How do hormones coordinate slower, longer-lasting responses?
Describe how the endocrine system uses hormones to coordinate responses and compare it with the nervous system
The endocrine system releases hormones into the blood to act on target cells with matching receptors, giving slower but longer-lasting coordination than the nervous system.
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What this dot point is asking
You need to describe how hormones work, identify key glands and hormones, and compare the endocrine and nervous systems as the body's two coordination systems.
How the endocrine system works
The endocrine system is a collection of glands that secrete hormones directly into the bloodstream. A hormone is a chemical messenger carried in the blood to all parts of the body.
Although a hormone reaches every cell, it only affects target cells that have a specific receptor for it. The hormone binds to the receptor (like a key fitting a lock), triggering a response in that cell. Cells without the receptor are unaffected, which is how a blood-borne signal can still be specific.
Key glands and hormones
Examples that recur across Topic 3:
- Pancreas - releases insulin and glucagon to regulate blood glucose.
- Adrenal glands - release adrenaline for "fight or flight" responses.
- Thyroid gland - releases thyroxine, which controls metabolic rate.
- Pituitary gland - the "master gland", releasing hormones (such as ADH) that control other glands and processes.
- Hypothalamus - links the nervous and endocrine systems and controls the pituitary.
These hormones are central to the later dot points on blood glucose regulation, thermoregulation and osmoregulation.
Comparing the nervous and endocrine systems
Both systems coordinate the body and work together in homeostasis, but they differ:
| Feature | Nervous system | Endocrine system |
|---|---|---|
| Signal | Electrical impulse (and neurotransmitter) | Hormone (chemical) |
| Transport | Along neurons | In the bloodstream |
| Speed | Very fast | Slower |
| Duration | Brief | Longer-lasting |
| Target | Specific muscles/glands | Target cells with the receptor, often widespread |
In short, the nervous system handles rapid, short-term responses while the endocrine system handles slower, longer-lasting and more widespread responses.
Exam-style practice questions
Practice questions written in the style of SACE Board exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
2019 SACE Stage 21 marksHormones can be which one of the following: peptides, carbohydrates, or proteins; peptides, proteins, or steroids; amino acids, steroids, or nucleic acids; or carbohydrates, steroids, or proteins?Show worked answer →
Hormones can be peptides, proteins, or steroids. Peptide and protein hormones (such as insulin and ADH) are made of amino acids, and steroid hormones (such as testosterone) are made from cholesterol. Hormones are not carbohydrates or nucleic acids, which is why the other options are incorrect.
2019 SACE Stage 22 marksDescribe the role of thyroid-stimulating hormone (TSH).Show worked answer →
For 2 marks, name the gland it acts on and the effect.
Thyroid-stimulating hormone is released by the anterior pituitary gland and travels in the blood to its target, the thyroid gland.
It stimulates the thyroid gland to produce and release thyroxine, the hormone that increases the body's metabolic rate (and so contributes to heat production and temperature control).
2019 SACE Stage 22 marksDescribe the structural feature of all target cells that are affected by thyroxine that allows them to respond to thyroxine.Show worked answer →
For 2 marks, name the feature and explain its role.
Target cells have specific receptor proteins (receptors) whose shape is complementary to thyroxine.
Only cells with these receptors can bind thyroxine, and this binding triggers the cell's response. Cells without the matching receptor cannot bind the hormone and so do not respond, which is why hormones act only on particular target cells.