Graded Potentials Vs. Action Potential

- Dendrites & Cell Body
- Chemically Gated Channels
- Various input signals on dendrites or cell body
- Graded; incremental with distance but able to integrate signals

- Axon Hillock & Axon Length
- Voltage Gated Na+ and K+ Channels
- Local depolarization by gated channels in dendrite (i.e. graded potential
- All-or-None response once its voltage surpasses threshold

- action potential; voltage; neuron

If a cell reaches threshold a full action potential will occur.

The threshold, maximum voltage, and resting potential do not change.

Conduction is non-decremental (you get a perfect action potential along the whole membrane).

“Information” is frequency, not size of AP (signal depends on how fast a stimulus reaches CNS not the strength of the AP).

The influx of positive ions (Na+) at a specific point causes some positive ions to travel slightly down the axon. This causes a depolarization further down the cell which triggers another action potential.

The voltage-gated Na+ channels enter a temporary refactory period which prevents backwards depolarization.

Larger axons experience less resistance in conducting an action potential down its length.
Glia cells make up the myelin sheath which acts as an insulator. They increase the distance of electrotonic spread in the same amount of time because an action potential and be pushed further down the cell.

Oligodendrocytes in the CNS
Schwann cells in the PNS

First generated at the axon hillock and then at the nodes of Ranvier which are gaps in the myelin sheath. This is the only place where voltage gated Na+ channels are present.

The jumping between nodes of Ranvier is a termed salutatory conduction.