| Date | May 2011 | Marks available | 6 | Reference code | 11M.3.HL.TZ1.15 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 15 | Adapted from | N/A |
Question
Explain the control of ADH secretion.
Markscheme
ADH secreted by hypothalamus;
by neurosecretory cells;
transport of ADH to posterior pituitary for storage;
through axon;
osmoreceptor cells monitor concentration of blood plasma;
if blood plasma too concentrated, ADH released;
kidney produces a small volume of hypertonic urine / reabsorption of water in collecting ducts;
if plasma too dilute, ADH level of blood drops;
kidney produces a large volume of hypotonic urine / little water reabsorbed from collecting ducts;
controlled by negative feedback;
Examiners report
There were variable responses from very poor to very good with many responses being awarded full marks.
