Homeostasis Flashcards
Definition of homeostasis
The control of internal conditions to provide the optimum conditions inside cells for all the reactions needed for life
Examples of internal conditions that needs to be controlled through homeostasis: Temperature, water levels, blood pH, oxygen levels
Definition of thermoregulation
The control and maintenance of a constant body temperature
Why is it so important that our body temperature be kept within such a narrow range?
Enzymes work best at 37 degrees (where 37 degrees is body temperature for a human being)
What happens if conditions such that our body temperature gets too hot or too cold?
Too cold - reactions will be too slow - can lead to hypothermia and death
Too hot - enzymes denature - can lead to dehydration, heat stroke and death
What monitors and controls body temperature?
A part of the brain called the hypothalamus monitors and controls body temperature. It is known as the thermoregulatory centre of the brain
How does the hypothalamus gather their information?
What happens if the temperature of the body changes too much?
It gathers information via nerve impulses from temperature receptors in:
The brain - these are sensitive to the temperature of the blood flowing there
The skin - these are sensitive to skin temperature
If the temperature of the body changes too much, the hypothalamus bring about changes to return the temperature to normal
What 4 things happens when you get too cold?
- Hair stands on end - air currents cannot get to the skin and a layer of warm air is trapped to act as a insulator - goosebumps
- Vasoconstriction - blood vessels near the skin surface constrict (gets smaller) so less blood passes through them. This means less heat is lost by radiation. Muscles in the vessel walls contract to bring about vasoconstriction. Capillary networks near the surface of the skin are closed and blood is diverted away.
- Shivering - rapid involuntary of skeletal muscles. This requires energy from respiration, and some of this is released as heat which warms the blood flowing through the muscles.
- Behavioural responses - for example, having a hot drink or putting on more clothes
What 4 things happen when you get too hot?
- Hairs lie flat - this is so that air currents can get to the skin and remove the insulating layer of warm air
- Vasodilation - blood vessels near the skin dilates so more blood passes through them. This means more heat is lost to the environment by radiation and conduction. Capillary networks near the surface of the skin are opened and blood flows to the surface of the skin. This is why your face goes red when you are hot.
- Sweating - sweat glands release sweat onto the surface of the skin. Sweat is mostly water so the excess heat from body evaporates the water in the swat cooling the skin
- Behavioural responses - for example seeking shade, removing layers of clothing, cold drinks.
What is osmoregulation?
Water levels are constantly changing. The regulation of a constant body water content is known as osmoregulation.
What would cause the body to gain water?
Drinks
Food
Water
What would cause our bodies to lose water?
Excretion
Sweating
Egestion
Exhalation
If we contain too little water, what is there a risk of? So what does the hypothalamus do?
Dehydration
The hypothalamus initiates:
- Behavioural responses such as drinking more
- The production of a smaller quantity of more concentrated urine initiating the release of the hormone ADH from the pituitary gland. This affects the kidneys causing them to reabsorb water.
If there is too much water, what are the risks? What does the hypothalamus do then?
It can result in over hydration so the hypothalamus brings about the production of a larger quantity of more dilute urine by preventing the release of the hormone ADH from the pituitary gland
What is the hypothalamus in the brain responsible for?
It is responsible for bringing about osmoregulation by monitoring the concentration of water in the blood.
