Secondary 3 Biology Human Physiology Quiz

Answer Key - Secondary 3 Biology Quiz (Human Physiology)

1. Hepatic Portal Vein: Transports absorbed nutrients (glucose, amino acids) from the small intestine directly to the liver for processing. (1)

2. Peristalsis: Rhythmic contraction and relaxation of muscles in the wall of the gut. (1) It pushes food along the digestive tract in one direction. (1)

3. Villus Adaptations:

   • Large surface area due to finger-like projections (1)
   • One-cell thick epithelium/wall to shorten diffusion distance (1)
   • Rich network of blood capillaries to transport nutrients away quickly (1)

4. Liver/Glucose: Converts excess glucose into glycogen for storage (or vice versa). (1)

5. Artery vs Vein: Arteries have thicker, more elastic walls to withstand high pressure; veins have thinner walls and contain valves to prevent backflow of blood. (2)

6. Capillaries: To minimize the diffusion distance for the exchange of gases, nutrients, and wastes between the blood and tissue fluid. (2)

7. Blood Group AB: Group AB individuals have both A and B antigens on their red blood cells. (1) Consequently, they do not produce anti-A or anti-B antibodies in their plasma. (1) This prevents agglutination regardless of the donor's blood group (A, B, AB, or O). (1)

8. Aerobic Respiration: The process of breaking down glucose in the presence of oxygen to release energy. (1) Equation: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}$. (1)

9. Inhalation: Diaphragm contracts and flattens; external intercostal muscles contract, pulling the ribcage upwards and outwards. (2)

10. Alveoli:

    • Large total surface area for maximum gas exchange (1)
    • Very thin walls (one cell thick) for short diffusion distance (1)
    • Moist lining to allow gases to dissolve before diffusing (1)

11. Oxygen Debt: The amount of oxygen required to break down lactic acid accumulated during anaerobic respiration. (1) Panting occurs to take in extra oxygen to "repay" this debt. (1)

12. Excretion: The removal of metabolic waste products from the body. (1) Nitrogenous wastes (like urea) are toxic and would damage cells/organs if they accumulated. (1)

13. Ultrafiltration: High blood pressure in the glomerulus forces small molecules (water, glucose, salts, urea) through the basement membrane into the Bowman's capsule. (3)

14. Selective Reabsorption: The process where useful substances are taken back into the blood from the filtrate. (1) Substances include glucose, amino acids, and varying amounts of water. (2)

15. Homeostasis: Maintenance of a constant internal environment. (1) Negative feedback is a mechanism where a change in a variable triggers a response that counteracts the initial change to return to a set point. (1)

16. Cold Response:

    • Hypothalamus detects drop in temperature (1)
    • Vasoconstriction (blood vessels narrow to reduce heat loss) (1)
    • Shivering (rapid muscle contraction to generate heat) (1)

17. Glucose Regulation:

    • Insulin: Secreted by pancreas to lower blood glucose by converting it to glycogen in the liver/muscles. (1.5)
    • Glucagon: Secreted by pancreas to raise blood glucose by converting glycogen back to glucose. (1.5)

18. Nervous vs Endocrine: Nervous system is rapid (milliseconds) but short-lived. (1) Endocrine system is slower (hormones in blood) but effects are longer-lasting. (1)

19. Reflex Arc: Stimulus (heat) $\rightarrow$ Receptor (skin) $\rightarrow$ Sensory neurone $\rightarrow$ Relay neurone (spinal cord) $\rightarrow$ Motor neurone $\rightarrow$ Effector (muscle) $\rightarrow$ Response (withdrawal). (3)

20. Pupil Reflex: Circular muscles of the iris contract and radial muscles relax, causing the pupil to constrict (become smaller) to protect the retina from excessive light. (2)