Comparing nervous and hormonal control revision notes

Edexcel International GCSE Biology (4BI1), chapter 6: Coordination, specification point 2.86. Free lesson.

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Nervous and hormonal coordination both control body responses, but they carry signals in different ways and act at different speeds, for different lengths of time and over different areas. Comparing several features helps you identify which system is involved.

How nervous and hormonal control compare

The nervous system uses electrical impulses along neurones. The hormonal system uses chemicals called hormones, which are dissolved in the blood. These different routes help explain why nervous responses are usually fast and precise, while hormonal responses are usually slower and more widespread. Nervous responses take milliseconds. Hormonal responses usually take seconds to hours. Nervous effects are usually short-lived. Hormonal effects can last much longer, sometimes for years. Nervous signals act at one precise place, such as a particular muscle or gland. Hormones can…

Examples of each system

Pulling your hand away from something hot is a nervous response. It happens quickly and acts on specific muscles. Oestrogen driving the changes of puberty is a hormonal response. It acts over a long time and affects the body more widely. Nervous example: pulling your hand from something hot. Hormonal example: oestrogen driving puberty.

How to identify the system behind a response

You can use the response's speed, duration and reach to work out which control system is likely to be involved. Think about how many organs need to respond, too. If a signal must reach many parts of the body, the blood can carry it widely.

Why both systems are needed

The systems solve different problems. A blink is instant, brief and local, so nervous control suits it. Growth at puberty is slow, sustained and affects the whole body, so hormonal control suits it. Adrenaline is an exception to the usual speed pattern. It is a hormone carried in the blood and can act within seconds. Adrenaline still acts widely, so speed alone cannot always identify the system.

How to answer a comparison question

A comparison question needs several valid differences, not just one. Use words such as whereas to show how the systems differ on each point. Compare what carries the signal: nervous impulses travel along neurones, whereas hormones travel in the blood. Compare how long effects last: nervous effects are short-lived, whereas hormonal effects last much longer. Other valid points include speed and where each system acts.