Justin Miller
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Justin Miller
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Practice Exam 3

Pregunta 1 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • TTX

  • local anesthetics

  • TEA

  • saxitoxin

  • none of the above

Explicación

Pregunta 2 de 40

1

nAChR channels at the endplate:

Selecciona una de las siguientes respuestas posibles:

  • open when the nAChR are activated

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

  • Na and K ions pass through them by simple diffusion

  • also open when serotonin or glutamate is present

  • choices A & C

Explicación

Pregunta 3 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:

Selecciona una de las siguientes respuestas posibles:

  • a type of presynaptic inhibition results

  • the nerve terminal is depolarized to -62mV

  • the incoming action potential at the terminal is decreased in amplitude

  • the amount of transmitter released is decreased

  • All of the above

Explicación

Pregunta 4 de 40

1

Which of the following statements is/are true:

Selecciona una de las siguientes respuestas posibles:

  • alkalosis can cause coma

  • action potential starts at the axon hillock

  • in the Renshaw circuit activity of one motor neuron result in self-inhibition.

  • removal of Ca2+from the vicinity of axon causes inhibition of AP conduction

  • none of the above

Explicación

Pregunta 5 de 40

1

Which of the following statements is/are true:

Selecciona una de las siguientes respuestas posibles:

  • the motor endplate is electrically not excitable

  • pinocytosis is the reverse of emeiocytosis

  • 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 6 de 40

1

What would happen to a muscle action potential if 50% of membrane sodium channels were 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 7 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • mitochondria

  • myelin

  • kinesin

  • synaptic vesicles

  • none of the above

Explicación

Pregunta 8 de 40

1

Multiple sclerosis (MS):

Selecciona una de las siguientes respuestas posibles:

  • also known as ALS

  • occurs both in the CNS and PNS

  • is commonly known as Lou Gehrig’s disease

  • occurs in the PNS only

  • none of the above

Explicación

Pregunta 9 de 40

1

The inhibitory postsynaptic potential (IPSP):

Selecciona una de las siguientes respuestas posibles:

  • is the result of negative ions moving through ligand-gated channels into the neuron

  • has a brief refractory period

  • is propagated

  • is the cause of stimulus artifact

  • is a depolarization

Explicación

Pregunta 10 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 A & B

  • choices A & C

Explicación

Pregunta 11 de 40

1

Long-term potentiation (LTP)

Selecciona una de las siguientes respuestas posibles:

  • is a form of functional synaptic plasticity

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

  • is same a perforated synapses

  • choices A & B

  • choices A, B & C

Explicación

Pregunta 12 de 40

1

Release of neurotransmitter (NT) takes place as:

Selecciona una de las siguientes respuestas posibles:

  • NT molecules in the neuroplasm diffuse across the terminal membrane through the synaptic cleft and onto the postsynaptic membrane.

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

  • NT diffuses through the connexins of the gap junction from the presynaptic to postsynaptic membrane

  • none of the above

Explicación

Pregunta 13 de 40

1

“Saturday night paralysis” is a proof that A fibers are:

Selecciona una de las siguientes respuestas posibles:

  • more susceptible to hypoxia than B fibers

  • more susceptible to pressure than B fibers

  • more susceptible to hypoxia than C fibers

  • more susceptible to pressure than C fibers

Explicación

Pregunta 14 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 nerve terminal

  • enters the postsynaptic membrane to generate an EPSP

  • generates the coated vesicles

Explicación

Pregunta 15 de 40

1

In the CNS, a severed or injured axon may undergo 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 A & B

  • choices A, B & C

Explicación

Pregunta 16 de 40

1

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

Selecciona una de las siguientes respuestas posibles:

  • resting potential is -90to -100mV in muscle fibers

  • muscle fibers conduct action potentials at relatively slower speeds

  • action potentials last longer in muscle fibers

  • muscle fibers conduct action potentials by saltatory conduction only

Explicación

Pregunta 17 de 40

1

How would the plateau 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 regular (muscle or nerve) action potential

  • it would not change in any aspect

  • it would change shape but would have no absolute refractory period

  • none of the above

Explicación

Pregunta 18 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 19 de 40

1

While studying the transport of molecule X 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 X 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 X is transported from outside to the cytoplasm.

