Action Potential Flashcards
What happens in the generation side of an action potential?
Electrical impulses pass along the axon & reaches the synapse terminal, where there are neurotransmitters stored in vesicles. The electrical impulse causes the neurotransmitters to be released into the synaptic cleft through a process called exocytosis. The neurotransmitters cross the synaptic cleft to reach specific receptors on the post-synaptic neuron. The neurotransmitters bind to this receptor, causing Na+ ion channels to open. When these channels open, Na+ ions flow through the post-synaptic neuron, causing membrane potential to become more positive. If the charge reaches the point of threshold, all Na+ ion channels will open & lots of Na+ ions will rush in, triggering an action potential. This stage is known as depolarisation.
Describe what happens in the recovery side of an action potential
The cell loses positivity as Na+ ions stop moving in & K+ ion channels open. K+ ions flow out of the cell, causing membrane potential to drop towards resting state. This stage is called repolarisation. K+ channels remain open after the potential reaches resting level, causing the electrical charge on the membrane to become negative (-90mV) - this stage is called hyperpolarisation. K+ channels slowly close and the resting level goes back to normal.
What is summation in relation to an action potential?
Sometimes the electrical signal is too weak to reach threshold level, however many weak signals can have a cumulative effect & eventually reach threshold level where an action potential will then be triggered. This is called summation.
