How do hormones control the body, and how is hormonal control different from nervous control?
The endocrine system as glands that secrete hormones into the blood, hormones acting on target organs with the correct receptors, the main endocrine glands, and a comparison of nervous and hormonal control.
A focused answer to the OCR Gateway GCSE Biology A topic B3 on the endocrine system, covering glands and hormones, target organs and receptors, the main endocrine glands, and how hormonal control compares with nervous control.
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What this dot point is asking
OCR wants you to describe the endocrine system as glands that release hormones into the blood, explain how hormones act on target organs with the correct receptors, name the main endocrine glands, and compare hormonal control with nervous control.
The endocrine system
Hormones control processes that need steady, longer-term regulation, such as growth, the menstrual cycle, blood glucose and the response to stress.
Target organs and receptors
A hormone travels in the blood, so it reaches every part of the body. Yet a hormone only affects certain organs, called its target organs. This is because only the target organs have the correct receptors for that hormone. The hormone binds to its receptors and causes a response; organs without the matching receptors are not affected.
The main endocrine glands
You should know the main glands and roughly what they do:
- Pituitary gland (in the brain). The "master gland": it releases hormones that control other glands (for example FSH and LH in reproduction).
- Thyroid gland (in the neck). Releases thyroxine, which controls the rate of metabolism.
- Pancreas. Releases insulin and glucagon, which control blood glucose.
- Adrenal glands (above the kidneys). Release adrenaline, which prepares the body for action ("fight or flight").
- Ovaries (in females). Release oestrogen and progesterone, involved in the menstrual cycle.
- Testes (in males). Release testosterone, which controls sperm production and male characteristics.
Nervous control versus hormonal control
The body has two coordination systems, and OCR often asks you to compare them:
| Feature | Nervous control | Hormonal control |
|---|---|---|
| Message carried by | Electrical impulses along neurones | Chemicals (hormones) in the blood |
| Speed | Very fast | Slower |
| Duration | Short-lived | Longer lasting |
| Area affected | Precise (a specific area) | Can affect several organs |
The two systems work together. For example, the nervous system triggers a fast response to danger, while hormones such as adrenaline keep the body ready for longer.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20194 marksCompare nervous control and hormonal control of the body. In your answer refer to how the message travels, the speed, and how long the effect lasts.Show worked answer →
A 4-mark Compare question.
How the message travels: nervous control uses electrical impulses carried along neurones; hormonal control uses chemicals (hormones) carried in the blood.
Speed: nervous responses are very fast; hormonal responses are slower (because hormones take time to travel in the blood).
How long the effect lasts: nervous responses are short-lived (act for a short time); hormonal responses last longer.
Markers reward the three paired contrasts: electrical impulses along neurones versus chemicals in the blood; fast versus slow; short-lived versus long-lasting. A strong answer notes the nervous system acts on a precise area while hormones can affect several organs.
OCR 20213 marksExplain how a hormone released into the blood affects only certain organs, even though it travels all around the body.Show worked answer →
A 3-mark question on target organs and receptors.
A hormone is carried in the blood, so it reaches all parts of the body. However, it only affects its target organs, which are the organs that have the correct receptors for that hormone. The hormone binds to these receptors and causes a response. Organs without the matching receptors are not affected.
Markers reward: the hormone travels everywhere in the blood; only target organs have the right receptors; the hormone binds to those receptors to cause an effect. The key idea is the specificity of the receptor.
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