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A Level H2 Biology Human Physiology Quiz

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A Level H2 Biology AI Generated Generated by Gemma 4 31B Updated 2026-06-03

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A-Level Biology H2 Quiz - Human Physiology

Name: ____________________
Class: ____________________
Date: ____________________
Score: ________ / 65

Duration: 90 Minutes
Total Marks: 65
Instructions: Answer all questions. Write your answers in the spaces provided. Use precise biological terminology.

Section A: Nervous Coordination and Response (Questions 1–7)

State the difference between the resting potential and the action potential of a neuron. [2]
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Explain the role of voltage-gated $\text{Na}^+$ channels in the generation of an action potential. [3]
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Describe the process of repolarization during an action potential. [3]
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Explain why the action potential is "all-or-nothing" in nature. [2]
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Describe the sequence of events that occurs at a chemical synapse when an action potential reaches the presynaptic terminal. [5]
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A toxin blocks the $\text{Ca}^{2+}$ channels in the presynaptic membrane. Predict and explain the effect of this toxin on synaptic transmission. [3]
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Compare the speed and duration of a signal transmitted via a neuron versus one transmitted via a hormone. [3]
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Section B: Hormonal Control and Homeostasis (Questions 8–14)

Distinguish between endocrine and exocrine glands. [2]
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Describe the negative feedback mechanism that regulates blood glucose levels when they drop below the set point. [5]
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Explain the role of the hypothalamus and the posterior pituitary gland in the regulation of water potential in the blood. [4]
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Describe how the kidney modifies the composition of the filtrate to maintain osmoregulation during a period of dehydration. [5]
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Explain the antagonistic relationship between insulin and glucagon in the liver. [4]
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Describe the role of the adrenal medulla in the "fight or flight" response. [3]
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Suggest why a person with Type 1 diabetes requires insulin injections rather than oral tablets. [2]
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Section C: The Immune System and Integrated Physiology (Questions 15–20)

Distinguish between the primary and secondary immune responses in terms of time taken and antibody concentration. [3]
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Explain the process of clonal selection and clonal expansion. [4]
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Describe the difference between the roles of B-lymphocytes and T-lymphocytes in the cell-mediated and humoral immune responses. [4]
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Explain how the body distinguishes between "self" and "non-self" antigens. [3]
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Discuss the mechanism by which antibodies neutralize a pathogen. [3]
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Explain how a fever (increased body temperature) can act as a defense mechanism against infection. [4]
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Answers

Answer Key - A-Level Biology H2 Quiz: Human Physiology

1. Resting vs Action Potential [2]

Resting potential: Stable membrane potential (approx -70mV) when not conducting an impulse.
Action potential: Rapid depolarization and repolarization of the membrane potential when a stimulus exceeds threshold.

2. Voltage-gated $\text{Na}^+$ channels [3]

Open when the membrane reaches threshold potential.
Allow $\text{Na}^+$ ions to flood into the axon down the electrochemical gradient.
Causes rapid depolarization of the membrane.

3. Repolarization [3]

$\text{Na}^+$ channels close.
Voltage-gated $\text{K}^+$ channels open.
$\text{K}^+$ ions diffuse out of the axon, returning the membrane potential to a negative value.

4. All-or-nothing [2]

If the stimulus is below threshold, no action potential is generated.
If threshold is reached, a full action potential of constant magnitude is always produced.

5. Synaptic Transmission [5]

Action potential arrives at presynaptic terminal.
Voltage-gated $\text{Ca}^{2+}$ channels open $\rightarrow$ $\text{Ca}^{2+}$ influx.
Vesicles fuse with presynaptic membrane $\rightarrow$ exocytosis of neurotransmitters.
Neurotransmitters diffuse across synaptic cleft.
Bind to receptors on postsynaptic membrane $\rightarrow$ open ligand-gated ion channels.

