Resting potentials and action potentials Flashcards
what is the resting potential?
when a neurone isn’t conducting an impulse and there’s a difference between electrical charge inside and outside the neurone
what parts are there to a myelinated motor neurone?
cell body
dentrites
axon
schwann cells
myelin sheath
nodes of ranvier
what is the cell body?
the neurone containing typical animal organelles, making proteins and neurotransmitters
what do dentrites do?
they carry action potentials to surrounding cells
what is an axon?
a conductive, long fibre that carries nervous impulses along a motor neurone
what do schwann cells do?
wrap around the axon to form the myelin sheath. there are then gaps called nodes of ranvier, where ions can pass through and an action potential is generated
what is the myelin sheath?
a lipid which does not allow ions to pass through
are there more positive ions outside or inside the neurone and what does this mean?
there are more K+ and Na+ ions outside, so inside is more negative at -70mV
describe how the resting potential is established
the sodium-potassium pump moves 2 K+ ions in and 3 Na+ ions out, creating an electrochemical gradient. this causes K+ ions to diffuse out and Na+ to diffuse in, however the membrane is more permeable to K+ so more are moved out, resulting in the -70mV
done by active transport, so requires ATP
what is an action potential?
when a neurone’s voltage increases beyond a set point from the resting potential, generating a nervous impulse
why are action potentials created?
due to a neurone membrane becoming more permeable to Na+ (this is depolarisation). the action potential then moves along the axon
what will a bigger stimuli increase?
the action potential frequency
why is the all or nothing principle important?
so that animals don’t react to every small, non harmful stimulus
what is the refractory period?
when the membrane cannot be stimulated after an action potential has just been generated, due to sodium channels still recovering and unable to be opened
why is the refractory period important?
-it ensures discrete impulses are produced,so an action potential cannot be generated immediately after another, so they’re separate
-it ensures action potentials travel in one direction, stopping it from spreading in 2 directions and preventing a response
-it limits the number of impulse transmission, preventing over reaction to a stimulus and overwhelming senses
