Higher: how the pituitary and thyroid hold thyroxine steady by negative feedback, reading TSH and thyroxine test results, and why adrenaline is a different kind of response.
What you will learn
- Explain how negative feedback through TSH keeps the thyroxine level steady
- Use thyroxine and TSH results to say where a fault is
- Describe what adrenaline does in fight or flight and calculate a percentage change in heart rate
- Tell negative feedback apart from other responses
What negative feedback means
Many levels in the body are held close to a set value: blood glucose, body temperature, water, and the hormone thyroxine.
In each case the body uses negative feedback: a change away from normal is detected, and the response pushes the level back the other way.
- A level changes (it rises or falls)
- The change is detected
- A response reverses the change
- The level returns to normal, and the response stops
Negative feedback always works against the change. If a response made the change bigger, it would not be negative feedback.
The rest of this lesson and its 12 practice questions are locked.
In this lesson
- What negative feedback means
- The thyroxine loop
- Reading test results
- Adrenaline: fight or flight
- Try it: Find the fault
12 practice questions, marked as you go; about 25 minutes in all.
Key terms
Thyroxine, Thyroid gland, Pituitary gland, TSH, Inhibits, Hypothalamus, TRH, Adrenaline, Adrenal glands
In this unit: Homeostasis and response
How the nervous and hormonal systems keep the body's internal conditions steady: reflexes and reaction time, blood glucose and diabetes, reproductive hormones and contraception, the brain, eye, temperature and kidneys, and plant hormones.