S5 Biology Practice Paper: Coordination, The Nervous System And Hormones (12 Questions, 100 Marks, 75 Minutes)

S5 Biology Practice Paper: Coordination, the Nervous System and Hormones (12 Questions, 100 Marks, 75 Minutes)

2026-11-09

S5 Biology: Coordination, Neurones and Hormones

12-question S5 Biology paper (100 marks, 75 minutes) on coordination: neurones, reflex arc, synapses, blood glucose, water balance and diabetes. Answers included.

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Paper details　Subject: Biology | Time: 75 minutes | Marks: 100 | Questions: 12

Instructions: This paper has three sections, A, B and C. Answer all questions. Total marks: 100. Time allowed: 75 minutes.

Show the formula used, the values substituted and the correct units. Give numerical answers to three significant figures.

In explanations, name the principle used, for example limiting factors, cohesion and adhesion, or source and sink.

Spend about 20 minutes on Section A, 30 minutes on Section B and the last 25 minutes on Section C.

Section A Neurones, Reflex Arc and Synapses (4 questions, 28 marks)

Answer all questions. Write your answers in the answer book.

#	Question	Answer and marking notes
1	State the three main parts of a neurone and give one function of each. (6 marks)	Cell body: contains the nucleus and controls metabolism and protein synthesis, 2 marks. Dendrons and dendrites: receive messages from receptors or other neurones and carry signals towards the cell body, 2 marks. Axon: carries the action potential away from the cell body to the axon terminals, 2 marks.
2	Explain the five components of a reflex arc, and use the withdrawal reflex to explain why reflex actions are faster than voluntary actions. (6 marks)	Receptor detects the stimulus, sensory neurone carries the impulse to the central nervous system, the spinal cord integrates the information, motor neurone carries the impulse to the effector, and the effector (muscle or gland) responds: 1 mark each, 5 marks. A reflex does not involve conscious decision making in the cerebrum and the pathway is shorter, so the response is faster, 1 mark.
3	An action potential travels 0.90 m along a nerve pathway in 15 ms. (a) Calculate the average conduction speed in m/s. (b) If the same pathway consisted of unmyelinated fibres with a conduction speed of only 0.5 m/s, calculate the time taken in seconds. (c) Explain how the myelin sheath increases conduction speed. (8 marks)	(a) Speed = 0.90 / 0.015 = 60 m/s, 3 marks (formula, substitution, answer with unit). (b) Time = 0.90 / 0.5 = 1.8 s, 3 marks. (c) The myelin sheath is an insulator, so the action potential jumps between nodes of Ranvier (saltatory conduction); fewer regions have to depolarise, so conduction is faster, 2 marks.
4	Describe how an action potential crosses a synapse, using acetylcholine as an example, and explain why transmission across a synapse is one-way only. If a drug inhibits the enzyme acetylcholinesterase, predict and explain its effect on skeletal muscle. (8 marks)	The action potential reaches the axon terminal, calcium ions enter and synaptic vesicles fuse with the presynaptic membrane to release acetylcholine, 2 marks; acetylcholine diffuses across the synaptic cleft and binds to receptors on the postsynaptic membrane, 2 marks; sodium channels open and the postsynaptic membrane depolarises, 1 mark. One-way: vesicles occur only in the presynaptic knob and receptors only on the postsynaptic membrane, 1 mark. Inhibiting acetylcholinesterase allows acetylcholine to accumulate, so the postsynaptic membrane is stimulated continuously and the muscle stays contracted or goes into spasm, 2 marks.

Section B Blood Glucose, Water Balance and Hormones (4 questions, 32 marks)

Your explanations should refer to the relevant physiological mechanisms.

