Justin Miller
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Justin Miller
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Practice Exam 2

Practice Exam 2

Question 1 of 40

1

The Na/K transporter (pump) is blocked by:

Select one of the following:

  • TTX

  • local anesthetics

  • TEA

  • none of the above

  • all of the above

Explanation

Question 2 of 40

1

nAChR channels at the endplate:

Select one of the following:

  • open when the endplate is depolarized

  • are non-selective in that they allow positive and negative ions to pass through

  • ions pass through them by simple diffusion

  • open when serotonin or glutamate is present

  • none of the above

Explanation

Question 3 of 40

1

Axons X and Y are myelinated and of equal diameter, suppose that, in X the internodal distance is 10 nm while in Y the internodal distance is 20 nm. Based on this information:

Select one of the following:

  • axon X is faster conducting than Y

  • axon Y is faster conducting than X

  • axons X and Y have equal conduction velocity

  • axon X save more energy than axon Y

  • axons X and Y save same amount of energy

Explanation

Question 4 of 40

1

As a result of repetitive activity the K concentration immediately outside the nerve terminal rises to 10 meq whereas the K concentration inside decreases to 100 meq. Thus: (hint: log 10=1)

Select one of the following:

  • a type of presynaptic inhibition results

  • the nerve terminal is depolarized

  • the incoming action potential is decreased in amplitude

  • the amount of transmitter released is less

  • All of the above

Explanation

Question 5 of 40

1

The fate of Na and K ions that enter and leave respectively during the action potential:

Select one of the following:

  • Na ions exit through their channels just before they close

  • K ions enter through the delayed rectifier channels before they close

  • the Na/K pump returns the ions to their original concentrations

  • Na ions are trapped, but they slowly diffuse out across the membrane.

  • all of the above

Explanation

Question 6 of 40

1

Which of the following statements is/are incorrect:

Select one of the following:

  • alkalosis can cause excitation of the CNS

  • termination of epileptic seizures can be due to Wedensky inhibition

  • in the Renshaw circuit activity of one motor neuron result in self-inhibition as well as inhibition of an antagonist second motor neuron

  • removal of Ca from the vicinity of a synapse causes increased excitability of the axon but also causes inhibition of synaptic transmission

  • none of the above

Explanation

Question 7 of 40

1

Which of the following statements is/are incorrect:

Select one of the following:

  • the motor endplate is electrically not excitable

  • pinocytosis is the reverse of phagocytosis

  • demarcation (injury) potential is a monophasic action potential

  • water is a polar molecule but can cross the cell membrane freely

  • all of the above

Explanation

Question 8 of 40

1

If the voltage-regulated sodium channels failed to become inactivated, then the duration of action potential

Select one of the following:

  • would be longer

  • would be shorter

  • would be the same

  • would be the same but with no relative refractory period

  • there would be relative refractory period only.

Explanation

Question 9 of 40

1

What would happen to a muscle action potential if 50% of the sodium channels are blocked?

Select one of the following:

  • it would be similar to a pacemaker action potential

  • it would be similar to a heart ventricular muscle action potential

  • it would be the same but with no relative refractory period

  • it would be the same but with no absolute refractory period

  • it would be of much smaller amplitude

Explanation

Question 10 of 40

1

Postsynaptic density (opacity) is due to the presence of ______ in the membrane:

Select one of the following:

  • mitochondria

  • myelin

  • receptors

  • synaptic vesicles

  • all of the above

Explanation

Question 11 of 40

1

Multiple sclerosis (MS):

Select one of the following:

  • lesions are more diffused than they are in ALS

  • occurs both in the CNS and the PNS

  • is commonly known as Lou Gehrig’s disease

  • occurs in the PNS only

  • none of the above

Explanation

Question 12 of 40

1

The resting membrane potential of a nerve is:

Select one of the following:

  • less negative when Na+ concentration in extracellular fluid [Na]o is decreased

  • more negative when [K+]o is increased

  • more negative when [Na+]o is increased

  • more negative when [Ca2+]o is increased

  • none of the above

Explanation

Question 13 of 40

1

Which of the following statement(s) is/are True?

Select one of the following:

  • Compound action potentials are seen only when a nerve bundle containing a large number of axons of different conduction velocities is stimulated

  • Extracellular fluid contains more Ca2+ than intracellular fluid

  • Transfer of electrical signal across synapses is called transmission, whereas
    travel of signal along axons is called conduction

  • specific Na+ channels are not the same as acetylcholine channels.

