4.5 Homeostasis and Response

4.5.1 Homeostasis

Maintaining a Constant Environment

• Homeostasis maintains a constant body environment
• It makes sure all of the systems and reactions in the body are performing optimally
• Optimum conditions are required for enzyme action and cell functions

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Changes in the Internal and External Environment

• Homeostasis resists changes in the internal environment
  • E.g. if glucose concentration rises, the body will work to reduce glucose levels
• Homeostasis also resists changes in the external environment
  • E.g. if air temperature rises, the body will activate cooling mechanisms

Blood Glucose

• If homeostasis fails, a person could become hyperglycaemic or hypoglycaemic
• Both of these conditions have negative effects on the body

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Body Temperature

• If the temperature is too high, enzymes will denature, stopping the body’s natural processes
• If the temperature is too low, the enzymes will work too slowly

Water Levels

• In order for osmosis and general body processes to work perfectly, the water balance must be kept stable
• Water is key to many processes in the body

Nervous and Hormonal Systems

• Nervous response: consists of many neurones which respond quickly to short term changes
  • The response can happen within seconds
• Hormonal response: this is the chemical response and involves hormones which are released by glands
  • It takes time for the hormones to travel around the body

Order of Control Systems