Homeostasis

Homeostasis:

The internal environment of the body must remain stable. It needs enough water for substances to dissolve and for chemical reactions to take place inside the cells. But too much water can cause swellings and high blood pressure. Keeping the internal environment of the body stable is called homeostasis.

The body loses water when we breathe and sweat. Sweat is produced by sweat glands in the skin. It can also lose water in urine so if the body contains too much water the kidneys produce more urine. If the body has little water the kidney produces little water and the brain responds by making you feel thirsty. The control of water in the body is called osmoregulation. The control of glucose in the blood is blood glucose regulation. 

The body's temperature is 37C. The control of body temperature is Thermoregulation.

Hypothalamus is part of the brain that constantly monitors temperature. It receives information from nerve endings in the dermis of the skin about temperature outside of the body. If body temperature goes below 37C hypothalamus causes muscles to shiver. It releases heat which warms you up.

Hypothalamus also causes erector muscles in the dermis to contract. It causes body hairs to stand upright. Oils released from sebaceous glands at the base of the hair keep the skin lubricated and in good condition. It also reduces blood flow near the skin.

If body temperature goes above 37C hypothalamus causes us to sweat. When sweat evaporates it transfer heat energy from the skin to the surroundings so the skin cools down. Hypothalamus also increases blood flow near the skin so we look pinker.

When it's cold hypothalamus reduces blood flow by narrowing blood vessels. This is called vasoconstriction. Vasodilation (when blood vessels widen) happens when the body needs to lose heat.

The control of body temperature is an example of negative feedback. This means as a change to the body happens in one direction mechanisms in the body work to make it change in the opposite direction. This helps conditions in the body stay under control.


Key Words:

Internal environment
Homeostasis
Sweat glands
Urine
Kidneys
Osmoregulation
Blood glucose regulation
Thermoregulation
Hypothalamus
Dermis
Erector Muscles
Sebaceous glands
Vasoconstriction
Vasodilation
Negative feedback


Questions:

1. What is Homeostasis?
2. What is getting thirsty a sign of?
3.  Why do people shiver when it's cold?
4. What is vasocontriction and vasodilation?
5. What changes would happen to your body if you spent 1hr in a greenhouse? Why?


What you should've learnt:

Homeostasis as the maintenance of a stable internal environment.

An understanding of the homeostatic mechanisms of: a. thermoregulation and the effect of temperature on enzymes  b. Osmoregulation  c. Blood glucose regulation. 

How thermoregulation takes place, with reference to the function of the skin , including: a. the role of the dermis-sweat glands, blood vessels, nerve endings, hair, erector muscles and sebaceous glands  b. the role of the hypothalamus-regulating body temperature.

How thermoregulation takes place, with reference to: a, vasoconstriction  b. vasodilation  c. Ngeative feedback.