  • the transport process involves a carrier protein.

  • the system exhibits saturation.

  • choices A & B

  • choices A,B &C

Explicación

Pregunta 20 de 40

1

Exocytosis is involved in:

Selecciona una de las siguientes respuestas posibles:

  • A neurotransmitter release

  • action of dynein and kinesin

  • simple diffusion

  • active transport

  • none of the above

Explicación

Pregunta 21 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

Pregunta 22 de 40

1

SNAREs and synaptotagmin:

Selecciona una de las siguientes respuestas posibles:

  • SNAREs are proteins that exist only on the vesicles

  • SNAREs exist on the vesicles as well as on the cytoplasmic side of the nerve terminal

  • SNAREs bind calcium ion directly

  • Calcium ions bind synaptotagmin

  • choices B & D

Explicación

Pregunta 23 de 40

1

A drug closes potassium channels of an axon and causes a 15 mV change in the resting membrane potential (RMP). The change is:

Selecciona una de las siguientes respuestas posibles:

  • similar to EPSP

  • similar to action potential

  • similar to IPSP

  • a reversal potential

  • a plateau potential

Explicación

Pregunta 24 de 40

1

Which of the following statements is/are false?

Selecciona una de las siguientes respuestas posibles:

  • a single Schwann cell forms a single segment of myelin on peripheral axons

  • EPP results from opening of acetylcholine-gated channels

  • presynaptic inhibition requires longer time to develop than postsynaptic inhibition.

  • synaptic spines are presynaptic nerve terminal

  • all of the above

Explicación

Pregunta 25 de 40

1

Which of the following statement(s) is false?

Selecciona una de las siguientes respuestas posibles:

  • action potential starts at the initial segment of the axon

  • oligodendrocytes are found within the brain.

  • Na -K pump exists on the myelinated part of a nerve

  • a single oligodendrocyte can myelinate multiple segments of axon membrane

  • re-creation of electrical signal across synapses is called transmission

Explicación

Pregunta 26 de 40

1

Which of the following is True?

Selecciona una de las siguientes respuestas posibles:

  • all-or-none law applies to action potential from a single neuron

  • the ion channels in the synaptic area of all chemical synapses are G-protein dependent

  • Conduction velocity in myelinated axons depends on whether the nerve is sensory or motor

  • Phagocytosis is an endocytosis whereas pinocytosis is an exocytosis

  • Intracellular fluid has more Na+ and less K+ than extracellular fluid

Explicación

Pregunta 27 de 40

1

The membranes that most commonly form synapses are the _____and the _____.

Selecciona una de las siguientes respuestas posibles:

  • axon terminals--dendrites

  • soma--glial

  • dendrites--soma

  • axon terminals--soma

  • choices A and D are correct.

Explicación

Pregunta 28 de 40

1

Which of the following is true regarding axoplasmic transport?

Selecciona una de las siguientes respuestas posibles:

  • The kinesin molecule is involved in retrograde transport.

  • Retrograde transport involves moving substances from the soma to the axon

  • The kinesin molecule is involved in anterograde transport

  • The dynein molecule is involved in anterograde transport.

Explicación

Pregunta 29 de 40

1

Which of the following is/are true of oligodendrocytes and Schwann cells?

Selecciona una de las siguientes respuestas posibles:

  • Schwann cells provide myelin for peripheral nerve cells.

  • A single Schwann cell wraps a single segment of a peripheral nerve cell.

  • A single oligodendrocyte can myelinate up to 50 segments of axon membrane.

  • Oligodendrocytes are found within the brain.

  • All of the above are correct.

