Neurone Action Potential Flashcards
What is cell charge
-65mV due to K and A- ions while theres Na Cl and Ca outside cell
What happens to resting membranes potential of -65mV when neurotransmitter binds to receptor on dendrite
Ligand gated ion channel opens allowing ion eg Na into cell so cell becomes less negative so less polar (depolarisation) and some K may leave but net influx of postive = excitatory post synaptic potential (EPSP)
How is IPSP
ligand gated Cl open causing net influx of negative - more negative cell potential- repolarising it
Threshold value
-55mV causes opening of voltage gated Na channels at axon hillock, more Na in axon means more channels open= chain reaction across axon= action potential at +40mV where channels r inactivated
Inactive Na
Not closing, done by inactivation gate to block Na influx just after depolarisation and stays until repolarisation and channel enters closed state
K channels after Na
Slow to respond and dont open until Na have opened AND become inactivated causing K to move out of cell down own electrochemical gradient, they lack inactivation gate so stay open longer causing membrane potential to repolarise
What else does repolarsation rely on to go back to RMP
NaK pump which pumps 3 Na out of cell and 2 K into cell causing absolute refractory period since Na are inactivated and wont respond to stimuli keeping AP not in quick succession and keeps unidirectional AP. This causes hyperpolarised -75mV and Na channels close while K stay open = relative refractory period since Na channels are closed but can be activated but takes stronger stimulus to do so as K channels still open. When they shut= resting membranes potential
Where does fatty myelin come from
Schwann cells or oligodendrocytes
Fatty myelin use
No channels, only ion transfer on either side in the nodes of ranvier. Na bump each other through the myelin = saltatory conduction
