B12 - Homeostasis In Action

Question 1

What is homeostasis?

Answer 1

Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

Question 2

Why is homeostasis important?

Answer 2

Homeostasis is important as cells and organs can become damaged if the internal environment changes too much. This is because enzymes cannot work properly.

Question 3

Which part of the brain controls body temperature?

Answer 3

The hypothalamus is a part of the brain that monitors blood temperature.

Question 4

Other than the brain, how else is body temperature controlled?

Answer 4

The skin has receptors that monitor the external temperature. Nerves carry messages from these to the brain.

Question 5

Describe some changes that take place in/on the body it body temperature is too low

Answer 5

• Shivering - uses energy
• Less sweating
• Increased respiration- releasing energy from food
• Vasoconstriction (narrowing) of blood vessels near surface of skin
• Hairs stand upright to trap air (insulating)

Question 6

Describe some changes that take place in/on the body if body temperature is too high

Answer 6

• Sweating (water evaporates from skin surface taking heat away)
• Vasodilation (widening) of blood vessels near surface of skin
• Hairs lie flat

Question 7

What is your understanding of the term ‘negative feedback’.

Answer 7

Negative feedback means that whenever a change occurs in a system, this automatically causes a corrective mechanism to start, which reverses the original change and brings the system back towards the set point (i.e. ‘normal’).

Question 8

Describe the ways that water is lost from the body.

Answer 8

• Water leaves the body via the lungs during exhalation (breathing out)
• Water, ions and urea are lost from the skin in sweat.

Question 9

List the 4 main waste products that are released from the body.

Answer 9

• Water
• Urea
• Ions
• Carbon dioxide

Question 10

From which organ is there CONTROLLED loss of water?

Answer 10

Controlled loss of excess water, ions and urea is controlled by the kidneys when they filter the blood to produce urine.

Question 11

What is deamination?

Answer 11

Deamination is the process of breaking down excess amino acids (from proteins).

Question 12

Using a brief flow chart, describe the process of deamination

Answer 12

Protein -> amino acids -> ammonia (toxic) -> Urea (excreted in urine & sweat)

Question 13

Where does deamination take place?

Answer 13

The liver

Question 14

What are the 3 main functions of the kidneys?

Answer 14

1. Filters the blood (this is called ultrafiltration).
2. Reabsorb water (and other useful substances e.g. glucose, some salts, water) back into the blood stream. This is called selective reabsorption.
3. Excrete urea, water, and salts (in urine)

Question 15

What are the functional units of the kidney where filtration and selective reabsorption takes place called?

Answer 15

Nephrons

Question 16

Describe the process of ultrafiltration.

Answer 16

• Blood enters the kidneys via the renal artery.
• Blood is filtered under very high pressure.
• Large plasma proteins and blood cells are too large to pass through the filter.
• The filtered blood is now called filtrate.
• This is occurs in the nephron of the kidney

Question 17

Describe the process of ‘selective reabsorption’

Answer 17

• Useful substances (that the body doesn’t want to lose) are selectively reabsorbed by the nephron back into the bloodstream.
• E.g. All of the glucose, amino acids, some ions, some water are reabsorbed.
• The rest of the filtrate passes through the rest of the nephron.

Question 18

Describe the process of urine formation and excretion.

Answer 18

• Urine is formed with the substances that were not reabsorbed.
• Urine is a solution of excess water, salts and urea.
• Urine is collected in the collecting duct.
It passes through the ureter to the bladder.

Question 19

What does ADH stand for and what is it’s function?

Answer 19

Anti-diuretic hormone (ADH) is a hormone involved in the control of the loss of water as urine.

Question 20

Which part of the brain releases ADH?

Answer 20

The pituitary gland

Question 21

In what situation is ADH released?

Answer 21

It is released into the bloodstream by the pituitary gland when receptors in the brain detect that the blood is too concentrated.

Question 22

Where does ADH travel to once released and what effect does it have?

Answer 22

ADH acts on the walls of the kidney tubules making them more permeable, therefore more water is reabsorbed back into the blood from the kidney tubules.

Question 23

If the blood water potential rises, the pituitary gland will release __________ ADH.

Answer 23

LESS

Question 24

Which part of the brain detects the level of water in the bloodstream.

Answer 24

The hypothalamus

Question 25

If the hypothalamus detects a low water concentration in the bloodstream, what volume & concentration of urine would be produced?

Answer 25

A low volume of concentrated urine. As the body is trying to conserve water.

Question 26

What is dialysis?

Answer 26

Dialysis is a medical procedure that filters waste products and excess fluids from the blood artificially using a dialysis machine, replicating the function of the kidneys for individuals with impaired kidney function.

Question 27

What are some of the problems associated with dialysis?

Answer 27

• The possibility of blood clots forming
• The amount of time it takes
• You have to follow a strict diet.
• It is also an unpleasant experience, and the build up of waste products between sessions can leave you feeling ill.

Question 28

The only possible cure for kidney disease is a kidney transplant. Outline some issues that surround transplants.

Answer 28

• Risk of the transplanted kidney being rejected from the body as a result of the immune system recognising the antigens -on the donor organ as foreign.
• The chance of this happening can be reduced by using immunosuppressant drugs.
• However, this means that the person can be left vulnerable to other diseases.
• In addition, transplanted kidneys do not last forever.

Question 29

List some advantages of having a kidney transplant.

Answer 29

• Can resume a normal lifestyle as no dialysis.
• Dialysis takes several hours in hospital three times a week and makes a person very tired.
• Dialysis machines are expensive.