Deck 4: Neuronal Physiology

Question 1

In the nervous system, the term membrane potential refers to the

A) ability of a cell membrane to conduct an electrical impulse
B) separation of charges across a biological membrane.
C) ability of a membrane to give rise to vesicles.
D) ability of a cell membrane to transport Na⁺ and K⁺ ions
E) ability of the plasma membrane to form T-tubules.

Answer 1

separation of charges across a biological membrane.

Question 2

Resting (membrane) potential is determined primarily by ____________ in the plasma membrane.

A) leak channels.
B) voltage-gated channels.
C) ligand-gated channels.
D) stretch-activated channels.
E) phosphorylation-dependent channels.

Answer 2

leak channels.

Question 3

When compared to normal resting conditions, a neuron will become hyperpolarized

A) when there is an increase in transmembrane potential.
B) if positive ions such as Ca2⁺ ions leak into the neuron.
C) if there is a decrease in number of intracellular potassium ions.
D) if positive ions such as Ca2⁺ ions leak into the neuron or when there is an increase in transmembrane potential.
E) if there is a decrease in number of intracellular potassium ions or when there is an increase in transmembrane potential .

Answer 3

if there is a decrease in number of intracellular potassium ions or when there is an increase in transmembrane potential .

Question 4

In terms of Ohm's law, three factors vary during an action potential. Which of the following factors is NOT constant during voltage-clamp operations?

A) current
B) membrane potential
C) equilibrium potential
D) None of these answers the question.

Question 5

Which of the following characteristics are associated with graded potentials?

A) They exhibit an "all-or-none" character.
B) Their magnitude is related to the intensity of the stimulus that elicits them.
C) They spread by active conductance.
D) They occur only in axons.

Question 6

Local passive current flow decreases with distance because

A) ion pumps which drive current flow run out of energy (ATP) as they drift from the stimulus site.
B) current leakage across the membrane attenuates current available for intracellular current flow.
C) as it gets away from the active zone, the membrane fluidity decreases and prevents influx of booster current.
D) of all of these reasons.
E) of none of these reasons.

Question 7

Increasing axonal diameter increases the length constant for that axon by

A) decreasing longitudinal resistance.
B) increasing longitudinal resistance.
C) decreasing membrane resistance.
D) increasing membrane resistance.
E) increasing capacitance.

Question 8

Threshold potential is

A) typically between -50 mV and -55 mV.
B) typically 10 mV to 15 mV higher than resting potential.
C) the membrane potential at which a graded potential is converted to an action potential.
D) all of these.
E) none of these.

Question 9

During the initial, depolarizing phase of the action potential, the voltage-gated Na⁺-channel is in which conformation?

A) closed but capable of opening
B) open, or activated
C) closed and not capable of opening
D) activation gate open; inactivation gate closed
E) activation gate closed; inactivation gate closed

Question 10

Once threshold potential has been achieved, the permeability of the membrane to Na⁺ is

A) greater than it was at rest.
B) greater than its permeability to K⁺.
C) increased due to activation of voltage-gated Na⁺ channels.
D) all of these.
E) none of these.

Question 11

Which of the following is responsible for initiating changes in membrane potential resulting in an electrical signal?

A) opening of voltage-gated ion channels
B) changes in membrane permeability in response to a stimulus
C) closing of voltage-gated ion channels
D) a change in the movement of ions through leak channels
E) closing of voltage-gated potassium channels

Question 12

During the absolute refractory period for a neuron, most voltage-gated Na⁺-channels are in which conformation?

A) closed but capable of opening
B) open, or activated
C) closed and not capable of opening
D) Any of these.
E) None of these.

Question 13

A scientist genetically engineers a neuron whose voltage-gated Na⁺ channels lack the inactivation gate but which is otherwise normal. This neuron would be expected to

A) conduct action potentials bidirectionally.
B) lack an absolute refractory period.
C) lack a relative refractory period.
D) all of these.

Question 14

Myelination of axons is accomplished in the nervous system by and in the nervous system by .

