Nerve Impulse

Na being pumped out. Thus, both a concentration and an electrical gradient wants to push sodium inside.

Difference in electrical charge bet inside and outside of cell - Polarization. At rest is called resting potential. -70mV.

When emmbrane is depolarized, sodium and potassium channels in the membrane open. Sodium rushes in, due to concentration and electrical gradient. At the peak of the action potential, sodium channels close, potassium channels remain open. Potassium channels (in the beginning) make little difference, but now, potassium gets pumped outside the cell, as a result of concentration and electrical gradient.

Period that resists the production of further action potentials.

Sometimes an action potential back-propagates into the cell body/dendrites. Important for learning.

All-or-none: amplitude and velocity of action potential are independent of intensity of stiumulus (if threshold reached). Analogy: flushing a toilet.

Thus, in order to diff bet weak vs strong stimulus, action potential frequency increases.

So exchange info w neighbors, using a graded potential (a membrane potential that varies in maginitude in proportion to intensity of stimulus).

On the axon hillock.

Sodium ions enter a point in axon.

Depolarizes membrane, causes next to open its voltage-gated channels.

Positive ions get transferred from nodes of Ranvier. This allows the action potential to jump (saltatory conduction), allowing for fast conduction of impulses.