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Q:
Which two factors affect the speed of an action potential?a. the strength and frequency of the stimulusb. the location of the cell body and the length of the axonc. the length and diameter of the axond. the presence of myelin and the diameter of the axon
Q:
The presence of myelin and the diameter of the axon:a. affect the strength and frequency of the stimulusb. affect the speed of an action potentialc. affect the strength of an action potentiald. affect the frequency of an action potential
Q:
How is the speed of an action potential down an unmyelinated axon BEST described?
a. the speed of electricity, regardless of the size of the axon
b. less than 1 meter per second, regardless of the size of the axon
c. faster in thin axons than in thick ones
d. faster in thick axons than in thin ones
Q:
What will NOT affect the speed of an action potential?a. the presence of myelinb. the diameter of the axonc. the length of the axond. the number of sodium gates
Q:
What will affect the speed of an action potential?a. the strength of the stimulusb. the time since the last action potentialc. the length of the axond. the resistance of the membrane
Q:
What happens once an action potential starts?a. It is conducted the rest of the way as an electrical current.b. It needs additional stimulation to keep it going along the axon.c. It increases in speed as it goes.d. It is regenerated at other points along the axon.
Q:
Where do most action potentials begin?
a. in the dendrites
b. in the cell body
c. at the axon hillock
d. at the tip of the axon
Q:
During the relative refractory period:
a. the sodium gates are firmly closed.
b. the sodium gates are reverting to their usual state.
c. the sodium gates are wide open.
d. the potassium gates are firmly closed.
Q:
A neuron's sodium gates are firmly closed and the membrane cannot produce an action potential during:
a. the absolute refractory period.
b. the relative refractory period.
c. depolarization.
d. saltatory conduction.
Q:
Which feature of a neuron limits the number of action potentials it can produce per second?
a. the threshold
b. the refractory period
c. saltatory conduction
d. the length of the axon
Q:
Under what conditions is it impossible for a stimulus to produce an action potential?
a. if the membrane is in its absolute refractory period
b. if it occurs at the same time as a hyperpolarizing stimulus
c. if sodium ions are more concentrated outside the cell than inside
d. if the potassium gates have been blocked
Q:
The primary feature of a neuron that prevents the action potential from traveling back from where it just passed is the:
a. concentration gradient.
b. refractory period.
c. sodium potassium pump.
d. phospholipid bilayer.
Q:
According to the all-or-none law:
a. all neurons produce an action potential at the same time or none at all.
b. all of the extracellular sodium enters the axon, or none at all.
c. once an axon reaches threshold, the amplitude and velocity of an action potential are nearly equal each time.
d. neurons are either active all the time or not at all.
Q:
The presence of an all-or-none law suggests that neurons can only convey different messages by changing their:
a. rate or pattern of action potentials.
b. size of action potentials.
c. speed of action potentials.
d. sodium-potassium pump activity.
Q:
The all-or-none law applies to:
a. cell bodies of neurons.
b. dendrites.
c. axons.
d. all parts of a neuron.
Q:
The all-or-none law states that:
a. a neuron produces an action potential of maximal strength, or none at all.
b. all neurons fire or none at all.
c. all neurons in a pathway fire at the same time, or none do.
d. all ions move in the same direction, or none do.
Q:
Which of the following represents the all-or-none law?
a. Every depolarization produces an action potential.
b. Every hyperpolarization produces an action potential.
c. The size of the action potential is independent of the strength of the stimulus that initiated it.
d. Every depolarization reaches the threshold, even if it fails to produce an action potential.
Q:
Local anesthetic drugs, such as Novocain, work by:
a. opening the potassium gates.
b. blocking the sodium gates.
c. inactivating the sodium-potassium pump.
d. decreasing blood flow to certain areas of the brain.
Q:
Local anesthetic drugs attach to the sodium channels of the membrane, which:
a. allows sodium ions to enter and stop action potential.
b. prevents potassium ions from entering and stopping action potential.
c. allows potassium ions to enter and stop action potential.
d. prevents sodium ions from entering and stopping action potential.
Q:
A drug would prevent an action potential if it:
a. lowers the threshold of the membrane.
b. blocks the movement of potassium across the membrane.
c. blocks the movement of sodium across the membrane.
d. increases the movement of sodium across the membrane.
