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15 Cards in this Set
- Front
- Back
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Leak channels
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Selectively permeable to K+ or Na+
Set resting potential -65mV |
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Voltage gated channels
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Selectively permeable
Generate action potentials |
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Ligand gated ion channels
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Em changes at synapses
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Chemical gradient
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Due to an uneven ion distribution
Doesn't vary with time |
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Electrical force
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Ions attracted or repelled by Em
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Permeability
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Measure of the ease of ion movement across a membrane
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ENa
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+62 mV
Chemical gradient + electrical force = influx |
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EK
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-80mV
Chemical gradient = efflux Electrical force = influx No net movement |
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Ion pumps
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3 Na+ out
2 K+ in Set conditions allowing leak channels to set rest potential Maintain ion concentrations in the long term Insignificant electrical impact |
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Rest potential
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-65 mV
Set by leak channels Na influx = K efflux Na influx = chemical + electrical K efflux = electrical influx < chemical efflux |
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Conductance g
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= 1/R membrane acts as a resistor
Proportional to number of ion channels g change = Em change = ion redistribution |
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Delay in voltage gated K+ channels opening
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Allows depolarisation
Without, there would be no net change |
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Delay in voltage gated Na+ channels inactivating
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Allows hyperpolarisation
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Absolute refractory period
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No action potentials - impossible
Most Na+ channels inactivated Many K+ channels open For action potential - Na influx > K efflux - impossible to achieve |
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Relative refractory period
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Greater threshold potential - stronger stimulus required to open sufficient Na channels to generate an action potential
Na channels are still recovering from inactivation Some K channels still open |
