Neurophysiology: Graded Potentials

Chapter 11.4-.5

Neurophysiology

Neurons are excitable and irritable

stimulus=capable of altering RMP

If stimulus is strong enough, action potential is initiated

Resting Membrane Potential

Na+/K+ ATPase

More K+ leakage

Large anions inside

Membrane potential changes

Produced by changes in membrane permeability to ions

Membrane ion channels (leakage, chemically gated, voltage-gated, and mechanically-gated)

graded potentials and action potentials result

Graded Potentials

Short-lived, local changes in membrane potential due to a gated channel

dendrites, cell body locations

die out over distance

magnitude depends on strength of stimulus (how many ion channels are open/closed)

Graded potential types

Excitatory postsynaptic potential- EPSP

Inhibitory postsynaptic potential- IPSP

EPSP

Local depolarization of the postsynaptic membrane

EPSPs bring the neuron closer to the AP threshold

Neurotransmitter binging opens chemically gated ion channels allowing Na+ and K+ to pass simultaneously (Na+ Influx > K+ efflux)

IPSP

Local hyperpolarization of the postsynaptic membrane

drive the neuron away from AP threshold

Neurotransmitter binding opens chemically gated ion channels permeable to either K+ OR Cl-

the spread and decay of graded potential

if at threshold value when it reaches axon hillock, an AP will be initiated and propagate down the length of the axon to the axon terminals (requires voltage-gated channels)

if too weak, the VG channels will not open