• In order to?function?properly and?efficiently, organisms have different?control systems?that ensure their?internal conditions?are kept relatively?constant
• The process of maintaining constant internal body conditions is known as?homeostasis
• Homeostasis is?critically important?for organisms as it ensures the maintenance of?optimal conditions?for?enzyme action?and?cell function
• Sensory cells?can?detect?information about the?conditions?inside and outside of the body
• Examples of physiological factors that are?controlled?by?homeostasis?in?mammals?include:
  • Core body temperature
  • Metabolic waste (eg. carbon dioxide and urea)
  • Blood pH
  • Concentration of glucose in the blood
  • Water potential of the blood
  • Concentration of the respiratory gases (carbon dioxide and oxygen) in the blood

• The majority of homeostatic control mechanisms in organisms use?negative feedback?to maintain?homeostatic balance?(ie. to keep certain physiological factors, such as blood glucose concentration,?within certain limits)
• Negative feedback control loops involve:
  • A?receptor?(or sensor) – to?detect?a?stimulus?that is involved with a condition / physiological factor
  • A?coordination system?(nervous system and endocrine system) – to?transfer information?between different parts of the body
  • An?effector?(muscles and glands) – to?carry out a response
• Outcome of a negative feedback loop:
  • The factor / stimulus is?continuously monitored
  • If there is an increase in the factor, the body responds to make the factor decrease
  • If there is a decrease in the factor, the body responds to make the factor increase

A negative feedback control loop

• Homeostasis in?mammals?relies on?two different coordination systems?to transfer information between different parts of the body:
  • Nervous system?– information is transmitted as?electrical impulses?that travel along?neurones
  • Endocrine system?– information is transmitted as?chemical messengers?called?hormones?that travel in the?blood