A) central, Schwann cells, peripheral, oligodendrocytes
B) vertebrate, Schwann cells, invertebrate, oligodendrocytes
C) central, oligodendrocytes, peripheral, Schwann cells
D) vertebrate, oligodendrocytes, invertebrate, Schwann cells

Question 15

Which of the following evolutionary adaptations would result in an increase in the speed of conduction of action potentials by decreasing the longitudinal resistance of the axon?

A) increasing the number of channels in the plasma membrane
B) myelinating the axon
C) increasing the diameter of the axon
D) placing all voltage-gated ion channels at distant intervals
E) None of these.

Question 16

Which of the following evolutionary adaptations would result in an increase in the speed of conduction of action potentials by increasing the membrane resistance of the axon?

A) increasing the number of channels in the plasma membrane
B) myelinating the axon
C) increasing the diameter of the axon
D) placing all voltage-gated ion channels at distant intervals
E) decreasing the number of channels in the membrane.

Question 17

Neurotransmitters are

A) chemical messengers used at chemical synapses.
B) found in synaptic vesicles in the synaptic knob.
C) released in response to elevated calcium in the axon terminal.
D) able to bind to receptors on the post-synaptic cell.
E) All of these.

Question 18

An investigator places an isolated neuron in a calcium-free medium. They give the neuron a suprathreshold stimulus and then perform an assay to test whether neurotransmitter is released into the medium. Which of the following outcomes would you predict?

A) No neurotransmitter is detected since influx of calcium into the synaptic knob is required for neurotransmitter release.
B) No neurotransmitter is detected since influx of calcium is required in order for the neuron to conduct an action potential.
C) Neurotransmitter is detected since calcium is not required for action potential conduction and the initial stimulus was suprathreshold.
D) We cannot predict the outcome without knowing whether the neuron was myelinated.
E) None of these.

Question 19

If an electrical synapse conducted an action potential "backward" (from what would normally be the postsynaptic neuron to the presynaptic neuron), would an action potential be conducted in a retrograde direction (along the axon toward the cell body)?

A) Yes.
B) No, since the normally presynaptic neuron lacks receptors for the ions carrying current from the normally postsynaptic neuron.
C) No, since the normally presynaptic neuron would be refractory to retrograde conduction.
D) No, unless the concentration gradients for all the relevant ions were reversed.
E) No, since there's no axon hillock at the axon terminal of the normally presynaptic neuron.

Question 20

Which of the following pairs are NOT related?

A) leak channels and nongated channels
B) gated channels and triggering event
C) chemically gated channels and ligand gated channels
D) mechanically gated channel and stretch activated channels
E) graded potentials and leak channels

Question 21

Which of the following statements is true?

A) The lower the resistance the lower the current flow between two regions of an
Axon.
B) The lower the resistance the greater the current flow between two regions of an
Axon.
C) Capacitance is a measurement of current flow along an axon.
D) Neurons that rely on electronic flow of current for communication purposes are
Noted for their low membrane resistance.
E) None of these statements are true.

Question 22

In cells where the equilibrium potential for Cl^- equals the resting potential, opening Cl^- channels in the subsynaptic membrane

A) has no effect on the probability of the postsynaptic cell reaching threshold since there's no movement of Cl^-.
B) increases the probability of the postsynaptic cell reaching threshold since the entry of Na⁺ into the cell (through another route) will make the cell less negative and allow Cl^- to leave the cell, offsetting the effect of Na⁺.
C) decreases the probability of the postsynaptic cell reaching threshold since the entry of Na⁺ into the cell (through another route) will make the cell less negative and Cl^- will enter the cell, offsetting the depolarizing effect of Na⁺.
D) none of these.

Question 23

Which of the following statements about the Na⁺ and K⁺ gradients in neurons is NOT true?

A) In a resting neuron the electrical gradient for sodium is inward.
B) In a resting neuron the electrical gradient for potassium is inward.
C) In a resting neuron the concentration gradient for sodium is outward.
D) In a resting neuron the concentration gradient for potassium is outward.
E) In a resting neuron, the electrical and concentration gradients for sodium and
Potassium result in a membrane potential.

