Which of the following is TRUE about the concentration gradient of Na⁺ in a neuron at rest?

a. It favors the movement into the cell at the resting membrane potential

b. It favors its movement out of the cell at the resting membrane potential

c. It is equal and opposite to the electrical potential acting on Na+ at the resting membrane potential

d. It is in the same direction as the diffusion potential due to the concentration gradient for K+

e. It favors movement of Na+ in the opposite direction as the electrical potential acting on Na+ at the resting membrane potential.

a. It favors the movement into the cell at the resting membrane potential

Which is TRUE about typical, resting neurons?

a. The plasma membrane is most permeable to sodium ions

b. The concentration of sodium ion is greater inside the cell than outside

c. The permeability of the plasma membrane to potassium ions is much greater than its permeability to sodium ions

d. The plasma membrane is completely impermeable to sodium ions

e. The plasma membrane is completely impermeable to potassium ions

c. The permeability of the plasma membrane to potassium ions is much greater than its permeability to sodium ions

Which is FALSE about neurons?

a. a given neuron can be either a presynaptic neuron or a postsynaptic neuron

b. An individual neuron can receive information from multiple other neurons

c. An individual neuron can transmit information to multiple other neurons

d. A neuron can simultaneously release more than one type of neurotransmitter

e. A neuron receives information on its axon and delivers it to other neurons through its dendrites

e. A neuron receives information on its axon and delivers it to other neurons through its dendrites

Which is TRUE about the Na⁺, K⁺ ATPase pump in neurons?

a. It generates a small electrical potential such that the inside is made negative with respect to the outside

b. It maintains a concentration gradient for K+ such that diffusion forces favor movement of K+ into the cell

c. It maintains an electrical gradient at the equilibrium potential of K+

d. It transports equal numbers of sodium and potassium ions with each pump cycle

e. It pumps 3 Na+ ions into the cell for every 2K+ ion it pumps out

a. It generates a small electrical potential such that the inside is made negative with respect to the outside

Which of the following statements concerning the permeability of a typical neuron membrane at rest is TRUE?

a. The permeability to Na+ is much greater than the permeability to K+

b. All the K+ channels in the membrane are open

c. The voltage-gated Na+ channels are in the inactivated state

d. Most of the voltage-gated Na+ channels are in the closed state

e. There is equal permeability to Na+ and K+

d. Most of the voltage-gated Na+ channels are in the closed state

Which is NOT an example of a graded potential?

a. A receptor potential is a sensory receptor cell

b. A depolarizing excitatory postsynaptic potential (EPSP)

c. A hyperpolarizing inhibitory postsynaptic potential (IPSP)

d. A depolarizing pacemaker potential

e. A depolarizing action potential

e. A depolarizing action potential

An action potential in a neuronal membrane differs from a graded potential in that

a. An action potential requires the opening of Ca2+ channels whereas a graded potential does not

b. an action potential is propagated without decrement whereas a graded potential decrements with distance

c. an action potential has a threshold, whereas a graded potential is an all-or-none phenomenon

d. movement of Na+ and K+ across cell membranes mediate action potentials, while graded potentials do not involve movement of Na+ and K+

e. action potentials vary in size with the size of stimulus, while graded potentials do not

b. an action potential is propagated without decrement whereas a graded potential decrements with distance

A threshold stimulus applied to an excitable membrane is one that is just sufficient to

a. trigger an excitatory postsynaptic potential

b. cause a change in membrane potential

c. trigger an action potential

d. be conducted to the axon hillock

e. depolarize a dendrite

c. trigger an action potential

Which describes the response of the voltage-gated channels when an axon is stimulated to threshold?

a. K+ channels open before the Na+ channels

b. Na+ channels are activated and then inactivated

c. K+ channels open at the same time as the Na+ channels

d. K+ channels are opened when Na+ binds to the channel

e. K+ influx causes Na+ channels to inactivate

b. Na+ channels are activated and then inactivated

During the rising (depolarizing) phase of a neuronal action potential,

a. Pk+ becomes much greater than PNa+

b. PNa+ becomes much greater than PK+

c. Pk+ is the same as PNa+

d. Na+ efflux (flow out of the cell) occurs

e. K+ flows rapidly into the cell

b. PNa+ becomes much greater than PK+

Which is most directly responsible for the falling (repolarizing) phase of the action potential?

a. Voltage-gated Na+ channels are opened

b. The Na+/K+ pump restores the ion to their original locations inside and outside of the cell

c. The permeability to Na+ increases greatly

d. ATPase destroys the energy supply that was maintaining the action potential at its peak

e. The permeability to K+ increases greatly while that to Na+ decreases

e. The permeability to K+ increases greatly while that to Na+ decreases

An action potential does not re-stimulate the adjacent membrane that was previously depolarized because

a. Stimulation is inhibited by the myelin sheath

b. It is impossible for an action potential to be propagated along an axon toward the nerve cell body

c. The resting membrane potential of the axon is too positive

d. The resting membrane potential of the axon is too negative

e. The area of the membrane is in the absolute refractory period

e. The area of the membrane is in the absolute refractory period

Which best describes temporal summation?

