lecture 5 - threshold and propagation

excitatory post synaptic potential (EPSP)

caused by the influx of cations or efflux of anions, depolarizing the cell, and making the membrane potential more positive, decay over space and time

inhibitory post synaptic potential (IPSP)

caused by the influx of anions or the efflux of cations, hyperpolarizing the cell, and making the membrane potential more negative

gluatamate mediated excitation

glutamate binds to a glutamate receptor. specifically, to an AMPA receptor that have sodium channels that open (ligand gated ion channel) (increases sodium permeability) and sodium ions enter the cell. this depolarizes the membrane, leading to an EPSP (the result depends on the kind of receptors and ion concentrations, but specifically AMPA receptors do this)

GABA mediated inhibition

GABA binds to a GABA-A receptor, that has chloride channels (ligand gated ion channel) (increasing chloride permeability) and chloride ions enter the cell, leading to an IPSP

spacial summation

different points in space in dendrites that the IPSP and EPSPs happen in, but the summation of when they reach the axon hillock leads to an action potential (pretty much at the exact same time)

temporal summation

different points in time that the IPSP and EPSPs happen in, but the summation of when the reach the axon hillock leads to an action potential

action potentials are…

“all or none” - each spike from a given neuron is the same size

axon hillock

where the axon leaves the soma, high concentration of voltage gated sodium channels

absolute refractory period

voltage gated ion channels (sodium) become inactivated, there is a physical block so sodium cannot get through

relative refractory period

undershoot phase of the action potential, potassium permeability increases, pulls membrane potential towards potassium equilibrium potential (lower than rest, much lower than threshold)

myelin

axons are wrapped in this fatty insulating layer, decreases the ability of ions to leak out of axon (decreases signal loss), increases the speed of passive ionic diffusion along the axon

nodes of ranvier

action potentials are regenerated along the length of the axon at these locations where the myelin isn’t present

what ion is required for transmitter release?

calcium