Nervous System Flashcards
Potential differences
Action potential = +40mV
Resting potential = -70mV
Axons
Peripheral neurone
Dendrons
Motor neurones
Dendrites
Intermediary neurones
Resting potential features
Much more Na+ outside axon
Any Na+ that diffuse in are expelled by Na-K pump
-causes polarisation: +ve outside, -ve inside
Potential difference = ~-70mV
Action potential aka depolarisation features
Na+ channel proteins allow Na+ into axon
Causes depolarisation: -ve charge outside and +ve charge inside
Potential dufference = ~+5mV
Repolarisation
K+ channel lets K+ leave axon
Causes membrane to repolarise
Excess Na+ are removed by Na+-K pump
Saltatory Conduction
Faster speeds due to myelination
Synapse sequence
1) Ca2+ ions pass through pre-synaptic membrane’s channel proteins from synaptic cleft to synaptic knob
2) vesicles merge with pre-sm for transmitter secretion into receptor protein sites in post-sm
3) each receptor protein opens a channel protein and Na+ depolarise the post-sm
4) if enough Na+ enter, threshold level is reached and action potential is generate
5) enzymes remove transmitters and breakdown transmitter products are absorbed into synaptic knob for re-synthesis
Rod cells
Light intensity sensitive
Reaction: rhodopsin→opsin+retinal
Summation: Many rods can synapse to 1 bipolar cell for threshold level to be raachec
Opsin and rhodopsin key features
Opens ion channels in CSM. Can lead to AP generation
Rhodopsin can be regenerated without light
Cone cells
Colour mechanism
Reaction: idopsin→photopsin+retinal
3 cone types: red, blue, green
=high visual acuity as large no.s are packed closely together
1 cone→1 bipolar cell→1 ganglion
Visual acuity
Measures visible detail.
Na+ role
Na+ →receptor cell during depolarisation (i.e due to action potential)
Na+←membrane during repolarisation. Can’t re-enter
Na+ enters during EPSP
K+ role
K+→membrane during repolarisation
K+ channels opened during IPSP.
Hyperpolarisation
K+ outflow or Cl- inflow during IPSP
Excitatory post-synaptic potential
Aka EPSP
NeuroT depolarises post-synaptic neurone via Na+ influx through Na+ channel
Inhibitory post-synaptic potential
NeuroT opens K+ or Cl- channels in post-synaptic membrane
Prevents depolarisation
-cell = less likely to generate action potential
Electrical impulse speed increasers
↑myelination
↑temp
↓axon diameter
Synapse
Gap between neurones
1) impulse reaches synaptic knob = Ca+ influx
2) synaptic vesicles containing neuroT fuse with pre-synaptic membrane
3) neuroT diffuses across synaptic gap and fuses with specific receptor on post-synaptic membrane
4) causes action potential
Agonistic drugs
Can mimic neuroTs in an by amplifying their effect
Can prevent enzyme breaking down neuroT
E.g LSD
Antagonistic drugs
Can inhibit synaptic transmission
Can destroy neuroT, inhibit its formation and prevent its action
