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A Level H2 Biology Human Physiology Quiz
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Questions
A-Level Biology H2 Quiz - Human Physiology
Name: _________________________ Class: _________________________ Date: _________________________ Score: ______ / 60
Duration: 1 hour 15 minutes Total Marks: 60
Instructions:
- This quiz contains 20 questions on Human Physiology.
- Answer ALL questions in the spaces provided.
- Marks for each question are indicated in brackets.
- Where calculations are required, show your working.
- Use appropriate scientific terminology throughout.
Section A: Short Answer Questions (15 marks)
Answer all questions in this section.
1. State the primary function of the sinoatrial node in the human heart. [1]
2. Name the valve that prevents backflow of blood from the left ventricle into the left atrium. [1]
3. Define the term tidal volume as it relates to human ventilation. [1]
4. State one structural difference between an artery and a vein. [1]
5. Name the type of neurone that carries impulses from the central nervous system to an effector. [1]
6. Identify the hormone produced by the alpha cells of the islets of Langerhans. [1]
7. State the role of the loop of Henle in the mammalian kidney. [1]
8. Name the specific molecule that binds to troponin to initiate muscle contraction. [1]
9. Define the term homeostasis. [1]
10. State the function of surfactant in the human lungs. [1]
11. Name the region of the brain that coordinates voluntary muscle movement and balance. [1]
12. Identify the type of white blood cell responsible for producing antibodies. [1]
13. State the role of the atrioventricular node in the cardiac cycle. [1]
14. Name the process by which carbon dioxide is transported in the blood as bicarbonate ions. [1]
15. Define the term osmoregulation. [1]
Section B: Structured Questions (25 marks)
Answer all questions in this section.
16. Figure 1 shows the changes in membrane potential of a neurone during an action potential.
| Time (ms) | Membrane potential (mV) |
|---|---|
| 0 | -70 |
| 1 | -55 |
| 2 | +30 |
| 3 | -75 |
| 4 | -70 |
(a) Using the data in Figure 1, state the resting potential of this neurone. [1]
(b) Explain the events that occur at the neurone membrane between 1 ms and 2 ms to cause the change in membrane potential. [3]
(c) Describe the role of the sodium-potassium pump in restoring the resting potential after an action potential. [2]
(d) Explain why a second action potential cannot be generated during the refractory period. [2]
17. The human kidney plays a vital role in excretion and osmoregulation.
(a) Describe the process of ultrafiltration that occurs in the Bowman's capsule. [3]
(b) Explain how the proximal convoluted tubule is adapted for the selective reabsorption of glucose. [3]
(c) A person with untreated diabetes mellitus may have glucose present in their urine. Explain why this occurs. [2]
18. The sinoatrial node (SAN) initiates the heartbeat.
(a) Describe how the wave of electrical excitation spreads from the SAN through the heart. [3]
(b) Explain why there is a short delay between atrial contraction and ventricular contraction. [2]
(c) During vigorous exercise, the heart rate increases. Explain the role of the medulla oblongata and the autonomic nervous system in bringing about this increase. [4]
Section C: Data-Based and Extended Response Questions (20 marks)
Answer all questions in this section.
19. A student investigated the effect of exercise on ventilation rate. The student measured the volume of air breathed in and out per minute (minute ventilation) at rest and during increasing intensities of exercise on a treadmill. The results are shown in Figure 2.
| Exercise intensity | Minute ventilation (dm³ min⁻¹) | Tidal volume (dm³) | Breathing rate (breaths min⁻¹) |
|---|---|---|---|
| Rest | 6.0 | 0.5 | 12 |
| Light | 30.0 | 1.5 | 20 |
| Moderate | 60.0 | 2.0 | 30 |
| Heavy | 90.0 | 2.5 | 36 |
(a) Calculate the minute ventilation at rest using the tidal volume and breathing rate data. Show your working and confirm it matches the value given in the table. [1]
(b) Describe the trend in tidal volume and breathing rate as exercise intensity increases. [2]
(c) Explain why minute ventilation must increase during heavy exercise. Refer to the demands of the muscle cells in your answer. [4]
(d) During heavy exercise, the concentration of carbon dioxide in the blood increases. Explain how this increase is detected and how it leads to an increase in breathing rate. [4]
20. Discuss the role of negative feedback in the regulation of blood glucose concentration in humans. In your answer, you should include:
- the hormones involved and their sites of production;
- the target organs and their responses;
- the importance of maintaining blood glucose concentration within narrow limits. [9]
END OF QUIZ
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Answers
A-Level Biology H2 Quiz - Human Physiology: Answer Key
Total Marks: 60
Section A: Short Answer Questions (15 marks)
1. State the primary function of the sinoatrial node in the human heart. [1]
- Answer: The sinoatrial node acts as the pacemaker of the heart / initiates the electrical impulse that triggers each heartbeat / generates the cardiac rhythm.
