Part 1: The Action Potential

• excitatory signal

Increases possibility of a neuron to fire an AP

(-) inhibitory

Decreases the potential for a cell to fire an AP

Electrical potential

Store of energy produced by a greater (-) charge on the intracellular side relative to the extracellular side

Where do signals build up to determine an AP?

Axon hillock

Resting potential

Electrical charge across the cell membrane in absence of stimulation

When cell is resting, the inside of the cell is more (-) ~70 mV

• this difference gives the cell electrical potential

Graded potentials

Small voltage fluctuations across the cell membrane restricted to the vicinity of the axon where ion concentration changes

NA can’t move freely

*can change very small voltage inside cell, brief, lasting milliseconds

Hyperpolarization

Increase in electrical charge across a membrane, inside the cell becomes more negative

Depolarization

Decrease in electrical charge making inside more positive

Action potential

If enough excitatory signals come in & depolarize the cell (meeting the threshold) then gated Na+ channels open allowing Na to come through, then the cell will fire an AP

It is brief and there can be multiple

an AP is all of none

During an AP what is there an inflow of and what is there an outflow of?

Inflow of Na, outflow of K

Relative refractory period

Hyper polarized axon is in state needing an increase in excitatory signals