Neurophysiology Of Nerve Impulses

A negative membrane potential was recorded when the tip of the microelectrode was a. in the extracellular solution, just outside the cell body b. just inside the cell body c. just inside the axon d. both inside the cell body and inside the axon

Which of the following caused a change in membrane potential from -70 to -49 in the cell body? a. an increase in extracellular K+ b. a decrease in extracellular K+ c. an increase in extracellular Na+ d. a decrease in extreacellular Na+

Which of the following has the most negative voltage? a. between the outside aof the axon and outside the cell bodu with control K+ ECF b. between the outside of the axon and outside the cell body with High K+ ECF c. between the inside of the axon and the outside of the axon with control K+ ECF d. between the inside of the axon and the outside of the axon with High K+ ECF

Assuming that the resting potential of a sensory neuron is -70 mV, which of the following represents a depolarization? a. a change to -90mV b. staying at -70 mV c. a change to -60 mV

Which of the following is a sensory modality (type of sense)? a. touch b.smell c.sight d.pain e.all of the above

Which of the following is a sensory stimulus? a. pressure b.chemical odorants c. light d. all of the above

Which of the following is true of the response of a sensory neuron to the appropriate sensory stimulus? a. it can be called a receptor potential, and it is a graded potential b. it is a change in the resting membrane potential c. both A and B

A very intense stimulus can sometimes stimulate sensory neurons that have evolved for a different modality. THus, with a blow to the eye, one "sees stars." In this example the photoreceptors in the eye are responding to? a. light b. heat c. intense pressure

Olfactory receptor neurons respond to low concentrations of chemical odorants because there are membrance proteins in the receptor ending of the sensory neuron that? a. respond to pressure b.can bind and respond to the specific odorant c.can convert light energy into a change in membrane potential

The sequence of events starting with a sensory stimulus and ending with a chnage in membrane potential is called? a. an adequate stimulus b. a sensory modality c. sensory transduction d. sensory receptor

Starting at a resting membrane potential of -70 mV, a change to which of the following represents the largest receptor potential? a. a change to -80 mV b. a change to -75 mV c. a change to -60 mV d. a change to -50 mV

Axons are a. conductors of chemical signals, called graded potentials b. bundles of nerves c. the sites of graded receptor potentials in sensory neurons d. long, thin structures that extend from a neuronal cell body

Which of the follwoing is easier? a.extracellular recordings of the action potential b. intracellular recordings of the action potential c. intracellular and extracellular recordings of the action potential are equally difficult

An action potential is usually initiated in an axon at or near a. the axon hillock b. the initial segment c. the trigger zone d. all of the above

The initiation of an action potential in a sensory neuron in the body normally a. follows a sufficiently large depolarizing receptor potential b. occurs when the membrane potential of the axon hillock reaches -70 mV c. requires a nerve chamber d. occurs in the dendrites

The threshold voltage in an axon is usually a. less negative than the resting membrane potential b. more negative than the resting membrane potential c achieved in the laboratory by applying -20 mV d. the same value as the resting membrane potential

If graded receptor potential made the resting membrane potential of the axon more negative (for example, -70mV changes to -75 mV), you would expect a. it to be easier for this axon to reach the threshold voltage b. subsequent action potentials to be shorter in duration c. no change in the ability of this axon to reach threshold voltage d. it to be more difficult for this axon to reach the threshold voltage

Failure to reach the threshold voltage in the axon of a sensory neuron could be caused by a. generation of a receptor potential that makes the anonal resting membrane potential more negative b. an insufficient depolarizing receptor potential c. application of the wrong stimulus modality d. all of the above

Voltage-gated Na+ channels are membrane channels that open a. when the membrane is at the resting membrane potential b. when the membrane depolarizes c. when TTX is applied to the membrane d. when lidocaine is applied to the membrane

When open, Na+ channels allow a. Na+ ions diffuse into the cell b. Na+ ions to diffuse out of the cell c. K+ ions diffuse into the cell d. K+ ions diffuse out of the cell

Which of the following is true of an action potential? a. the generation of an action potential uses voltage-gated Na+ channels b. an action potenial is generated when the membrane potential reaches threshold c. an action potential is a large, all-or-none change in membrane potential d. all of these answers are correct

Which of the following can reduce the likelihood of an action potential? a. TTX b. lidocaine c. increasing the leak of K+ from a cell d. All of these can reduce the likelihood of an action potential

In the control, the amplitudes of the action potentials at R1 and R2 are the same. Which of the following explains this? a. there are voltage-gated Na+ channels all along the axon b. the action potential is an all-or-none event c.action potentials propagate or remake themselves at each point along the axon d. all of these are reasonable explations

Blocking the voltage-gated Na+ channels between R1 and R2 with TTX blocks a. the resting membrane potential b. the action potential generation at the stimulus c. the propagation of the action potential to R1 d. the propagation of the action potential from R1 to R2

