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Neurones (Action potential (At -55mV Na+ voltage gated channels open…
Neurones
Action potential
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This triggers the K+ voltage gated channels to open, but the 0.2ms delay means the sodium influx causes depolarisation tpo 30mV
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Na+/K+ pump pumps 3 Na+ out of the cell and 2K+ in, reestoring the normal concnetration gradient
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Temperature - temperature increases diffusion hence faster action potential
Myelin sheath - allows salutatory conduction rather than a wave of depolarisation. Less ATP because fewer voltage gated channels - hence quicker action potential
The thicker axon, the quicker the action potential - because the diffusion along the axon is greater than the leakage out of the neuron - constitutes a faster action potential
Unmylinated neurones
The Na+ ions diffuse across the axon, reaching the threshold at the next part of the axon which is at rest
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At the 1st site of depolarisation, K+ voltage gated channels open and K+ moves out of the neuron. Then the Na/K+ pump returns the 1st site to rest
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Refractory period where the Na+ voltage gated channel becomes inactive means the impulse only flows in one direction
Mylinated neurones
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The Na+ diffusion is enough to decrease potential difference and trigger an action potential at the next node
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Axon resting potential
Both move along the concentration gradient however neuron more K+ channels, so more K+ out of the neuron than Na+ into it
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-70mV is the point at which an equilibrium is established between the chemical and electrical gradient - hence no net movement of K+ ions
Neurones
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sensory neurone
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axon inside CNS, cell body outside
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Synapses
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Excitary synapses
Spatial summation: Impulses from different neurons all have an effect on stimulating an action potential in the next neuron
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Excitory synapses more permeable to sodium ions. Work via summation - where each impulse has a cumulative effective . Work by either spatial or temporal summation
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