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What occurs during hyperpolarization in the action potential process?
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Due to slow closure of potassium channels, the membrane potential may overshoot to around -90mV.
What happens at the threshold level of -55mV in neurons?
Voltage-gated sodium channels open, triggering depolarization and an action potential.
Explain the repolarization phase following an action potential.
Voltage-gated potassium channels open, allowing potassium to exit the cell, restoring the membrane potential to resting levels.
What is the typical range for the resting membrane potential in neurons?
-70 to -90 millivolts
What distinguishes the absolute refractory period from the relative refractory period?
No new action potential can occur during the absolute refractory period, while a stronger stimulus is required during the relative refractory period.
How do the gates in voltage-gated sodium channels behave at rest compared to during an action potential?
At rest, the activation gate is closed and the inactivation gate is open; during an action potential, the activation gate opens and the inactivation gate begins to close.
How does the sodium-potassium ATPase contribute to the resting membrane potential?
It pumps 3 sodium ions out of the cell and 2 potassium ions into the cell, creating a concentration gradient and a slight negative charge inside the cell.
What is the state of sodium channels during the inactivation phase of an action potential?
Sodium channels begin to inactivate at +30mV, stopping further sodium influx.
Why is the resting membrane potential closer to the equilibrium potential of potassium?
The cell membrane is much more permeable to potassium than sodium.
Describe the process of depolarization during an action potential.
Sodium channels open, allowing sodium ions to rush into the cell, increasing the membrane potential to +30mV.
Describe the role of leaky potassium channels in maintaining the resting membrane potential.
Leaky potassium channels allow potassium to leave the cell passively, increasing the negativity inside the cell.
What mechanism allows EPSPs to move the resting potential closer to the threshold?
EPSPs involve neurotransmitters opening ligand-gated ion channels, allowing positive ions to enter the cell and depolarize it.
What is temporal summation in the context of graded potentials?
Temporal summation is the cumulative effect of multiple signals from one presynaptic neuron in rapid succession.
How do IPSPs move the resting potential further away from the threshold?
IPSPs involve inhibitory neurotransmitters opening channels for negative ions to enter or positive ions to leave, hyperpolarizing the cell.
How is spatial summation different from temporal summation?
Spatial summation involves simultaneous signals from multiple presynaptic neurons.
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