Question

Why can't the action potential travel across the myelinated sheaths? How does the action potential travel along the axon? What facilitates the conduction between nodes? Myelination increases the RATE of conduction but how does it conserve energy?

Answer 1

The myelin sheath acts as an insulator, preventing current leakage and enabling the action potential to travel faster along the axon via saltatory conduction. Energy is conserved because ion channels are only needed at the nodes of Ranvier, not along the entire axon.

Step-by-step explanation:

The action potential cannot travel across the myelinated sheaths because myelin acts as an insulator, preventing current from leaking out of the axon. Instead, action potentials are regenerated at the nodes of Ranvier, which are small gaps in the myelin sheath that contain voltage-gated Na+ and K+ channels. The process of the action potential jumping from one node to the next is known as saltatory conduction.

Myelination increases the rate of conduction by enabling the electrical signal to travel quickly over the myelinated regions without losing strength. Energy is conserved because voltage-gated ion channels, which require energy to open and close, only need to be present and active at the nodes, rather than throughout the entire length of the axon. Thus, myelination allows for faster conduction with less energy expenditure compared to unmyelinated axons.