Justin Miller
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Justin Miller
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Practice Exam 2

Questão 1 de 40

1

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

Selecione uma das seguintes:

  • TTX

  • local anesthetics

  • TEA

  • none of the above

  • all of the above

Explicação

Questão 2 de 40

1

nAChR channels at the endplate:

Selecione uma das seguintes:

  • 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

Explicação

Questão 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:

Selecione uma das seguintes:

  • 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

Explicação

Questão 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)

Selecione uma das seguintes:

  • 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

Explicação

Questão 5 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 6 de 40

1

Which of the following statements is/are incorrect:

Selecione uma das seguintes:

  • 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

Explicação

Questão 7 de 40

1

Which of the following statements is/are incorrect:

Selecione uma das seguintes:

  • 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

Explicação

Questão 8 de 40

1

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

Selecione uma das seguintes:

  • 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.

Explicação

Questão 9 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 10 de 40

1

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

Selecione uma das seguintes:

  • mitochondria

  • myelin

  • receptors

  • synaptic vesicles

  • all of the above

Explicação

Questão 11 de 40

1

Multiple sclerosis (MS):

Selecione uma das seguintes:

  • 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

Explicação

Questão 12 de 40

1

The resting membrane potential of a nerve is:

Selecione uma das seguintes:

  • 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

Explicação

Questão 13 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 14 de 40

1

The inhibitory postsynaptic potential (IPSP):

Selecione uma das seguintes:

  • 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

Explicação

Questão 15 de 40

1

The refractory periods (RP):

Selecione uma das seguintes:

  • 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

Explicação

Questão 16 de 40

1

Long-term potentiation (LTP)

Selecione uma das seguintes:

  • 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

Explicação

Questão 17 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 18 de 40

1

Presynaptic inhibition:

Selecione uma das seguintes:

  • requires longer time to develop

  • lasts longer

  • all types result in decreased neurotransmitter release

  • choices 1 & 2

  • choices 1, 2 & 3

Explicação

Questão 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?

Selecione uma das seguintes:

  • 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

Explicação

Questão 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:

Selecione uma das seguintes:

  • 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

Explicação

Questão 21 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 22 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 23 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 24 de 40

1

Myelination:

Selecione uma das seguintes:

  • 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

Explicação

Questão 25 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 26 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 27 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 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:

Selecione uma das seguintes:

  • 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

Explicação

Questão 29 de 40

1

Lysosomes are stabilized by:

Selecione uma das seguintes:

  • asbestos

  • endomethacin

  • high vitamin A intake

  • choices 1 & 2

  • choices 2 & 3

Explicação

Questão 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:

Selecione uma das seguintes:

  • 1 cm

  • 5 cm

  • 10 cm

  • 100 cm

  • not enough information is provided to make this determination

Explicação

Questão 31 de 40

1

synaptic transmission decreases when:

Selecione uma das seguintes:

  • 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

Explicação

Questão 32 de 40

1

About Receptors:

Selecione uma das seguintes:

  • 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

Explicação

Questão 33 de 40

1

The All-or-nothing rule applies to:

Selecione uma das seguintes:

  • IPSP

  • mEPP

  • EPSP

  • EPP

  • none of the above

Explicação

Questão 34 de 40

1

IPSPs:

Selecione uma das seguintes:

  • 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

Explicação

Questão 35 de 40

1

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

Selecione uma das seguintes:

  • spatial summation

  • temporal summation

  • inhibition of the action potential

  • hyperpolarization

Explicação

Questão 36 de 40

1

Exocytosis is involved in:

Selecione uma das seguintes:

  • neurotransmitter release

  • action of dynein and kinesin

  • simple diffusion

  • active transport

  • none of the above

Explicação

Questão 37 de 40

1

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

Selecione uma das seguintes:

  • neurotransmitter receptors e.g. ACh receptors

  • K+ channels

  • Glucose transporters in insulin-sensitive cells.

  • Microtubules transporting synaptic vesicles

  • the Na-K pump

Explicação

Questão 38 de 40

1

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

Selecione uma das seguintes:

  • 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

Explicação

Questão 39 de 40

1

Threshold for an action potential:

Selecione uma das seguintes:

  • 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.

Explicação

Questão 40 de 40

1

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

Selecione uma das seguintes:

  • extracellular Na+

  • extracellular K+

  • intracellular Ca2+

  • extracellular Cl-

  • none of the above

Explicação