BRAINCAKETransmission of Nerve Impulses
An action potential at one point on an axon triggers an action potential in the region next to it, so the impulse moves along the neurone as a wave of depolarisation. In an unmyelinated axon this happens as follows.
1. At the site of an action potential, voltage-gated sodium ion channels are open and Na+ diffuses into the axon. The inside of this region is positive.
2. The Na+ ions diffuse sideways inside the axon towards the neighbouring region, which is still at resting potential and negative inside. On the outside of the membrane, positive ions move the opposite way. These movements of charge are called local currents.
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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
- Depolarisation
- Repolarisation
- Hyperpolarisation
- Refractory Period
- Saltatory Conduction
- Synapses
- Pre-synaptic Membrane
- Post-Synaptic Membrane
All 38 lessons in Mammalian Nervous System · All Edexcel A-level Biology topics