AQA GCSE Endocrine system of humans (Biology)
Endocrine system of humans.
The endocrine system is a communication system in the body.
The endocrine system is composed of endocrine glands which secrete chemicals called hormones directly into the bloodstream.
Hormones are chemical messengers
The blood carries the hormone to a target organ, where it binds to a receptor on the cell membrane of a target cells.
Only target organs with the correct receptor respond. Hormones cause specific effects
Diagram below will show how hormones bind to specific receptors.
Location of endocrine glands in the body
Pituitary gland (Master gland)
The pituitary gland is found in the brain as shown below.
The pituitary gland is a master gland. It can secrete hormones into the blood in response to body conditions. These hormones will act on other endocrine glands, stimulating them to release their own hormones to bring about specific effects.
For example the pituitary gland secretes follicle stimulating hormone (FSH) into the blood that stimulates the ovaries to secrete oestrogen.
Comparing nervous and hormonal communication
| Nervous responses | Chemical (Hormonal) responses |
|---|---|
| Faster | Slower |
| Short lasting | Longer lasting |
| Use electrical impulses | Involve hormones in blood |
| Example: body temperature control | Example: blood glucose control |
Practice Questions
1.Describe how a hormone released by a gland produces an effect in a target organ.
2.The pituitary gland is described as a “master gland”.
Explain what is meant by this term.
3. A hormone is released into the bloodstream but has no effect on some organs.
Explain why.
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