A-LevelBiologyHomeostasis9700/43 · May/June 2017 · Q111 Marks

The mammalian kidney is an organ involved in homeostasis. [Figure 1.1]

(a)Explain what is meant by the term homeostasis.[1]
(b)(i)With reference to Fig. 1.1, name structures A and B.[2]
(b)(ii)On Fig. 1.1, use label lines and letters to label where: U - ultrafiltration occurs L - the loop of Henle is found C- blood urea concentration is low.[3]
(c)Describe the roles of the hypothalamus and the posterior pituitary in osmoregulation.[5]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.

[1] maintain / keep / restore, constant / stable / set-point / within narrow limits, internal environment / in body;
[2] A - pelvis; note if labelled medulla as affects ecf in part (ii)
B - ureter;
[3] A full labels instead of letters
if region A (pelvis) was mislabelled as medulla in (i) can apply:
ecf for L placed in pelvis
ecf U placed in medulla only if word cortex also written by U/ultrafiltration
U - pointing to the cortex ;
L - pointing to the medulla ;
C - pointing to the renal vein ;
[5] max 5 of:
1 hypothalamus detects (changes in) water potential (of the blood) ;
2 osmoreceptors shrink when, low / less, water in blood; ora
3 ADH, produced / made, in hypothalamus ;
4 if low, water / Ψ, ADH secreted from posterior pituitary ; ora R ADH produced in posterior pituitary
5 ref. to neurosecretory cells
or
impulse / ADH transported, from hypothalamus to posterior pituitary ;
6 aquaporins;
7 ADH increases permeability of, distal convoluted tubule / collecting duct; ora
8 ADH causes, more water reabsorption / smaller volume of urine / more concentrated urine; ora A both with and without ADH compared

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