BRAINCAKEHyperpolarisation
Hyperpolarisation is the brief period after repolarisation when the membrane potential becomes more negative than the resting potential, falling to about −80 mV instead of −70 mV.
It happens because the voltage-gated potassium ion channels are slow to close. During repolarisation K+ diffuses out of the axon. When the potential gets back to −70 mV, many K+ channels are still open, so K+ keeps leaving and the inside becomes more negative than at rest. This is sometimes called the undershoot.
The resting potential is then restored in two ways:
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Key terms in this lesson
- refractory period
- The short time after an action potential during which a new action potential cannot be generated, or only by a stronger than normal stimulus.
More in Mammalian Nervous System
- Resting Potential
- Action Potential
- Depolarisation
- Repolarisation
- Refractory Period
- Transmission of Nerve Impulses
- Saltatory Conduction
- Synapses
All 38 lessons in Mammalian Nervous System · All Edexcel A-level Biology topics