  • all of the above

Explanation

Question 14 of 40

1

The inhibitory postsynaptic potential (IPSP):

Select one of the following:

  • is the result of positive ions moving through ligand-gated channels

  • has a brief refractory period

  • is propagated

  • is the cause of stimulus artifact

  • none of the above

Explanation

Question 15 of 40

1

The refractory periods (RP):

Select one of the following:

  • the absolute RP is due to complete closure and inactivation of Na channels

  • are due to opening of the delayed rectifier

  • can be seen in nerve action potentials but not in muscle action potentials

  • choices 1 & 2

  • choices 2 & 3

Explanation

Question 16 of 40

1

Long-term potentiation (LTP)

Select one of the following:

  • is a form of structural synaptic plasticity

  • is manifested as an increase in synaptic strength (i.e. increased EPSP)

  • is same a perforated synapses

  • choices 1 & 2

  • choices 1, 2 & 3

Explanation

Question 17 of 40

1

Depolarization of the terminal button leads to release of neurotransmitter in the following way:

Select one of the following:

  • neurotransmitter in the neuroplasm diffuses across the terminal membrane through the synaptic cleft and onto the postsynaptic membrane.

  • the vesicles are released into the synaptic cleft where they diffuse and fuse into the postsynaptic membrane.

  • neurotransmitter diffuses through gap junction from the presynaptic to postsynaptic membrane

  • none of the above

Explanation

Question 18 of 40

1

Presynaptic inhibition:

Select one of the following:

  • requires longer time to develop

  • lasts longer

  • all types result in decreased neurotransmitter release

  • choices 1 & 2

  • choices 1, 2 & 3

Explanation

Question 19 of 40

1

While studying the transport of molecule B across the cell membrane, you discover that as you increase the concentration of B in the extracellular fluid, the rate of transport also initially increases. If the concentration of extracellular B is further increased, the rate becomes constant. Based on this information, which of the following statements best describe this situation?

Select one of the following:

  • molecule B is transported from outside to the cytoplasm.

  • the transport process involves a carrier protein.

  • the system exhibits saturation.

  • choices 1 & 2

  • choices 1, 2 & 3

Explanation

Question 20 of 40

1

A man falls into deep sleep with one arm under his head. This arm is paralyzed when he awakens, but it tingles, and he can feel pain sensation in it. The reason for the loss of motor function without loss of pain sensation is that:

Select one of the following:

  • A fibers are more susceptible to hypoxia than B fibers

  • A fibers are more susceptible to pressure than B fibers

  • A fibers are more susceptible to hypoxia than C fibers

  • A fibers are more susceptible to pressure than C fibers

Explanation

Question 21 of 40

1

Which of the following statement(s) is/are False?

Select one of the following:

  • compound action potential is seen when a single axon is stimulated

  • Schwann cells provide myelin for CNS nerve axons

  • a compound action potential is an all-or-none phenomenon

  • choices 1 and 2

  • choices 1, 2 and 3

Explanation

Question 22 of 40

1

When an action potential depolarizes a terminal button, Ca2+:

Select one of the following:

  • enters the synaptic vesicles

  • is released into the synaptic cleft

  • enters the terminal button

  • enters the postsynaptic membrane to generate an EPSP

  • generates the coated vesicles

Explanation

Question 23 of 40

1

Presynaptic facilitation (i.e. increased transmitter release) occurs when:

Select one of the following:

  • extracellular concentration of sodium increases

  • extracellular concentration of potassium increases

  • calcium channels in the presynaptic membrane are inhibited

  • calcium channels in the presynaptic membrane remain open longer

  • temporal summation occurs

Explanation

Question 24 of 40

1

Myelination:

Select one of the following:

  • occurs only in A type nerve axon

  • of the dendrites (unlike axons) continues uninterrupted (no nodes of Ranvier)

  • action potentials occur at the nodes of Ranvier along the axon

  • choices 1 and 3

  • choices 2 and 3

Explanation

Question 25 of 40

1

In the CNS, a severed or injured axon undergoes Wallerian degeneration but virtually no regeneration takes place because:

Select one of the following:

  • astrocytes produce certain chemicals that prevent regeneration

  • astrocytes produce scar tissue to block regeneration

  • there are no glial cells to lay the track for a growing axon

  • choices 1 and 2

  • choices 1, 2 and 3

Explanation

Question 26 of 40

1

Which of the following comparisons between neurons and muscle tissue is incorrect?