When voltage-gated Na+ channels between R1 and R2 are blocked with TTX, an action potential is still recorded at R1 because a. the TTX had spread and blacked the channels at R1 b. the voltage-gated Na+ channels between the stimulus and R1 are unaffected by the TTX c. the membrane potential at R1 cannot depolarize d. the membrane potential at R1 stas at -70 mV

Puffer fish must be prepared carefully and properly before they can be eaten. Eating puffer fish can cause numbness of the lips, probably because a. action potentials from sensory neurons in the lips are blocked b. puffer fish do not taste good c. TTX alters the resting membrane potential fo all neurons in the lips d. there are no neurons in the lips

Which of the following occurs after the peak of the action potential? a. the membrane repolarizes b. voltage-gated K+ channels open c. some voltage-gated Na+ channels inactivate d. all of these occur

What is meant by Na+ channel inactivation? a. the Na+ channel opens when the membrane reaches threshold b. the Na+ channel no longer allows Na+ ions to pass through it c. the Na+ channel allows Na+ ions to diffuse out of the cell d. the Na+ channel allows K+ ions to diffuse into the cell

What happens when voltage-gated K+ channels open? a. K+ ions can diffuse out of the cell b. the membrane repolarizes from the peak of the action potential c. it becomes harder for a subsequent stimulus to depolarize the membrane to threshold d. all of these occur

It is harder to generate a second action potential soon after the first action potential because a. some voltage-gated Na+ channels are inactivated b. voltage-gated K+ channels have opened c. the efflux of K+ ions opposes a depolarization toward threshold d. all of these make it harder to generate a second action potential

What is the original threshold for this neuron? a. a 20mV depolarization to -50 mV b. a 30 mV depolarization to -40 mV c. a 45 mV depolarization to -25 mV d. a 60 mV depolarization to -10 mV

As the interval between stimuli decreases, the depolarization needed to generate the second action potential a. increases b. stays the same c. decreases d. there is never a second action potential

Judging from your results, what time period after the first action potential best describes the relative refractory period (the time when a second action potential can be generated only of the stimulus intensity is increased)? a. 125-250 msec b. 60-125 msec c. 7.5 ms - 60 msec d. less than 3.75 msec

At what interval between stimuli did the second action potential fail, regardless of the stimulus intensity? a. 250 msec b. 60 msec c. 15 msec d. 3.75 msec

What is the absolute refractoy period for this neuron? a. 250 msec b. 60 msec c. 15 msec d. 3.75 msec

The time after an action potential when a second action potential cannot be generated no matter how intense the stimulus is called the a. threshold b. absolute refractory period c. relative refractory period d. prolonged stimulus

The time an action potential when a second action potential can be generated only if the stimulus intensity is increased is called the a. threshold b. absolute refractory period c. relative refractouy period d. prolonged stimulus

The term frequency refers to a. the number of millivolts needed to reach threshold b. the potential in millivolts when a neuron is at rest (resting membrane potential) c. the number of action potentials per second d. the potential in millivolts at the peak of the action potential

If the interval between action potentials (the interspike interval) is 0.1 (1/10) seconds, what frequency of action potentials would be observed? a. 1 Hz b. 5 Hz c. 10 Hz d. 100 Hz

With a prolonged stimulus that is just above (more depolarized than) threshold, you would expect to get additional action potentials when the membrane has completed a. the absolute refractory period b. the absolute and relative refractory periods c. the absolute refractoyr period and half of the relative refrectory period d. you would never get additional action potentials at this intensity

Which of the following changes occurs when you increase the stimulus intensity? a. the resting membrane potential becomes more negative b. the amplitude of the action potential increase c. the frequency of action potentials increases d. the diameter of the axon increase

The absolute refractory period is about 3.75 msec. What intensity stimulus would produce action potentials with this interspike interval? a. 20 mV b. 30 mV c. 45 mV d. none of these stimuli would produce action potentials at this high frequency

An action potential can be propagated along an axon because there are ________ channels in the membrane. a. pressure-sensitive b. temperature-sensitive c. odor-sensitive d. voltage-gated

The units of conduction velocity are a. millivolts b. volts c. seconds d. meters/seconds

Which of the following will affect axonal conduction velocity? a. the diameter of the axon b. the amount of myelination c. both the diameter of the axon and the amount of myelination d. neither the diameter of the axon nor the amount of myelination

Which of the following describes an A fiber? a. large diameter, heavily myelinated b. medium diameter, lightly myelinated c. small diameter, unmyelinated d. none of the above

Which of the following describes a C fiber? a. large diameter, heavily myelinated b. medium diameter, lightly myelinated c. small diameter, unmyelinated d. none of the above

