Coordination & Response
Structures and Functions in Living Organisms · 7 question types
Exam Frequency Analysis
Past paper frequency (2018 to 2024)
This topic accounts for approximately 14% of your exam marks.
Nervous system structure, reflex arcs, and hormones are all commonly examined.
The two systems differ in speed, signal type, target, and duration of effect.
| Feature | Nervous system | Endocrine (hormonal) system |
|---|---|---|
| Signal type | Electrical impulses along neurones | Chemical signals (hormones) carried in the blood |
| Pathway | Through nerves (bundles of neurones) | Through the bloodstream |
| Speed | Very fast (impulses up to 100 m/s) | Slower (seconds to hours) |
| Target | Specific cells at the end of the neurone | Many cells, but only those that have the matching receptors respond |
| Duration of response | Short (the response stops the moment the signal stops) | Long (the response lasts until the hormone is broken down) |
| Example | The pain-withdrawal reflex | Insulin lowering blood glucose; adrenaline raising heart rate |
The nervous system is the right tool for jobs that need an immediate response: pulling away from a sharp object, flinching from a loud noise, balancing on a moving bus. The endocrine system is the right tool for longer-lasting changes that affect lots of cells at once: growing taller, going through puberty, regulating blood sugar between meals.
Nervous vs hormonal system
Giving differences between the nervous and hormonal systems comes up (3 marks), so you need to know: nervous = electrical impulses along neurones, localised, short-term; hormonal = chemical hormones carried in the blood, affecting many cells, longer-lasting. "The nervous system is faster" is ignored — use signal type, target, and duration.