- Marking note: Accept any one correct function. Award 1 mark for correct identification of pacemaker/impulse initiation role.
2. Name the valve that prevents backflow of blood from the left ventricle into the left atrium. [1]
- Answer: Bicuspid valve / mitral valve / left atrioventricular valve.
- Marking note: Award 1 mark for any of the accepted names.
3. Define the term tidal volume as it relates to human ventilation. [1]
- Answer: Tidal volume is the volume of air inhaled or exhaled during a normal, resting breath.
- Marking note: Must include reference to "resting" or "normal" breath. Award 1 mark.
4. State one structural difference between an artery and a vein. [1]
- Answer: Arteries have thicker muscular/elastic walls than veins / arteries have a narrower lumen than veins / veins have valves while arteries do not (except at the base of the pulmonary artery and aorta).
- Marking note: Award 1 mark for any one correct structural difference.
5. Name the type of neurone that carries impulses from the central nervous system to an effector. [1]
- Answer: Motor neurone / efferent neurone.
- Marking note: Award 1 mark for either term.
6. Identify the hormone produced by the alpha cells of the islets of Langerhans. [1]
- Answer: Glucagon.
- Marking note: Award 1 mark.
7. State the role of the loop of Henle in the mammalian kidney. [1]
- Answer: To create a concentration gradient in the medulla / to enable water reabsorption from the collecting duct / to concentrate urine.
- Marking note: Award 1 mark for any correct role.
8. Name the specific molecule that binds to troponin to initiate muscle contraction. [1]
- Answer: Calcium ions (Ca²⁺).
- Marking note: Award 1 mark. Accept "calcium" but "calcium ions" is preferred.
9. Define the term homeostasis. [1]
- Answer: Homeostasis is the maintenance of a constant internal environment within narrow limits, despite changes in the external environment.
- Marking note: Must include concept of "constant internal environment" or "maintaining stable conditions". Award 1 mark.
10. State the function of surfactant in the human lungs. [1]
- Answer: Surfactant reduces surface tension in the alveoli, preventing their collapse during exhalation / allowing easier inflation of the lungs.
- Marking note: Award 1 mark for reference to reducing surface tension or preventing alveolar collapse.
11. Name the region of the brain that coordinates voluntary muscle movement and balance. [1]
- Answer: Cerebellum.
- Marking note: Award 1 mark.
12. Identify the type of white blood cell responsible for producing antibodies. [1]
- Answer: B-lymphocyte / B-cell / plasma cell.
- Marking note: Award 1 mark for any of the accepted terms.
13. State the role of the atrioventricular node in the cardiac cycle. [1]
- Answer: The AVN delays the electrical impulse to allow the atria to complete contraction / to allow ventricles to fill with blood before they contract.
- Marking note: Award 1 mark for reference to delay or coordination of atrial and ventricular contraction.
14. Name the process by which carbon dioxide is transported in the blood as bicarbonate ions. [1]
- Answer: The chloride shift / Hamburger phenomenon / carbonic anhydrase reaction (in red blood cells).
- Marking note: Award 1 mark for any accepted term describing the conversion and transport mechanism.
15. Define the term osmoregulation. [1]
- Answer: Osmoregulation is the control of water potential / solute concentration of body fluids.
- Marking note: Award 1 mark for correct definition.
Section B: Structured Questions (25 marks)
16. Action potential data interpretation.
(a) Using the data in Figure 1, state the resting potential of this neurone. [1]
- Answer: -70 mV.
- Marking note: Award 1 mark for correct value with units.
(b) Explain the events that occur at the neurone membrane between 1 ms and 2 ms to cause the change in membrane potential. [3]
- Answer: At 1 ms, the threshold potential (-55 mV) is reached, causing voltage-gated sodium ion channels to open (1). Sodium ions diffuse rapidly into the neurone down their electrochemical gradient (1). This influx of positive ions causes depolarisation, changing the membrane potential from -55 mV to +30 mV (1).
- Marking note: Award marks as indicated. Must include threshold, sodium channel opening, and sodium influx causing depolarisation.
(c) Describe the role of the sodium-potassium pump in restoring the resting potential after an action potential. [2]
- Answer: The sodium-potassium pump actively transports sodium ions out of the neurone and potassium ions into the neurone (1), using ATP. It moves 3 Na⁺ out for every 2 K⁺ in, restoring the original ion distribution and thus the resting potential of -70 mV (1).