Q:
A drug that decreases the flow of potassium through the potassium gates of the membrane would:
a. block action potentials.
b. increase the threshold of the membrane.
c. slow the return of the membrane to its resting potential.
d. cause the membrane to be hyperpolarized.
Q:
What causes potassium ions to leave the axon just after the peak of the action potential?
a. a continuing concentration gradient and the opening of the potassium gates
b. an increase in the concentration gradient across the membrane
c. increased tendency of the sodium-potassium pump to pump potassium out
d. binding of potassium ions to proteins that leave at this time
Q:
Just after the peak of the action potential, what movement of ions restores the membrane to approximately the resting potential?
a. Sodium ions enter the cell.
b. Potassium ions enter the cell.
c. Potassium ions leave the cell.
d. Sodium ions travel down the axon.
Q:
At what point do the sodium gates begin to close, shutting out further entry of sodium into the cell?
a. at the peak of the action potential
b. when the threshold is reached
c. at the end of the relative refractory period
d. when the concentration gradient for sodium is eliminated
Q:
After the peak of an action potential, what prevents sodium ions from continuing to enter the cell?
a. There is no longer a concentration gradient for sodium.
b. The sodium-potassium pump greatly increases its rate of activity.
c. All the available sodium ions have already entered the cell.
d. The sodium gates in the membrane close.
Q:
A drug that blocks the sodium gates of a neuron's membrane would:
a. decrease the threshold.
b. block the action potential.
c. cause repeated action potentials.
d. eliminate the refractory period.
Q:
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?
a. sodium in, potassium in
b. sodium out, potassium out
c. sodium in, potassium out
d. sodium out, potassium in
Q:
Suppose we applied a drug to a neuron that caused its sodium gates to suddenly open wide. What would happen?
a. hyperpolarization of the membrane
b. an increase in the threshold
c. an action potential
d. nothing, because potassium gates would compensate
Q:
When the potential across a membrane reaches threshold, the sodium channels:
a. open to let sodium enter the cell rapidly.
b. close to prevent sodium from entering the cell.
c. open to let sodium exit the cell rapidly.
d. close to prevent sodium from exiting the cell.
Q:
At the peak of the action potential, the electrical gradient of potassium:
a. is the same as during the resting potential.
b. pulls sodium into the cell.
c. pushes potassium out of the cell.
d. pulls potassium into the cell.
Q:
Voltage-activated channels are channels for which a change in the voltage across the membrane alters their:
a. permeability.
b. length.
c. number.
d. threshold.
Q:
In the normal course of an action potential:
a. sodium channel remain open for long periods of time.
b. the concentration of sodium equalizes across the membrane.
c. sodium remains much more concentrated outside than inside the neuron.
d. subthreshold stimulation intensifies the action potential.
Q:
The action potential of a neuron depends mostly on what movement of ions?
a. sodium ions entering the cell
b. sodium ions leaving the cell
c. potassium ions entering the cell
d. potassium ions leaving the cell
Q:
Stimulation of a neuron beyond a certain level is called the:
a. firing threshold
b. hillock threshold
c. threshold of excitation
d. threshold of inhibition
Q:
Which of the following actions would depolarize a neuron?
a. decreasing membrane permeability to calcium
b. increasing membrane permeability to potassium
c. decreasing membrane permeability to sodium
d. increasing membrane permeability to sodium
Q:
If depolarization is less than the cell's threshold:
a. sodium is prevented from crossing the membrane.
b. potassium is prevented from crossing the membrane.
c. sodium crosses the membrane only slightly more than usual.
d. the cell will still produce an action potential.
Q:
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?
a. Stimulus B will produce an action potential that is conducted at a faster speed than A.
b. Stimulus B will produce an action potential of greater magnitude than stimulus A.
c. Stimulus B will produce an action potential but stimulus A will not.
d. Stimulus A and stimulus B will produce the same response in the neurons.
Q:
What happens to the ion gates when the membrane of a neuron starts to be depolarized?
a. Potassium gates close.
b. Chloride gates open.
c. Sodium gates close.
d. Sodium gates open.
Q:
What tends to open the sodium gates across a neuron's membrane?
a. hyperpolarization of the membrane
b. depolarization of the membrane
c. increase in the sodium concentration outside the neuron
d. passing the peak of the action potential and entering the refractory period
Q:
The sodium gates in the axon are usually closed. Which of the following opens them?
a. depolarization of the membrane
b. increased concentration of socium outside the cell
c. increased concentration of sodium inside the cell
d. increased activity of the sodium-potassium pump
Q:
If there is a depolarizing effect on a neuron, the result will be that the neuron will fire:
a. no matter how slight the effect.
b. forever.
c. only if it reaches threshold.
d. only if the cell is in its relative refractory period.
