Question

Compare and contrast the voltage-gated sodium and potassium channels introduced in Chapter 8, with the acetylcholine receptor/channel. What may be confusing to the beginning physiology student trying to understand the ion specificity of the acetylcholine receptor? What type of change in the cell is produced by ion movement through each type of channel?

Answer 1

Voltage-gated sodium channels and potassium channels are specific for Na+ and K+ ions and open in response to changes in membrane potential, whereas acetylcholine receptor/channels are ligand-gated and less specific, allowing multiple types of cations to pass through when acetylcholine binds to the receptor.

Step-by-step explanation:

Comparison of Ion Channels

Comparing and contrasting the voltage-gated sodium channels and potassium channels with the acetylcholine receptor/channel illustrates key aspects of their function and ion specificity. Voltage-gated sodium channels open in response to electrical stimulation, allowing Na+ ions to rush into the cell and initiate an action potential by depolarizing the cell membrane. These channels have two gates—an activation gate that opens with a sufficient change in membrane potential and an inactivation gate that closes after a certain time. In contrast, potassium channels open when the membrane potential is high enough, allowing K+ ions to exit the cell and restore the resting potential through repolarization.

The acetylcholine receptor/channel is a type of ligand-gated ion channel that opens when acetylcholine binds to it, permitting the passage of cations, such as Na+, Ca2+, and K+. This can be confusing for beginners as it does not discriminate among these cations as selectively as the voltage-gated channels do for their respective ions. Ion movement through the acetylcholine receptor can lead to depolarization and, if the threshold is reached, can generate an action potential leading to muscle contraction or neuronal excitation.