- Marking note: Award 1 mark for active transport/ATP use and ion movement, 1 mark for restoring ion distribution/resting potential.
(d) Explain why a second action potential cannot be generated during the refractory period. [2]
- Answer: During the refractory period, voltage-gated sodium ion channels are inactivated and cannot be opened (1). Therefore, no sodium ion influx can occur, preventing depolarisation and the generation of a new action potential (1).
- Marking note: Award 1 mark for sodium channel inactivation, 1 mark for consequence (no depolarisation possible).
17. Kidney function.
(a) Describe the process of ultrafiltration that occurs in the Bowman's capsule. [3]
- Answer: Blood enters the glomerulus under high pressure due to the afferent arteriole being wider than the efferent arteriole (1). This high hydrostatic pressure forces water, glucose, amino acids, urea, and ions out of the blood through pores in the capillary endothelium, the basement membrane, and podocytes (1). Large molecules such as proteins and blood cells are retained in the blood because they are too large to pass through the filtration barrier (1).
- Marking note: Award 1 mark for high pressure and its cause, 1 mark for substances filtered, 1 mark for substances retained and filtration barrier.
(b) Explain how the proximal convoluted tubule is adapted for the selective reabsorption of glucose. [3]
- Answer: The cells of the proximal convoluted tubule have microvilli to increase surface area for reabsorption (1). They contain many mitochondria to provide ATP for active transport (1). Glucose is reabsorbed by co-transport with sodium ions across the apical membrane, followed by facilitated diffusion into the blood (1).
- Marking note: Award 1 mark each for microvilli/surface area, mitochondria/ATP, and mechanism of glucose transport.
(c) A person with untreated diabetes mellitus may have glucose present in their urine. Explain why this occurs. [2]
- Answer: In diabetes mellitus, blood glucose concentration is abnormally high (1). The filtered load of glucose exceeds the maximum reabsorptive capacity of the proximal convoluted tubule, so not all glucose can be reabsorbed and it appears in the urine (1).
- Marking note: Award 1 mark for high blood glucose, 1 mark for exceeding reabsorptive capacity.
18. Cardiac cycle and control.
(a) Describe how the wave of electrical excitation spreads from the SAN through the heart. [3]
- Answer: The SAN initiates an electrical impulse that spreads across the atria, causing atrial systole (1). The impulse reaches the atrioventricular node (AVN), where it is delayed briefly (1). The impulse then travels down the Bundle of His and through Purkyne fibres to the apex of the ventricles, causing ventricular systole from the apex upwards (1).
- Marking note: Award 1 mark for atrial spread, 1 mark for AVN delay, 1 mark for ventricular conduction pathway.
(b) Explain why there is a short delay between atrial contraction and ventricular contraction. [2]
- Answer: The delay at the AVN allows time for the atria to complete their contraction and fully empty blood into the ventricles (1). This ensures the ventricles are filled with blood before they contract, maximising the efficiency of the heartbeat (1).
- Marking note: Award 1 mark for delay allowing atrial emptying, 1 mark for ventricular filling/efficiency.
(c) During vigorous exercise, the heart rate increases. Explain the role of the medulla oblongata and the autonomic nervous system in bringing about this increase. [4]
- Answer: During exercise, increased carbon dioxide concentration in the blood is detected by chemoreceptors in the carotid and aortic bodies, which send impulses to the cardiovascular centre in the medulla oblongata (1). The medulla oblongata increases the frequency of impulses along the sympathetic nerve to the SAN (1). The sympathetic nerve releases noradrenaline, which binds to receptors on the SAN, increasing its rate of depolarisation (1). Simultaneously, the medulla reduces impulses along the parasympathetic (vagus) nerve, which normally slows the heart rate, further contributing to the increase (1).
- Marking note: Award 1 mark each for detection and medulla role, sympathetic stimulation, neurotransmitter effect on SAN, and reduced parasympathetic activity.
Section C: Data-Based and Extended Response Questions (20 marks)
19. Ventilation during exercise.
(a) Calculate the minute ventilation at rest using the tidal volume and breathing rate data. Show your working and confirm it matches the value given in the table. [1]
- Answer: Minute ventilation = tidal volume × breathing rate = 0.5 dm³ × 12 breaths min⁻¹ = 6.0 dm³ min⁻¹. This matches the table value.
- Marking note: Award 1 mark for correct calculation and confirmation.
(b) Describe the trend in tidal volume and breathing rate as exercise intensity increases. [2]
- Answer: Both tidal volume and breathing rate increase as exercise intensity increases (1). Tidal volume increases from 0.5 dm³ to 2.5 dm³, while breathing rate increases from 12 to 36 breaths per minute (1).
