nervous and synaptic impulses Flashcards
what do dendrites do
carry nerve impulses to the body
what does does the cell body of a nerve cell contain
organelles - lots of rough er and mitochondria
what is the axon
long fibres that carry impulses away from the cell body
what are schwann cells and what do they do
wrap around axon many times forming the myelin sheath and are rich in lipids
providing insulation
what are the nodes of ranvier
gaps between schwann cells
what is the resting potential
the potential difference (voltage) across the membrane of a neurone when not transmitting an impulse
what do the sodium potassium pumps do maintain resting potential
actively transports 3 sodium ions (Na⁺) out of neurone and 2 potassium ions (K⁺) into neurone
what ion is the membrane more permeable to
K+ ions
why does a neuron have an overall negative charge
potassium diffuses out quicker that sodium diffuses in
because the membrane is more permeable / has more ion channels
for potassium
what is the voltage of resting potential
~ -70mV
what are the intrinsic membrane proteins in the membrane of a neuron
sodium potassium pumps
leak channels
gated channels
how is the resting potential established
active transport of 3Na+ out and 2K+ in by sodium potassium pumps
membrane more permeable to K+
K+ diffuse back out faster than Na+ back in
membrane is polarised
what is action potential
when a stimulus caused a temporary reversal in the charges and the axon is depolarised
what are the stages of causing action potential
stimulus
depolarisation
repolarisation
hyperpolarisation
refractory period
resting state
what happens in depolarisation
stimulus causes gated sodium ion channels to open
Na+ ions rapidly diffuse into axon
potential difference increases to +40mV
gated sodium ion channels close
what happens in repolarisation
gated potassium ion channels open
K+ ions diffuse rapidly out of axon
what is hyperpolarisation
so many K+ ions diffuse out that the axon becomes more negatively charged than normal
what restored the resting potential
sodium potassium pump restored the concentration gradients of Na+ and K+
what is the all or nothing principle
if the stimulus is large enough, action potential is generated at a constant size and speed
increasing initial stimulus will not produce a larger or faster action potential
what is the refractory period
a short period where axon recovers from its depolarisation
gated channels can’t be opened
