To create voluntary movement the CNS processes sensory information supplied by the eyes, ears and other sense organs and receptors of the body. It then selects the appropriate response, plans, and then carries out the movement by sending nerve impulses through the motor branch of the peripheral nervous system.

You will turn your head towards the person that tapped your shoulder. If you know the person, the conversation will turn into the “Hi, how are you? What are you doing here type”.

Nerve impulses begin in a dendrite, move toward the cell body, and then move down the axon. A nerve impulse travels along the neuron in the form of electrical and chemical signals. The axon tip ends at a synapse. A synapse is the junction between each axon tip and the next structure.

An impulse travels along the neuron pathways as electrical charges move across each neural cell membrane. Ions moving across the membrane cause the impulse to move along the nerve cells. When the impulse reaches the end of one neuron (the axon), the impulse reaches a synapse. A synapse is the space between neurons.

Axon, also called nerve fibre, portion of a nerve cell (neuron) that carries nerve impulses away from the cell body. A neuron typically has one axon that connects it with other neurons or with muscle or gland cells.

The axon arises from the soma at a region called the axon hillock, or initial segment. This is the region where the plasma membrane generates nerve impulses; the axon conducts these impulses away from the soma or dendrites toward other neurons.

The largest mammalian axons can reach a diameter of up to 20 µm. The squid giant axon, which is specialized to conduct signals very rapidly, is close to 1 millimetre in diameter, the size of a small pencil lead.

Once an electrical impulse has reached the end of an axon, the information must be transmitted across the synaptic gap to the dendrites of the adjoining neuron. Neurotransmitters are chemical messengers that are released from the axon terminals to cross the synaptic gap and reach the receptor sites of other neurons.

When an axon is damaged with a laser, it sends out signals to the surrounding tissue to be ‘cleaned up’, triggering the release of proteins that hastens degeneration of the axon. If such molecules are prevented from showing up, it could slow down the progress and extent of nerve damage.

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A synapse is the small gap between two neurons, where nerve impulses are relayed by a neurotransmitter from the axon of a presynaptic (sending) neuron to the dendrite of a postsynaptic (receiving) neuron. It is referred to as the synaptic cleft or synaptic gap.

The synapse, rather, is that small pocket of space between two cells, where they can pass messages to communicate. A single neuron may contain thousands of synapses. In fact, one type of neuron called the Purkinje cell, found in the brain’s cerebellum, may have as many as one hundred thousand synapses.

In particular, the cerebral cortex — a thin layer of tissue on the brain’s surface — is a thicket of prolifically branching neurons. “In a human, there are more than 125 trillion synapses just in the cerebral cortex alone,” said Smith.