Question 24

When a single synaptic input fires repeatedly, generating a cumulative effect on the postsynaptic membrane potential, that phenomenon is known as summation.

A) temporary
B) temporal
C) lateral
D) spatial
E) grand

Question 25

If an excitatory synapse is activated at the same time as an inhibitory synapse, the effect on postsynaptic membrane potential will be

A) no change.
B) a net depolarization since excitation normally triumphs over inhibition.
C) a net hyperpolarization since inhibition normally overwhelms excitation.
D) impossible to predict since we don't know the relative strength of these synapses.

Question 26

Action potentials are normally initiated at the axon hillock because

A) there is a particularly high density of voltage-gated sodium channels there.
B) threshold potential is lower there than at other sites along the plasma membrane.
C) activation of sodium channels at the axon hillock results in a particularly strong inward current and consequent depolarization.
D) all of these.
E) none of these.

Question 27

Which of the following statements about graded potentials and action potentials is NOT true?

A) The duration of a graded potential is related to the duration of the stimulus.
B) Graded potentials can by produced by the net movement of Na⁺, Cl^-, K⁺ or Ca⁺
Across the plasma membrane.
C) Graded potentials can occur as the result of either hyperpolarization of
Depolarization of the plasma membrane.
D) Action potentials show temporal and spatial summation.
E) Action potentials are triggered through the passive spread of membrane
Depolarization.

Question 28

Retrograde signaling occurs when

A) receptors on the presynaptic membrane are activated resulting in a depolarization of the presynaptic dendrites.
B) acetylcholinesterase levels in a synapse are too high .
C) a postsynaptic cell secretes a signaling molecule that influences the sensitivity of the presynaptic terminal.
D) enzymes responsible for the breakdown of the neurotransmitter at a synapse are not produced in sufficient quantity.
E) none of these.

Question 29

The drug cocaine exerts its stimulatory effect by

A) inhibiting phosphodiesterase activity, allowing an accumulation of cAMP and stimulation of PKA.
B) activating purinergic receptors.
C) inhibiting dopamine reuptake, resulting in prolonged activation of dopamine receptors by endogenous dopamine.
D) none of these.

Question 30

The venom from black widow spiders causes massive release of neurotransmitters which means its primary effect is on which membrane?

A) presynaptic
B) postsynaptic
C) subsynaptic
D) suprasynaptic

Question 31

If increased atmospheric pressure decreases the activity of the Na⁺-K⁺ pump, an animal that lives in the deep sea would be expected to have ________ density of Na⁺-K⁺ pumps in their neuronal membranes compared with animals living in shallow water.

A) a higher
B) an equal
C) a lower

Question 32

Which of the following statements about voltage-gated sodium channels is true?

A) All cells contain voltage-gated sodium channels.
B) Voltage-gated sodium channels are integral membrane proteins.
C) Voltage-gated sodium channels have roughly equal permeability to Na⁺ and K⁺.
D) Voltage-gated sodium channels open in response to any change in membrane potential.
E) Voltage-gated sodium channels open in response to binding of acetylcholine.

Question 33

Which of the following statements about giant axons is NOT true?

A) They can be found in annelids and cockroaches.
B) They can be unicellular.
C) They are involved in the coordination of abrupt movements.
D) They were first identified and studied in squid.
E) They may arise as the result of fusion of smaller fibers.

Question 34

Which of the following reasons explains why channels are required in membranes in order for neurons to perform their function?

A) Neurons have to function in reception (e.g. sensory); therefore, they must be able to switch channels in order to get the appropriate information.
B) The lipid bilayer is impermeable to ions and polar molecules, and ion flow through the membrane is essential for nervous transmission of information.
C) Channels permit the flow of water through the membrane, and water is necessary for hydrolysis reactions in the cytoplasm.
D) Channels are required in order to keep Ca²⁺ levels low inside the cytoplasm.