Action potential conduction velocity is fastest in which of the following fibers? a. A fibers b. B fibers c. C fibers d. the conduction velocity is the same for all three fibers

Action potential conduction velocity is slowest in which of the following fibers? a. A fibers b. B fibers c. C fibers d. the conduction velocity is the same for all three fibers

Why did the timescale have to be changed to measure the conduction velocity of the C fibers? a. the total time shown on the oscilloscope would have been too long to see the action potential at R2 b. the total time shown on the oscilloscope would have been too short to see the action potential at R2 c. the conduction velocity was too fast to see the action potential on the oscilloscope d. the length of the C fiber was different from the length of the A and B fibers

The axons from touch fibers are A fibers, and the axons from pain fibers are C fibers. When you stub your tow, which would you expect to perceive first? a. pain b. your toe touching something c. both would be perceived at the same time d. neither would be perceived

The end fo the axon where it contacts a target is called the a. cell body b. myelin sheath c. axon terminal d. nucleus

Neurotransmitter is released into the synaptic gap by a. exocytosis b. voltage-gated neurotransmitter channels c. muscle contraction d. the postsynaptic membrane of the target cell

Exocytosis of neurontransmitter form the axon terminal is triggered by an increase in the intracellular concentration of a. Na+ b. K+ c. Ca2+ d. none of theses

Neurotransmitter released into the synaptic gap reaches the target cell by a. exocytosis b. diffusion c. muscle contraction d. conduction down the axon

At the target, neurotransmitter a. binds to receptor proteins b. causes membrane channels to open or close c. causes a change in membrane potential d. does all of the above

How is the neurotransmitter stored in the axon terminal before it is released? a. bound to the mitochondrion b. bound to Ca2+ channels c. contained in synaptic vessicles d. neurotransmitter moves freely throughout the axon terminal

Are neurotransmitter molecules released one at a time or in packets? a. one at a time b. in packets c. both one at a time and in packets d. neurotransmitters do not get released

With the normal extracellular calcium concentration, [Ca2+], when the action potential reaches the axon terminal it triggers a. contraction of the axon terminal b. release of neurotransmitter by exocytosis c. a chemical reaction where Ca2+ is converted to Mg2+ d. no response

Comparing the low intensity stimulus to the high intensity stimulus, the high intensity stimulus causes a. more neurotransmitter to be released from each synaptic vesicle b. more synaptic vesicles to undergo exocytosis c. fewer synaptic vesicles to undergo exocytosis d. a chemical reaction where Ca2+ is converted to Mg2+

Sensory neurons respond to an appropriate stimulus with a change in membrane potential that is a. all or nothing b. graded wiht the stimulus intensity c. always small and subthreshold d. always large and suprathreshold

If the depolarization that reaches the axon is large and suprathreshold, the result in the axon is a. a graded depolarization b. a larger-than-normal action potential c. action potentials at higher frequency d. no response

At the axon terminal, each action potential causes the release of neurotrnasmitter. This neurotransmitter diffuses to the receiving end of an interneuron, where it binds to receptors and causes a. ion channels to open, so that the receiving end of the interneuron deplarizes b. a sensory stimulus in the interneuron c. the interneuron to move away d. no response

Interneurons respond to chemical (neurotransmitter) stimulation with a change in membrane potential that is a. all or nothing b. graded with the stimulus intensity c. always small and subthreshold d. always large and suprathreshold

What determines the amplitude of the depolarization at the sensory receptor (R1)? a. the strength of the stimulus applied to the sensory receptor b. the frequency of action potentials at the sensory receptor c. the amount of calcium that enters the sensory receptor d. the amount of neurotransmitter released by the sensory receptor

What determines the frequency of action potentials in the axon of the sensory neuron (R2)? a. the amplitude of the depolarization at the sensory receptor (R1) b. the ampltude of the action potential at R2 c. the amount of calcium tht enters the sensory receptor d. the amount of neurotransmitter released by the sensory receptor

Which of the following directly determines the amount of neurotransmitter released at the axon terminal of hte sensory neuron? a. the strength of the stimulus applied to the sensory receptor b. the frequency of action potentials at the sensory receptor c. the amount of calcium that enters the sensory receptor d. the depolarization at the interneuron's cell body

Which of the following directly or indirectly determines the amount of neurotransmitter released at the axon terminal of the sensory neuron? a. the strength of the stimulus applied to the sensory receptor b. the frequency of action potential at the sensory receptor c. the amount of calcium that enters the sensory receptor d. all of the above play a role in determining the amount of neurotransmitter released

Which of the following directly or indirectly determines the frequency of action potentials in the axon of the interneuron? a. the strength of the stimulus applied to the sensory receptor b. the amount of neurotransmitter released by the sensory neuron c. the depolarization at the interneuron's cell body d. all of the above play a role in determing the frequency of action potentials in the axon of the interneuron