Chapter 3 MCQ from Lecture

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What best describes the 'all or nothing' principle of action potentials?

An action potential occurs only if a stimulus reaches a certain minimum intensity. (correct)

Action potentials vary in intensity depending on the strength of the stimulus.

All stimuli, regardless of strength, produce an action potential.

Action potentials can be stopped once initiated.

During an action potential, what causes rapid depolarization?

Closing of potassium channels

Opening of chloride channels

Rapid influx of sodium ions through voltage-gated channels (correct)

Efflux of calcium ions

What is the primary cause of repolarization during an action potential?

Influx of sodium ions

Efflux of potassium ions (correct)

Influx of chloride ions

Efflux of sodium ions

What is the significance of the absolute refractory period?

No new action potential can be initiated, regardless of stimulus strength. Signup and view all the answers

How do myelinated nerve fibers enhance conduction?

By facilitating saltatory conduction, increasing speed Signup and view all the answers

Which phase is characterized by increased permeability to potassium ions?

Repolarization phase Signup and view all the answers

What triggers the opening of voltage-gated sodium channels at the beginning of an action potential?

The reaching of a threshold level of depolarization Signup and view all the answers

What is the significance of the relative refractory period?

It is a phase where a stronger-than-normal stimulus is required to initiate an action potential. Signup and view all the answers

What is the role of myelin in the conduction of action potentials along nerve fibers?

It facilitates faster conduction through saltatory conduction. Signup and view all the answers

During an action potential, what is the primary cause of the initial rapid depolarization?

Inflow of sodium ions Signup and view all the answers

What results from the opening of voltage-gated potassium channels during an action potential?

Repolarization and eventual hyperpolarization Signup and view all the answers

During an action potential, what is the function of the sodium-potassium pump?

Re-establishing the resting membrane potential Signup and view all the answers

How does the absolute refractory period contribute to action potential directionality?

Prevents backward movement Signup and view all the answers

What effect does myelin have on nerve fiber capacitance and resistance?

Decreases capacitance, increases resistance Signup and view all the answers

Why is conduction faster in myelinated nerve fibers?

Saltatory conduction Signup and view all the answers

What causes hyperpolarization during the action potential?

Prolonged outflow of potassium ions Signup and view all the answers

How does the absolute refractory period affect action potential frequency?

Limits maximum frequency Signup and view all the answers

What is the role of voltage-gated sodium channels in action potentials?

Initiate depolarization Signup and view all the answers

What determines action potential propagation speed in a nerve fiber?

Nerve fiber diameter Signup and view all the answers

What is unique about action potential propagation in myelinated fibers?

Saltatory conduction Signup and view all the answers

What is the effect of the plateau phase in cardiac action potentials?

Prolongs action potential Signup and view all the answers

During depolarization, what change occurs in membrane permeability?

Increased permeability to sodium Signup and view all the answers

What characterizes the relative refractory period?

Stronger-than-normal stimulus required. Signup and view all the answers

How does axon diameter affect conduction velocity in non-myelinated fibers?

Larger diameter faster. Signup and view all the answers

What factor contributes to high conduction velocity in myelinated fibers?

Nodes of Ranvier and saltatory conduction. Signup and view all the answers

How does hyperosmotic damage in diabetes affect nerve conduction?

Damages Schwann cells, impairing conduction. Signup and view all the answers

What is the relation between axon diameter and conduction velocity in non-myelinated fibers?

Larger diameter faster. Signup and view all the answers

Why is conduction velocity increased in myelinated fibers?

Saltatory conduction at nodes. Signup and view all the answers

What is the effect of increasing stimulus intensity on action potential frequency?

Increases frequency. Signup and view all the answers

What role does the time constant play in action potential propagation?

Speed of membrane response to stimuli. Signup and view all the answers

What effect does the action potential have on sodium-potassium pump activity?

Increases the pump's activity. Signup and view all the answers

What causes the 'undershoot' phase after an action potential?

Delayed potassium channel closure. Signup and view all the answers

How does action potential frequency correlate with stimulus intensity?

Increases with intensity. Signup and view all the answers

What role does the time constant play in nerve signal transmission?

Speed of depolarization and propagation. Signup and view all the answers

What is the primary role of voltage-gated potassium channels during an action potential?

Re-establish resting potential. Signup and view all the answers