Homeostasis
- 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
- 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
Exam Tip
Learn the following definition for homeostasis:
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.
Negative Feedback
- 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