#	Question	Answer and marking notes
5	After a meal an adult blood glucose concentration rises from 4.5 mmol/L to 7.2 mmol/L. (a) Calculate the percentage increase. (b) Explain how insulin returns the concentration to normal. (c) Name one hormone with the opposite effect and state its source. (8 marks)	(a) (7.2 – 4.5) / 4.5 x 100% = 60%, 2 marks. (b) A rise in blood glucose stimulates beta cells of the islets of Langerhans to secrete insulin, which increases glucose uptake by muscle and liver cells and promotes glycogen formation, speeds up cell respiration and inhibits glycogen breakdown, 4 marks. (c) Glucagon, secreted by the alpha cells, 2 marks.
6	Compare nervous coordination with hormonal coordination in terms of transmission pathway, speed of transmission and duration of effect. (8 marks)	Pathway: nervous coordination uses action potentials and neurotransmitters along neurones, 2 marks; hormonal coordination uses the blood to carry hormones to target organs, 2 marks. Speed: nervous coordination is very fast, in milliseconds, 1 mark; hormonal coordination is slower, taking minutes to hours, 1 mark. Duration: nervous effects are short lived, 1 mark; hormonal effects last longer, 1 mark.
7	An adult daily urine output falls from 1.5 dm³ to 0.4 dm³. (a) Calculate the percentage decrease. (b) Use the concept of negative feedback to explain how antidiuretic hormone causes this change. (c) State the symptoms that may appear if ADH secretion is persistently too low. (8 marks)	(a) (1.5 – 0.4) / 1.5 x 100% = 73.3%, 2 marks. (b) When the water potential of the blood falls, osmoreceptors in the hypothalamus detect the change, 2 marks; the posterior pituitary releases more ADH, 1 mark; the distal tubule and collecting duct become more permeable to water, so more water is reabsorbed, urine volume falls and the urine becomes more concentrated, 1 mark. (c) A large increase in urine volume (diabetes insipidus) together with persistent thirst, 2 marks.
8	During a sudden emergency a person heart rate rises from 70 to 105 beats per minute. (a) Calculate the percentage increase. (b) Name the gland that secretes adrenaline. (c) Describe two effects of adrenaline and explain their value in the fight-or-flight response. (8 marks)	(a) (%.0f – %.0f) / %.0f x 100%% = %.0f%%, 2 marks. (b) The adrenal glands, specifically the medulla, 2 marks. (c) It speeds up the heart and breathing rate, converts liver glycogen to glucose and diverts blood from the digestive system and skin to skeletal muscle: 2 marks per effect, 4 marks for any two. These effects supply extra oxygen and glucose to muscle quickly so the person can run away or struggle.

Section C Experimental Design, Data Handling and Applications (4 questions, 40 marks)

Show all working and controlled variables, and state the units.

#	Question	Answer and marking notes
9	A student uses the ruler drop test to compare the reaction times of two classmates. Describe the procedure, three factors that must be controlled, and how reaction time is calculated from the drop distance. (10 marks)	Procedure: the subject holds the open fingers level with the lower end of the ruler and the tester releases it without warning; the subject catches it as quickly as possible and the drop distance is recorded; repeat five times and take the mean, 4 marks. Controlled factors: the same ruler, the same release method with no warning, the same hand, the same posture and level of attention, 3 marks. Calculation: from d = ½ g t², t = √(2d / g) with g = 9.81 m s⁻², 3 marks.
10	Results: student A catches the ruler after it falls 0.20 m and student B after 0.28 m (take g = 9.81 m s⁻²). (a) Calculate both reaction times to three significant figures. (b) Calculate the percentage by which B is slower than A. (c) State two factors that make this comparison unreliable. (10 marks)	(a) tA = √(2 x 0.20 / 9.81) = 0.202 s and tB = √(2 x 0.28 / 9.81) = 0.239 s, 4 marks. (b) (0.239 – 0.202) / 0.202 x 100% = 18.3%, 4 marks. (c) Only one trial without repeats, a different degree of warning, tiredness or distraction, and an inaccurate reading of the starting position, 1 mark each for any two, 2 marks.
11	Use blood glucose regulation and body temperature regulation to explain negative feedback, give one example of positive feedback, and explain why most control mechanisms in the body are negative. (10 marks)	Negative feedback: when a value moves away from the set point the body responds to bring it back, 2 marks. Glucose example: a rise in blood glucose increases insulin secretion, which lowers it, while a fall increases glucagon secretion, which raises it, 3 marks. Temperature example: a rise in body temperature causes sweating and vasodilation, which increase heat loss, 2 marks. Positive feedback example: during childbirth uterine contractions stimulate oxytocin release, and oxytocin makes the contractions stronger, 2 marks. Negative feedback keeps correcting deviations and therefore maintains homeostasis, whereas positive feedback is only suitable for processes that must be completed rapidly and once, 1 mark.
12	A patient must inject insulin regularly. (a) State which type of diabetes he most likely has and explain why. (b) Explain why insulin cannot be taken by mouth. (c) Describe the immediate symptoms of an overdose and how they should be treated. (10 marks)	(a) Type 1 diabetes: the beta cells of the islets are destroyed by an autoimmune response, so too little insulin is produced, 3 marks. (b) Insulin is a protein, so taken by mouth it is hydrolysed by pepsin and trypsin into amino acids and loses its activity, 4 marks. (c) Hypoglycaemia: dizziness, sweating, trembling, a fast heart rate and confusion, 2 marks; the patient should immediately eat or drink something containing sugar, 1 mark.

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