Factors affecting a persons reaction to caffeine?

Question

Im completing my coursework on the effects of caffeine on the pulse rate. For the conclusion I want to explain the results I obtained.
1. Does anyone know the reason why females tend to have a higher resting pulse rate?
2. How / why does body size affect how fast and u react to caffeine and also how much of a change you show in the PR reading.
3. What else will affect how fast u react ?

Answer 1

2. A larger body has the effect of diluting the caffeine. If you think of the dosage of caffeine as mg caffeine per kg of body mass, you can see that the caffeine will be "spread out" more in a larger body than it is in a smaller body.
3. The person's usual caffeine intake may affect how fast the person reacts. If the person is accustomed to exposure to caffeine, the caffeine may take longer to show a reaction, and it may also take more caffeine to show any effect.