Homeostasis Flashcards
Define the term ‘homeostasis’.
The maintenance of a stable internal environment
What conditions need to be kept constant in the human body?
- Temperature
- Blood glucose levels so cells have constant supply of energy
- Water
What mechanisms are used to reduce body temperature?
- Sweating
- Hairs lie flat
- Vasodilation
Explain the role of vasodilation in reducing body temperature.
- Capillaries near surface of skin dilate
- Increases blood flow to them
- More heat lost through skin via radiation
Explain the role of hairs lying flat in reducing body temperature.
- Erector pili muscles relax so hair lies flat
2. Less air is trapped between hair and skin, meaning body is less insulated. Therefore, heat can be lost more easily.
Explain the role of sweating in reducing body temperature.
Water in sweat evaporates from skin surface, helping to cool the skin because heat is taken with it
What mechanisms are used to increase body temperature?
- Shivering
- Hair stands up
- Vasoconstriction
- Hormones
Explain the role of shivering in increasing body temperature.
The rate of respiration increases when muscles contract so more heat is produced
Explain the role of hairs standing up in increasing body temperature.
- Erector pili muscles contract so hair stands up
2. This traps more air in insulating air, reducing heat loss
Explain the role of vasoconstriction in increasing body temperature.
- Capillaries near skin surface constrict
2. Heat loss reduced because blood flow to skin is reduced
Explain the role of hormones in increasing body temperature.
- Body releases adrenaline and thyroxine
2. This increases metabolism of cells so more heat is produced
What does the hypothalamus do?
Controls body temperature
How does the hypothalamus control body temperature?
- It receives information from thermoreceptors via sensory neurones
- Hypothalamus sends impulses to effectors (muscles or glands) via motor neurones to initiate an action.
