Human Physiology
Scope
Digestion, breathing, circulation, excretion, locomotion, neural control and endocrine regulation are tested. Expect calculations and pathway questions.
Core rules
- Enzymes: salivary amylase digests starch; pepsin digests protein in acid; trypsinogen is activated by enterokinase; lipase needs bile salts for emulsification.
- Breathing: tidal volume × respiratory rate = minute ventilation; vital capacity is the maximum volume after maximal inspiration and expiration.
- Cardiac output = stroke volume × heart rate. The SA node is the normal pacemaker.
- Nephron: filtration at the glomerulus, reabsorption in the proximal tubule, loop of Henle creates a medullary gradient, ADH increases collecting-duct water reabsorption.
- Sliding filament theory: myosin heads bind actin, power stroke shortens sarcomere; ATP and Ca2+ are required.
- Hormones act on specific receptors; insulin lowers blood glucose, glucagon raises it.
Worked example
A person has a stroke volume of 70 mL and a heart rate of 72 beats per minute. Calculate cardiac output. Reasoning: cardiac output = 70 mL × 72 min⁻¹ = 5,040 mL min⁻¹, about 5 L min⁻¹. If heart rate doubles with unchanged stroke volume, output doubles; in exercise, both stroke volume and rate usually rise.
Traps
- Trypsinogen is activated by enterokinase, not by trypsin itself in the first instance.
- ADH increases water reabsorption, not sodium reabsorption directly.
- The pacemaker is the SA node; the AV node delays the impulse.
- Oxygen dissociation curves shift right with increased CO2, H+ and temperature, reducing affinity.