Key biology revision, Homeostasis

Question 1

What is maintained by homeostasis

Answer 1

1) Ion content / controlled by kidneys
2) Sugar content / controlled by pancreas
3) Water content / controlled by kidneys + ADH released by brain
4) Temperature / controlled by the brain (hypothalamus)
5) Removal of C02 is important, C02 is exhaled. It is a product of respiration. It’s toxic in high quantities.
6) Urea waste product of excess amino acids being broken down by the liver. It is removed by the kidneys.

Question 2

What happens when you get too hot. How does the body control body temperature.

Answer 2

Hypothalamus contains receptors that are sensitive to the temperature of blood flowing through the brain. It also receives impulses from the skin giving information about skin temperature.

1) hairs lie flat
2) sweat is produced by sweat glands and evaporates from the skin which removes heat.
3) the blood vessels supplying the skin dilate so more blood flows close to the surface of the skin. This makes it easier for heat to be transferred from the blood to the environment.

Question 3

What happens when you get too cold.

Answer 3

1) hairs stand up to trap an insulating layer of air
2) no sweat is produced
3) blood vessels supplying skin capillaries constrict to close of the skins blood supply.
4) when your cold you shiver , your muscles contract automatically this requires respiration which release energy to warm the body.

Question 4

What three main roles do kidneys perform.

Answer 4

1) removal of waste products such as urea from the blood.
2) adjustment of ions in the blood.
3) adjustment of water content of the blood.

Question 5

What is Urea

Answer 5

Proteins can’t be stored by the body - so any access amino acids are converted into fats and carbohydrates by the liver, which can be stored.

This process occurs in the liver. Urea is a waste product of these reactions.

Urea is toxic it is released into the blood stream by the liver where it is filtered out by the kidneys.

Question 6

What is water balance

Answer 6

Water is taken in as food and drink and is lost in three main ways.

1) In the urine.
2) In sweat.
3) In the air we breath out.

The water balance is between.

1) liquids consumed.
2) amount sweated out.
3) amount excreted by the kidneys in the urine.

Question 7

What is the definition of homeostasis

Answer 7

Homeostasis is the ‘Maintenance of a constant internal environment’

Question 8

What are the main components of the urinary system.

Answer 8

1) Kidneys
2) renal vein and artery
3) ureter descends down from kidneys brings urine into the bladder
4) bladder stores urine
5) sphincter muscles control opening and closing or bladder
6) urine leaves via the urethra

Question 9

What is ‘ultra filtration’?

Answer 9

A high pressure is built up which squeezes water, urea, ions, and sugar out of the blood and into the bowman’s capsule.

The membrane between the blood vessels and the bowman’s capsule act like filters, so big molecules like proteins and blood cells are not squeezed out they stay in the blood.

Question 10

What is selective reabsorption.

Answer 10

As the liquid flows along the nephron, useful substances are reabsorbed back into the blood.

1) all the sugar is reabsorbed. This involves the process of active transport against the concentration gradient.
2) sufficient ions are reabsorbed. Excess ions are not. Active transport is needed.
3) sufficient water is reabsorbed.

Remaining substances including urea, continue out of the nephron into the ureter and down to the bladder as urine.

Question 11

What are ‘Nephrons’?

Answer 11

Nephrons are the filtration units of the kidneys.

Question 12

How do dialysis machines work.

Answer 12

In a dialysis machine a patients blood flows alongside a partially permeable membrane surrounded by dialysis fluid. It’s permeable to things like ions and waste substances but not big molecules like proteins or blood cells.

The dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood. This means that useful dissolved ions and glucose won’t be lost from the blood during dialysis.

Only waste products such as urea and excess ions and water diffuse across the membrane.

Question 13

What happens when blood glucose levels get too high.

Answer 13

1) blood glucose is to high.
2) insulin secreted by pancreas
3) too much glucose but insulin as well
4) glucose removed by liver
5) insulin makes the liver convert glucose into glycogen
6) blood glucose is reduced.

Question 14

What happens when blood glucose levels get too low.

Answer 14

1) Blood with to little glucose
2) glucagon secreted by pancreas
3) too little glucose but glucagon as well
4) glucagon makes the liver convert glycogen into glucose. glucose added by liver.
5) blood glucose increased.

Question 15

What causes type 1 diabetes

Answer 15

Type 1 diabetes is a condition where the pancreas produces little or no insulin.

Question 16

What controls and treats type 1 diabetes

Answer 16

1) Limiting intake of foods rich in simple carbohydrates. Eg sugars which cause blood glucose to rise rapidly.
2) Regular exercise which helps to lower the blood glucose levels.
3) Insulin therapy this involves injecting insulin, sufferers of type 1 diabetes usually have several injections of insulin a day usually at mealtimes. This makes sure that glucose is removed from the blood quickly once the food has been digested. This stops the levels of glucose getting too high.
4) The amount of insulin injected depends on the persons diet and how active they are
5) Insulin can be extracted from the stomachs of pigs and cows, but now human insulin is made by genetic engineering. This human insulin does not cause adverse reactions like animal insulin did.
6) Insulin helps to maintain blood sugar levels but it cannot be controlled as accurately as having a normal working pancreas so they may still have long term health problems.
7) Diabetics can have a pancreas transplant. A successful operation means they won’t have inject insulin again. But as with any organ transplant your body can reject the tissue, if this happens you will often have to take costly immunosuppressive drugs. Which often have serious side effects.
8) Modern research into artificial pancreases and stem cell research may mean the elimination of organ rejection but there’s a long way to go yet.

Question 17

What is a stent and how is it used.

Answer 17

Stents keep arteries open. Coronary heart disease is when the arteries that supply the blood the the muscle of the heart become blocked by fatty deposits.

This causes the arteries to become narrow and blood flow is restricted, this can result in a heart attack.

Stents are tubes that are inserted inside arteries. They keep them open making sure blood can flow through to the heart muscle. This keeps the persons heart beating and alive.

Question 18

What is the chemical equation for aerobic respiration.

Answer 18

Glucose + oxygen > C02 + water + energy

Question 19

What is the chemical equation for photosynthesis.

Answer 19

6C02 + 6H20 > Sunlight > C6H1206 + 602

Question 20

What is the equation for anaerobic respiration

Answer 20

Glucose&raquo_space; lactic acid + energy

C6H1206&raquo_space; 2C3H603 + energy (chemical equation)