Homeostasis In Action

Question 1

What does the control of our body temperature rely on

Answer 1

Thermoregulatory centre in the hypothalamus

Question 2

What does the thermoregulatory centre contain

Answer 2

Receptors that are sensitive to temperature changes in the blood

Question 3

How does your body cool you down?

Answer 3

Vasodilation = blood vessels dilate allowing more blood to flow, skin flushes transferring more energy to the surroundings
Sweat = sweat glands in skin sweat, water evaporates from skin, transferring energy to the surroundings

Question 4

How does your body keep you warm?

Answer 4

Vasoconstriction = blood vessels constrict, reduce blood flow, reduce energy transferred to surroundings
Sweat production stops = less water from sweat evaporates, less energy transferred
Shiver = skeletal muscles contract and relax quickly, exothermic process, energy transferred raises body temperature

Question 5

Removing CO2

Answer 5

Produced during respiration
Dissolved CO2 is acidic = affect enzymes working
CO2 diffuses out of cells into blood down concentration gradient = diffuses from blood into our alveoli in lungs
Air containing excreted CO2 removed when exhales
Side effect = lost water when exhale

Question 6

Removing Urea

Answer 6

Produced = eat too much protein and tissue worn out
Extra protein can’t be stored = broken down
Amino acids can’t be used as fuel so,
Liver removes amino group from amino acids by deamination = forming ammonia
Ammonia immediately converted into urea and excreted from body
Rest of amino acids used in respiration/to make molecules

Question 7

What is controlled in your body in terms of water and mineral ions?

Answer 7

No control:
-Water leaves lungs when exhale
-Water, mineral ions and urea lost in skin in sweat
Control:
-Urea, excess water and excess mineral ions secreted in urine = maintains water and mineral content within narrow limits and removes urea

Question 8

What happens if you drink too much water?

Answer 8

Homeostasis in water balance
Short of water = kidneys conserve it -> produce very little very concentrated ruin and water is saved
Drink too much = kidneys produce lots of dilute urine to get rid of excess

Question 9

How are mineral ions lost in your body?

Answer 9

Sweat through skin

Excrete in urine

Question 10

How do your kidneys work

Answer 10

Filter your blood
Blood cells and large proteins = too big to leave blood in filtering process and can’t go into kidney tissues
So glucose selectively reabsorbed back into the blood by diffusion and active transport
Amount of water reabsorbed controlled by feedback mechanism and kept within a narrow range

Question 11

How do kidney tubules work and effect the body?

Answer 11

Kidney tubules selectively reabsorb water and mineral ions

Amount of water in blood = maintained by negative feedback with releasing ADH

Question 12

What happens if solutes are concentrated?

Answer 12

Receptor cells in brain detect concentration of solutes in blood
Too concentrated = released lots of ADH
Tubules reabsorb more water
Urine = concentrated

Question 13

What happens if solutes are dilute?

Answer 13

Less ADH is released into blood
Less water reabsorbed into tubules
Produce large volume of dilute urine and blood solute concentration is turned back to normal

Question 14

What is dialysis

Answer 14

The function of the kidney is carried out artificially

Question 15

What does a dialysis machine do?

Answer 15

Persons blood leaves their body and flows between partially permeable membrane
The other side of the membranes is the dialysis fluid with the same concentration of blood of a healthy person
Restores concentrations of dissolved substances to normal levels
Takes 8 hours
Have to manage diet to keep blood chemistry stable

Question 16

What happens if your kidneys don’t work?

Answer 16

Concentrations of urea and minerals ions build up in blood

Question 17

How does a dialysis machine work?

Answer 17

1) Blood removed from patient and flows into the dialyzer - kept separated from dialysis fluid by a partially permeable membrane
2) The dialysis fluid contains the same concentration of glucose and salts as normal blood plasma = no net movement of glucose out of the blood by diffusion
3) Excess salts diffuse into dialysis fluid
4) The dialysis fluid contains no urea, so all of the urea diffuses from the blood in to the dialysis fluid from the high concentration in the blood to the lower concentration in the dialysis fluid
5) The blood and dialysis fluid move in opposite directions across the membrane = maintains concentration gradients all the way along
6) The clean blood is returned to the patient and the waste dialysis fluid is disposed of.

Question 18

What do you have to do if you have dialysis?

Answer 18

Controlled diet
Long sessions with machine
Feel tired and unwell
Over many years gets more difficult to control
Control protein intake
Control salt intake

Question 19

Rejection in kidney transplants?

Answer 19

Antibodies attack antigens = destruction of donated kidney
Match antigens with same tissue type
Drugs to suppress immune response for the rest of their lives
Immunosuppressant drugs
Prevents patients from dealing effectively with infectious diseases
Don’t last forever

Question 20

Dialysis vs Transplant

Answer 20

Transplant
\+ cheaper
\+ lead relatively normal life
- take immunosuppressant drugs
- shortage of donors
- don’t last forever
- risk of rejection
- operation risks

Dialysis
\+ available to all kidney patients
\+ no drugs
- expensive
- regular dialysis sessions
- limit salt and protein intake