A-LevelBiologyControl and coordination9700/43 · Oct/Nov 2025 · Q513 Marks

The endocrine system and the nervous system both coordinate responses in mammals.

(a)Complete Table 5.1 to show the features of three cell-signalling molecules of the endocrine system: antidiuretic hormone (ADH), glucagon and insulin. Use a tick (✔) if the molecule has the feature and a cross (X) if the molecule does not have the feature. Put a tick (✔) or a cross (X) in every box. feature binds to receptors on cell surface membranes results in molecules moving from cells into the blood is secreted as a result of detection by osmoreceptors [Table 5.1][3]
(b)The endocrine system has a slower transmission speed than the nervous system. Describe other ways in which the endocrine system and the nervous system differ.[4]
(c)(i)The endocrine system and the nervous system can affect muscle function. Fig. 5.1 shows a transmission electron micrograph of a longitudinal section of striated muscle tissue that is in a relaxed state. [Figure 5.1] State the letter on Fig. 5.1 that indicates the length of a sarcomere.[1]
(c)(ii)State the letter on Fig. 5.1 that indicates a region where actin and myosin overlap.[1]
(c)(iii)Describe and explain how the region labelled D on Fig. 5.1 changes during muscle contraction.[4]

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 (Oct/Nov 2025). The mark or mark type is shown in brackets.

[1] binds to receptors on cell surface membranes | ✔ | ✔ | ✔ ;
[1] results in molecules moving from cells into the blood | ✔ | ✔ | X ;
[1] is secreted as a result of detection by osmoreceptors | ✔ | X | X ;
[1] 1 impulses / action potentials / neurotransmitters, in nervous system and hormones in endocrine system ;
[1] 2 electrical in nervous system and chemical in endocrine system ;
[1] 3 neurones / nerve cells, in nervous system and blood in endocrine system ;
[1] 4 effects are / target is, specific / localised, in nervous system and (can be) widespread in endocrine system ;
[1] 5 effect / response, happens quickly in nervous system and slowly in endocrine system ;
[1] 6 effect / response, lasts a short time in nervous system and long time in endocrine system ;
[1] 7 AVP ;
[1] C ;
[1] B ;
[1] 1 (D / it), shortens / contracts / decreases ;
[1] and any three from: 2 calcium ions / Ca2+, bind to troponin ;
[1] 3 tropomyosin, moves / shifts position / exposes binding sites on actin ;
[1] 4 myosin (head) binds to actin / myosin-actin cross-bridges form ;
[1] 5 power stroke / myosin head, pulls actin ;
[1] 6 more actin, enters / overlaps with, A band / B or more overlap between actin and myosin ;

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.