Justin Miller
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Justin Miller
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Practice Exam 2

Pregunta 1 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • TTX

  • local anesthetics

  • TEA

  • none of the above

  • all of the above

Explicación

Pregunta 2 de 40

1

nAChR channels at the endplate:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 3 de 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:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 4 de 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)

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 5 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 6 de 40

1

Which of the following statements is/are incorrect:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 7 de 40

1

Which of the following statements is/are incorrect:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 8 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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.

Explicación

Pregunta 9 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 10 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • mitochondria

  • myelin

  • receptors

  • synaptic vesicles

  • all of the above

Explicación

Pregunta 11 de 40

1

Multiple sclerosis (MS):

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 12 de 40

1

The resting membrane potential of a nerve is:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 13 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 14 de 40

1

The inhibitory postsynaptic potential (IPSP):

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 15 de 40

1

The refractory periods (RP):

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 16 de 40

1

Long-term potentiation (LTP)

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 17 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 18 de 40

1

Presynaptic inhibition:

Selecciona una de las siguientes respuestas posibles:

  • requires longer time to develop

  • lasts longer

  • all types result in decreased neurotransmitter release

  • choices 1 & 2

  • choices 1, 2 & 3

Explicación

Pregunta 19 de 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?

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 20 de 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:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 21 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 22 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 23 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 24 de 40

1

Myelination:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 25 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 26 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 27 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 28 de 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:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 29 de 40

1

Lysosomes are stabilized by:

Selecciona una de las siguientes respuestas posibles:

  • asbestos

  • endomethacin

  • high vitamin A intake

  • choices 1 & 2

  • choices 2 & 3

Explicación

Pregunta 30 de 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:

Selecciona una de las siguientes respuestas posibles:

  • 1 cm

  • 5 cm

  • 10 cm

  • 100 cm

  • not enough information is provided to make this determination

Explicación

Pregunta 31 de 40

1

synaptic transmission decreases when:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 32 de 40

1

About Receptors:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 33 de 40

1

The All-or-nothing rule applies to:

Selecciona una de las siguientes respuestas posibles:

  • IPSP

  • mEPP

  • EPSP

  • EPP

  • none of the above

Explicación

Pregunta 34 de 40

1

IPSPs:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 35 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • spatial summation

  • temporal summation

  • inhibition of the action potential

  • hyperpolarization

Explicación

Pregunta 36 de 40

1

Exocytosis is involved in:

Selecciona una de las siguientes respuestas posibles:

  • neurotransmitter release

  • action of dynein and kinesin

  • simple diffusion

  • active transport

  • none of the above

Explicación

Pregunta 37 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • neurotransmitter receptors e.g. ACh receptors

  • K+ channels

  • Glucose transporters in insulin-sensitive cells.

  • Microtubules transporting synaptic vesicles

  • the Na-K pump

Explicación

Pregunta 38 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 39 de 40

1

Threshold for an action potential:

Selecciona una de las siguientes respuestas posibles:

  • 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.

Explicación

Pregunta 40 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • extracellular Na+

  • extracellular K+

  • intracellular Ca2+

  • extracellular Cl-

  • none of the above

Explicación