| Date | May 2019 | Marks available | 3 | Reference code | 19M.2.SL.tz0.2 |
| Level | Standard Level | Paper | Paper 2 | Time zone | time zone 0 |
| Command term | Explain | Question number | 2 | Adapted from | N/A |
Question
State one component transported by blood.
Explain how cardiac output is maintained during prolonged exercise.
Markscheme
Cells (erythrocytes / leucocytes / platelets) ✔
plasma ✔
electrolytes ✔
proteins ✔
gases ✔
nutrients ✔
waste products ✔
hormones ✔
Accept suitable examples of any component eg oxygen would be awarded the mark for gases
[1 max]
HR and/or SV need to increase to maintain/increase Q during prolonged exercise ✔
sweating/fluid loss/decrease in blood plasma/increased viscosity/decrease in SV can be compensated for by a «gradual» increase in HR / cardiovascular drift ✔
rise in body temperature / diversion of blood flow to the skin / reduced blood volume to working muscles can be compensated for by an increase in HR / cardiovascular drift ✔
to maintain blood volume / to maintain Q an athlete can ingest electrolyte drink or water and foods during prolonged exercise «to avoid cardiovascular drift» ✔
Simply stating the equation for cardiac output is not enough for a mark
[3 max]
Examiners report
Almost all students could name one component
Full marks were rare on this question with many candidates unable to make the connection with cardiac drift. Commonly, they did not answer the question which asked how to maintain cardiac output. The majority of candidates understood the relation between cardiac output, HR and SV but could not apply it to the context of the question.
