Homeostasis under pressure

Question 1

How is homeostasis of water balance affected by extreme heat?

Answer 1

Release of ADH = thirst, water retention and production of tiny amount of urine (0.3 ml/min) that is hyperosmotic to the blood (1400 mOsm/L).
This constitutes a 99.8% recovery of water entering the nephrons

Question 2

How is homeostasis of temperature affected by extreme heat?

Answer 2

Excessive sweating to cool body temperature - thickening of the blood, straining the heart and eventually death by heart failure.

Question 3

What is the max capacity of kidney to conc. urine?

Answer 3

1400mOsm

Question 4

How much Na+ can the body excrete per L of urine? How much Na+ is in 1 L of urine?

Answer 4

-We can excrete approx 6g of Na+ per litre of urine
-seawater contains around 12g of Na+ per litre

Question 5

What is the water loss from drinking seawater?

Answer 5

For every 1000ml of seawater you produce 1350ml of urine
Net Loss is 350ml

Question 6

What is the effect of alcohol on urine production?

Answer 6

For every 1g of alcohol consumed, urine excretion increases by 10ml. Causes imbalances of ions

Question 7

How does the body cope with over-hydration?

Answer 7

• Lack of thirst
  -Collecting ducts become less permeable to water
  -Copious amounts of urine produced (25 ml per min;100 mOsm)
  -stretch receptors in the aorta and carotid arteries further inhibiting ADH release

Question 8

What is diabetes insipidus?

Answer 8

-lack of ability to produce ADH or Kidneys do not react to ADH
-excessive thirst and the production of copious quantities of urine (> 5 litres per day)
-you can’t produce more concentrated urine