Q:
A membrane produces an action potential whenever the potential across it reaches what level?
a. the resting potential
b. -90 mV
c. the threshold of excitation
d. the refractory period
Q:
The neuron will produce an action potential only if the depolarization exceeds what level?
a. the threshold of excitation
b. the resting potential
c. hyperpolarization
d. the refractory period
Q:
What is the result if a stimulus shifts the potential inside a neuron from the resting potential to a potential slightly closer to zero?
a. hyperpolarization
b. depolarization
c. selective permeability
d. a refractory period
Q:
Which of the following would produce a hyperpolarization of a neuron?
a. applying a negative charge inside the neuron with a microelectrode
b. applying a positive charge inside the neuron with a microelectrode
c. increasing the membrane's permeability to sodium
d. decreasing the membrane's permeability to potassium
Q:
Hyperpolarization is:
a. increased polarization.
b. decreased polarization.
c. the threshold of the cell.
d. the resting potential of the cell.
Q:
What is the result if a stimulus shifts the potential inside a neuron from the resting potential to a more negative potential?
a. Hyperpolarization
b. Depolarization
c. an action potential
d. a threshold
Q:
Ordinarily, stimulation of a neuron takes place:
a. through hyperpolarization.
b. at the synapse.
c. in the mitochondria.
d. in the endoplasmic reticulum.
Q:
Negatively charged ions like ____ are mostly located outside the cell.
a. sodium
b. chloride
c. calcium
d. potassium
Q:
Which of the following is an advantage of having a resting potential?
a. The toxic effects of sodium are minimized inside the cell.
b. No energy is required to maintain it.
c. The cell is prepared to respond quickly to a stimulus.
d. All of the ions are maintained in equal concentrations throughout the cytoplasm.
Q:
When the neuron is at rest, what is responsible for moving sodium ions out of the cell?
a. a concentration gradient
b. an electrical gradient
c. both a concentration gradient and an electrical gradient
d. the sodium-potassium pump
Q:
When a membrane is at rest, what attracts sodium ions to the inside of the cell?
a. an electrical gradient
b. a concentration gradient
c. both an electrical gradient and a concentration gradient
d. neither an electrical gradient nor a concentration gradient
Q:
When a membrane is at rest, what attracts potassium ions to the inside of the cell?
a. an electrical gradient
b. a concentration gradient
c. both an electrical gradient and a concentration gradient
d. neither an electrical gradient nor a concentration gradient
Q:
When the neuron is at rest, what is responsible for moving potassium ions into the cell?
a. concentration gradient
b. an electrical gradient
c. the sodium-potassium pump
d. both the sodium-potassium pump and electrical gradient
Q:
When the neuron is at rest, what is responsible for moving potassium ions OUT of the cell?
a. a concentration gradient
b. an electrical gradient
c. both a concentration gradient and an electrical gradient
d. the sodium-potassium pump
Q:
Which of the following is NOT true for sodium ions when the cell is at resting potential?
a. Sodium ions remain outside the cell because the sodium- potassium pump drives them out.
b. Sodium gates are tightly closed.
c. Sodium tends to be driven into the neuron by the concentration gradient.
d. Sodium tends to be driven out of the neuron by the electrical gradient.
Q:
The concentration gradient for potassium tends to:
a. draw potassium into the cell.
b. push chloride out of the cell.
c. push sodium out of the cell.
d. push potassium out of the cell.
Q:
Which of the following events would increase the concentration gradient of sodium?
a. decreased permeability to potassium ions
b. increased activity of the sodium potassium pump
c. increased membrane permeability to sodium ions
d. increased membrane permeability to chloride ions
Q:
Concentration gradients lead to what kind of movements?
a. the general movement of ions into the neuron
b. the general movement of ions out of the neuron
c. the movement of ions to areas of their highest concentrations
d. the movement of ions to areas of their lowest concentrations
Q:
What is meant by the term "concentration gradient" with respect to neurons?
a. Sodium is more concentrated in the dendrites and potassium in the axon.
b. Negative charges are more concentrated outside the cell.
c. Sodium and potassium ions are more concentrated on opposite sides of the membrane.
d. Potassium is more concentrated in the dendrites and sodium in the axon.
