×

Action potentials - electrical characteristics and generation

6526

0

HWC

• An action potential is the nervous impulse or signal for long distance communication. Each action potential is generated at the cell's trigger zone. • Action potentials are considered an all-or-nothing phenomena because they are either generated or not. • The generation of an action potential is dependent on the strength of its stimulus -graded potentials. • Generating and conducting an action potential requires both Na+ and K+ voltage gated channels. • An action potential is a sequence of electrical events that briefly reverses the charge of the membrane and then restores the resting membrane potential. • At rest, the voltage gated K+ and Na• channels are closed. • The Na+ channels must be opened for an action potential to be generated. • Na+ channels have both activation and inactivation gates. • The generation of an action potential is dependent on the strength of its stimulus -graded potentials. • if the graded potential is a hyperpolarization then the voltage activated Na+ channel gates will remain closed. • A graded potential that is a weak depolarization, or sub-threshold (below -55 mV), will also result in the gates remaining closed. • Strong depolarization, above threshold (above -55 mV), will cause the Na+ gates to open and generate an action potential. • Once the activation gates are open the inflow of Na+ causes further depolarization of the membrane until its voltage is completely reversed. • Action potentials are considered an all-or-nothing phenomena because they are either generated or not. • The reversal of the membrane charge opens the voltage gated K+ channels and closes the Na+ gates. • This process begins to repolarize the membrane potential. • Repolarization continues and the IC gates remain open until the resting membrane potential is nearly restored. • Redistribution of Na+ and K+ ions by the Na+/K+ pump finishes repolarization. • During the depolarizing and repolarizing of an action potential the membrane is unable to undergo a second action potential. This is known as the refractory period.

Share

Embed

Copy and paste this code into your website or blog.

Add To

You must login to add videos to your playlists.

Comments

0 Comments total

to post comments.

No comments have been posted for this video yet.