Adrenaline, thyroxine and negative feedback

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This topic is for students studying the higher tier courses course only

Adrenaline

Adrenaline and thyroxine are two important hormones with specific roles in the body.

Adrenaline: Preparing for "Fight or Flight"

Produced by: Adrenal glands, located just above the kidneys.
When released: During times of fear or stress, adrenaline prepares the body for a "fight or flight" response.
Effects:
- Increases heart rate, ensuring that more oxygen and glucose are delivered to the brain and muscles.
- Boosts delivery of oxygen and glucose to tissues, enabling a quick response to dangerous or stressful situations.

In summary, adrenaline helps the body respond quickly and effectively in emergency situations by providing energy to muscles and sharpening focus.

Thyroxine

Thyroxine: Regulating Metabolism and Supporting Growth

Produced by: Thyroid gland, located in the neck.
Role:
- Stimulates the basal metabolic rate (the rate at which the body uses energy at rest).
- Plays a key part in growth and development.

Thyroxine helps regulate important processes that influence how quickly cells use energy and how the body grows and develops over time.

Negative feedback

Control of Hormone Levels Through Negative Feedback

Both adrenaline and thyroxine levels are controlled to maintain balance in the body.

Adrenaline: Released only in response to stress or fear, so its levels are not constantly regulated by feedback.
Thyroxine: Controlled by a negative feedback system to maintain stable levels.
- If thyroxine levels fall below the normal range, the brain releases TSH (Thyroid Stimulating Hormone), which signals the thyroid gland to release more thyroxine.
- If thyroxine levels rise above the normal range, TSH release is reduced, leading to a decrease in thyroxine levels.

Negative feedback helps keep thyroxine levels within a stable range, ensuring the body’s metabolism remains steady and growth processes continue as needed.

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