Responding to change

A neuron (or neurone) is an individual cell of the nervous system. Neurones communicate with one another and other tissues through long processes that extend from their cell bodies. There are different names for these processes; some are called dendrites, others are called axons. Often it is fine to be vague and just call them fibres.

Fibres of multiple neurones surviving a similar function can come together and be wrapped up in a piece of connective tissue. These fibres and their surrounding connective tissue are called nerves.

Basically - 

Once a sensory receptor detects a stimulus, the information (sent as an electrical impulse) passes along special cells called neurones. these are usually found in bundles of hundreds or even thousands of neurones known as nerves.

The impulse travels along the neurone until it reaches the central nervous system or CNS. The CNS is the brain and the spinal cord. The cell which carries impulses from your sense organs to your CNS are called sensory neurones.

Summary - 

Your nervous system carries fast electrical impulses. Your hormones are chemical messengers secreted by special glands and carried around the body in the blood.

Part 1

Nervous system - enables you to know and react to whats happening in your surroundings. Your nervous system carries electrical signals (impulses) which travel from 1 to 120 metres per second. This allows you to react to things very fast.

Hormones - Hormones are chemical substances (messengers). They control many of the processes going on inside your body. Special glands make and release (secrete) these hormones into your body. Then the hormones are carried around your body in the bloodstream to their target organs. They can act quickly, but often their effects are quite slow and long lasting.

Special glands - Special glands make and release hormones into your body.

Part 2

Stimuli - Any changes picked up by receptors.

Receptors - Receptors are usually found clustered together in special sense organs, such as your eyes and your skin. You have many different types of sensory receptors.

Sense organs - Your sense organs are for example your ears, eyes, nose, tongue and skin.

Motor neurones - Carry information from the CNS to the rest of the body.

Central nervous system - Made up of the brain and the spinal cord.