| Date | November 2017 | Marks available | 2 | Reference code | 17N.3.SL.tz0.17 |
| Level | Standard Level | Paper | Paper 3 | Time zone | time zone 0 |
| Command term | List | Question number | 17 | Adapted from | N/A |
Question
List three places where extracellular fluid is located in the body.
Compare and contrast water distribution in Olympic sprinters and inactive individuals.
Explain how an antidiuretic hormone helps conserve water when sweating during muscular activity.
Markscheme
blood plasma ✔
lymph ✔
saliva ✔
eyes ✔
glands ✔
digestive tract / lumen ✔
gall bladder ✔
surrounding nerves & spinal cord ✔
skin/kidneys ✔
synovial joints ✔
Award [2 max] for three correct.
Award [1 max] for two correct.
Award [0] for one or zero correct.
Similarities
sprinters and inactive individuals will have water distributed in the same places of their body/ intra and extracellularly ✔
although body water content varies greatly between individuals the water content of the various tissues remains relatively constant ✔
glycogen in both muscle «and liver» is stored with about 3 gram of water for every gram of glycogen ✔
Differences
Olympic sprinters will have higher water content in plasma «associated with improved thermoregulation» ✔
sprinters have a lower percentage of their body composition as adipose tissue/fat which has a low water content «10%» ✔
sprinters have higher amounts of muscle glycogen compared to untrained individuals which increases water content ✔
sprinters will have a higher muscle mass than inactive individuals which has a high water content «76%» ✔
athletes have higher proportion of fat free mass, which contains water so therefore higher water content for athletes ✔
Award [3 max] for each.
sweating leads to reduced blood plasma ✔
loss of blood plasma results in increased blood osmolality / increased salinity ✔
increased blood osmolality/salinity stimulates the hypothalamus ✔
hypothalamus sends neural signal to the pituitary gland ✔
pituitary gland secretes ADH into the blood ✔
ADH acts on the kidneys, increasing water permeability of the «distal» tubules/ collecting ducts ✔
ADH acting on the kidneys leads to increased reabsorption of water ✔
Award [2 max] for the first 5 mark points.
Examiners report
Also done well overall.
Was challenging because it was worth four marks. The command term is demanding and requires some points to be about similarities and differences. In this case the difficult last point was the similarity.
The responses to this were mixed where some candidates connected the hormone to affecting sweating rather than having an effect on the kidney.
