6. Local vs. Action Potentials

Neuron RMP?

About −70 mV

Two types of electrical change?

Local potentials and action potentials

Local potential?

Small, temporary change in one region of the membrane

Local potentials can be?

Depolarizing or hyperpolarizing

Graded?

Size varies with stimulus (duration, number/type of channels opened)

Reversible?

Neuron returns to RMP when stimulus stops

Decremental?

Shrinks as it spreads

short-distance signal only

Where do local potentials occur?

Dendrites and cell body

Action potential?

Uniform, rapid depolarization and repolarization

What triggers an AP?

Membrane potential reaches threshold

Where are APs generated?

Axons only, at the trigger zone (initial segment)

What does the all-or-none principle mean for an action potential?

Once threshold is reached the AP occurs and can’t be stopped; irreversible

Does a stronger stimulus make a bigger AP?

No; always the same size

Nondecremental?

Regenerated along axon; no loss of amplitude

Local vs. AP: size?

Local: varies (graded)

AP: always the same

Local vs. AP: distance?

Local: short

AP: entire axon

Local vs. AP: location?

Local: dendrites, cell body

AP: axon

Local vs. AP: reversibility?

Local: reversible

AP: irreversible, all-or-none