Homeostasis

All organisms and cells require specific internal conditions in order to function. This is mostly due to the continuous enzymatic reactions that occur in every cell that will only work under certain conditions.

The body must detect and respond to internal and external changes to maintain the optimum internal conditions; this is called homeostasis. 

Examples include:

• Maintaining blood glucose concentration.
• Maintaining body temperature.
• Maintaining water levels. 

The process by which the body maintains the conditions of the internal environment is autonomic which means it happens automatically, without thought. 

Autonomic control system:

1. Receptors detect stimuli (changes in the environment) and send information to coordination centres such as the brain, spinal cord and pancreas.
2. Coordination centres process the information and organise a response.
3. Effectors produce a response to return the condition to its optimum level. The response may be chemical (e.g. hormones secreted from glands) or nervous (e.g. electrical impulses causing muscle contraction). 

The autonomic control system works using negative feedback.