Q:
The concentration gradient refers to:
a. the fact that the concentration of ions is greater on the inside of a neuron.
b. the fact that the concentration of ions is greater on the outside of a neuron.
c. the difference in distribution for various ions between the inside and outside of the membrane.
d. the negatively charged proteins inside the cell.
Q:
The sodium-potassium pump pumps sodium ions ____ and potassium ions ____.
a. into the cell; into the cell
b. into the cell; out of the cell
c. out of the cell; out of the cell
d. out of the cell; into the cell
Q:
What is one major cause for the resting potential of a neuron's membrane?
a. a difference in size between axons and dendrites
b. a high permeability of the membrane to water molecules
c. the refractory period of the membrane
d. the sodium-potassium pump
Q:
The net effect of each cycle of the sodium-potassium pump is to:
a. decrease the number of positively charged ions within the cell.
b. increase the number of positively charged ions within the cell.
c. decrease the number of positively charged ions outside the cell.
d. increase the number of negatively charged ions within the cell.
Q:
Under which conditions would the sodium-potassium pump be far less effective in creating a concentration gradient?
a. if dendrites were generally longer than axons
b. if the glia-to-neuron ratio were higher
c. if selective permeability of the membrane did not exist
d. if it were an active transport system that required energy
Q:
Electrical gradients lead to what kind of movements?
a. the general movement of ions into the neuron
b. the general movement of ions out of the neuron
c. the movement of ions to areas having the same electrical charges
d. the movement of ions to areas having the opposite electrical charges
Q:
The sodium-potassium pump repeatedly transports three ____ ions out of the cell while drawing two ____ ions into it.
a. calcium; potassium
b. potassium; calcium
c. potassium; sodium
d. sodium; potassium
Q:
The sodium-potassium pump repeatedly transports ____ sodium ions out of the cell while drawing ____ potassium ions into it.
a. three; two
b. two; three
c. one; three
d. one; two
Q:
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.
a. into, into
b. into, out of
c. out of, into
d. out of, out of
Q:
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.
a. into, into
b. into, out of
c. out of, into
d. out of, out of
Q:
Which of the following describes selective permeability?
a. Ions can only travel in certain directions across the membrane.
b. Only certain molecules are allowed to cross the membrane freely.
c. Only certain types of stimulation will result in an action potential.
d. All molecules must pass through designated channels.
Q:
When the neuronal membrane is at rest, the sodium channels:
a. permit sodium ions to pass quickly and easily.
b. permit potassium ions to cross instead of sodium.
c. are closed.
d. fluctuate rapidly between open and closed.
Q:
When the neuronal membrane is at rest, the potassium channels:
a. permit potassium ions to pass quickly and easily.
b. permit potassium ions to pass slowly.
c. prohibit any movement of potassium ions.
d. help to open up the sodium channels.
Q:
When a neuron's membrane is at rest, which of the following molecules crosses through it MOST slowly?
a. potassium
b. sodium
c. water
d. carbon dioxide
Q:
Allowing only certain people to cross the street, and only at certain times, is comparable to a neuron's ____ with respect to ions.
a. threshold of excitation
b. all-or-none law
c. resting potential
d. selective permeability
Q:
The selectivity of a neuron membrane is analogous to:
a. the blood-brain barrier.
b. the action potential.
c. the resting potential.
d. myelin.
Q:
What is the approximate resting potential of the inside of a neuron's membrane, relative to the outside?
a. -70 millivolts
b. +10 millivolts
c. 0 millivolts
d. +90 millivolts
Q:
The resting potential of a neuron refers to:
a. the net positive charge on the inside of the neuron.
b. ions which rest in one place in the cell.
c. the movement of ions to the outside of the neuron.
d. the net negative charge on the inside of the neuron.
Q:
The resting potential is mainly the result of:
a. negatively charged proteins inside the cell.
b. positively charged proteins inside the cell.
c. negatively charged proteins outside the cell.
d. positively charged proteins outside the cell.
Q:
When stating that the neuron's membrane is polarized, you are referring to a difference in electrical potential between:
a. the axons and the dendrites.
b. the axon hillock and the cell body.
c. sodium ions and potassium ions.
d. the inside and the outside of the membrane.