C2.2 Flashcards
central nervous sytem
brain and spinal cord
peripheral system
all nerves
bundle of nurons
nerves
transer from CNS
sense organs
axon
the long part of the nerve fibre
a never impluse
electrical signal
dendrites
sort nerve fibres
sensory neurons
from receptors to the CNS
relay neurons
connect sensory and motor neurons
motor neurons
connect CNS to effector neurons
axons carry signal
away from cell body
impulse
a momentary reversal in the electrical potential difference across the neurone cell surface membrane
resting potential
negative on the inside of the neuron compared to the outside
-70mV
depolarization
- sodium chanells open and allow Na+ in down the concentration gradient
- inside of the neuron becomes positive
-70mv becomes -50ismv
repolarization
- sodium channels close
- potassium channels open and potassium travels out down the concentration gradient
- back to -70
rebuilding of gradients
- the sodium potassium pump rebuilds the correct gradients
- for ever 3 na pumped out 2 k are pumped in restablishing negativeness
- the membrane is more permeable to K than NA so more of the K diffuses out the neuron and leak back across
polarized
neuron is resting
depolarization
reversal of electrical potential
where are synapses found
- mostly brain and spine
- also in sensory receptors
- neurons and effectors such as muscle fibre and gland cells
transmitting neuron
presynaptic membrane
reciving neuron
postsynaptic membrane
process of neurotransmission in synaptic gap
1)arrival of the nerve impulse causes opening of ca2+ and as the concentration is higher on the outside they diffuse in.
2)influx of ca2+ causes the neurotransmitter to be pushed to membrane
3)exocytosis causes the vesicle to merge and push the neurotransmitter into the gap
4)the binding causes the sodium channels to open and an action potential
5)neurotransmitter is broken down by enzymes to avoid reated action potentials
diamater in neurotransmission
1)large diameters
- reduced resistance
- faster
squid with a 25ms- vs humans of 1ms- due to 500um diameter
worms just have 3 giant axons
myelin shealth in neurotransmission
- schwan cells cause myelin to form wich is loads of bilayers around the axon
- causes high electrical resistance
- allows for jumping which increases speed
- this is called saltatory conduction
steps in synapse
1) mollecuse diffuse rapidly across gap
2) binding causes Na cahnnels to open
3) diffusion in of na down concentration gradient
4) neurotransmitter removed
5)excitatory postsynaptic potential
6)propagation of messafe
