Neurophysiology revision Flashcards
what happens to info in a neuron
info arrives at cello body (where it is processed) via dendrites
processed info digitised into APs transmitted along axon
info passed to target at bouton
where to action potentials start
axon hillocks
how are action potentials graded
all or none response
but increasing frequency increases intensity
why does the inside of a neuron have a negative potential and what is it
-70mV (resting membrane potential)
3Na out
2k in for each atp consumed
describe to action potential
stimulus causes the potential to push to the threshold (-55mV)
membrane depolarises, Na channels open and flows in
peaks
na channels become refractory
k channels open and k flows out therefore becomes more negative
hit absolute refractory period (all na channels closed) and relative refractory period (some na channels open but more k open-need large stimulus)- so only 1 direction and stimulates the next one
vectoial transmission
what happens when voltage gated sodium channels close
resting potential na channels and activation gate is closed
depolarisation opens activation gate and causes a conformational change
blocking of channel by inactivation gate
repolarisation of cell resets gates to their equilibrium
what increases efficiency of conduction
myelin sheath
increased diameter
where are oligodendrocytes found
cns
what is saltatory conduction
describes the way an electrical impulse skips from node to node down the full length of an axon
flows rapidly inside axon to node
ap takes place (only a few ions are needed- energy saving)
normal conduction velocity
50-60 metres/second
fastest alpha motor neurons 120m/s
are neurons hard wired
no they are separate entities
are neurons elongated secretory cells
yes and they are polaried
secretion at bouton
exocytosis occurs
explain vesicle docking
v-snare on vesicle complexes and t-snare at pre-synaptic membrane
allow vesicle to dock by drawing them close to membrane
exocytosis clamped by complexin
ap triggers calcium influx at end bulb, induces synaptotagmin (displaces complexin and causes exocytosis
what does botulinum toxin do
inactivates snare and therefore ach process
what is clostridium botulinum
bacteria that releases the toxin botulinum
what are the two receptors
ionotropic
metabotropic
can be excitatory or inhibitory
how to visualise opening of pores
cryo-electron microscopy
what are post synaptic responses
excitatory or inhibitory post synaptic responses
EPSP AND IPSP
Single ones rarely result in ap
therefore add multiple
how do epsp and ipsp work together
spatial and temporal summation
spatial- add together
temporal-ap separate
what does summation lead to
integration of information
sensory receptors need to reach threshold
how to sensory receptors respond
slowly adapting from constant input then constant output
rapidly adapting respond when it is changing then falls off (only respond on up phase)
one to change and one to extent of change
what is a stretch reflex there for
stabalising effect
prevent damage to muscle by activating reflexes via spindle fibre mechanisms
feedback info on stretch
contraction therefore controlled by output of stretch recpetors
what does gamma motor neuron efferent from spinal cord do
regulate degree of contraction
