The endocrine system
Laura Armstrong & Joe Wolfensohn
Teachers
Recall Questions
This topic requires prior knowledge of the nervous system and hormones.
What is a hormone?
A chemical messenger secreted by a gland and transported in the blood to a target organ.
How do hormones travel around the body?
In the bloodstream.
How do the effects of hormones compare to those of the nervous system?
Hormones act more slowly but their effects last longer than those of the nervous system.
Topic Explainer Video
Check out this @lauradoesbiology video that explains the endocrine system, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
What is the Endocrine System?
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A system of glands that secrete hormones.
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Hormones travel through the bloodstream to target organs.
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Hormones are described as ‘chemical messengers’.
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Hormones regulate many processes including growth, metabolism, and reproduction.
Hormonal Coordination
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Hormones are secreted in response to changes in body conditions.
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They help maintain homeostasis by coordinating the functions of organs and tissues.
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The response is slower than a nerve impulse, but lasts longer.
The Master Gland – Pituitary Gland
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Found at the base of the brain.
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Called the "master gland" because it secretes several hormones that act on other glands.
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Controls functions such as growth, water balance, and reproductive hormone release.
Key Endocrine Glands and Their Locations
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Pituitary gland - base of the brain - secretes FSH, LH, ADH and TSH.
- Thyroid - in the neck - controls metabolism - secretes thyroxine.
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Adrenal glands - on top of kidneys - secrete adrenaline.
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Pancreas - behind the stomach - regulates blood glucose – secretes insulin and glucagon.
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Ovaries - in females - secrete oestrogen and progesterone.
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Testes - in males - secrete testosterone.
We will look at some of these hormones specifically in future study notes. For now, just try to learn the examples of named hormones released by each gland given.
Key Terms
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Endocrine system - A system of glands that release hormones into the blood.
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Hormone - A chemical messenger that travels in the blood to a target organ.
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Target organ - An organ that responds to a hormone.
- Pituitary gland -Master gland that controls other endocrine glands.
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Exam Tip
Make sure you can label the main endocrine glands on a diagram and give examples of hormones secreted by each one.
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Practice Question
Describe the main features of the endocrine system. (4 marks)
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The endocrine system is made up of glands that secrete hormones.
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Hormones are chemical messengers.
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They travel in the bloodstream.
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Hormones travel to target organs where they produce a response.
More Practice
Try to answer these practice questions from the TikTok videos on your own, then watch the videos to see how well you did!