The table shows mean heart rates in the same group of volunteers.
Table
| Condition | Mean heart rate in beats per minute |
|---|---|
| Resting | 68 |
| During a frightening film | 92 |
A student concludes that adrenaline caused the increase.
Which additional measurement would most directly test the proposed hormonal explanation?
Blood insulin concentration in both conditions.
Blood thyroxine concentration in both conditions.
Blood testosterone concentration in both conditions.
Blood adrenaline concentration in both conditions.
89 exam-style questions on Edexcel GCSE Biology 7.1 Hormones and coordination, covering 7.1.1 Endocrine glands and hormone transport, 7.1.2 Adrenalin and fight or flight, and 7.1.3 Thyroxine and negative feedback. Each one has a worked solution and a mark scheme showing where the marks go.