Sophia Bammler BIO 201 Assignment 10 Digital Artifact

Created by Sophia Bammler

What is the resting membrane potential?

Resting membrane potential (aka RMP) is the “resting” voltage of a neuron that is mediated by ion leakage (K+ leak channels) and ion pumping (Na+/K+ ATPase). Resting potential = -70 mV.

What is threshold potential?

Threshold potential is the voltage required to trigger an action potential. Threshold potential = -55 mV.

How is an action potential initiated?

In order for an action potential to be initiated, a stimulus must open a ligand- or mechanically-gated Na+ or Ca+ channel, causing depolarization of the membrane to threshold (-55 mV).

What causes cell depolarization?

Cell depolarization is caused by the opening of voltage-gated sodium/Na+ channels, followed by a rapid influx of Na+ causing the membrane potential to rise/move toward zero. Once Na+ has entered the cell, membrane potential rises to ~ +30 mV.

What causes cell repolarization?

Cell repolarization is caused by the inactivation of sodium/Na+ channels and the opening of voltage-gated potassium/K+ channels, leading to K+ moving out of the cell.

What causes cell hyperpolarization?

Cell hyperpolarization is caused by potassium/K+ channels closing slowly, causing excess K+ to leave the cell. This results in a more negative (~ -90 mV) membrane potential.

What is the “all-or-none” principle?

The all-or-none principle states that if membrane potential reaches threshold, an action potential occurs, and if it does not than no action potential occurs.

What is the absolute refractory period?

During the absolute refractory period, another action potential cannot begin, regardless of the strength of the stimulus. This is because Na+ channels are inactivated at this point.

What is the relative refractory period?

During the relative refractory period, another action potential can begin ONLY IF a stimulus stronger than the one that initiated the current action potential occurs. This is because K+ channels are still open at this point.

What is continuous conduction?

Continuous conduction refers to the propagation of an action potential down an unmyelinated axon. Continuous conduction is slower (than saltatory conduction) because time is required for voltage-gated Na+ channels to open and close. Therefore, the electrical signal must be regenerated at each channel for the entire length of the nerve fiber.

What is saltatory conduction?

Saltatory conduction refers to the propagation of an action potential down a myelinated axon. Saltatory conduction is faster (than continuous conduction) because myelin sheath provides insulation, enabling the action potential to “jump” from one node to the next.

What is the value of resting membrane potential?

-70 mV

What is the value of threshold?

-55 mV

What is the value associated with the “peak” of an action potential?

+30 mV