how concentrated urine is made

Question 1

concentrated urine

Answer 1

1. When water is in short supply, the concentration of inorganic ions in the blood rises and the water potential becomes more negative
2. The change is detected by osmoreceptors in the hypothalamus and nerve impulses are sent to to the posterior pituitary which releases ADH
3. ADH is picked up by receptors in the kidneys and INCREASES permeability of the distal tubule and collecting duct to let water back into the blood

Question 2

hypothermia positive feedback

Answer 2

Detection by Receptors – Thermoreceptors in the skin and hypothalamus detect a drop in core body temperature and send signals to the heat loss center of the hypothalamus.
Failure of Effectors & Positive Feedback – Normally, effectors like skeletal muscles (shivering) and blood vessels (vasoconstriction) help retain heat. However, in severe hypothermia, the heat loss center of the hypothalamus remains active, causing widening of blood vessels (vasodilation) instead of constriction, which increases heat loss instead of conserving heat.
Worsening Response & Further Cooling – As body temperature continues to drop, metabolic processes slow down, reducing heat production. This reinforces the drop in temperature, creating a positive feedback loop that can lead to unconsciousness and even death.