Nervous and chemical co-ordination

Co-ordination in the body happens in two ways.

Nervous co-ordination

Electrical impulses along nerves.

Very fast.

Short-lived, and aimed at a precise target.

Chemical co-ordination

Hormones carried in the blood.

Slower.

Longer-lasting, and can reach many organs.

Neurons

The nervous system is built of nerve cells, neurons, with long fibres that carry impulses.

Figure to be added

Figure — a neuron: the cell body with its nucleus, the branching dendrites, and the long axon ending at nerve endings.

Sensory neurons

Carry impulses from receptors to the central nervous system.

Relay neurons

Link neurons inside the central nervous system.

Motor neurons

Carry impulses from the central nervous system to effectors.