Keeping Internal Conditions Constant

Question 1

What is homeostasis?

Answer 1

The maintenance of constant internal body conditions

Question 2

What body conditions must be controlled for homeostasis?

Answer 2

• Temerature
• Blood glucose level
• Water levels
• Ion content levels
• Levels of waste products

Question 3

What waste products are removed by the body and how?

Answer 3

• CO₂ produced by respiration is removed via the lungs when we breathe out
• Urea, produced in the liver from the breakdown of amino acids, is removed by the kindeys in urine and temporarily stored in the bladder

Question 4

How do water and mineral ions enter the body?

Answer 4

When we eat and drink

Question 5

What could happen if the water or ion content of the body is wrong?

Answer 5

To much water may move into or out of the cells

This could destroy or damage the cells

Question 6

What does the kindey do?

Answer 6

Filters the blood, excereting substances you do not want and keeping those your body needs

Question 7

How do the kindeys produce urine?

Answer 7

• First filtering the blood
• Reabsorbing all the sugar
• Reabsorbing the dissolves ions needed by the body
• Reabsorbing as much water as the body needs
• Releasing urea, excess ions, and excess water in the urine

Question 8

Where does the urine go before it exits the body?

Answer 8

It is temporarily stored in the bladder

Question 9

What is the ureter?

Answer 9

Tube through which urine passes from the kindey to the bladder

Question 10

What is the urethra?

Answer 10

Tube through which urine passes to the outside of the body

Question 11

What are the names of the blood vessels that supply blood to the kindeys and take it away?

Answer 11

The aorta and renal artery

The renal vein and vena cava

Question 12

What does the renal artery and renal vein do?

Answer 12

Renal artery brings blood containing urea + other susbstances in solution to the kidney

Renal vein carries blood away after these have been removed

Question 13

Why don’t we constantly piss all the time?

Answer 13

There’s a ring of at the bottom of the bladder which controls when it opens and closes

Question 14

What is dialysis?

Answer 14

The process of cleaning blood through a dialysis machine when a person’s kindeys don’t work properly or have failed

Question 15

How does dialysis work?

Answer 15

• The dialysis fluid contains the same concentration of useful substances (ions + sugars) as the patient’s blood
• This means that they do not diffuse out of the patient’s blood so do not need to be reabsorbed
• Urea diffuses out from the blood into the fluid
• Dialysis restores the concentration of substances in the blood back to normal, but needs to be carries out at regular intervals

Question 16

If a person has a kindey transplant, what will this mean?

Answer 16

They will no longer require further dialysis

Question 17

Draw and label a diagram of the process of dialysis

Answer 17

The dialysis machine has a partially permiable membrane

Blood cells and proteins are too large to pass through this

Question 18

How can kidney rejection be prevented?

Answer 18

• Must be a very good ‘tissue match’
• Following the transplant, the recipient must take drugs to suppress the immune response to prevent rejection
• These are called immunosuppressant drugs

Question 19

What would cause a kidney to be rejected?

Answer 19

• There are proteins called antigens on the surface of cells
• These act as markers for the cells and body
• The recipient’s body may recognise these as ‘foreign’
• This would cause the immune response, which is to release antibodies to attack and kill the foreign cells

Question 20

What are the advantages of kidney transplants over dialysis?

Answer 20

• Cheaper (for patient/NHS)
• Patient no longer requires dialysis

Question 21

What are the disadvantages of kidney transplants?

Answer 21

• Some risks from the operations
• Immunosuppressant drugs need to be taken before and after the opperation. This leaves the patient vulnerable to infection

Question 22

How is the new kidney usually positioned in the body?

Answer 22

In the groin, attached to the blood vessels + bladder

The old kidneys are left in the body

Question 23

What is the core body temperature and why must it be kept constant?

Answer 23

37°

Must be kept constant so enzymes work efficiently and do not denature

Question 24

What monitors and controls body temperature?

Answer 24

The thermoregulatory system in the brain

It detects and controls blood temperature only

Question 25

How is blood temperature monitored?

