electrical stuff

neurophysiology

examining electrical/chemical signaling processes

electrical signals

info conveyed in neuron

chemical signal

info conveyed between neuron

action potential

rapid electrical depolarization down axon

axon hillock

cell body where AP initiates

process of AP

ap arrives to axon terminal/bouton, released neurotransmitter vesicles across synapse

electrical gradient (called resting potential)

in membrane of neuron, which is difference between in/out of cell (sum of all EP’s)

what does RP do

allows neuron to make dynamic response

what does plasma membrane do for RP

allows uncharged chemicals NOT IONS (only protein channels) to pass

equilibrium potential (EP)

concentration gradient and electrical gradient are balanced

why k+ a major determinant

only ion freely permeable, gradient pushes k+ out, electrostatic (-) pulls in until E

voltage

measure of stored PE

current

measure of the rate of flow

permeability of player in RP

k+ permeable, Na+ impermeable, Cl- pp, Ca++ pp

4 factors that determine RP

selective membrane to K+, concentration gradient for K+, electrical gradient, sodium potassium pump (3NA o 2K i)

hyperpolarization

more neg (-70mV)

depolarization

more positive (-50mV)

excitation threshold

levels which stimulation produces massive depolarization (AP)

what happens to stim of neruon past threshold

triggers AP (nerve impuse)

voltage sensitive ion channels

protein forming channels whose permiabilty depends on voltage

v-sens Na channels

open rapidly at depolarization potential (-40mV), induce AP

v-sens K channels

open slowly, repolarize membrane

afterpolarization

v-sens k channels stay open longer, membrane becomes more neg than RP

refractory period

time during where neuron resists the production of another AP

absolute refractory period

membrane cant producse AP cause v-sense Na channels are open

relative refractory period

stronger stim is required cause v-sens Na channels are recovering and v-sens k channels are open

all or none law

states amplitude/velocity of AP are independent of intensity of stimulus that initiated it

two factors of faster velocity

large diameter and myelination (produces saltatory conduction)

nodes of ranvier

myelin sheath of axons are interrupted by unmyelinated sections

saltatory conduction

‘jumpin’ action of AP from nodes

multiple sclerosis

autoimmune attack on cns myelin

why is saltatory conduction faster

Myelin insulates axon, more energy efficient, passive spreadis faster

local neuros/interneurons

short axon, exchange info w/ neighbors