Question

Explain how an action potential is propagated down an axon in continuous conduction. Why is saltatory conduction faster than continuous conduction?

Accepted Answer

Understand that an action potential is a rapid change in membrane potential that travels along the axon of a neuron. Continuous conduction occurs in unmyelinated axons, where the action potential is propagated step-by-step along the entire length of the axon. In continuous conduction, the action potential begins at the axon hillock. Sodium (Na⁺) channels open in response to a stimulus, allowing Na⁺ ions to enter the neuron, causing depolarization. This depolarization triggers adjacent voltage-gated Na⁺ channels to open, propagating the action potential down the axon. As the action potential moves, the previously depolarized region undergoes repolarization. Voltage-gated potassium (K⁺) channels open, allowing K⁺ ions to exit the neuron, restoring the resting membrane potential. This ensures the action potential moves in one direction. Saltatory conduction, in contrast, occurs in myelinated axons. The myelin sheath insulates the axon, preventing ion exchange along the myelinated segments. Action potentials 'jump' between the nodes of Ranvier, which are gaps in the myelin sheath where voltage-gated Na⁺ and K⁺ channels are concentrated. Saltatory conduction is faster than continuous conduction because the action potential only needs to be regenerated at the nodes of Ranvier, rather than along the entire axon. This reduces the time and energy required for ion exchange and propagation, making the process more efficient.

Explain how an action potential is propagated down an axon in continuous conduction. Why is saltatory conduction faster than continuous conduction?

비슷한 문제에 대한 검증된 영상 답변:

주요 개념

Action Potential

Continuous Conduction

Saltatory Conduction