what is a neurocrine? - ✔️✔️- a chemical substances released from neurons used for cell to cell
communication
- Neurotransmitters, neuromodulators and neuro hormones
What is neurotransmitters? - ✔️✔️a chemical that is released, acts on a postsynaptic cell in close vicinity
can causes a rapid response in the postsynaptic cell
what is action potential (AP)? - ✔️✔️electrical signals of uniform strength (all or none) that travel from
the trigger zone to the axon terminals
What ion channels does the conduction of AP require? - ✔️✔️- voltage gated Na+ and K+ channels as well
as the leak channels that help set the resting membrane potential
do Na+ or K+ channels open and close faster? - ✔️✔️Na+ channels open faster then K+ channels
what is the rising phase (depolarization) of action potential? - ✔️✔️- depolarizing stimuli open voltage
gated Na+ channels (-55mV), allow Na+ to travel down electrochemical gradient
- at about 30mV Na+ channels inactivate
What is the falling phase (repolarization) of action potential? - ✔️✔️- voltage gated K+ channels also open
in response to depolarization
- they open more slowly than Na+ channels causing delayed efflux
what is the after-hyperpolarization phase (undershoot) of action potential? - ✔️✔️- voltage gated K+ do
not immediately close when reaching -70mV causing membrane potential to dip below the resting
membrane potential
- Leak channels bring membrane potential back to -70mV
, what two gates do AP contain? - ✔️✔️- activation gate
- inactivation gate
which gate is faster, activation or inactivation? - ✔️✔️activation is the faster gate
what happens once the inactivation gate is closed? - ✔️✔️K+ will reactivate it again and it will return to its
resting point
what is the refractory period? - ✔️✔️period of time following the generation of an action potential where
either a second action potential cannot be generated at all or it takes a larger then normal stimulus to
generate it
what happens at the absolute refractory period? - ✔️✔️- a second AP cannot be initiated 1-2 msec
- action potential can't be generated at all
- all Na+ channels are inactivated
what happens at the relative refractory period? - ✔️✔️- a second AP can be initiated but requires a larger
than normal stimulus (graded potential) 2-5 msec
- threshold goes up
- some Na+ channels still inactivated
- must overcome more negative membrane potential
why do we need higher then normal stimulus in relative refractory period? - ✔️✔️- some sodium channels
are still partially inactivated (starting to swing out of way)
- starting further away from threshold so need larger stimulus
what is the purpose of refractory period? - ✔️✔️- ensure an AP travels in one direction
- limits the rate at which signal can be transmitted down a neuron
- slows down rate action potential can be generated
- information is often encoded in the frequency of AP's
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