- Marking note: Award 1 mark for stating both increase, 1 mark for quoting data.
(c) Explain why minute ventilation must increase during heavy exercise. Refer to the demands of the muscle cells in your answer. [4]
- Answer: During heavy exercise, muscle cells have a higher rate of aerobic respiration to produce more ATP for contraction (1). This increases their demand for oxygen and produces more carbon dioxide (1). Increased minute ventilation brings more oxygen into the lungs for diffusion into the blood and delivery to muscles (1). It also removes the excess carbon dioxide produced, preventing a dangerous decrease in blood pH (1).
- Marking note: Award marks as indicated. Must link increased respiration to oxygen demand and carbon dioxide removal.
(d) During heavy exercise, the concentration of carbon dioxide in the blood increases. Explain how this increase is detected and how it leads to an increase in breathing rate. [4]
- Answer: Increased carbon dioxide in the blood reacts with water to form carbonic acid, which dissociates to release hydrogen ions, lowering blood pH (1). This decrease in pH is detected by chemoreceptors in the medulla oblongata (central chemoreceptors) and in the carotid and aortic bodies (peripheral chemoreceptors) (1). The chemoreceptors send impulses to the respiratory centre in the medulla oblongata (1). The respiratory centre increases the frequency of nerve impulses to the diaphragm and intercostal muscles, increasing the rate and depth of breathing (1).
- Marking note: Award 1 mark each for pH decrease mechanism, chemoreceptor detection, impulse transmission to respiratory centre, and increased stimulation of respiratory muscles.
20. Discuss the role of negative feedback in the regulation of blood glucose concentration in humans. [9]
-
Answer: Blood glucose concentration is maintained within narrow limits (approximately 70–110 mg per 100 cm³) by a negative feedback mechanism involving the pancreas, liver, and other tissues.
Detection and hormonal response:
- When blood glucose concentration rises above the set point (e.g., after a meal), this is detected by the beta cells of the islets of Langerhans in the pancreas (1). The beta cells secrete the hormone insulin into the bloodstream (1).
- When blood glucose concentration falls below the set point (e.g., during fasting or exercise), this is detected by the alpha cells of the islets of Langerhans, which secrete the hormone glucagon (1).
Target organs and responses:
- Insulin acts on target cells, primarily hepatocytes (liver cells) and muscle cells, by binding to specific receptors on the cell surface membrane (1). This increases the permeability of these cells to glucose, allowing more glucose to enter by facilitated diffusion (1). Insulin also activates enzymes that convert glucose to glycogen (glycogenesis) in the liver and muscles, and promotes the conversion of glucose to fats (1). These actions lower blood glucose concentration back towards the set point.
- Glucagon acts mainly on hepatocytes, binding to receptors and activating enzymes that break down glycogen to glucose (glycogenolysis) (1). It also promotes gluconeogenesis, the synthesis of glucose from non-carbohydrate sources such as amino acids and glycerol (1). These actions raise blood glucose concentration back towards the set point.
Negative feedback:
- As blood glucose concentration returns to the set point, the stimulus for insulin or glucagon secretion is reduced, and hormone secretion decreases. This is the essence of negative feedback: the response counteracts the initial change, restoring the system to its normal level (1).
Importance of regulation:
- Maintaining blood glucose within narrow limits is essential because glucose is the primary respiratory substrate for cells, particularly brain cells, which cannot store glycogen and rely on a constant supply (1). Hypoglycaemia (low blood glucose) can lead to confusion, loss of consciousness, and coma. Hyperglycaemia (high blood glucose) can cause dehydration and long-term damage to tissues, as seen in diabetes mellitus. Thus, precise homeostatic control is vital for health.
-
Marking scheme:
- 1 mark: Introduction stating normal range and negative feedback principle.
- 1 mark: Beta cells detect high glucose and secrete insulin.
- 1 mark: Alpha cells detect low glucose and secrete glucagon.
- 1 mark: Insulin action on target cells (receptors, glucose uptake).
- 1 mark: Glycogenesis and fat synthesis promoted by insulin.
- 1 mark: Glucagon promotes glycogenolysis.
- 1 mark: Glucagon promotes gluconeogenesis.
- 1 mark: Explanation of negative feedback loop (response reduces stimulus).
- 1 mark: Importance of regulation (brain function, consequences of dysregulation).
- Total: 9 marks. Award marks for any correct points that cover the required areas. Answers should be well-structured and use appropriate scientific terminology.
END OF ANSWER KEY