Analyse how hypothalamic osmoreceptors regulate ADH and how aquaporins in collecting ducts increase water reabsorption and concentrate urine.
Feedback mechanisms are used in living organisms both to promote and respond to change.
Outline the role of ADH in osmoregulation.
ADH (secreted by pituitary) if body/blood is dehydrated/hypertonic/has high solute concentration;
more aquaporins / aquaporins open (in collecting duct);
collecting duct more permeable to water/reabsorbs more water (from filtrate/urine);
water reabsorbed by osmosis/water reabsorbed because medulla is hypertonic;
(reabsorbed) water passes (from filtrate) to blood / blood solute concentration reduced;
less water lost in urine / smaller volume of (more concentrated) urine;
negative feedback / less/no ADH secreted when blood solute concentration returns to normal;