Homeostasis

• In negative feedback, a change in a regulated variable triggers a response that opposes the change, bringing the variable back to its normal range.
• Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.
• Homeostasis is important for maintaining optimal conditions for enzyme action and all cell functions.
• In the human body homeostasis includes control of blood glucose concentration, body temperature and water levels.
• The automatic control systems may involve nervous or chemical responses.
• All control systems include recpetors, coordination centres and effectors.
• The nervous system uses electrical impulses to enable you to react quickly to your surroundings and coordinate your behaviour.
• Cells called receptors detect stimuli. Stimuli are the changes in the environment.
• Impulses from receptors pass along sensory neurones to the brain or spinal cord. The brain coordinates the response, and impulses are sent along motor neurones from the brain to the effector organs.
• The brain and spinal cord are known as the central nervous system.
• Reflex actions are automatic and rapid and do not involve the conscious parts of the brain.
• Reflexes involve sensory, relay and motor neurones.
• Reflex actions control everyday bodily functions, such as breathing and digestion, and help you to avoid danger.
• The main stages of a reflex arc are: Stimulus -> Receptor -> Sensory Neurone -> Relay Neurone -> Motor Neurone -> Effector -> Response