The Arrangement of the Nervous System

The Arrangement of the Nervous System

The nervous system carries messages around the body using specialised cells called neurones. Neurones convey their 'messages' using electrical impulses.

The nervous system (NS) is made up of two parts:

  • Central nervous system comprising the brain and spinal cord.

  • Peripheral nervous system.

A simple way of thinking about the interaction between the two systems is to imagine them as roads, and the messages as cars.

The 'car' starts off in small roads (peripheral nervous system) and heads towards to the brain. In order to get there faster it takes the motorway (central nervous system) which gets the 'car' to its final destination - the brain - very quickly.

See how this happens in the diagram below:

central nervous system

Different areas of the nervous system are used for different types of nervous reaction:

  • Conscious control - for example, your brain consciously deciding to move a moving skeletal muscle, and this uses the somatic/voluntary NS.

  • Non-conscious control - for example, your body automatically reacting to, and this uses the autonomic NS.

Generally, with the autonomic NS, if the outcome increases activity - for example, if the heart rate goes up, it involves the sympathetic NS.

If the outcome is to decrease activity - for example, if the breathing rate goes down, it involves the parasympathetic NS.

central nervous system

Receptors are cells that detect stimuli - for example, heat, pressure, light.

Sensory neurones bring impulses from receptors to the central nervous system (CNS).

From there, the impulse may pass on to a motor neurone to be taken to a muscle or gland (the effector).

Sometimes there is an intermediate neurone (also known as a 'relay' neurone) within the CNS linking the sensory neurone with the motor neurone.

To be able to understand how the impulses are transmitted through a neurone, you must first know what the cell is like at rest.