Answer 25

* The thermoregulatory centre has receptors which detect the temperature of the blood flowing through the brain * Temperature recepters in the skin also send implulses to the brain to give information about skin temperature

Question 26

What happens if the core body temperature rises?

Answer 26

* Blood vessels near the surface of the skin dilate allowing more blood to flow through the skin capillaries * Energy is transfered by radiation and the skin cools * Sweat glands produce more sweat. The water evaporates from the skin's surface * The energy required to make the water evaportate comes from the skin, so it cools down

Question 27

What happens if the core body temperature falls?

Answer 27

* Blood vessels near the surface of the skin constrict and less blood flows through the skin capillaries * This means less energy is lost by radiation * We 'shiver'. Muscles contract quickly. This requires respiration * Some of the energy released by this warms the blood * Hairs on the skins surface become erect * This traps a layer of insulating air

Question 28

What do doctors need to consider when thinking of treating patients with kidney failure using dialysis or a transplant?

Answer 28

* The general health of the patient * How long the patient has been on dialysis * The total cost of the treatment - long term costs of dialysis vs. operation costs + drugs * Risks of operation - anaethetics, infection * The availability of donor kindeys

Question 29

What are the ethical issues surrounding kindey transplants and dialysis?

Answer 29

* Should everyone automatically be on a transplant register or should they opt in? * Should people be paid to be donors? * Should people pay for a new kidney to jump the queue? * Should people be given a preference? E.g. the young

Question 30

Why is it important to carry a donor card or tell your family you want to be a donor?

Answer 30

It is distressing to families having to make a descision immediately after the death of a loved one You can decide what happens

Question 31

Small children have a large surface area to volume ratio. What can this cause?

Answer 31

* They transfer energy to the surroundings very quickly in cold conditions and dehydrate quickly in hot ones * If the body temperature is too low the respiratory enzymes work too slowly and too little energy is released * If the child dehydrates they cannot cool down and overheat, meaning that enzymes denature

Question 32

What can happen to elderly people in cold conditions and why?

Answer 32

They can suffer from hypothermia in cold conditions because they do not move around much to release energy from respiration in muscles

Question 33

What do explorers in extreme environments have to learn how to recognise?

Answer 33

The symptoms of hypothermia and dehydration

Question 34

Why can extreme temperatures be dangerous for survival?

Answer 34

Because the body's enzymes do not work properly

Question 35

Which organ controls and monitors the level of glucose in the blood?

Answer 35

The pancreas

Question 36

What does the pancreas do if there is too much glucose in the blood?

Answer 36

Produces the hormone insulin

Question 37

What does insulin do?

Answer 37

Causes blood glucose levels to fall Causes glucose to move from the blood into our cells

Question 38

What happens to excess glucose in the liver?

Answer 38

It is converted into glycogen for storage

Question 39

What is Type 1 diabetes?

Answer 39

Diabetes caused when the pancreas produces none or too little insulin. Causes the blood glucose level to become very high Usually occurs in children and young adults and lasts throughout their lives

Question 40

How is Type 1 diabetes controlled?

Answer 40

By regular injections of insulin Careful attention to diet Carful attention to levels of exercise

Question 41

Describe fully how blood glucose level is controlled in the body

Answer 41

* **Insulin** causes blood glucose levels to fall * If the level gets too low **receptors in the pancreas** detect this * The pancreas released **glucagon**, another hormone * The glucagon causes the **glycogen** in the **liver** to change into **glucose** * The glucose is released back into the blood

Question 42

What do some diabetics use instead of injections?

Answer 42

Pumps attached to the body They can adjust the level of insulin injected by the pump

Question 43

What are the new methods of treating and potentially curing Type 1 diabetes that are currently being developed?

Answer 43

* Pancreas transplants * Transplanting pancreas cells * Using embryonic stem cells to produce insulin secreting cells * Using adult stem cells from diabetic patients * Genetically engineering pancreas cells to make them work properly