Unequal distribution of ions across membrane maintained by pumps and selective permeability of the cell membrane.
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What is depolarisation and hyperpolarisation
Depolarisation is the cell becomes more positive. Hyperpolarisation is when cells become more negative.
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What is threshold
t is the degree of depolariation that triggers an action potential
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What happens when a stimulus is fired
If the stimulus is bg enough the threshold will be reached which will cause an action potential to be fired causing depolarisation of the cell membrane.
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What is a resting potential
The potential difference acoss the membrane of a cell when no nervous impulse is being conducted.
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What happens when the cell membrane is at resting potential
The membrane is polarised. Sodium-potassium gated pumps pump K+ from the outside to inside and Na+ from inside to outside to create an unequal distribution. -70mV
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Whats ac action potential
The rapid rise and fall of the electrical potential across an excitable cell membrane as a nervous impulse pass.
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What happens during depolarisation
The energy of the stimulus causes the threshold to be reached causing an action potential to be released. This energy opens the voltage-gated Na+ channel allowing Na+ to flood in. This depolarises the membrane (more positive). +40mV.
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What happens during repolarisation
The voltage-gated Na+ channels close and ms later the K+ ones open. This causes K+ to flood out of the cell causing the cell membrane to repolarise. An excess leaved before the sodium-potassium pumps restore the resting potential. >-70mV.
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What is the refractory period
Period in which no further action potential can occur. This is when the sodium-potassium pumps are restoring the resting potential.
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Other cards in this set
Card 2
Front
When do action potential occur
Back
When positive ions come into an excitable cells and change the potential difference.
Card 3
Front
What the usual potential difference for most cells
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