a. A synapse is stimulated a second time before the effect of a first stimulus at the synapse has terminated

b. It only refers to addition of EPSPs

c. Two synapses on different regions of a cell are stimulate at the same time

d. It always brings a postsynaptic cell to threshold

e. The size of an EPSP depends on the size of the stimulus

a. A synapse is stimulated a second time before the effect of a first stimulus at the synapse has terminated

A presynaptic (axo-axonal) synapse

a. Is a synapse between an axon terminal and a dendrite that can either be excitatory or inhibitory

b. Is a synapse between an axon terminal and another axon's terminal that can be either excitatory or inhibitory

c. Is any synapse onto a cell body and they can be either stimulatory or inhibitory

d. Is a synapse between an axon terminal and a dendrite of the same cell which is always inhibitory

e. Is a synapse between an axon terminal and another axon's terminal that is always inhibitory

b. Is a synapse between an axon terminal and another axon's terminal that can be either excitatory or inhibitory

Which of the following statements regarding neurotransmitters is TRUE?

a. Acetylcholine is broken down by enzymes present on postsynaptic cell membranes

b. Acetylcholine that is released at synapses binds to adrenergic receptors in the postsynaptic cell membrane

c. Catecholamines are the most abundant neurotransmitters in the central nervous system

d. Opiate drugs such as morphine are antagonists of a class of neurotransmitters called endorphins

e. Gamma-aminobutyric acid (GABA) is a major excitatory transmitter in the central nervous system

a. Acetylcholine is broken down by enzymes present on postsynaptic cell membranes

Acetylcholine is the main neurotransmitter released by

a. preganglionic sympathetic neurons and cells of the adrenal medulla

b. cells of the adrenal medulla and postganglionic parasympathetic neurons

c. motor neurons and postganglionic sympathetic neurons

d. preganglionic sympathetic neurons and postganglionic sympathetic neurons

e. preganglionic sympathetic neurons and motor neurons

e. preganglionic sympathetic neurons and motor neurons

Which is one of the major inhibitory neurotransmitters in the CNS?

a. glutamate

b. dopamine

c. norepinephrine

d. Gamma-aminobutyric acid (GABA)

e. Beta-endorphin

d. Gamma-aminobutyric acid (GABA)

Which is one of the most abundant excitatory neurotransmitters in the CNS?

a. glutamate

b. dopamine

c. norepinephrine

d. Gamma-aminobutyric acid (GABA)

e. endorphin

a. glutamate

Which of the following statements about the refractory period of a membrane is TRUE?

a. The absolute refractory period refers to the period of time during which another action potential cannot be initiated in that part of the membrane that is undergoing an action potential, no matter how great the strength of the stimulus.

b. The relative refractory period refers to the period of time during which another action potential can be initiated in that part of the membrane that has just undergone an action potential if a stronger than normal stimulus is applied.

c. The refractory period prevents the action potential from spreading back over the part of the membrane that just underwent an action potential.

d. The refractory period places an upper limit on the frequency with which a nerve cell can conduct action potentials.

e. All of the answer choices are correct

e. All of the answer choices are correct

The relative refractory period of an axon coincides with the period of

a. activation and inactivation of voltage-dependent Na⁺ channels.

b. Na⁺ permeability that is greater than that during the depolarization phase.

c. increased K⁺ flux into the cell.

d. increased K⁺ permeability of the cell.

e. Increased Na⁺ flux through K⁺ channels.

d. increased K⁺ permeability of the cell.

How is the strength of a stimulus encoded by neurons?

a. By the size of action potentials

b. By the frequency of action potentials

c. By the duration of action potentials

d. By whether the action potential peak is positive or negative

b. By the frequency of action potentials

Which of the following statements about EPSPs is FALSE?

a. They are produced by the opening of ligand-gated sodium channels.

b. They transmit signals over relatively short distances.

c. They depolarize postsynaptic cell membranes.

d. They are able to summate.

e. They are always the same amplitude.

e. They are always the same amplitude.

During which of the following phases is K⁺ permeability greater than at rest?

a. During the after-hyperpolarization phase of an AP

b. During vesicular release of neurotransmitter from the presynaptic neuron

c. During the repolarizing phase of an AP

d. During the depolarizing phase of an AP

e. None of these, K⁺ permeability is greatest at rest

c. During the repolarizing phase of an AP

You are studying the role of a newly discovered neurotransmitter. You find that there are receptors for this neurotransmitter on interneurons in the brain and that when it binds, it causes the opening of K⁺ channels. What can we expect of the postsynaptic cells under influence of this neurostransmitter?

a. The postsynaptic cell will immediately undergo an action potential.

b. The postsynaptic cell will undergo an IPSP.

c. The postsynaptic cell will undergo an EPSP.

d. There will be no change to the membrane potential in the postsynaptic cell.

b. The postsynaptic cell will undergo an IPSP.

In clinical trials, scientists discover that use of drug X results in a decrease in norepinephrine signaling. In the process of making a list of possible mechanisms of this drug to test, which of the following is NOT a plausible explanation for the effects of drug X?

a. X inhibits synthesis of norepinephrine at the axon terminal.

b. X inhibits norepinephrine release from the terminal.

c. X blocks reuptake of norepinephrine by the terminal

d. X is an adrenergic receptor antagonist.

e. X stimulates the catabolism of norepinephrine.

c. X blocks reuptake of norepinephrine by the terminal