Neuronal Physiology

Nervous, fast and short term. Endocrine, moderate and long or short term.

Nerve and muscle
Undergo rapid changes in membrane potentials.
An electrical signal is generated

Polarization - Any state other than 0 mV.
Resting membrane potential - Vrest is negative (-70).
Depolarization - Becoming less negative, closer to zero. Opening of Na+ channels. (-70 to -30). Flow of positive ions into ICF.
Repolarization - Back to Vrest. Closure of Na+ and opening of K+ channels.
Hyperpolarization - More negative than its resting potential. K+ channels remain open after the potential reaches the resting level. (-70 to -90). A flow of positive ions out of ICF.

Potassium (K+).

- Local change
- Strength depends on the size of stimuli
- Local ion channels open
- Greater stimuli open more channels
- Gated Na+ channels opening lead to depolarization
- Loss of charge away from the stimulus.

- An all or nothing change, same potential or magnitude everytime.
- Not local, long distance signals.
- Graded potentials initiate action potentials
- An action potential is a rapid depolarization followed by a repolarization to the membrane potential.
- Occurs at small portion of membrane.

Depolarize or Hyperpolarize. -20mv above Vrest, which is -50mv.

Reverses the polarity of the cell and increases positive charges exponentially, +30mv.
Repolarization will often overshoot Vrest.

Resting membrane potential, leaky channels and Na+/K+ pump. -70mV.

- Depolarization, drip feeds Na+ ions into cell.
- Ligand gated Na+ ion channels and VLTG gated Na+ ion channels triggered but only ligand opens
- Na+ moves into cell along the gradient.

Upshoot, "flood gates" open and Na+ rapidly floods into the cell. Vltg gated Na+ channels open.

Peak, vltg gated Na+ channels close.

Downshoot, K+ ion channels open and repolarize the cell
- K+ ions escape the ICF/cell and increase negativity

Hyperpolarization, Overshoots and K+ channels close.