Explicación

Pregunta 30 de 40

1

The force that moves sodium ions out of the axon is

Selecciona una de las siguientes respuestas posibles:

  • retrograde transport.

  • electrostatic pressure.

  • the sodium-potassium transporter.

  • diffusion.

  • antidromic flow

Explicación

Pregunta 31 de 40

1

Choose the correct ion channel action with the resulting effect:

Selecciona una de las siguientes respuestas posibles:

  • entry of a positive ion--hyperpolarization

  • entry of a negative ion--hyperpolarization

  • exit of a negative ion--hyperpolarization

  • exit of a positive ion--depolarization

  • choices B and D are correct.

Explicación

Pregunta 32 de 40

1

The “all-or-none law” refers to the observation that an action potential (AP):

Selecciona una de las siguientes respuestas posibles:

  • will diminish to near zero when transmitted down a long axon.

  • is conducted more rapidly down the axon as it reaches the axon terminal.

  • is produced whenever the membrane potential reaches threshold.

  • when triggered, the amplitude of AP is the same rate regardless of the inputs to the neuron.

  • travels only in one direction

Explicación

Pregunta 33 de 40

1

The essential event for the release of neurotransmitter from the presynaptic membrane is

Selecciona una de las siguientes respuestas posibles:

  • the hyperpolarization of the axon membrane.

  • the activation of the sodium-potassium pumps.

  • the influx of calcium ions into the axon terminal.

  • the opening of channels within the microtubules.

  • the arrival of an EPSF at the axon terminal.

Explicación

Pregunta 34 de 40

1

In which portion of a neuron would you expect to find the largest number of small vesicles?

Selecciona una de las siguientes respuestas posibles:

  • the active (release) zone

  • just before the axon hillock

  • the soma

  • the dendritic spines

  • beneath the postsynaptic membrane

Explicación

Pregunta 35 de 40

1

Choose the correct statement about receptors:

Selecciona una de las siguientes respuestas posibles:

  • ionotropic--more time required to open an ion channel

  • metabotropic--direct opening of an ion channel

  • metabotropic--rapid short-lived effects on ion channels

  • ionotropic--direct opening of an attached ion channel

Explicación

Pregunta 36 de 40

1

Which of the following will “neutralize” an EPSP?

Selecciona una de las siguientes respuestas posibles:

  • opening a chloride channel

  • allowing intracellular anions to leave the cell

  • closing a potassium channel

  • further opening a sodium channel

  • choices B and D are correct.

Explicación

Pregunta 37 de 40

1

The process, which blocks the postsynaptic potentials (EPSP and IPSP) induced by most neurotransmitters is:

Selecciona una de las siguientes respuestas posibles:

  • inhibition of the postsynaptic receptor.

  • facilitation of transmitter release.

  • enzymatic degradation of the transmitter molecule.

  • inhibition of axonal transport.

  • reuptake of the molecule into the axon terminal.

Explicación

Pregunta 38 de 40

1

The absolute refractory period of a neuron

Selecciona una de las siguientes respuestas posibles:

  • is due to the high negative polarity of the inside neuron.

  • occurs only during the repolarization phase.

  • occurs only during the depolarization phase.

  • occurs during depolarization and the first part of repolarization phase.

Explicación

Pregunta 39 de 40

1

The summation of EPSPs from numerous presynaptic nerve fibers converging at the exact same time onto one postsynaptic neuron called

Selecciona una de las siguientes respuestas posibles:

  • spatial summation.

  • long-term potentiation.

  • temporal summation.

  • synaptic plasticity.

Explicación

Pregunta 40 de 40

1

Which of the following is true of the action potential?

Selecciona una de las siguientes respuestas posibles:

  • During the action potential, the interior becomes even more negative.

  • The potassium channels are opened at a lower voltage than are sodium channels.

  • The sodium channels are opened at a lower voltage than are potassium channels.

  • The action potential requires 5 msec for completion.

  • The overshoot is due to a prolonged change in sodium conductance.

Explicación

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