Resting and Action Potentials Flashcards
What is the resting potential?
potential difference/voltage across membrane while neurone at rest, about -60mV inside cell, gated Na+ channels closed
How many Na+ out for every K+ in?
sodium/potassium ion pumps, 3 Na+ out for every 2 K+ in
What is the threshold potential?
potential difference across membrane of about -50mV, if depolarisation doesn’t reach this then no AP happens
How are the gated channels opened in the Pacinian corpuscle?
opened by deformations, gates further along opened by changes in the potential difference: voltage gated channels, respond to depolarisation
What can an action potential be transmitted across?
along axon or dendron plasma membrane
How are action potentials self-perpetuating?
once it starts at one point on neurone, it will continue along to end of neurone
What are the first 2 steps of an action potential?
membrane starts in resting state (-60mV), sodium ions channels open and some Na+ diffuse into cell
What are the second 2 steps of an action potential?
membrane depolarises and reaches threshold value of -50mV, voltage-gates sodium ion channels open and many Na+ flood in so cell becomes positively charged
What happens when the cell is positively charged (stages of action potential)?
potential difference reached +40mV, sodium ion channels close and potassium channels open
What happens when the potassium ion channels open (stages of action potential)?
potassium ions diffuse out of cell so potential difference back to negative (repolarisation), potential difference overshoots slightly (hyperpolarised), original resting potential restored by sodium/potassium pumps
What is the refractory period?
for a short time after each action potential it is impossible to stimulate another one, allows cell to recover, also ensures action potentials can only be transmitted in one direction
