PhysiologyWeb Logo  Search

PhysiologyWeb Loading...

PhunnyPhysiology
Glossary of Physiology Terms – R
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Search






Refractory period
Definition:
See absolute refractory period and relative refractory period.

Related glossary terms/phrases:
Absolute refractory period
Relative refractory period

See also:
Neuronal Action Potential - Refractory Periods



Relative refractory period
Definition:
The relative refractory period refers to a period during the action potential. This is the time during which a stronger than normal stimulus is needed in order to elicit an action potential. The relative refractory period immediately follows the absolute refractory period.

Related glossary terms/phrases:
Absolute refractory period

See also:
Neuronal Action Potential - Refractory Periods



Repolarization
Definition:
Refers to the return of the membrane potential toward the normal resting value after a membrane depolarization.

Related glossary terms/phrases:
Depolarization
Hyperpolarization

See also:
Resting Membrane Potential - Introduction
Figure showing depolarization, repolarization, and hyperpolarization



Resting membrane potential
Definition:
The voltage difference across a cell plasma membrane in the resting or quiescent state. It is also simply referred to as the resting potential (Vrest). The value of the resting membrane potential varies from cell to cell. Depending on the cell type, it can range from −90 mV to −20 mV.

For example, Vrest is −90 mV in skeletal and cardiac muscle cells as well as in astrocytes. In a typical neuron, Vrest is approximately −70 mV. In many non-excitable cells, Vrest ranges from −60 to −50 mV. In photoreceptors, Vrest is about −20 mV.

See also:
Resting membrane potential



Retrograde
Definition:
Moving from the axon terminal back toward the neuronal cell body.

Related glossary terms/phrases:
Anterograde



Right atrioventricular valve
Definition:
The one-way valve between the right atrium and right ventricle of the heart. It is also known as the tricuspid valve.

The direction of blood flow through the right atrioventricular valve is from the right atrium to the right ventricle.

Related glossary terms/phrases:
Tricuspid valve









Posted: Tuesday, July 3, 2012
Last updated: Saturday, January 10, 2015