6. $\text{Ca}^{2+}$ Channel Blocker [3]

Prediction: Synaptic transmission will be inhibited/stopped.
Explanation: Without $\text{Ca}^{2+}$ influx, synaptic vesicles cannot fuse with the membrane.
Result: Neurotransmitters are not released into the cleft, preventing the postsynaptic neuron from being stimulated.

7. Neuron vs Hormone [3]

Neuron: Very fast transmission, short-lived/transient effect.
Hormone: Slower transmission (via blood), longer-lasting effect.

8. Endocrine vs Exocrine [2]

Endocrine: Ductless; secrete hormones directly into the blood.
Exocrine: Have ducts; secrete substances (e.g., enzymes) onto a surface or into a cavity.

9. Low Blood Glucose Feedback [5]

Stimulus: Blood glucose drops below set point.
Sensor/Control: $\alpha$ -cells in the islets of Langerhans (pancreas) detect the drop.
Effector: $\alpha$ -cells secrete glucagon.
Action: Liver converts glycogen to glucose (glycogenolysis) and fats/amino acids to glucose (gluconeogenesis).
Result: Blood glucose rises, inhibiting further glucagon secretion (negative feedback).

10. Hypothalamus and Posterior Pituitary [4]

Hypothalamus contains osmoreceptors that detect low water potential (high solute conc).
Hypothalamus produces Antidiuretic Hormone (ADH).
ADH is transported to and stored in the posterior pituitary.
Posterior pituitary releases ADH into the blood in response to signals from the hypothalamus.

11. Kidney and Dehydration [5]

High ADH levels in the blood.
ADH increases permeability of the collecting duct walls to water (via aquaporins).
More water is reabsorbed from the filtrate back into the blood/interstitial fluid.
Volume of urine decreases and concentration of urine increases.
Water potential of blood is restored.

12. Insulin vs Glucagon [4]

Insulin: Lowers blood glucose by stimulating glycogenesis (glucose $\rightarrow$ glycogen) in the liver.
Glucagon: Raises blood glucose by stimulating glycogenolysis (glycogen $\rightarrow$ glucose) in the liver.
They act antagonistically to maintain a narrow range of blood glucose.

13. Adrenal Medulla [3]

Secretes adrenaline (epinephrine) and noradrenaline.
Increases heart rate, breathing rate, and blood glucose (via glycogenolysis).
Prepares the body for immediate physical action.

14. Type 1 Diabetes Insulin [2]

Insulin is a protein/peptide; if taken orally, it would be digested by proteases in the stomach/small intestine.
Must be injected to enter the bloodstream intact.

15. Primary vs Secondary Response [3]

Primary: Slower onset, lower peak antibody concentration.
Secondary: Faster onset (due to memory cells), significantly higher peak antibody concentration.

16. Clonal Selection and Expansion [4]

Selection: A specific antigen binds to a B-cell with a complementary receptor.
Activation: The B-cell is activated (often with T-helper cell assistance).
Expansion: The activated B-cell undergoes rapid mitosis to produce a large clone of identical cells.
Differentiation: These cells become plasma cells (secreting antibodies) and memory cells.

17. B-cells vs T-cells [4]

B-lymphocytes: Humoral response; produce antibodies that target extracellular pathogens/toxins.
T-lymphocytes: Cell-mediated response; directly attack and kill infected or abnormal (cancerous) cells.

18. Self vs Non-self [3]

All nucleated cells have Major Histocompatibility Complex (MHC) markers on their surface.
These markers are unique to the individual ("self").
Immune cells recognize foreign antigens that do not possess the correct MHC markers.

19. Antibody Neutralization [3]

Antibodies bind to specific antigens on the surface of the pathogen.
This blocks the pathogen's ability to bind to and enter host cells.
Agglutination: Antibodies can clump pathogens together, making them easier for phagocytes to ingest.

20. Fever as Defense [4]

Inhibits the growth/replication of some pathogens (temperature-sensitive).
Increases the metabolic rate of the host, speeding up the immune response (e.g., faster leukocyte migration).
Increases the activity of enzymes involved in the inflammatory response.