Human Body Systems
MYP Year 5 Biology — Human Body Systems
Every question on this unit is really asking the same thing: how does a system detect a change and respond to keep the body stable? Glands respond with hormones, the immune system responds to pathogens, the nervous system responds to stimuli — same logic, different tools. Examiners lean hard on data (antibody graphs, cytokine tables, HR/breathing figures), so the skill you actually need is reading a trend and explaining the mechanism behind it, not just naming parts.
Overview — How the Body Stays in Balance
Human body systems don't work in isolation — the organisation is cells → tissues → organs → organ systems → organism, and every system you study here exists to help maintain a stable internal environment (homeostasis) or to respond to a threat to it.
- Control systems come in two flavours: chemical (endocrine — slow, long-lasting, travels in blood) and electrical (nervous — fast, short-lived, travels along neurons).
- The immune system is really two systems layered together: a fast, non-specific innate response and a slower, highly specific adaptive response that 'remembers'.
- Circulatory, respiratory, digestive and excretory systems are the body's logistics network — getting gases, nutrients, hormones and wastes to and from every cell.
- Muscular and skeletal systems form one functional unit (the musculoskeletal system) — bones can't move themselves, and muscles have nothing to pull against without bone.
The shape of the chapter
Command terms this unit tests constantly
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| State / Identify | give a brief answer or name, no reasoning required | AO1 | one correct term = full marks; adding explanation wastes time but isn't penalised |
| Describe | give a detailed account of what is shown — including the trend or pattern in data | AO2 | must quote actual figures/trend from the graph or table, not a vague 'it goes up' |
| Explain | give reasons — the mechanism behind a fact, the 'why' or 'how' | AO3 | a mark is reserved specifically for the causal link — restating the fact scores zero for that mark |
| Discuss | present more than one side or factor and weigh them | AO3/AO4 | an answer arguing only one side cannot reach top marks even if that side is well written |
| Compare | state both similarities AND differences between two things | AO3 | listing only differences when asked to 'compare' loses marks |
Key point
Overview