⚡ Very fast
Impulses travel quickly, so the response happens almost at once.
Co-ordination and Response » Nervous and Hormonal Communication
What you'll learn this session
Study time: 30 minutes
Edexcel spec: 2.86
- How the nervous system sends messages using electrical impulses along neurones
- How the hormonal system sends messages using chemicals in the blood
- How each system controls a response, with one example of each
- The differences between the two systems: speed, duration and how widespread the effect is
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Unlock This CourseTwo ways to send a message
Your body has billions of cells, and they must work together. To do that, the body needs to send messages from one place to another. It has two systems for this job: the nervous system and the hormonal system. Both help to control responses, but they work in very different ways.
In the lesson Stimulus, Response and Homeostasis you saw the pathway stimulus, receptor, co-ordinator, effector, response. Both systems carry messages along that pathway. The difference is what carries the message and how it travels.
Key terms:
- Neurone: a nerve cell that carries messages around the body.
- Electrical impulse: a tiny electrical signal that travels along a neurone.
- Endocrine gland: a gland that makes hormones and releases them straight into the blood.
- Target organ: an organ that has cells able to respond to a particular hormone.
Nervous communication
The nervous system sends messages as electrical impulses. These travel along neurones, which form a network of pathways between receptors, the co-ordinator and the effectors. An impulse can only go where a neurone leads, so the message reaches a precise place.
🎯 Precise and short-lived
The message goes to one muscle or gland, and the effect stops soon after the impulses stop.
Example of a nervous response
A bee flies at your face and you blink.
- Stimulus: the moving object.
- Receptor: cells in the eye.
- Message: electrical impulses along neurones.
- Effector: the muscles of the eyelid.
- Response: you blink in a fraction of a second, then the blinking stops.
Hormonal communication
Remember, hormones are chemical messengers. They are made in endocrine glands. A gland releases a hormone straight into the blood, and the blood carries it all around the body. The hormone only affects its target organs, which are the organs with cells that can respond to it. Other cells it passes by are not affected.
The blood has to carry the hormone round the body, so this takes longer than an impulse along a neurone. Hormones also stay in the blood for a while before they are broken down, so their effects last longer.
🕒 Slower
The chemical must travel in the blood, so the response is not instant.
⏳ Longer-lasting
The hormone stays in the blood for some time, so the effect carries on.
🌎 Widespread
The blood reaches the whole body, so a hormone can affect several target organs at once.
Example of a hormonal response
You get a big fright, such as a loud bang in the dark.
- Gland: the adrenal glands release the hormone adrenaline into the blood.
- Message: adrenaline is carried round the body in the blood.
- Target organs: including the heart.
- Response: your heart beats faster, and the effect lasts for a while after the fright has passed.
You will meet adrenaline and other named hormones in later lessons. Here, one example is enough to show how the hormonal system works.
Comparing the two systems
| Feature | Nervous system | Hormonal system |
|---|---|---|
| Type of message | Electrical impulses | Chemical hormones |
| Carried by | Neurones | The blood |
| Speed | Very fast | Slower |
| How long the effect lasts | Short | Longer |
| How widespread | Precise, one place | Widespread, several target organs |
The two systems often work as a team. In the fright example above, nerves make you jump at once, and adrenaline keeps your body ready to act for longer. A good way to remember the difference is to think of a phone call and a radio broadcast. The nervous system is the phone call: quick and sent to one person. The hormonal system is the broadcast: slower to arrive but heard by many and lasting longer.
Common mistakes
- Saying hormones travel along neurones. They travel in the blood. Impulses travel along neurones.
- Saying the nervous system is "stronger". The correct words are faster and short-lived.
- Saying hormones affect every cell. They only affect their target organs, even though they reach the whole body in the blood.
- Writing "quick" or "slow" with nothing to compare. Say "faster than" or "slower than".
Exam-style question
(a) State what carries the message in the nervous system. [1 mark]
(b) State what carries the message in the hormonal system. [1 mark]
(c) Give two differences between the effects of a nervous response and a hormonal response. [2 marks]
(d) Explain why a hormone released into the blood can affect organs in many parts of the body. [2 marks]
Model answer
(a) Electrical impulses (along neurones). (1)
(b) Hormones (chemicals) carried in the blood. (1)
(c) Any two from: the nervous response is faster (1); the nervous response is shorter-lasting (1); the nervous response affects a precise place while the hormonal response is more widespread (1).
(d) The hormone is carried all around the body by the blood (1), so it reaches every organ, including its target organs (1).
Exam tip
In a "differences" question, name the same feature for both systems, for example "nervous is fast, hormonal is slower". A statement about only one system may not earn the mark.