

In the normal course of an action potential: sodium channel remain open for long periods of time the concentration of sodium equalizes across the membrane sodium remains much more concentrated outside than inside the neuron subthreshold stimulation intensifies the action potential

Answer 30

sodium remains much more concentrated outside than inside the neuron

Question 31

When the potential across a membrane reaches threshold, the sodium channels: open to let the sodium enter the cell rapidly close to prevent sodium from entering the cell open to let sodium exit the cell rapidly close to prevent sodium from exiting the cell

Answer 31

open to let the sodium enter the cell rapidly

Question 32

During the entire course of events from the start of an action potential until the membrane returns to its resting potential, what is the net movement of ions? sodium in, potassium in sodium out, potassium out sodium in, potassium out sodium out, potassium in

Answer 32

sodium in, potassium out

Question 33

A drug that blocks the sodium gates of a neuron's membrane would: decrease the threshold block the action potential cause repeated action potentials eliminate the refractory period

Answer 33

block the action potential

Question 34

After the peak of an action potential, what prevents sodium ions from continuing to enter the cell? There is no longer a concentration gradient for sodium The sodium-potassium pump greatly increases its rate of activity All the available sodium ions have already entered the cell The sodium gates in the membrane close

Answer 34

The sodium gates in the membrane close

Question 35

Just after the peak of the action potential, what movement of ions restores the membrane to approximately the resting potential? Sodium ions enter the cell Potassium ions enter the cell Potassium ions leave the cell Sodium ions travel down the axon

Answer 35

Potassium ions leave the cell

Question 36

A drug that decreases the flow of potassium through the potassium gates of the membrane would: block action potentials increase the threshold of the membrane slow the return of the membrane to its resting potential cause the membrane to be hyperpolarized

Answer 36

slow the return of the membrane to its resting potential

Question 37

Local anesthetic drugs attach to the sodium channels of the membrane, which: allows sodium ions to enter and stop action potential prevents potassium ions from entering and stopping action potential allows potassium ions to enter and stop action potential prevent sodium ions from entering and stopping action potential

Answer 37

prevent sodium ions from entering and stopping action potential

Question 38

Which of the following represents the all-or-none law? Every depolarization produces an action potential Every hyperpolarization produces an action potential The size of the action potential is independent of the strength of the stimulus that initiated it Every depolarization reached the threshold, even if it fails to produce an action potential

Answer 38

The size of the action potential is independent of the strength of the stimulus that initiated it

Question 39

The presence of an all-or-none law suggests that neurons can only convey different messages by changing their: rate or pattern of action potentials size of actions potentials speed of action potentials sodium-potassium pump activity

Answer 39

rate or pattern of action potentials

Question 40

The primary feature of a neuron that prevents the action potential from traveling back from where it just passed is the: concentration gradient refractory period sodium potassium pump phospholipid bilayer

Answer 40

refractory period

Question 41

Which feature of a neuron limits the number of action potentials it can produce per second? the threshold the refractory period saltatory conduction the length of the axon

Answer 41

the refractory period

Question 42

A neuron's sodium gates are firmly closed and the membrane cannot produce an action potential during: the absolute refractory period the relative refractory period depolarization saltatory conduction

Answer 42

the absolute refractory period

Question 43

Where do most action potentials begin? in the dendrites in the cell body at the axon hillock at the tip of the axon

Answer 43

at the axon hillock

Question 44

What happens once an action potential starts? It is conducted the rest of the way as an electrical current. It needs additional stimulation to keep it going along the axon. It increases in speed as it goes. It is regenerated at other point along the axon.

Answer 44

It is regenerated at other point along the axon.

Question 45

The presence of myelin and the diameter of the axon: affect the strength and frequency of the stimulus affect the speed of an action potential affect the strength of an action potential affect the frequency of an action potential

Answer 45

affect the speed of an action potential

Question 46

In a myelinated axon, where are sodium gates abundant? in the areas covered my myelin at the nodes of Ranvier throughout the axon only in the axon hillock

Answer 46

at the nodes of Ranvier

Question 47

To what does saltatory conduction refer? the production of an action potential by the movement of sodium ions the transmission of an impulse along a myelinated axon the transmission of impulses along dendrites the transmission of an impulse between one neuron and another

Answer 47

the transmission of an impulse along a myelinated axon

Question 48

What disease is related to the destruction of myelin sheaths? multiple sclerosis cystic fibrosis myasthenia gravis Parkinson's disease

Answer 48

multiple sclerosis

Question 49

In what way is a myelinated axon that has lost its myelin (through disease) different from an axon that was never myelinated? It has a smaller diameter. It lacks sodium gates along parts of its surface. It has a longer refractory period. It has a much higher threshold.

Answer 49

It lacks sodium gates along parts of its surface.

Question 50

A local neuron: has an axon approximately a meter long conveys information to other neurons across great distances is a small neuron with no axon or a very short one has an axon with many branches far from the cell body

Answer 50

is a small neuron with no axon or a very short one