1. rapid communication 2. coordination of body systems
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afferent nerves
send info towards the brain
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efferent nerves
send info away from the brain
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How do we know RMP/ the inside of the cell is negative relative to the outside ?
an experiment that used a glass capillary electrode with a heated coil- to penetrate the outer mem and measure voltage
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Why is RMP negative compared to outside?
K channels are open, K diffuse out - loss of +ve charge
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RMP is maintained by the ....
Na-K pump . 3Na out, 2K in
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Nernst equation
Ek+= 61 log ([K+]/o[K+]i)
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what does the nernst eq show?
that RMP is influence by ration of ions and conductance of ions
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But, K+ conductance is x100 better than Na so therefore
the actual factors really are K+ ration in/out and K+ conductance
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Why is the MP diff in diff cells?
due to differences in intra/extracellular ion conc
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2 types of channels which induce changes to the MP
1. Passive/leak channels- always open- perm changes due to protein shape changes. 2. Active/gated channels- only open in response to spec stimulus
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what is a graded potential?
a small change in MP, that is not large enough to spread. They can however sum-mate to reach the threshold
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Excitatory NT cause
depolarization and EPSP ( excitatory postsynaptic potential)
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Inhibitory NT cause
hyperpolarization and IPSP
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Response of EPSP
Increase nerve stim/repeated nerve stim
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Temporal summation
repeated release of NT to overcome threshold to gen AP
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Spacial summation
many neurones release NT to reach threshold to gen AP
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which channels open faster
Na channels - explaining fast depolarisation once channels opened
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Na channels also display inactivation (closing of channels based on voltage)
TRUE
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Activation is slower than inactivation
FALSE - inactivation is slower
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Depolarisation causes (in terms of Na conductance)
Increase in conductance followed by a decrease
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Refractory period
peroid when no APs can form due to Na channels being closed
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Absolute refractory
caused by Na channels being closed - No chance of AP - ever
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Relative refractory
caused by RMP falling below normal, due to K channels being open. AP can form if stimulus is large enough to overcome
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Factors affecting speed of conduction
1. Diameter of axon 2. Myelinated 3. Temperature
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Myelinated Vs unmyelinated
Speed is faster in myelinated due to saltatory conduction
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Temperature
increased temp - increased diffuse of ions - but if temp too high denature protein channels etc
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Diameter
large the diamter the faster speed of conduction
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Saltatory conduction
only occurs in myelinated axons, due to myelin being an electrical insulator. Therefore AP mus jump from node of ranvier to another to pass - this is much faster than conduction in a unmyelinated axon
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Other cards in this set
Card 2
Front
afferent nerves
Back
send info towards the brain
Card 3
Front
efferent nerves
Back
Card 4
Front
How do we know RMP/ the inside of the cell is negative relative to the outside ?
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