HOMEOSTASIS IN ACTION (12) Flashcards
What does the core body temperature rely on?
The thermoregulatory centre in the hypothalamus of your brain. This centre contains receptors that are sensitive to temperature changes in the blood flowing through the brain itself.
How does the body cool down?
The blood vessels dilate - this is called vasodilation.
It lets more blood flow through the capillaries. Your skin flushes so you transfer more energy by radiation from your skin to the surroundings, cooling you down and warming the air around you.
Produce more sweat. This cools you down because as the sweat evaporates, it transfers energy to the environment. (Hard when it is humid as the sweat does not evaporate).
How does the body keep warm?
The blood vessels constrict to reduce the flow of blood through the capillaries. This is called vasoconstriction. It reduces the blood flow and the energy transferred by radiation through the surface of your skin.
Sweat production is stopped.
Your skeletal muscles contract and relax rapidly, causing you to shiver. These contractions needs lots of respiration, an exothermic reaction. The energy transferred from these reactions raises your body temperature until shivering stops.
What is urea?
This is the nitrogenous waste produced by the breakdown of amino acids in your liver.
What is deamination?
The process by which the kidneys removes the amino acid group. This forms ammonia which is very toxic. The ammonia is immediately converted into urea to be excreted from the body.
What is the role of the kidney?
To remove toxic urea from the body in your urine, along with other excess water and mineral ions not needed by the body.
How do the kidneys work?
They filter your blood. Glucose, mineral ions, urea and water all move out of your blood and into the kidney. The blood cells pass through the kidney as the molecules are too large to filter out of the blood.
The glucose is reinforced back into the blood by diffusion and active transport. Selective reabsorption is the process by which the amount of mineral ions reabsorbed varies.
How is water balanced? (In the kidney).
ADH hormone.
This maintains a level water balance in the body.
If the blood becomes more concentrated, the pituitary gland releases lots of ADH into the blood. This affects the kidney tubules so they reabsorb much more water. This results in relatively small volumes of very concentrated urine.
If the solute concentration becomes too dilute, less ADH is released into the blood. Less water is absorbed into the kidney tubules. This results in a large volume of dilute urine and the blood solute concentration returns back to normal.
What is dialysis?
When the function of the kidney is carried out artificially.
What is the renal artery?
Brings blood containing urea and other substances in solution to the kidney.
What is the renal vein?
Carries blood away from the kidney, after urea and other substances have been removed from the blood.
How does dialysis work?
There is dialysis fluid containing the same amount (concentration) of glucose and mineral ions as the blood of a person without kidney disease. This ensures there is no net movement of glucose out of the blood.
The excess ions move out of the blood by diffusion down a concentration gradient. This leaves the blood plasma levels at normal levels.
However, the dialysis fluid contains no urea meaning there is a steep concentration gradient from the blood down into the fluid. As a result, much of the urea leaves the blood.
The whole dialysis process depends on diffusion down a concentration gradient, no active transport.
What are the disadvantages of dialysis?
Maintain a planned diet, controlling the intake of proteins as this would increase the levels of urea.
