B12: Homeostasis in Action Flashcards
What is the normal human body temp?
37C
Where is the body temperature monitored?
By the thermoregulatory centre in the brain
How does the thermoregulatory centre control body temperature?
Contains receptors which are sensitive to the temperature of the blood. The skin also contains these receptors - they send electrical impulses down sensory neurones to the thermoregulatory centre.
What happens when the body temperature of a person gets too high?
- Sweat glands release sweat onto the surface of the skin, which evaporates and takes thermal energy away from the body.
- Flushing - under the surface of the skin, there is a network of fine blood capillaries, supplied with blood by blood vessels. These blood vessels dilate (get wider - vasodilation), therefore more blood can flow into the capillaries and heat can now transfer out of the blood
What happens when the temperature of a person drops too low?
- Vasoconstriction - less blood vessels flow into the capillaries and therefore less heat is transferred outside of the body
- Shivering - skeletal muscles contract. To generate energy for contraction, muscles increase their rate of respiration and the body warms up as heat is generated.
- No sweat
Why does the body have to maintain water levels?
Water moves in and out of body cells through osmosis. If blood is too dilute, water moves into cells by osmosis. If it’s too concentrated, then water moves out of the cells. If body cells gain or lose too much water by osmosis then they don’t work efficiently. Therefore, water levels must be kept constant.
How can water in the body be lost?
Exhalation
Sweat (+ sodium ions also lost)
Urine
Why can the body not control how much water, ions or urea is lost by sweat?
Sweating is part of the temperature control system
What happens if blood is too dilute?
If blood is too dilute, kidneys remove excess water, as well as urea and excess ions are removed as urine
Describe how the kidneys filter the blood
Humans have 2 kidneys. Blood enters the kidneys via arteries - this blood contains urea. The kidneys remove this, as well as excess ions and excess water; which leave the kidney as urine (stored in the bladder). Clean blood now leaves the kidney through the vein.
How do the kidneys adjust the levels of molecules in the blood (ultrafiltration)?
Blood passes through the capillaries, where small molecules are filtered out of the blood, including ions, urea and water as well as glucose. These pass into a tube. Now all of the glucose, some ions and some water is reabsorbed back into the blood (selective reabsorption). Urea, excess ions and water are released as urine.
How does the body deal with excess amino acids?
Liver breaks down excess amino acids to make ammonia (deamination). Ammonia is toxic, so the liver converts it into urea, which is safely excreted by the kidneys
Describe what happens to the release of ADH if the blood becomes too concentrated (water level drops)
Water level falls, therefore more ADH is released by the pituitary gland. It travels to the kidneys and causes the tubules to become more permeable to water (more water can pass out of the tubules), meaning more is reabsorbed from the tubules back into the blood. This means less urine is produced and the water level rises.
Describe what happens to the release of ADH if the blood becomes too dilute
Pituitary gland stops releasing ADH, meaning kidneys absorb less water into the blood and more urine is excreted.
What is kidney dialysis?
When water level, ion levels and urea need to be adjusted using a machine
