Question

The fixed pattern of changes in membrane potential during an action potential is coordinated by the sequential opening and closing of voltage-gated ion channels. Can you identify the status (open/closed) of the voltage-gated Na and K channels during each phase of an action potential?

Answer 1

Na-K channels

Explanation:

• Brief sequential change in the membrane potential of excitable cells after stimulus is called action potential whereas membrane potential represent charge difference across the membrane
• In a typical neuron cell, membrane potential of cytoplasm is negative at rest and hence called resting membrane potential
• Resting membrane potential of excitable cells is established by Na+ K+ pump and maintained by K+ leaky channels at rest
• Phases of action potential includes: depolarization, repolarization, hyperpolarization and resting membrane potential
• Depolarization starts when a threshold stimulus is applied on a neuron when via Na+ mechanically operated channels that trigger action potential
• Depolarization of membrane potential is due to influx of Na+ via voltage gated Na+ channels
• Repolarization starts with the efflux of K+ by the opening of voltage gated K+ channels, voltage gated K+ channels starts to open when voltage gated Na+ channels becomes inactive
• Hyperpolarization occurs due to excessive efflux of K+ by voltage gated K+ channels
• Additional efflux of K+ occurs due to slow inactivation of voltage gated K+ channel