Anatomy Lab Exam 4- PhysioEx

What causes a change in membrane potential from -70 to -40 inside the cell body

An increase in extracellular K+

The sequence of events starting with a sensory stimulus and ending with a change in membrane potential is called

Sensory transduction

Assuming that the resting potential of a sensory neuron is -70 mV, which of the following represents a depolarization?

a change to -60 mV

Which of the following is true of the response of a sensory neuron to the appropriate sensory stimulus?

it can be called a receptor potential, it is a graded potential & it is a change in the resting membrane potential

If a graded receptor potential made the resting membrane potential of the axon more negative (for example, -70 mV changes to -75 mV), you would expect

it to be more difficult for this axon to reach the threshold voltage.

4. Which of the following describes an A fiber?

large diameter, heavily myelinated

The threshold voltage in an axon is usually

less negative than the resting membrane potential.

Which of the following is a sensory stimulus?

light, pressure, chemical odorants

4. Comparing the low intensity stimulus to the high intensity stimulus, the high intensity stimulus causes

more synaptic vesicles to undergo exocytosis

1. If the interval between action potentials (the interspike interval) is 0.1 (1/10) seconds, what frequency of action potentials would be observed?

10 Hz

3. Exocytosis of neurotransmitter from the axon terminal is triggered by an increase in the intracellular concentration of

Ca2+

2. When open, Na+ channels allow

Na ions to diffuse into the cell

4. Which of the following can reduce the likelihood of an action potential?

TTX, lidocaine, increasing the leak of K from a cell

3. Which of the following directly determines the amount of neurotransmitter released at the axon terminal of the sensory neuron?

The amount of calcium that enters the sensory receptor.

2. What determines the frequency of action potentials in the axon of the sensory neuron (R2)?

The amplitude of the depolarization at the sensory receptor (R1).

1. What determines the amplitude of the depolarization at the sensory receptor (R1)?

The strength of the stimulus applied to the sensory receptor.

3. Why did the timescale have to be changed to measure the conduction velocity of the C fibers?

The total time shown on the oscilloscope would have been too short to see the action potential at R2.

Axons are

You correctly answered: d. long, thin structures that extend from a neuronal cell body.

What are the typical concentrations of [K+] and [Na+] inside and outside of the cell?

[K] inside: 150mM [K] outside: 5 mM [Na] inside: 5 mM [Na] outside: 150 mM

Starting at a resting membrane potential of -70 mV, a change to which of the following represents the largest receptor potential?

a change to -50mV

2. If the depolarization that reaches the axon is large and suprathreshold, the result in the axon is

action potentials at higher frequency

4. Puffer fish must be prepared carefully and properly before they can be eaten. Eating puffer fish can cause numbness of the lips, probably because

action potentials from sensory neurons in the lips are blocked.

1. In the control, the amplitudes of the action potentials at R1 and R2 are the same. Which of the following explains this?

all of the above (action potential is all or none event, action potentials propagate themselves along each point of an axon, there are Na channels all along the axon)

Failure to reach the threshold voltage in the axon of a sensory neuron could be caused by

all of the above (application of wrong stimulus modality, insufficient depolarizing of receptor potential, generation of receptor potential that makes axonal RP more more negative)

An action potential is usually initiated in an axon at or near

axon hillock/initial segment/trigger zone

What has the most negative voltage? a. between the outside of the axon and outside the cell body with control K+ ECF b. between the inside of the axon and the outside of the axon with control K+ ECF

between the inside of the axon and the outside of the axon with control K+ ECF

Olfactory receptor neurons respond to low concentrations of chemical odorants because there are membrane proteins in the receptor ending of this sensory neuron that

can bind and respond to the specific odorant

4. Neurotransmitter released into the synaptic gap reaches the target cell by

diffusion

Which of the following is easier?

extracellular recordings of the action potential

The initiation of an action potential in a sensory neuron in the body normally

follows a sufficiently large depolarizing receptor potential.

3. Which of the following changes occurs when you increase the stimulus intensity?

frequency of action potentials increases

1. Sensory neurons respond to an appropriate sensory stimulus with a change in membrane potential that is

graded with stimulus intensity

4. Interneurons respond to chemical (neurotransmitter) stimulation with a change in membrane potential that is

graded with stimulus intensity

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

intense pressure

3. At the axon terminal, each action potential causes the release of neurotransmitter. This neurotransmitter diffuses to the receiving end of an interneuron, where it binds to receptors and causes

ion channels to open, so that the receiving end of the interneuron depolarizes.

4. The absolute refractory period is about 3.75 msec. What intensity stimulus would produce action potentials with this interspike interval?

none can produce this high a frequency

2. Are neurotransmitter molecules released one at a time or in packets?

packets

3. With the normal extracellular calcium concentration, [Ca2+ ], when the action potential reaches the axon terminal it triggers

release of neurotransmitters by exocytosis

5. Which of the following describes a C fiber?

small diameter, unmyelinated

1. How is the neurotransmitter stored in the axon terminal before it is released?

synaptic vesicles

2. 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

the absolute and relative refractory period

2. Blocking the voltage-gated Na+ channels between R1 and R2 with TTX blocks

the propagation of the action potential from R1 to R2

3. When voltage-gated Na+ channels between R1 and R2 are blocked with TTX, an action potential is still recorded at R1 because

the voltage-gated Na+ channels between the stimulus and R1 are unaffected by the TTX.

Which of the following is a sensory modality (type of sense)?

touch, smell, sight, pain

1. Voltage-gated Na+ channels are membrane channels that open

when the membrane depolarizes