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Hormones and the endocrine system
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Hormones are chemical messengers carried in the blood. They act more slowly than nerves but their effects last longer.
Endocrine glands
Adrenaline (Higher)
Released in times of fear or stress. It increases heart rate and breathing, and sends more blood and glucose to the muscles.
Thyroxine and negative feedback (Higher)
Low thyroxine makes the pituitary release TSH, which stimulates the thyroid. High thyroxine reduces TSH.
This negative feedback keeps levels steady.
This negative feedback keeps levels steady.
Compare hormones with nerves.
- Nerves: electrical impulses, very fast, short-lived, precise.
- Hormones: chemicals in the blood, slower, longer-lasting, more widespread.
Answer: Nerves are fast and brief; hormones are slower and last longer.
Hormones are chemical messengers from endocrine glands, carried in the blood. The pituitary is the master gland. Adrenaline prepares for fight or flight. Thyroxine is controlled by negative feedback.
The interactive lesson includes the diagrams for this topic.
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