Nervous System part 3: nerve impulses

nerve impulse

weak electric current, like a wave

membrane potential

difference in electrical charge between the outside and inside of a neuron

potential

stored energy

resting membrane potential (RMP)

polarized membrane, outside is slightly positive, inside is slightly negative, -70mV difference from inside to outside of cell

Resting membrane potential (RMP) is maintained by

an imbalance in ions

Na+/K+ pump

evenly pumps 3 Na out and 2 K in, keeps inside negative

K+ leak channels

allow K+ to drift out, makes inside negative

negative charge inside

proteins trapped in the cell are negative, volage gated ion channels are closed

hyperpolarized

membrane potential becomes more negative than -70mV

depolarized

membrane potential becomes less negative than -70mV

repolarized

membrane potential becomes more negative as it returns to RMP

polarization is

graded or proportional, greater stimulation = greater depolarization

if the depolarization is large enough it will reach

threshold potential (-55mV), a nerve impulse begins, starting action poetential

refractory period

ensures that action potential moves in one direction