The Human Body and Health
The Human Body and Health tests how the main organ systems are built and how they work together, and your ability to apply that knowledge to diet, disease and lifestyle. Questions commonly ask you to sequence a process, explain how a structure suits its function, or decide whether a condition is communicable or non-communicable and how it can be prevented.
Levels of organisation
Cells are grouped into tissues, tissues into organs, organs into systems, and systems cooperate to keep conditions steady.
Systems and their jobs
Digestive: enzymes break food down, for example amylase converting starch to maltose, with absorption through villi that have a large surface area, thin walls and a rich blood supply. Respiratory: gas exchange in alveoli. Circulatory: the heart pumps blood; arteries carry blood away from the heart, veins carry it back. Excretory: the kidneys filter blood, reabsorb useful substances and pass urine to the bladder. Nervous: the reflex arc coordinates rapid responses.
Health and disease
A balanced diet supplies carbohydrates, proteins, fats, vitamins, minerals, fibre and water. Deficiencies: vitamin C and scurvy, vitamin D or calcium and rickets, iron and anaemia, protein and kwashiorkor. Communicable diseases spread by pathogens through air, water, food, vectors and contact, and are prevented by hygiene, safe water, vector control and immunisation. Non-communicable conditions such as obesity, type 2 diabetes and hypertension are linked to diet, inactivity, smoking and alcohol.
Worked example
Reflex arc when a hand touches a hot pan: heat receptor in the skin, sensory neurone, relay neurone in the spinal cord, motor neurone, muscle (effector) contracts and the hand is pulled away. Reasoning: the relay neurone in the spinal cord allows the response without waiting for the brain to decide, shortening reaction time and limiting damage; a signal still travels to the brain, which is why the pain is felt just after the hand has moved. Marks come from naming the components in the correct order.
Traps that cost marks
The pulmonary artery carries deoxygenated blood away from the heart; writing villus and villi inconsistently; claiming blood in veins is blue; putting the brain into the reflex pathway before the spinal cord; mixing communicable and non-communicable diseases; naming the wrong nutrient for a deficiency.