Question

During a neurobiology lecture, a professor repeatedly refers to saltatory conduction, absolute refractory period and nodes of Ranvier. Define these terms.

Answer 1

Nodes of Ranvier

Nodes of Ranvier are the microscopic periodic myelin sheath gaps present along the myelinated axon which facilitate the rapid conduction of nerve impulse.

The myelin sheath electrically insulate the neuron except at the Nodes of Ranvier. So voltage gated sodium channels are found only at the Nodes of Ranvier, and depolerization of membrane can occur only at the Node of Ranvier. Thus action potential jumping from one Node of Ranvier to another.

Saltatory conduction

It is the propagation of nerve's action potential along the myelinated axons from one Node of Ranvier to the next by skipping the myelin sheath, increasing the conduction velocity of impulse.

Absolute refractory period

It is a time interval during which another stimulus given to the neuron will not initiate a second action potential, no matter how large is the applied stimulus.