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UNIT 5 TOPIC 7: Run For Your Life
The Heart

The location of the SAN is in the right atrium.

Describe the changes in the heart that bring about an increase in cardiac output during exercise
(4) *The heart rate, *stroke volume and *SAN activity increases whilst the *AVN time…

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Using the information in the table, describe the effect of an increase in heart rate on both the
ventilation rate and oxygen uptake by the blood, after the first ten seconds of exercise. (3)
*There is little difference in ventilation rate compared to the *oxygen uptake which increases.
*Credit use…

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Joints and Muscles
The structures that connect muscles to bones are TENDONS

Protein in the thin filament is made up of ACTIN. Protein in the thick filament is made of MYOSIN

Describe the interaction between troponin and tropomyosin when a skeletal muscle fibre
contracts. (2)
*Ca2+ bind to troponin, causing…

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Using the information in the graphs, compare the effect of pH on slow twitch and fast twitch
fibres. (2)
*The lower the pH, the less sensitive both become to calcium ions, so more calcium ions are needed
for (50%) contraction. But *the effect on slow twitch is greater though the…

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fibres than less flexible tendons/P; this means the *repaired tissue will need to be stretched

Describe the function of a ligament (2)
It is strong to *hold/attach bones together, but it is flexible to *allow movement at the joint.


*As there is more muscle contraction/respiration more *heat energy…

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Describe the role of the human nervous system in returning a slightly raised body temperature
to its normal level. (4)
*Thermoreceptors in the hypothalamus *detect the increase in (core) blood temperature and
*activate the heat loss centre. This stimulates aspects of the *autonomic nervous system to send
*impulses down motor…

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*Carbon dioxide/CO2, because *the C has been removed from C6 or C5 compound.
Using information in the diagram, suggest what would happen in the Krebs cycle if acetyl CoA
became unavailable. (3)
*The cycle would stop and the *4 carbon compound would accumulate but the *6 & *5 carbon

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Describe how a spirometer trace recorded immediately after a short period of exercise would
differ from this trace. (2)
There would be *a higher frequency of peaks in the same time/distance between consecutive peaks
would decrease, whilst the *distance from peak to trough would increase.
Name two substances, other than…

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Lactate (lactic acid) can build up in the muscles of a sprinter. Suggest why the build-up of
lactate may prevent any further increase in speed. (2)
Because *lactate build up causes a drop in pH so it becomes more acidic and there's an increase in H+.
*The low pH may…

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Describe the role of the hydrogen ion concentration gradient in making available an accessible
supply of energy for biological processes (chemiosis). (2)
*On the stalked particles,*H+ ions follow the diffusion gradient *which causes an energy change/
makes energy available *forming ATP. *ATP is an energy source for (biological processes)



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