B12 - Homeostasis in Action

Question 1

Give three things that the body can do to reduce heat loss if it gets too cold.

Answer 1

• Hairs erect - trap insulating layer of air
• No sweat produced
• Vasoconstriction - close of skin’s blood supply
• Shiver (muscles contracting) - needs respiration which transfers some energy to warm the body.

Question 2

Name three things that are reabsorbed by the kidneys

Answer 2

• Urea
• Ions
• Water

Question 3

What are the advantages and disadvantages of a kidney transplant over dialysis?

Answer 3

DIALYSIS
Advantages:
- Can buy a patient with kidney failure valuable time until organ donor found
Disadvantages:
- Three sessions a week
- Each session is 3-4 hours
- Can cause blood clots or infections
- Expensive
TRANSPLANT
Advantages:
- Can be transplanted from people still alive
- Cheaper
- One process
Disadvantages:
- Donor kidney can be rejected
- Immunosuppressant drugs
- Long waiting lists

Question 4

What hormone controls the amount of water reabsorbed by the kidneys and how does it work?

Answer 4

• Anti-Diuretic hormone (ADH)
  => Water content of blood too high
  => Less ADH released from pituitary gland
  => Less water reabsorbed from kidney tubules (more lost via urine)
  (opposite happens when content is too low)