What are the main endocrine glands, and which hormones do they produce?
The principal glands of the endocrine system (pituitary, thyroid, pancreas, adrenal glands, ovaries and testes), the hormones they release, and the role of thyroxine and adrenaline.
A focused answer to AQA GCSE Biology 4.5.3.1, covering the principal endocrine glands, the hormones they produce, and the roles of thyroxine and adrenaline in the body.
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What this dot point is asking
AQA wants you to name the principal endocrine glands and the hormones they produce, and explain the roles of thyroxine and adrenaline, including how thyroxine is controlled by negative feedback.
The principal endocrine glands
The endocrine system is generally slower than the nervous system, but its effects last longer and are more widespread, because hormones are carried in the blood to the whole body and only the target organs respond. AQA often shows a diagram of the body and asks you to label these glands or match a gland to its hormone.
Thyroxine
Thyroxine levels are controlled by negative feedback: if the level in the blood falls below normal, the pituitary releases TSH (thyroid stimulating hormone), which stimulates the thyroid to make more thyroxine; when the level rises above normal, less TSH is released, so the thyroid makes less. This keeps thyroxine, and therefore the metabolic rate, at a steady level.
Adrenaline
Unlike thyroxine, adrenaline is not controlled by negative feedback. It is released in response to a stressful situation and its effects wear off once the situation passes. Its effects include a faster, stronger heartbeat, wider airways and the release of stored glucose, all of which prepare the body to respond quickly to danger by increasing the supply of oxygen and glucose to the muscles and brain.
A useful comparison AQA expects you to make is between the endocrine system and the nervous system. The endocrine system uses chemical hormones carried in the blood, so its responses are slower to start, longer lasting and spread over a wider area, whereas the nervous system uses electrical impulses along neurones, which are faster, shorter lived and more precisely targeted. Thyroxine and adrenaline illustrate two patterns of hormonal control: thyroxine is kept at a steady level by negative feedback for a long-term process (metabolic rate), while adrenaline is released as a one-off surge in response to a stimulus (fear or stress) and is not regulated by feedback. Being able to state which gland makes which hormone, and whether it is controlled by feedback, is the level of detail the higher-tariff questions reward.
Try this
Q1. Name the gland that produces thyroxine and state what it controls. [2 marks]
- Cue. The thyroid gland; it controls the metabolic rate.
Q2. Describe two effects of adrenaline on the body. [2 marks]
- Cue. Increases heart rate and increases delivery of oxygen and glucose to the muscles and brain.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20194 marksName four endocrine glands and, for each, state one hormone it produces and one effect of that hormone.Show worked answer →
A 4-mark question rewards a correct gland, hormone and effect for each of four glands.
The pancreas produces insulin, which lowers blood glucose by making the liver store it as glycogen. The thyroid produces thyroxine, which controls the metabolic rate. The adrenal glands produce adrenaline, which increases heart rate and prepares the body for fight or flight. The ovaries produce oestrogen, which controls the menstrual cycle and the development of female secondary sexual characteristics. The testes produce testosterone, which stimulates sperm production.
Markers reward any four correct gland and hormone pairs, each with a correct effect.
AQA 20214 marksExplain how the level of thyroxine in the blood is controlled by negative feedback, and describe the effect of thyroxine on the body.Show worked answer →
A 4-mark higher-tier question rewards the feedback loop plus the effect.
Thyroxine, from the thyroid gland, controls the basal metabolic rate (the rate of chemical reactions in cells at rest) and is important for growth and development.
Its level is controlled by negative feedback. If the thyroxine level in the blood falls below normal, the pituitary releases more TSH (thyroid stimulating hormone), which stimulates the thyroid to release more thyroxine. When the thyroxine level rises above normal, less TSH is released, so the thyroid makes less thyroxine. This keeps thyroxine at a steady level.
Markers reward thyroxine controlling metabolic rate, and the negative-feedback loop involving the pituitary and TSH.
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Sources & how we know this
- AQA GCSE Biology (8461) specification — AQA (2016)