Exam 2

Question 1

1) Traces A, B, and C in the above diagram summarize the changes in membrane potential (Vm) and the underlying membrane permeabilities (P) that occur in a nerve cell over the course on an action potential. Choose the combination of labels that accurately identifies each of the traces.
Trace A is the tallest, with a hyperpolarization

Trace B is shorter and flattens out

Trace C is delayed, fat and short

 Trace A Trace B Trace C
(A) PK: PNa,  Vm,   PK
(B) PNa,         Vm,   PK
(C) Vm,          PNa,  PK
(D) Vm,          PK,    PNa
(E) PK,           Vm,   PNa

Answer 1

C) Vm, PNa, Pk

Question 2

2) Which of the following is a consequence of myelination in large nerve fibers?

(A) Increase in the energy required to maintain ion gradients across the membrane

(B) Increase in the nonselective diffusion of ions across the axon membrane

(C) Decrease in the velocity of nerve impulses along the axon

(D) Generation of action potentials only at the nodes of Ranvier

(E) Increase in the membrane capacitance of the axon

Answer 2

D) Generation of action potentials only at the nodes of Ranvier

Question 3

3) Trace A represents a typical action potential recorded under control conditions from a “normal” nerve cell in response to a depolarizing stimulus.
Which of the following perturbations would
explain the conversion of the response shown in trace A to the action potential shown in trace B?

Trace A is typical. Trace B begins normal, starts to drop, plateaus a bit, and drops quickly

A)Blockade of Na+-K+ “leak” channels
B) Blockade of voltage-sensitive Na+
channels
C) Blockade of voltage-sensitive K+ channels
D)Replacement of the voltage-sensitive K+ channels with “slow” Ca+2 channels
E) Replacement of the voltage-sensitive Na+ channels with “slow” Ca+2 channels

Answer 3

C) Replacement of voltage sensitive Na+ channels with “slow” Ca2+ channels

Question 4

4) Which of the following perturbations would account for the failure of the same stimulus to elicit an action potential in trace C?

A) Blockade of voltage-sensitive K+ channels

B) Blockade of voltage-sensitive Na+ channels

C) Blockade of Na+-K+ “leak” channels

D) Replacement of the voltage-sensitive K+ channels with “slow” Ca+2 channels

E) Replacement of the voltage-sensitive Na+ channels with “slow” Ca+2 channels

Answer 4

B) Blockage of voltage-sensitive Na+ channels

Question 5

5) For the eye to adapt to intense light, which of the following may occur?

A) Bipolar cells continuously transmit signals at the maximum rate possible

B) Photochemicals in both rods and cones are reduced to retinal and opsins

C) Levels of rhodopsin are very high

D) Pupil size increases

E) Vitamin A converts into retinal

Answer 5

B) Photochemicals in both rods and cones are reduced to retinal and opsins

Question 6

6) Which of the following events prompts the auditory system to interpret a sound as loud?

A) Fewer inner hair cells become stimulated

B) Fewer outer hair cells become stimulated

C) Hair cells excite nerve endings at a diminished rate

D) Amplitude of vibration of the basilar membrane decreases

E) Amplitude of vibration of the basilar membrane increases

Answer 6

E) Amplitude of vibration of the basilar membrane increases

Question 7

7) Which of the following is primarily responsible for the change in membrane potential between points B and D?

(A)Movement of K+ into the cell
(B) Movement of K+ out of the cell
(C) Movement of Na+
 into the cell
(D)Movement of Na+ out of the cell
(E) Inhibition of the Na+, K+-ATPase

Answer 7

C) Movement of Na+ into the cell

Question 8

8) Which of the following is primarily responsible for the change in membrane potential between points D and E?

(A)Movement of K+ into the cell
(B) Movement of K+ out of the cell
(C) Movement of Na+
 into the cell
(D)Movement of Na+ out of the cell
(E) Inhibition of the Na+, K+-ATPase

Answer 8

B) Movement of K+ out of the cell

Question 9

9) Point at which membrane potential (Vm) is closest to the Na+ equilibrium potential (____)

Answer 9

Point D

Question 10

10) Point at which the driving force for Na+ is the greatest (____)

Answer 10

Point F

Question 11

11) Point at which the ratio of K+ permeability to Na+ permeability (PK/PNa) is the greatest (___)

Answer 11

Point E (part of the way down the K+ slope)

Question 12

12) Which of the following statements regarding color vision is correct?

(A) Green is perceived when only green cones are stimulated

(B) The stimulation ratio of the three types of cones allows specific color perception

(C) The wavelength of light corresponding to white is shorter than that corresponding to blue

(D) When there is no stimulation of red, green, or blue cones, there is the sensation of seeing
white

(E) Yellow is perceived when green and blue cones are stimulated equally

Answer 12

B) The stimulation ratio of the three types of cones allows specific color perception

Question 13

13) Which of the following retinal cells has action potentials?

A) Rods
B) Bipolar cells
C) Ganglion cells
D) Horizontal cells
E) Cones

Answer 13

C) Ganglion cells

Question 14

14) Visual contrast is enhanced due to lateral inhibition by which retinal cells?

A) Rods
B) Bipolar cells
C) Ganglion cells
D) Horizontal cells
E) Cones

Answer 14

D) Horizontal cells

Question 15

15) Which of the following best describes the concept of specificity in sensory nerve fibers that transmit only one modality of sensation?

