Adrenaline and Thyroxine
What Are Adrenaline and Thyroxine?
These are two key hormones involved in controlling the body’s internal environment. They help the body respond to stress (adrenaline) and regulate metabolism (thyroxine).
Adrenaline – The ‘Fight or Flight’ Hormone
Feature | Details |
Produced by | The adrenal glands (above the kidneys). |
Triggered by | Fear or stress (detected by the brain). |
Effect | Prepares the body for action. |
How Adrenaline Affects the Body
✔ Increases heart rate → more oxygen to muscles.
✔ Increases blood flow to muscles.
✔ Pupils dilate to improve vision.
✔ Converts glycogen to glucose in the liver for energy.
💡 Adrenaline works very quickly and is part of an automatic response system.
Thyroxine – Regulating Metabolism
Feature | Details |
Produced by | The thyroid gland (in the neck). |
Main Role | Regulates basal metabolic rate – the speed at which chemical reactions happen in cells. |
Other Effects | Affects growth and development (especially in children). |
💡 Thyroxine levels are controlled by a negative feedback loop.
Thyroxine and Negative Feedback
1️ The pituitary gland releases TSH (thyroid stimulating hormone).
2️ TSH stimulates the thyroid to release thyroxine.
3️ If thyroxine levels get too high, TSH is inhibited.
4️ If levels fall too low, TSH is released again.
💡 This keeps thyroxine levels stable, ensuring the body’s metabolic rate remains balanced.
Questions
- Where is adrenaline produced?
- What does adrenaline do to heart rate?
- Which hormone controls the body’s metabolic rate?
- What is TSH and what does it do?
- What type of control system regulates thyroxine levels?
Summary
- Adrenaline prepares the body for “fight or flight” during stress – it increases heart rate and boosts energy supply.
- Thyroxine regulates the body’s metabolism and growth, and is controlled by a negative feedback loop involving TSH.
- Both hormones are part of the endocrine system, helping the body maintain internal balance and respond to external changes.