Human Physiology: Digestion, Circulation, Respiration, Excretion, Locomotion, Neural and Endocrine Control
Domain 6: Human Physiology - what is tested
The paper tests organ-system function and coordination: digestive enzymes and absorption, heart and blood vessels, gas exchange, nephron function, muscle and skeleton, nerve impulse, and endocrine glands with their hormones.
Core rules
- Digestion: amylase begins starch digestion in the mouth; pepsin acts on proteins in the stomach; pancreatic lipase, amylase and protease act in the small intestine; bile emulsifies fats. Absorption of glucose and amino acids occurs mainly in the small intestine.
- Circulation: SA node is the pacemaker; the heart has four chambers; arteries carry blood away from the heart, veins toward it. Pulmonary artery carries deoxygenated blood, pulmonary vein oxygenated blood.
- Respiration: alveolar exchange by diffusion; haemoglobin transports most oxygen; CO2 is mainly carried as bicarbonate. Breathing is controlled by the medulla.
- Excretion: nephron has glomerular filtration, tubular reabsorption and secretion. Urine formation begins in the glomerulus; glucose is normally fully reabsorbed.
- Locomotion: sliding filament theory; actin and myosin, calcium and ATP are required.
- Neural control: resting potential, depolarisation, synapse and neurotransmitters. Endocrine control: hormones are secreted by glands such as thyroid, adrenal, pancreas and pituitary.
Worked example
Trace a glucose molecule from a meal to a muscle cell. Starch is digested by salivary and pancreatic amylase to maltose, then maltase in the small intestine yields glucose. Glucose is absorbed by intestinal epithelial cells into blood and travels via the hepatic portal vein to the liver, then via the bloodstream to muscle. In the muscle cell, insulin promotes glucose uptake; glycolysis and aerobic respiration produce ATP. Reasoning: each step matches the enzyme, the absorption route and the hormonal control.
Traps
Saying the pulmonary artery carries oxygenated blood; confusing filtration and reabsorption; claiming bile contains lipase; saying the medulla controls heart rate only; mixing insulin and glucagon sources; forgetting that skeletal muscle is voluntary.