Flashcards in Nerves Deck (47)
describe the neurone at resting potential.
the outside is + the inside - , the membrane is polarised, the voltage is approx - 70mV,
describe how the Na/K pumps maintain the resting potential
Na is moved out using active transport, Na cannot diffuce back in = electrochemical gradient, pottasium is pumped in but can move out via facilitated diffusion - making the outside + compared to the inside
when is a neurone depolarised?
when it is stimulated
describe what happens when the neurone is stimulated
the stimulus excites the cell membrane, causing Na ion channels to open. Na diffuses down the electrochemical gradient, making the inside less negative
if the threshhold is reached (-55mV) more channels open and Na diffuses rapidly into the membrane
when +3mV is reached the sodium channels close up. K diffuses out through the opened channels, returning the membrane to resting potential
describe the nervous system in comparison to the endocrine system
nervous system is short lived, fast and localised (endocrine opposite)
what is included in the CNS?
brain and spinal cord
what is the peripheral system?
all other neurones
what do we dived the peripheral into?
sematic and autonomic
what is the sematic nervous system?
concious decision eg) muscle movement
what is the autonomic nervous system?
unconcious eg) heart rate
what 2 sections can we divide the autonomic system into?
parasympathetic and sympathetic
describe the parasympathetic
decreases/ slows things down eg) heart rate
what neurotransmitter controls the parasympathetic?
describe the sympathetic
increases/ speeds things up eg) heart rate
what neurotransmitter controls the sympathetic?
describe the route from stimulus to response
stimulus - receptor - sensory - intermediate (cns) - motor - effector - response
describe the receptor
specific, cell or protein, transforms stimulus into nerve impulse
describe the sensory neurone
Single long dendron, single short axon, (draw a diagram and check)
decribe the intermediate neurone
within cns, many short dendrites/ axons (draw a diagram)
describe the motor neurone
many short dendrites, single long axon, ends at neuromuscular junction
describe the effector
describe the sodium pottassium pump
maintains the resting potential by active transport of Na+ out and K+ in. some K+ diffuse out by facilitated diffusion
what happens at generator potential?
a weak stimulus causes some voltage gated Na+ channels to open, some Na+ diffuses in, threshold isnt reached so returns to resting potential.
what happens at threshold?
many voltage gated Na+ channels open, Na+ diffuse into axon, positive feedback (rapid depolarisation)
K+ channels open, K+ diffuses out, sodium ion channels close
what is hyperpolarisation?
membrane potential is more negative than resting potential because K+ channels are slow to close
what is the refractory period?
another action potential cannot be started, ensuring action potentials are discrete, unidirectional nervous impulse