GCSE workbooks https://www.amazon.co.uk/Dr-Shaun-Don...
School licenses from 40p per copy https://www.freesciencelessons.co.uk/...

In this video, we look at the roles of adrenaline and thyroxine and then explore how thyroxine levels are controlled by negative feedback.

This video is based on the AQA spec. If you are following a different exam board then you should check your specification. The Amazon link above is an affiliate link. This provides a small commission which helps to support freesciencelessons. The cost remains the same to you. If you prefer not to use this, you can search Amazon for the Freesciencelessons workbooks.

Image credit:

Beating heart By DrJanaOfficial - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index...

Music credit:

Deliberate Thought by Kevin MacLeod is licensed under a Creative Commons Attribution licence (https://creativecommons.org/licenses/...)
Source: http://incompetech.com/music/royalty-...
Artist: http://incompetech.com/