Question

Myelin wraps and insulates axons, thus decreasing the time constant. What does the time constant indicate?

1) How quickly a cell membrane depolarizes in response to an inward current
2) The amount of charge stored by the membrane
3) The charge leakage through the membrane
4) The resistance of the axon segments between nodes of Ranvier

Answer 1

The time constant indicates how quickly a cell membrane depolarizes in response to an inward current. Myelin decreases the time constant, allowing for faster depolarization and conduction of action potentials along the axon.

Step-by-step explanation:

The time constant indicates how quickly a cell membrane depolarizes in response to an inward current. This means it measures the rate at which the membrane changes its electrical charge when a current passes through it.

By wrapping and insulating axons, myelin decreases the time constant, allowing for faster depolarization and hence faster conduction of action potentials along the axon.

For example, when myelin is present, the action potential jumps from one node of Ranvier to the next, rather than propagating smoothly along the entire membrane. This saltatory conduction speeds up the transmission of the action potential.