B1aL1 Coordination

Key Words

Adrenaline - a hormone released in stressful situations.

Central nervous system - A system of nerve fibres that communicates electrically throughout the body

Coordination - muscles and other tissues working together;

Effector organs - organs that respond to nerve impulses

Glands - organs that secrete hormones

Hormones - a chemical released by the body to cause changes in the body.

Nerves - bundles of lots of neurones

Neurones - nerve cells;

Secrete - release a chemical.

Target organs - organs that respond to hormones.

Grade E

A simple task like walking is actually a very complex process.  Many muscles work together to ensure that we walk in a coordinated way.  They are made to work together by the central nervous system. 

Different parts of the body communicate with each other by nerve cells and the whole process is monitored by the brain.  The messages are passed using electrical pulses, a bit like the electrical signals that transmit data in electronic systems.

Changes are detected by receptor cells that pick up stimuli from the environment.  Stimuli might be things like:

• Smells;
• Colours;
• Sounds;
• Pokes and prods.

The receptor cells give out  electrical impulses that are carried by nerve cells (neurones) to the brain.  Nerves are bundles of nerve cells.  The nerve cells that transmit impulses from receptors are called sensory neurones.  The impulses are carried to the brain.  The brain then sends messages down motor neurones to effector organs like muscles.  This is summed up in the picture below

Grade C

Many processes are controlled by chemicals called hormones.  Hormones are made by glands and secreted into the blood.  They travel around the blood to the target organ.  Adrenaline is one such hormone that prepares the body for fight or flight.

In a stressful situation, the eyes, ears, and other receptors pick up stimuli (e.g. a lion charging at you).  The brain processes the information and sends nerve impulses to the adrenal glands which lie next to the kidneys.  The adrenals immediately secrete adrenaline, which is carried to the target organs:

• heart;
• eyes
• breathing muscles;
• stomach;
• and intestine.

You feel the following:

• Heart: it beats faster and harder.
• Breathing muscles: you breathe faster and deeper.
• Eyes: pupils dilate.
• Digestive organs: you may feel sick, or want to go to the lavatory.

While not many of us will be eaten by lions, athletes such as those above will feel all the effects above while waiting at the start of a competition.

Grade A

A hormone reaction can target a number of different organs at the same time, while a nerve fibre only travels to one effector organ.  The brain can, of course, stimulate a good number of effector organs at the same time. We can compare the actions of nerves and hormones: