Unit 5: The nervous and endocrine systems                    1   2   3   4   5

2.2. Nerve impulse and synapse

Neurons transmit and create nerve impulses. A nerve impulse is the electrical signal which spreads along the neuron. When neurons are stimulated they transmit impulses from their dendrites to their axons.

Neurons are not in contact. Between a neuron and other, there is a space called synaptic cleft. The nerve impulse has to cross this space. This occurs thanks to chemical substances called neurotransmitters. Synapse is the pass of nerve impulse from a neuron to another. 

We can divide the process in several stages:

1st) Nerve impulse arrives to the pre-synaptic neuron.

2nd) This provokes the production of neurotransmitter vesicles in the synaptic terminal.

3rd) Vesicles fuse with the cytoplasmic membrane and release the neurotransmitter molecules to the synaptic cleft.

4th) Neurotransmitter molecules bind to specific receptors on the membrane of dendrites of post-synaptic neuron.

5th) This provokes the transmission of the nerve impulse to this neuron.

2.9. Listen and related each step of the synapse with its correspondent

       number in the picture