action potentials and synapses

electricity

flow of electrons

force is electrical gradient

bioelectricity

flow of ions

force is chemical and electrical gradient

gated ion channels

chemically gated, voltage gated, mechanically gated

ions flow across membrane down concentration gradient, only open briefly

local currents

graded potential transmit bioelectrical signals across short distances

dendrites and cell bdoeis

action potentials

transmit electrical signals over long distances

axons

sodium ion channels

open in response to threshold depolarization

potassium ion channels

open slowly in response to depolarization, close slowly after repolarization

saltatory propagation

“jumping” of action potential across nodes of ranvier

continuous propagation

slow movement of action potential across unmyelinated axon

action potential movement

membrane depolarization to reach threshold, sodium channel opens, sodium channel closes quickly, potassium channel opens, potassium channel closes at normal levels

synapse

cell to cell junction between presynaptic and post synaptic cells

electrical synapses

utilize gap junctions

chemical synapses

neurotransmitters bind to receptors of chemically gated ion channels

direct acting chemically gated ion channel

neurotransmitter binds to receptor site a part of gated channel

indirect acting chemically gated ion channel

neurotransmitter binds to receptor that controls gated channel via secondary messenger

primary messenger

neurotransmitter

secondary messenger

intracellular molecule, cAMP or cGMP

excitatory post synaptic potential (ESPS)

gated channels open for sodium ion, depolarizing synaptic potential, promotes action potential initiation

inhibitory post synaptic potential (ISPS)

gated channels open for potassium and chloride ions, hyperpolarizing the cell, suppresses action potentials

spatial summation

two stimuli arrive simultaneously, generates action potential

temporal summation

a second stimulus is added to the first stimulus, action potential is generated

epsp and ipsp combine through

spatial and temporal summation