Question 1
1
Hypoxia is a condition in which tissues of the body are deprived of an adequate oxygen supply. A study was carried out in rats to examine the effects of continuing hypoxia on the structure of the diaphragm, and to determine whether nitric oxide is implicated in adaptation of the diaphragm to hypoxia. The diaphragm helps to supply oxygen to tissues and organs in the body by ventilating the lungs. A group of 36 adult male rats were kept for 6 weeks in low oxygen while 36 adult male rats were kept in normal oxygen levels.
10 marks
Question 1(b)
1(b)
The graph shows the effect of hypoxia on the endurance of rats' diaphragm muscle after 6 weeks. Endurance is the change in force measured as a percentage of the initial force. Using the data in the graph, deduce whether hypoxia increases or decreases the endurance of the rats' diaphragm muscle.
Mediumstructured2 marks
Answer
a. increases endurance «in relation to the control» b. higher force/endurance at every testing time/throughout OR smaller decreases in force «over time» c. the magnitude of the difference is similar throughout the five minutes experiment/testing d. differences are «statistically» significant e. endurance of control is «approximately» 35 % versus endurance of hypoxia «approximately» 55 \% «after 5 minutes» Accept \(\pm 5 \%\) for both percentages 2 max
Question 1(e)
1(e)
Skeletal muscle contractions can take two different forms: if they are stimulated by a single action potential they take the form of a twitch and if they are stimulated by a series of action potentials the contraction is longer lasting (tetanic). The table shows the effects of hypoxia on the force of twitch and peak tetanic contraction in the diaphragm.
0 marks
Question 1(e)(i)
1(e)(i)
Outline the effect of hypoxia on the force of contraction of the diaphragm.
Mediumstructured1 marks
Answer
reduces «force of» twitch AND peak tetanic contraction
Question 2
2
Ehlers-Danlos syndrome (EDS) causes joint hypermobility, where joint movement extends well beyond the normal range. Researchers used two different methods to measure angles of movement at a joint of the smallest (fifth) finger.
structured0 marks
Question 2(a)
2(a)
Suggest in which direction the finger was moved to assess hypermobility. The graph shows all angles of movement of the finger, measured in degrees ( \({ }^{\circ}\) ) using both methods. Key: - Individual with EDS - Individual without EDS
Mediumstructured1 marks
Answer
towards the back of the hand/upwards/backwards; Accept movement to the side if the hand is identified e.g. towards the left in the left hand. Accept clear description of the movement relative to the hand e.g. away from the palm. Do not accept only bending or flexing the finger. Direction must be included.
Question 2(b)
2(b)
Suggest a method which could have been used to measure the angle of movement of the finger.
Mediumstructured1 marks
Answer
(video and) computer/app analysis of images OR goniometer; Accept use a protractor on an image. Do not accept protractor on its own.
Question 2(c)
2(c)
Estimate the threshold (minimum) angle for a diagnosis of EDS.
Mediumstructured1 marks
Answer
63 to 65 (for method 1 - lowest value) OR 79 to 81 (for method 1 - value on correlation line) OR 88 to 90 (for method 2); Angle unit not required. Mark first answer only. Accept a value in the ranges given.
Question 2(d)
2(d)
Suggest which structure at the finger joint is affected by EDS.
Mediumstructured1 marks
Answer
ligaments/tendons; -
Question 2(e)
2(e)
Describe the level of correlation between the data from the two measurement methods.
Mediumstructured1 marks
Answer
strong/good/high correlation OR the two methods have good agreement;
Question 4
4
Strenuous short-duration exercise requires a lot of energy in different muscle fibre types. This causes a reduction in the mechanical power output. The graph shows the decreases in ATP concentration in different human muscle fibres during brief strenuous exercise. It also shows muscle fatigue, measured as the percentage decrease in power.
0 marks
Question 4(b)
4(b)
Distinguish between power decline for the three types of muscle fibre.
Mediumstructured3 marks
Answer
a. (both) type II fibres decline more than type I / type I declines the least; b. type Ilx decline the most; c. type II decrease more between 0 and 10 seconds than later whereas type I only decrease after 10 seconds;
Question 4(d)
4(d)
Scientists have distinguished muscle fibres on the basis of their colour as red or white and their contractile properties as fast or slow. White fibres have a low myoglobin content, few mitochondria and fatigue quickly. Using the data, deduce with reasons, which muscle fibre type is most probably a white muscle fibre.
Hardstructured2 marks
Answer
a. mitochondria/myoglobin required to make ATP; b. type Ilx need more ATP in a short period of time, so probably anaerobic respiration (therefore probably white fibre); c. type Ilx as shows a fast power decline, producing fatigue;
Question 4
4
In a study to investigate the effect of training on muscles, seven healthy males were subjected to training using the right leg only. They then exercised using both legs and the glycogen content was measured in both the untrained (left leg) and trained (right leg) muscle.
7 marks
Question 4(a)
4(a)
Calculate the percentage of type I muscle fibres containing moderate glycogen in the untrained leg. \%
Mediumstructured1 marks
Answer
32
Question 4(b)
4(b)
Distinguish between the results for type I and type IIA muscle fibres in untrained muscles.
Mediumstructured2 marks
Answer
type I have a lower percentage with high glycogen (than type IIA); type I have a higher percentage with moderate glycogen (than type IIA); type I have a higher percentage muscle fibres with low glycogen (than type IIA); type I have a higher percentage muscle fibres with no glycogen (than type IIA); Accept inverse statements and numerical comparisons.
Question 4(c)
4(c)
Describe the impact of training on the glycogen content of the three types of muscle fibres.
Mediumstructured3 marks
Answer
training decreases the glycogen content in all three muscle types; no muscle types have high glycogen content (after training); type IIB fibres use up more of its glycogen (than types I and IIA); all three fibre types increase in percentage of muscle fibres with low/no glycogen levels; Accept inverse statements and numerical comparisons.
Question 4(d)
4(d)
Based on the data for the trained muscle, deduce with a reason, which type of fibre could be fast muscle fibre.
Hardstructured1 marks
Answer
type IIB as it uses more glycogen in exercise (must include reason)