A) Frequency coding principle
B) Concept of specific nerve energy
C) Unity theory
D) Singularity principle
E) Labeled line principle

Answer 15

E) Labeled line principle

Question 16

16) Which of the following statements regarding the processing of sensory signals by a pool of neurons is correct?

A) Convergence of input signals to individual neurons in the pool, each of which contributes to the same output channel, can lead to amplification of the signal

B) Divergence of input signals to multiple neurons in the pool, each of which leads to a different output channel, can lead to diffusion of the signal

C) The combination of multiple input signals from multiple sources onto a single neuron in
the pool is an example of divergence
D) The distribution of multiple input signals from a single source onto many neurons in the pool is an example of convergence

E) In some instances, a sensory input to a neuronal pool causes a prolonged pause in the generation of output signals, called an after-discharge

Answer 16

B) Divergence of input signals into multiple neurons in the pool, each of which leads to a different output channel, can lead to a diffusion of the signal

Question 17

17) Which of the following statements concerning synaptic transmission is correct?

A) When a specific population of synaptic terminals is spread over the considerable surface of a neuron, their collective effects cannot spatially summate and lead to initiation of an action potential

B) Even if the successive discharges of an excitatory synapse occur sufficiently close in time, they cannot temporally summate and initiate an action potential

C) A neuron is “facilitated” when its membrane potential is moved in the hyperpolarizing direction

D) Dendrites do not typically propagate action potentials, but they can transmit electrical potentials by electrotonic conduction

Answer 17

D) Dendrites do not typically propagate action potentials, but they can transmit electrical potentials by electronic conduction

Question 18

18) Which of the following represents the basis for transduction of a sensory stimulus into nerve impulses?

A) Change in the ion permeability of the receptor membrane

B) Generation of an action potential

C) Inactivation of a G protein-mediated response

D) Protein synthesis

E) Conversion of electrical energy to mechanical energy

Answer 18

A) Change in the ion permeability of the receptor membrane

Question 19

19) As the receptor potential rises higher above a threshold, which of the following best characterizes the new frequency of action potentials?

A) Decreased
B) Increased
C) Unchanged
D) Increased only when the receptor potential increases to twice the threshold level
E) Unchanged until the receptor potential increases to twice the threshold level

Answer 19

B) Increased

Question 20

20) The ability to detect two points simultaneously applied to the skin is based on which of the following physiological mechanisms?

A) Presynaptic inhibition
B) Lateral inhibition
C) Medial inhibition
D) Feed-forward inhibition
E) Feedback inhibition

Answer 20

B) Lateral inhibition

Question 21

21) Which one of the following statements concerning sensory neurons or their functional properties is true?

A) All sensory fibers are unmyelinated

B) In spatial summation, increasing signal strength is transmitted by using progressively greater numbers of sensory fibers

C) Increased stimulus intensity is signaled by a progressive decrease in the receptor potential

D) Continuous subthreshold stimulation of a pool of sensory neurons results in disfacilitation of those neurons

E) In temporal summation, increased stimulus strength is signaled by decreasing the frequency of action potentials in the sensory fibers

Answer 21

B) In spatial summation, increasing signal strength is transmitted by using progressively greater numbers of sensory fibers

Question 22

22) Light entering the eye passes through which retinal layer first?

A) Inner nuclear layer
B) Outer nuclear layer
C) Outer plexiform layer
D) Photoreceptor layer
E) Retinal ganglion layer

Answer 22

E) Retinal ganglion layer

Question 23

23) Which of the following statements regarding the basilar membrane is correct?

A) It vibrates best at high frequency near the base of the cochlea whereas it vibrates best at low frequency at the apex of the cochlea

B) The spiral ganglion lies on its surface

C) It contains basilar fibers whose diameter increases from the base of the cochlea to the apex of the cochlea

D) It contains basilar fibers whose length decreases from the base of the cochlea to the apex of the cochlea

E) It separates the scala media from the scala vestibuli

Answer 23

A) It vibrates best at high frequency near the base of the cochlea whereas it vibrates best at low frequency at the apex of the cochlea

Question 24

A deficiency of which vitamin prevents the formation of an adequate quantity of retinal, eventually leading to night blindness?

A) Vitamin A
B) Vitamin C
C) Vitamin D
D) Vitamin E
E) Vitamin K

Answer 24

A) Vitamin A

Question 25

25) Which of the following events causes rods to hyperpolarize in response to light?

A) Decrease in sodium conductance into the outer segment

B) Decrease in sodium pump activity at the inner segment

C) Increase in potassium conductance into the outer segment

D) Increase in sodium conductance into the outer segment

E) Increase in sodium pump activity at the inner segment

Answer 25

A) Decrease in sodium conductance into the outer segment

Question 26

26) What is the difference between intrinsic and synaptic neuronal processing?

Answer 26

Intrinsic: processing in ONE cell

Synaptic: processing that occurs between multiple cells at synapses

Question 27

27) What is the advantage of a neuron generating “spontaneous” action potentials?

Answer 27

-> finely tuned response by increasing and decreasing frequencies

Question 28

28) Convergence achieves:

Divergence achieves:

Answer 28

• > Signal summation

- >Signal amplification

Question 29

29) What is saltatory conduction and what causes it?

Answer 29

Conduction from one motor node of Ranvier to another, caused by Myelin sheath and nodes of ranvier/gaps in sheath with voltage gated channels

Question 30

30) If Fiber one has a diameter of 3um, and fiber 2 has a diameter of 6 um, which supports a faster action potential conduction velocity?

Answer 30

Fiber 2, which is 2X faster since myelinated fiber velocity is directly proportional to diameter