Neurons

Nervous consists of neurons and neuroglia

The nervous system is made up of many millions of special cells called neurons that form a continuous network, extending all over the body. The form the structural units of the nervous system.

Neurons can function for a life time. They cannot undergo meiosis, so they cannot be replaced if destroyed. Neurons have a very high metabolic rate and and need continuous supplies of oxygen and glucose.

In addition to neurons there are supporting cells called glial cells which play a critical role in making myelin and supporting and protecting the neurons

A cell body made up of a cell, and have long, thin processes - fibres of a cytoplasm that extend from the body

Dendrites: that conduct impulses towards the cell body, they branch extensively to provide a large surface area to receive signals from other neurons Axon: conducts impulses away from the cell body, each neuron has a single axon although certain axons may give off branches along their length. Usually branches extensively to form terminal branches.

• Sensory/unipolar neurons: these are afferent (towards) neurons as they carry impulses from receptors towards the CNS. Unipolar - one fibre attached to the cell body • Connector neurons: these are multipolar neurons found in the CNS and make up 99% of the neurons of the body. They receive impulses from sensory neurons and pass them omn to other neurons. • Motor/multipolar neurons: these are efferent neurons as they carry impulses away from the CNS to effectors so that the appropriate response can be brought about.