Nerve Tissue: Structure, Function, and Transport

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Questions and Answers

The supporting cells that form myelin sheaths in the peripheral nervous system are:

Oligodendrocytes.
Schwann cells. (correct)
Microglia.
Astrocytes.

The trigger zone where neurons generate action potentials:

Initial segment. (correct)
Node of Ranvier.
Dendritic zone.
Terminal buttons.

Which part of the neuron where the action potential is initiated, a part that receives input from other neurons, and a part that conducts the action potential?

Cell membrane, soma, dendrite.
Axon hillock, soma, myelin sheath.
Soma, dendrite, axon.
Initial segment, dendrite, axon. (correct)

Which of the following is NOT correctly paired?

Conduction from cell body to axon: Antidromic conduction. (B) Signup and view all the answers

Axoplasmic flow is a cellular process responsible for movement of proteins and polypeptides within a neuron. Which of the following statements correctly describes a property of orthograde or retrograde axonal transport?

Some viruses use retrograde transport to move from the nerve terminal to the soma. (D) Signup and view all the answers

The electrical potential difference necessary for a single ion to be at equilibrium across a membrane is best described by the:

Nernst equation. (A) Signup and view all the answers

Suppose that gated ion channels for Na+ or Ca2+ opened in the plasma membrane of a muscle cell. The membrane potential of that cell would:

All of these. (B) Signup and view all the answers

Based upon the typical distribution of ions across a cell membrane, which of the following values best represents the appropriate resting membrane potential?

-70 mV (D) Signup and view all the answers

Resting membrane potential (RMP) of a nerve fiber:

Is due to the presence of negative charges on the inner surface in relation to its outer surface. (B) Signup and view all the answers

As regard resting membrane potential (RMP), all the following statements are incorrect EXCEPT:

It is the potential difference across the fiber membrane with negatively charged ions inside and a positively charged ions outside. (A) Signup and view all the answers

Which of the following most likely forms the resting membrane potential of the cell?

High potassium conductance and some sodium conductance. (C) Signup and view all the answers

The resting potential of a nerve membrane is primarily dependent on the concentration gradient of which of the following ions?

Potassium. (C) Signup and view all the answers

The most important diffusible ion in the establishment of the membrane potential is:

K+. (A) Signup and view all the answers

The resting membrane potential results when the tendency for.............to diffuse out of the cell is balanced by its attraction to opposite charges inside the cell.

K+ Signup and view all the answers

Concerning RMP of a cell, which of the following is CORRECT?

All of the above are true. (D) Signup and view all the answers

Which of the following is actively transported out of the neurons?

Na+. (C) Signup and view all the answers

About Na+-K+ pump, all the following is correct EXCEPT:

Is explained by facilitated diffusion. (B) Signup and view all the answers

The sodium-potassium pump transport:

Three sodium ions out of the cell & two potassium into the cell. (D) Signup and view all the answers

Na+-K+ pump:

Couples Nat and K+ with ratio 3:2. (A) Signup and view all the answers

The sodium pump of an excitable membrane:

Pumps sodium ions to the outside in the resting state. (D) Signup and view all the answers

Inactivation of the sodium-potassium pump will cause:

An increase in the intracellular volume. (D) Signup and view all the answers

The resting cell membrane is more permeable to ___ than to _. Although ___ contribute little to the resting membrane potential, they play a key role in generating electrical signals in excitable tissues.

K+, Na+, Na+ Signup and view all the answers

The equilibrium potential for potassium, as determined by the Nernst equation, differs from the resting potential of the neuron. Which of the following best accounts for this difference?

An active sodium-potassium pump makes an important contribution to the regulation of the resting potential. (A) Signup and view all the answers

If the resting membrane potential (RMP) of a nerve cell falls (becomes less negative), there is a net:

Gain of Na+ ions into the cell. (A) Signup and view all the answers

If the permeability of the plasma membrane to K+ increases, the resting membrane potential difference _. This is called _.

Increases, hyperpolarization Signup and view all the answers

The resting membrane potential is characterized by which of the following?

Passive fluxes of Nat and K+ are balanced by an active pump that derives energy from enzymatic hydrolysis of ATP. (D) Signup and view all the answers

Leak ion channels:

Are responsible for the ion permeability of the resting plasma membrane. (A) Signup and view all the answers

Any shift from resting membrane potential toward a more positive value is called:

Depolarization. (A) Signup and view all the answers

Which of the following statements is true regarding plasma membrane Na⁺ and K+ leak channels?

K+ passively moves through leak channels to exit cell. (C) Signup and view all the answers

Which of the following best describes the status of voltage-gated sodium channels at the resting membrane potential?

Activation gates are closed and inactivation gates are open. (B) Signup and view all the answers

Which of the following statements best characterizes a basic function of voltage gated sodium channels?

They open rapidly following depolarization of the membrane. (A) Signup and view all the answers

The first step in nerve impulse initiation is:

Membrane depolarization. (A) Signup and view all the answers

The membrane potential will depolarize by the greatest amount if the membrane permeability increases for:

Sodium. (C) Signup and view all the answers

The ascending limb of spike of nerve fiber action potential is caused by:

Rapid sodium influx. (A) Signup and view all the answers

During action potential, the rapid depolarization of the membrane is due to:

Increased sodium permeability. (A) Signup and view all the answers

During the upstroke of the nerve action potential:

There is net inward current and the cell interior becomes less negative. (C) Signup and view all the answers

Which of the following is primarily responsible for the rising phase of the action potential?

Voltage-gated sodium channel. (D) Signup and view all the answers

When a nerve fiber is stimulated, depolarization phase stops at +30 mV. This is because:

The inactivation gates rapidly close to prevent further entry of Nat ions. (D) Signup and view all the answers

The action potential of nerve:

Is terminated by K+ efflux. (D) Signup and view all the answers

After the occurrence of an action potential, there is a repolarization of the membrane. Which of the following is the principal explanation for this event?

Potassium channels have been opened. (D) Signup and view all the answers

Which of the following ionic changes is CORRECTLY matched with a component of the action potential?

Opening of voltage-gated Nat channels: Depolarization. (C) Signup and view all the answers

Preventing the inactivation of the sodium channels will decrease:

The downstroke velocity of nerve cell action potentials. (C) Signup and view all the answers

What would be the result of removing the inactivation gate from the Nat channels of a nerve axon?

The rate of repolarization during the action potential would be slowed. (B) Signup and view all the answers

In excitable cells, repolarization is most closely associated with which of the following events:

K⁺efflux. (C) Signup and view all the answers

The after-hyperpolarization phase of the action potential is due to:

Slow return of the K+ channels to the closed state. (C) Signup and view all the answers

The membrane potential becomes more negative during:

After hyperpolarization. (A) Signup and view all the answers

Tetrodotoxin blocks nerve impulse transmission by:

Blocking Nat channels. (C) Signup and view all the answers

Flashcards

Myelin Sheaths

Myelin sheaths in the peripheral nervous system are formed by Schwann cells, which insulate axons to enhance signal transmission.

Trigger Zone

The trigger zone of a neuron is the area where action potentials are generated, primarily located in the initial segment of the axon.

Resting Membrane Potential (RMP)

The resting membrane potential is the electrical charge difference across a neuron's membrane at rest, typically around -70 mV.

Equilibrium Potential

Equilibrium potential is the membrane voltage at which a particular ion is at equilibrium, meaning no net movement across the membrane.