1. Neural communication How do neurons send messages to each other?

2. The Synapse Two neurons meet at a synapse. Children have roughly 10 16 synapses. Adults somewhere from 1-5  10 15 A typical synapse is about 20nm wide (20 billionths of a meter). This is called the synaptic cleft

3. Neurotransmitter Neurons communicate by sending chemical messages called neurotransmitters to other neurons. These neurotransmitters travel from axon to either the dendrite or the cell body across the synapse. Where a synapse is depends on what the connection type is –Excitatory: Axon to dendrite –Inhibitory: Axon to cell body

5. Neurotransmitter release Neurotransmitters are held in the terminal button in synaptic vesicles. The action potential opens voltage-gated Ca + channels in the terminal. This causes the vesicles to bind with the cell membrane, which allows neurotransmitter to be released into the synaptic cleft.

6. Neurotransmitter absorbtion On the post-synaptic side of the synaptic cleft, neurotransmitters bind to chemical receptors that open chemically-gated ion channels. Some of these ion channels are K + channels, which allow K + ions to leave the cell. This has the effect of hyperpolarizing the area, which inhibits the post-synaptic cell. Others are Na + channels, which allow sodium into the cell, depolarizing the area. This excites the post-synaptic cell.

7. Re-uptake Once the neurotransmitter has done its job, it binds to a protein on the pre-synaptic membrane. This process allows the pre-synaptic cell to recycle the neurotransmitter, ensuring each action potential will generate the same sized signal in the synapse. It also lessens the effect of the neurotransmitter so that the receiving cell does not become desensitized to its effects, unless a rapid sequence of action potentials causes neurotransmitter to be continually present.