Saltatory conduction is a term applied to
A the appearance of jumping from one node of Ranvier to the next in a myeinated neuron
B conduction of impulses across synaptic cletts
C the appearance of jumping from one neuron to an adjacent neuron
D the rapid movement of an action potential song an unmyelinated axon
E an action potential that skips the con hilock when it moves from the dendriti region to the conterminal
The correct answer and explanation is :
The correct answer is:
A. The appearance of jumping from one node of Ranvier to the next in a myelinated neuron
Explanation:
Saltatory conduction is a process in which electrical impulses in myelinated neurons appear to “jump” from one node of Ranvier to the next rather than propagating continuously along the entire length of the axon. This unique method of impulse transmission significantly increases the speed and efficiency of neuronal communication.
Key Aspects of Saltatory Conduction:
- Role of Myelin Sheath
Myelinated axons have insulating layers of myelin, produced by Schwann cells (in the peripheral nervous system) or oligodendrocytes (in the central nervous system). Myelin prevents ion leakage and reduces the capacitance of the axonal membrane, which helps in faster signal transmission. - Nodes of Ranvier
These are small gaps between myelin sheaths where the axonal membrane is exposed. These nodes are rich in voltage-gated sodium (Na⁺) and potassium (K⁺) channels, which are essential for regenerating the action potential. - Jumping Conduction
Instead of depolarizing the entire axon, the action potential “leaps” from one node of Ranvier to the next, significantly increasing conduction velocity compared to unmyelinated axons. This process conserves energy since fewer ions need to be actively pumped back to restore resting potential. - Speed Advantage
In myelinated axons, saltatory conduction allows action potentials to travel at speeds up to 120 m/s, whereas conduction in unmyelinated axons is much slower (around 1 m/s). This speed is crucial for reflex actions and rapid responses.
Why Other Options Are Incorrect:
- B. Conduction of impulses across synaptic clefts → This describes synaptic transmission, not saltatory conduction.
- C. Jumping from one neuron to another → Action potentials do not jump between neurons; they transmit via synapses.
- D. Rapid movement in an unmyelinated axon → Unmyelinated axons use continuous conduction, which is much slower.
- E. Skipping the axon hillock → Action potentials always originate from the axon hillock, so they do not skip this region.
Conclusion:
Saltatory conduction is essential for rapid and efficient nerve impulse transmission in vertebrates. It enables fast reflexes, improves neural communication, and enhances overall cognitive and motor functions.