Select one of the following:

  • resting potentials are greater in muscle fibers

  • muscle fibers conduct action potentials at relatively slower speeds

  • action potentials last longer in muscle fibers

  • muscle fibers conduct action potentials only by saltatory conduction

Explanation

Question 27 of 40

1

How would the ventricular muscle action potential be affected if calcium channels were blocked?

Select one of the following:

  • it would look like a pacemaker action potential

  • it would look like a nerve action potential

  • it would be the same

  • it would be the same but with no absolute refractory period

  • none of the above

Explanation

Question 28 of 40

1

The generation of an action potential occurs when the following the main steps take place:
a. sodium channels are inactivated
b. voltage-regulated potassium channels open and potassium moves out of the
cell initiating repolarization
c. sodium channels regain their normal properties
d. a graded depolarization brings an area of an excitable membrane to threshold
e. a temporary hyperpolarization occurs
f. sodium channel activation occurs
g. sodium ions enter the cell and depolarization occurs,
the proper sequence of event is:

Select one of the following:

  • d, f, g, c, b, e, a

  • d, f, g, a, b, c, e

  • f, g, d, a, b, c, e

  • b, d, f, g, a, c, e

  • d, b, e, f, g, c, a

Explanation

Question 29 of 40

1

Lysosomes are stabilized by:

Select one of the following:

  • asbestos

  • endomethacin

  • high vitamin A intake

  • choices 1 & 2

  • choices 2 & 3

Explanation

Question 30 of 40

1

Action potential is recorded from a length of squid axon that has a conduction velocity of 100 m/sec; the latent period is 1 msec and the amplitude of the action potential is 100mV. With this information in hand the length of the axon must be:

Select one of the following:

  • 1 cm

  • 5 cm

  • 10 cm

  • 100 cm

  • not enough information is provided to make this determination

Explanation

Question 31 of 40

1

synaptic transmission decreases when:

Select one of the following:

  • a calcium ion chelating agent is present

  • postsynaptic receptors are blocked

  • the RMP of the presynaptic terminal is slightly (e.g. 3-5 mV) more negative

  • choices 1 & 2

  • choices 2 & 3

Explanation

Question 32 of 40

1

About Receptors:

Select one of the following:

  • ionotropic receptors exist only on postsynaptic membrane

  • metabotropic receptors exist only on presynaptic membrane

  • metabotropic receptors, which are G-protein coupled, exist on postsynaptic membrane of fast synapses

  • ionotropic receptors, which are not G-protein coupled, exist on postsynaptic membrane of fast synapses

  • none of the above

Explanation

Question 33 of 40

1

The All-or-nothing rule applies to:

Select one of the following:

  • IPSP

  • mEPP

  • EPSP

  • EPP

  • none of the above

Explanation

Question 34 of 40

1

IPSPs:

Select one of the following:

  • result in local depolarizations

  • result in local hyperpolarizations

  • increase membrane permeability to sodium ions

  • prevent the efflux of potassium ions

  • prevent the efflux of calcium ions

Explanation

Question 35 of 40

1

When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what occurs is:

Select one of the following:

  • spatial summation

  • temporal summation

  • inhibition of the action potential

  • hyperpolarization

Explanation

Question 36 of 40

1

Exocytosis is involved in:

Select one of the following:

  • neurotransmitter release

  • action of dynein and kinesin

  • simple diffusion

  • active transport

  • none of the above

Explanation

Question 37 of 40

1

Which of the following is not normally embedded in the plasma membrane?

Select one of the following:

  • neurotransmitter receptors e.g. ACh receptors

  • K+ channels

  • Glucose transporters in insulin-sensitive cells.

  • Microtubules transporting synaptic vesicles

  • the Na-K pump

Explanation

Question 38 of 40

1

The resting potential is due, in part, to the:

Select one of the following:

  • insulating effect of the Schwann cell

  • large negatively charged proteins on the outside

  • activity of the Na-K pump

  • Na+ equilibrium potential

  • Ca2+ equilibrium potential

Explanation

Question 39 of 40

1

Threshold for an action potential:

Select one of the following:

  • is the same for different nerves

  • is a measure of conduction velocity of the nerve

  • the higher it is the more excitable the nerve is.

  • is dependent on the number of Na channels in the nerve; the higher the
    number the lower the threshold.

  • All of the above.

Explanation

Question 40 of 40

1

The amplitude of action potential in an axon is dependent on:

Select one of the following:

  • extracellular Na+

  • extracellular K+

  • intracellular Ca2+

  • extracellular Cl-

  • none of the above

Explanation

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