SYNAPSES
The term synapse designates the point where the axon of one neuron connects to a dendrite of another. This word comes from the Greek syn (together) and haptein (join). Neurons can be connected in two very different ways:
- by an electrical synapse, in which the two cells touch and are connected by tiny holes, which lets the static electric impulse pass from neuron to neuron;
- by a chemical synapse, where the two cells do not touch e.o. and the nerve impulse needs particular molecules to bridge the gap between them.
The vast majority of the ≈150 trillion synapses are chemical. Although slower than electrical ones they are more flexible.
Variations in number of neurotransmitters released, receptors available, or affinity between them make the synapses undergo changes in size and enable us to learn.
Synaptic transmission, dozens of times per second at the ends of ≈100 billion neurons, is the omnipresent mechanism that is the source of the brain’s great plasticity.
