Adrenaline & Thyroxine

This lesson covers:

  1. Where adrenaline is released from, and what it does in the body
  2. Where thyroxine is released from, and what it does in the body

Adrenaline

Diagram showing the location of the adrenal glands on top of the kidneys.

Adrenaline is a hormone produced by the adrenal glands (which sit just on top of the kidneys).

When is adrenaline produced?

Illustration of a person cycling with adrenaline symbols indicating the fight or flight response.

Adrenaline is produced during the 'fight or flight' response, when you get scared, stressed, or need to exercise. It prepares the body for activity.

What does adrenaline do?

Illustration of a human heart showing its anatomy and structure.

1Increases heart rate

Illustration of a blood cell and a blood droplet on a black background.

2Increases blood pressure

Illustration of a muscular arm with a blood drop symbolising the fight or flight response triggered by adrenaline.

3Increases blood flow to muscles

Diagram showing the molecular structure of adrenaline with a blood droplet.

4Increases blood sugar (glucose) levels by stimulating the liver to break glycogen down into glucose

Which organ is adrenaline released from?

Liver

Pancreas

Thyroid gland

Adrenal gland

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What effect does adrenaline have on heart rate?

It decreaes heart rate

It increases heart rate

It has no effect on heart rate

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When is adrenaline released?

When you're sad

When you're happy

When you're resting

When you're scared

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Adrenaline causes changes in the body to prepare for a ‘fight or flight’ response.


Describe 3 of these changes. 

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Adrenaline causes the conversion of which substances? 

Glucose âž” glycogen

Glucagon âž” glucose

Glycogen âž” glucose

Glucose âž” glucagon

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Thyroxine

Diagram showing the location of the thyroid gland in the neck.

Thyroxine is produced by the thyroid gland, which is found in the neck.


What does thyroxine do?


Thyroxine has lots of roles in the body, including growth and development, but the main role is to increase your metabolic rate (the rate at which chemical reactions are taking place).

How is the production of thyroxine regulated?


Diagram showing the regulation of thyroxine production by the pituitary gland, TSH, and thyroid gland.


The pituitary gland produces Thyroid Stimulating Hormone (TSH), which stimulates the thyroid gland to produce thyroxine.


Thyroxine then inhibits the production of TSH from the pituitary gland.

Diagram illustrating the regulation of thyroxine production involving the pituitary gland, TSH, and negative feedback mechanisms.

The exact steps are as follows:

1If thyroxine levels are too low - the pituitary gland will release TSH. This then stimulates the thyroid gland to release more thyroxine. So thyroxine levels in the blood increase back up to normal.

2If thyroxine levels are too high - the thyroxine will inhibit the pituitary gland from producing TSH. Less TSH means that the thyroid gland won't release as much thyroxine. So thyroxine levels in the blood fall back to normal.

Diagram showing the negative feedback mechanism in the regulation of thyroxine levels by the hypothalamus and pituitary gland.

The control of thyroxine levels by the hypothalamus and pituitary gland is an example of negative feedback. If levels of thyroxine rise too high, it will bring about changes to lower the levels, and if they fall too low, it brings about changes to raise them back up.

Graph showing the regulation of thyroxine levels in the blood over time. High levels of thyroxine inhibit TSH release, while low levels of thyroxine stimulate TSH release.

Which organ is thyroxine released from?

Liver

Thyroid gland

Adrenal gland

Pancreas

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What is the main role of thyroxine?

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Which organ is TSH released from?

Testes

Pituitary gland

Thyroid gland

Kidneys

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The hormone TSH is involved in the regulation of thyroxine levels. 


What does TSH stand for?

Thyroid stimulating hormone

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Does thyroxine stimulate or inhibit the pituitary gland from releasing TSH?

Stimulate 

Inhibit

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Does TSH stimulate or inhibit the thyroid gland from releasing thyroxine?

Stimulate 

Inhibit

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Which type of feedback is involved in the regulation of thyroxine levels?

Positive feedback

Negative feedback

Recursive feedback

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Describe what will happen when thyroxine levels are too high.

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