Question 35

Tetrodotoxin (TTX) is generally associated with pufferfish, which in fact gain it from symbiotic bacteria residing in them. Interestingly, the pufferfish themselves aren't affected by this neurotoxin. The most plausible explanation for the fish's insensitivity to TTX is

A) the fish lack neurons.
B) the fish have neurons, but with very short axons that enable them to rely entirely on electrical conduction based on local passive current flow.
C) the fish lack voltage-gated sodium channels .
D) the fish have voltage-gated sodium channels, but they have a slightly different sequence from voltage-gated sodium channels found in other organisms, and this difference affects TTX's ability to bind the channel.

Question 36

Fluoxetine (Prozac) is a serotonin re-uptake inhibitor. Serotonin is generally an excitatory neurotransmitter; therefore, one would expect using fluoxetine to result in ___________ in the post-synaptic neuron.

A) action potentials of greater amplitude to be conducted
B) an increase in the conduction velocity of action potentials
C) graded potentials of lesser amplitude
D) graded potentials of shorter duration
E) graded potentials of longer duration

Question 37

Action potentials are transmitted unperturbed across electrical synapses.

Question 38

In myelinated fibers the action potential can be significantly slowed down by synaptic
delays of as much as 1-2 msec.

Question 39

The binding of a specific neurotransmitter at fast synapses with the appropriate
subsynaptic receipts always leads to the same chain in membrane permeability.

Question 40

At a neuromuscular synapse receptors of the cholinergic type bind acetylcholine.

Question 41

The depolarization of the muscle membrane that occurs at the neuromuscular junction is transmitted in both directions away from the motor end plate.

Question 42

If they arrive simultaneously, as few as 30 EPSPs can bring a postsynaptic membrane to threshold.

Question 43

Neruomodulators are chemical messengerse that do not cause either EPSPs or IPSPs.

Question 44

Tetraethylammonium (TEA) is one compound that is used to block Na⁺ channels.

Question 45

During the so called depolarization block the voltage-gated Na+ channels are in their
"closed and not capable" of opening configuration.

Question 46

Due to their size, single cell organisms such as the Paramecium can rely on simple
diffusion of signals to facilitate their movement.

Question 47

Gated channels are an example of flexible proteins.

Question 48

Match each sentence with the most appropriate choice:

-Synaptic vesicle

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 49

Match each sentence with the most appropriate choice:

-Neurotransmitter receptor

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 50

Match each sentence with the most appropriate choice:

-Electrical synapse

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 51

Match each sentence with the most appropriate choice:

-Neuropeptides

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 52

Match each sentence with the most appropriate choice:

-Action potential

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 53

Match each sentence with the most appropriate choice:

-Depolarization

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 54

Match each sentence with the most appropriate choice:

-Hyperpolarization

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 55

Match each sentence with the most appropriate choice:

-Graded potential

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 56

Match each sentence with the most appropriate choice:

-Myelination

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 57

Match each sentence with the most appropriate choice:

-Signal intensity

A) Calcium
B) Postsynaptic neuron
C) Gap junction
D) Dense-core vesicles
E) All-or-none
F) Reduced membrane potential
G) Increased membrane potential
H) Decremental
I) Salutatory conduction
J) Action potential frequency

Question 58

Explain what would happen to the resting membrane potential and the establishment and conductance of an action potential if a nerve were in an extracellular solution with a lower than normal level of extracellular potassium (hypokalemia).

Question 59

Neurons form three types of synapses: electrical, fast chemical and slow chemical. Describe these three synapses and the advantages associated with each.

Question 60

Based on the urgency of the information they convey, would you expect pain fibers to be myelinated or unmyelinated, large in diameter or small in diameter? Justify your answer.

Question 61

Distinguish between excitatory and inhibitory postsynaptic events. Your answer should include a definition of each and an explanation of the ion currents associated with each.

Question 62

In auditory hair cells depolarization of the membrane is achieved using a current carried by potassium ions. How must the potassium equilibrium potential compare to the membrane potential for that to be true? Justify your answer.