Question

“Jumping of the action potential” at the nodes of Ranvier is known as
A. Saltatory conduction
B. Neurotransmission
C. Recovery phase
D. Active phase

Answer 1

Hint: The vertebrates have developed a special mechanism with time for the quick conduction of nerve impulse. Myelinated nerve fibres help them to carry impulse 20 times faster than the ones that are non-myelinated.

Complete answer:
Myelin sheath which acts as a highly insulated covering which further prevents the flow of ions. This insulated myelin sheath is absent at Nodes of Ranvier. At these nodes of Ranvier, voltage gated channels are present in high numbers. Since the action potential jumps from one node to the other, this mode of transmission which is rapid due to myelinated fibres is known as saltatory conduction of the nerve impulse. Myelinated nerve fibres require very less amount of energy as only the nodes get polarised and very few ions are therefore required to be pumped back to the normal position which is an active transport mechanism as energy is used up. When we talk about non-myelinated nerve fibres here the same ionic flow and the depolarisation occurs and is repeated for several times along the length of the fibre. Henceforth, impulse conduction in case of such fibre is very slow.

Hence the correct answer is option A.

Additional information: In man, the impulse travels with speed of about 121 metres per second.

Note:
In myelinated nerve fibres, extracellular fluid is in contact with axon only at the nodes. These nerve fibres are present in the white matter of the brain along with spinal cord , cranial nerves and spinal nerves.