Human Anatomy and Physiology
What you must understand
Know the major organ systems and their functions: circulatory (heart, blood vessels, blood), respiratory (lungs, gas exchange by diffusion in alveoli), digestive (mechanical and chemical breakdown, absorption in the small intestine), excretory (kidneys, nephrons, filtration and reabsorption), nervous (neurons, synapses, reflex arcs), and endocrine (hormones such as insulin and adrenaline). Understand the structure of the heart and the double circulation (pulmonary and systemic). Know blood components: red blood cells (haemoglobin, oxygen transport), white blood cells (defence), platelets (clotting), plasma. Understand homeostasis and negative feedback, e.g., blood glucose regulation by insulin and glucagon.
Traps that appear in questions
- Confusing arteries (carry blood away from the heart) with veins (carry blood to the heart) - not by oxygen content.
- Saying the left side of the heart carries deoxygenated blood - the right side does.
- Mixing up insulin (lowers blood glucose) with glucagon (raises it).
- Forgetting that gas exchange in alveoli occurs by diffusion, not active transport.
- Confusing filtration (in the glomerulus) with reabsorption (in the tubules).
Worked example
After a sugary meal, blood glucose rises; the pancreas releases insulin, which stimulates cells to take up glucose and the liver to store it as glycogen. Blood glucose falls back to normal - a negative feedback loop. Rule of thumb: negative feedback always counteracts the change to restore the set point.