3. Action potential Flashcards
what is threshold potential
-55 mV
what is resting potential
-70 mV
what does an excitatory stimulus cause
membrane potential depolarised- if above threshold potential= action potential generated
what does an inhibitory stimulus cause
can reverse and hyper polarise the membrane- makes an action potential less likely
define polarisation
the difference in charge across the neural membrane
describe the activation and inactivation gates in na+ ion channels at rest
activation gate closed
inactivation gate open
describe the activation and inactivation gates in k+ ion channels at rest
TRICK QUESTION
has no inactivation gate lol
one activation gate which opens and closes
what happens when a stimulus reaches the neuron
ligand gated sodium channels open, diffuses into the neuron, resting potential becomes more positive
what happens when critical threshold is reached
voltage gates activation gates in sodium channels open -> sodium floods into the neuron
=DEPOLARISATION
when does the inactivation gate occur in the neuron
when the neuron becomes too highly positive
- the flow of sodium into the neuron stops
at what point do k+ channels open
REPOLARISATION
when the intracellular environment is positive enough, K+ diffuses out of the cell
why does hyper polarisation occur
voltage gated K+ channels close however this is a slow process, some K+ continues to move outside the cell, membrane potential becomes more negative than at rest
what is the refractory period
when the neuron is in hyper polarisation it cannot fire another action potential
at what point does the refractory period end
when the sodium potassium pump restores the resting membrane potential (-70 mV)
at what part of the neuron are action potentials generated
the axon hillock
what do the nodes of ranvier allow
allow sodium and potassium ion movement across the membrane
allow the action potential to ‘jump’ from one node to another
what Is saltatory conduction
where the action potential jumps from one node to another
what does the size of action potentials tell us
nothing- all action potentials are the same size, we can gather information based on the FREQUENCY
what do electrical synapses use
gap junctions
what do chemical synapses use
synaptic cleft
which is the most common type of synapse:
electrical or chemical
chemical synapses
what is the term that describes the amount of neurotransmitter in one vesicle
quantum
describe the mechanism of synaptic transmission
- depolarisation reaches synaptic terminal- ca2+ channels open
- calcium influx causes vesicle fusion with pre-synaptic membrane
- neurotransmitter released into the synaptic cleft
- transmitter binds to post-synaptic receptor site
what happens if an excitatory neurotransmitter binds to post-synaptic receptor site
sodium channels open triggering action potential
