B3.3 Homeostasis

Question 1

Define homeostasis.

Answer 1

The maintenance of a constant internal environment

Question 2

What are the three main roles of the kidney?

Answer 2

• Removal of urea
• Adjustment of ion content
• Adjustment of water content

Question 3

How does carbon dioxide leave the body?

Answer 3

Through the lungs when you exhale

Question 4

How is carbon dioxide produced in the body?

Answer 4

As a product of respiration

Question 5

Where is urea produced?

Answer 5

The liver

Question 6

How is urea produced?

Answer 6

• Excess amino acids are broken down into fats and carbohydrates (the body can’t store proteins)
• Urea is a waste poisonous product of this reaction

Question 7

How does urea leave the body?

Answer 7

• Stored temporarily in the bladder as urine

- Is excreted from the body

Question 8

What are six things the body has to regulate?

Answer 8

• Body temperature
• Glucose levels
• Ion content
• Water content
• Carbon dioxide removal
• Urea removal

Question 9

Where do ions (e.g sodium) enter the body?

Answer 9

In the food we eat

Question 10

What happens if ion/water content is wrong?

Answer 10

The balance between ions and water will be upset, causing too much or too little water to be draw into body cells by osmosis.

Question 11

Name 3 ways water is lost.

Answer 11

• Urine - Sweat - Air we breathe out

Question 12

When we sweat little, what is the urine produced by our bodies like?

Answer 12

• Dilute and pale

- Lots of it

Question 13

When we sweat a lot, what is the urine produced by our bodies like?

Answer 13

• Minimal

- Dark coloured and concentrated

Question 14

Describe the process in the kidneys.

Answer 14

1) Ultrafiltration. High pressure squeezes glucose, ions, water and urea out of the blood (that entered through the renal artery) and into the Bowman’s capsule.
2) Reabsorption. These molecules travel along the nephron which reabsorbs all glucose and some ions and water into the blood
3) Waste molecules are carried out of the nephron to the bladder where they are temporarily stored before excretion.

Question 15

What are nephrons?

Answer 15

Filtration units in the kidneys

Question 16

Why does the body need to control temperature?

Answer 16

Enzymes work best at 37 degrees C.

If temperature is too hot/cold it will cause enzymes to stop working and important reactions will be disrupted,

Question 17

What part of the brain detects temperature change?

Answer 17

The thermoregulatory centre

Question 18

How does the thermoregulatory centre detect temperature change?

Answer 18

• Receptors in the brain sense the temperature of the blood flowing through it.
• Receptors in the skin send impulses to the brain when the skin temperature changes.

Question 19

What happens when temperature increases too much?

Answer 19

• Sweat increases (evaporation cools skin)
• Hair lies flat
• Vasodilation (vessels wider and closer to the skin surface)

Question 20

What happens when temperature decreases too much?

Answer 20

• Hairs stand up (insulating layer)
• Vasoconstriction (vessels thinner and move deeper)
• Minimal sweating
• Shivering - contracting muscles respire - releasing energy

Question 21

What organ controls and monitors blood glucose?

Answer 21

The pancreas

Question 22

Describe the process when there is too much glucose in the blood.

Answer 22

• Insulin secreting cells in the pancreas are stimulated
• Insulin is secreted
• Insulin stimulates glucose uptake from the blood
• Glucose is stored as glycogen in the liver

Question 23

Describe the process when there is too little glucose in the blood.

Answer 23

• Glucagon secreting cells in the liver are stimulated
• Glucagon is secreted
• Glucagon stimulates the liver breakdown of glycogen into glucose

Question 24

What is type 1 diabetes?

Answer 24

A disease in which a person’s blood concentration level may rise to a high level because the pancreas doesn’t produce enough insulin.

Question 25

How can type 1 diabetes be controlled? (3)

Answer 25

• Avoid foods high in simple carbohydrates (e.g sugars)
• Take exercise after eating to use up extra glucose released in digestion
• Inject insulin into the blood at mealtimes making the liver remove glucose as soon as it enters the gut making it more effective.

Question 26

What do insulin injection dosages depend on?

Answer 26

Level of activity and diet

Question 27

Describe and evaluate a treatment for diabetes used in the past.

Answer 27

• Insulin was taken from pigs and cows and injected into diabetics.
• Advantage: saved many diabetic people’s lives
• Disadvantages: animal insulin isn’t the same as human insulin so can cause reactions, animals are killed, there isn’t enough insulin all the time.

Question 28

Describe and evaluate two treatments for diabetes used now.

Answer 28

1) Genetically engineering bacteria to produce insulin
- Advantage: constant supply of insulin, no harm to creatures
- Disadvantage: ethical objections from some
2) Pancreas transplants
- Advantage: Normal life, more ease
- Disadvantages: rejection, infection

Question 29

What are two methods that could be be used to treat diabetes in the future?

Answer 29

• Stem cell therapy

- Artificial pancreases

Question 30

What does dialysis do?

Answer 30

It restores the concentration of dissolved substances in the blood to normal levels.

Question 31

Describe the dialysis process.

Answer 31

• The person’s blood flows alongside a selectively permeable membrane (surrounded by dialysis fluid)
• This is permeable to ions, glucose, water and urea but not big molecules (e.g amino acids) - like kidney filters
• The dialysis fluid has the same concentration of glucose and ions and water as healthy blood - only excess ions and water and urea will diffuse across the barrier.

Question 32

How does rejection occur?

Answer 32

Foreign antigens are attacked by the person’s antibodies

Question 33

What are the two ways to prevent rejection?

Answer 33

• ‘Tissue-typing’, finding a donor with a tissue type (similar antigens) most closely matching the patient
• Immunosuppressant drugs (this can have serious side effects as immune system is lowered)

Question 34

What are the disadvantages of kidney transplants? (5)

Answer 34

• Immunosuppressant drugs
• Waiting for a donor
• Waiting for a match tissue
• Risk of infection
• Dangers of operation

Question 35

What are the disadvantages of dialysis? (3)

Answer 35

• Diet restrictions
• Long regular hours at the machine
• Blood clots