Edexcel IAL Biology 7.14 Fight-or-flight response

An answer that includes the following points:

Indicative content - description from graphs and experimental data

Heart rate:

- as the concentration of adrenaline increases, the increase in heart rate increases in both groups

- this increase is (slightly) \{greater in the older group of people / lower in younger people\}

- at all concentrations of adrenaline the older group have greater \{change/heart rate\} / at all concentrations of adrenaline the younger group have smaller \{change/heart rate\}

- but there are no error bars to judge whether or not this difference is significant

- due to stated effect of aging on heart - weaker muscle/effect on SAN/lower stroke volume

Cardiac index:

- as the concentration of adrenaline increases, the increase in cardiac index increases in both groups

- the increase is the same at $\{20 / 40\} \mathrm{ng} \mathrm{kg}^{-1} \mathrm{~min}^{-1}$

- at concentrations above $40 \mathrm{ng} \mathrm{kg}^{-1} \min ^{-1}$ the increase is \{lower in older people / greater in younger people\}

- overall the increase cardiac index is \{lower for the older people / greater for younger people\}

- due to lower cardiac output / increased body surface area/lower stroke volume / (accept converse for younger people)

- but there are no error bars to judge whether or not this difference is significant

(6)

Change in blood pressure

- blood pressures decrease and then increase in both groups (as adrenaline concentration increases)

- a concentration of $20 \mathrm{ng} \mathrm{kg}^{-1} \mathrm{~min}^{-1}$ decreases the blood pressure in both groups

- a concentration of $\{\mathbf{8 4 - 1 2 0}\} \mathbf{~ n g ~ k g}^{\mathbf{- 1}} \mathbf{m i n}^{-1}$ increases the blood pressure in older people

- in older people lower change in blood pressure (in response to higher concentrations of adrenaline) / converse for younger people

- due to stated changes of aging on heart muscle/ blood vessels/baroreceptors

- no overlap of error bars between older and younger people indicate that these differences are significant (at all concentrations of adrenaline) / the error bars overlap for some concentrations for older people meaning that these differences are not significant / the error bars do not overlap for some concentrations for younger people meaning that these differences are significant

Level 1:

1 or 2 graphs commented on changes in heart rate/cardiac index/blood pressure as concentration of adrenalin increases

Level 2:

2 or 3 graphs commented on, including details of the effect of adrenaline on older people

Level 3:

All 3 graphs commented on, including details of the effect of adrenaline on older people and discussion of the significance of the data.