Synapses and neurotransmitters


Synapses and neurotransmitters.

What is a synapse?

A synapse is the junction between a neurone and another neurone, or between a neurone and an effector cell (e.g a muscle or gland cell)

  • The tiny gaps between the cells at a synapse is called the synaptic cleft. 
  • The presynaptic neurone (the one before the synapse) has a swelling called a synaptic knob. This contains vesicles filled with chemicals called neurotransmitters.

Effect of an action potential:

When an action potential reaches the end of a neurone it causes neurotransmitters to be released into the synaptic cleft. They diffuse across to the postsynaptic membrane and bind to specific receptors. When this happens it might trigger an action potential, cause muscle contraction or cause a hormone to be secreted. 

How are impulses unidirectional? The receptors are only on the postsynaptic membranes, neurotransmitters are only released from the presynaptic neurone and neurotransmitters are removed from the cleft so the response doesn't keep happening. 

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