Topic 12 - Homeostasis in action Flashcards
Why is it necessary to keep the body’s temperature within narrow limits?
-Enzymes work best at an optimum temperature.
-Only a few degrees above optimum and enzymes denature, making them unable to fit with the active site, leading to death.
-A few degrees below and the metabolism is too slow to keep you alive.
How is your temperature controlled?
The thermoregulatory centre of the brain within the hypothalamus. The centre contains receptors sensitive to temperature changes in the blood flowing through the brain.
What is vasodilation?
The blood vessels supplying your surface skin capillaries dilate, letting more blood flow through the capillaries. The skin flushes, so you transfer more energy by radiation from your skin to the surroundings, cooling you down and warming air around you.
Apart from vasodilation, how does the body cool down?
Sweat production in the sweat glands increases. This extra sweat cools down your body as water evaporates from the skin, transferring energy to the environment.
What is vasoconstriction?
Blood vessels supplying your skin capillaries constrict (close) to reduce blood flow through the capillaries, reducing energy transferred by radiation through the skin’s surface.
Apart from vasoconstriction, how does the body stay warm?
-Sweat production is reduced or stopped. Less water from sweat evaporates, so less energy is transferred to the environment.
-Skeletal muscles contract and relax rapidly, causing shivering. Muscle contractions require lots of respiration, an exothermic reaction, which raises body temperature until shivering stops.
What is urea?
A nitrogenous waste product produced by the breakdown of excess amino acids in the liver.
How is urea excreted from the body?
The urea passes from liver cells into your blood. Urea is poisonous and if levels build up it can cause cell damage. It is filtered out of the blood by the kidneys and is passed out of the body in urine produced by the kidneys along with excess water and salt.
How and why is urea formed?
It is formed when you eat more protein than necessary, or when tissue is worn out. Excess protein can’t be stored and has to be broken down. Amino acids can’t be used as fuel by body cells. The liver removes the amino group from the amino acids by a process calld deamination. This forms the toxic ammonia. Ammonia is immediately converted to urea. Urea is toxic but can be safely removed by the body.
How do the kidneys affect water and mineral ion concentration in the body?
If you are short of water, your kidneys conserve it. You produce very little, very concentrated urine and water is saved for use in the body. If you drink too much water then your kidneys produce lots of dilute urine to get rid of the excess.
Your kidneys remove excess mineral ions, when they are in excess, and excrete them in urine.
What does the kidney do?
It filters the blood. Glucose, mineral ions, urea and water all move out of the blood into the kidney. The blood cells and large proteins are too big to leave the blood during filtration. All the blood in your body passes through your kidneys every five minutes. Your kidney produces around 1800cm3 of urine a day, this urine trickles down into the bladder where it is stored.
What is selective reabsorption?
Where the amount of water reabsorbed into the blood is controlled by a very sensitive feedback mechanism keeping water and mineral ion content within narrow limits.
How does ADH and water balance work?
The amount of water in the blood is controlled by a negative feedback system involving ADH. Receptors cells detect concentration. If the blood is too concentrated, the pituitary gland releases lots of ADH. The kidney reabsorbs more water. If the solution becomes too dilute, less ADH is released, less water is reabsorbed, and concentration returns to normal.
What is kidney dialysis?
When a machine is used to carry out the function of the kidney artificially, filtering the contents of the blood.
What is a kidney transplant and why is it a long term solution to kidney problems?
A kidney transplant is when a damaged kidney is replaced with a healthy one. As opposed to dialysis machines, when you have a transplant you don’t need to go to the doctors all of the time and it is far more convenient.
