What is homeostasis?
The maintenance of a stable internal environment
What do homeostatic mechanisms act to do?
Counteract the changes in the internal environment
At what level does homeostasis occur?
All levels -
- Whole body
What factors does homeostasis control?
- Supply of nutrients
- Supply of oxygen
- Blood flow
- Body temperature
- Removal of waste
- Control of CO2
What does failure of homeostasis lead to?
What are the components of the control systems in the body?
- Control centre
What are the main communication pathways in the body?
- Nervous system
- Endocrine system
What does the nervous system use?
What is paracrine control?
Local release (via ducts/exocrine) and action
What is autocrine control?
When agents are released by a cell which affects the releasing cell
What can the peripheral nervous system be divided into?
The afferent branch (sensory input) and the efferent branch (motor output)
What does the control centre do?
- Establishes the reference set point
- Analyses the afferent input
- Dtermines the appropriate response
Give two important control centres in the brain
- Medulla oblongata
Where is the dicephalon located?
In the hypothalamus
Where is the medulla oblongata located?
In the brain stem
What is the hypothalamus involved in the regulation of?
The endocrine system
What are regions of the medulla involved in the control of?
- Cardiovascular system
What are receptors required for in the bodies control systems?
Detect stimuli such as changes in the internal environment
Give two examples of receptors
What are receptors usually made of?
Specialised nerve endings
How do sensors communicate input to the control centre?
Via the afferent nerves
What do effectors do?
What happens to the output produced by the control centre?
It is communicated via efferent pathways to the effectors
Give an example of an effector?
Sweat glands, which can be activated to produce more sweat, causing heat loss
Give an example of a control system in the body
The hypothalamic-pituitary-adrenal axis
What is it called when the set point for homeostasis varies over time?
Give an example of a level varies during the day
Level of the hormone cortisol
When does cortisol levels reach their peak?
When are cortisol levels at their lowest?
What is it known as when levels vary over roughly a 24 hour cycle?