Graded Potential VS. Action Potentials

Changes in the membrane potential that cannot spread far from the site of stimulus.

Graded potential

Any stimulus that opens a channel creates a ...

Graded potential

The degree of depolarization decreases with distance away from the depolarization site.

Graded potential

Tend to fizzle out

Graded potential

Sodium ions only partly depolarize cells

Graded potential

All stimulus enters neuron at one place then diffuses, in order for a neuron to send a message, the axon hillock must reach a thresh-hold voltage.

Graded potential

Can trigger exocytosis and glandular secretion.

Graded potential

Also known as nerve impulses

Action poential

Has an all or none principle

Action potential

Contains refractory periods

Action potential

Depolarizing or hyperpolarizing

Graded potential

Always depolarizing

Action potential

No thresh-hold value

Graded potential

Depolarization to threshold must occur before action potential begins

Action potential

Amount of depolarization of hyperpolarization depends on the stimulus

Graded potential

All-or-none; all stimuli that exceed threshold produce identical potentials.

Action potential

Passive spread from site of stimulation

Graded potential

Potential at one site depolarizes adjacent sites to threshold.

Action potential

Effect on membrane potential decreases with distance from stimulation site

Graded potential

Propagated along entire membrane surface without decrease in strength.

Action potential

No refractory period

Graded potential

Refractory period occurs

Action potential

Occur in most plasma membranes

Graded potential

Occur only in excitable membranes of specialized cells such as neurons and muscle cells

Action potential