SNAB Run for you life

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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
delay decreases. Thus there is *more blood returning to the heart causing the heart muscle to
stretch and *the ventricles to contract with greater force.
Explain what is meant by the term myogenic: This means the *stimulation is generated from
within the muscle and not by external stimulation, leading to *depolarisation and contraction of
the heart.
State one factor, other than heart rate, that could have affected the rate at which blood passed
through the heart.
*Stroke volume; *strength of (cardiac) muscle contraction; *blood viscosity; *size of the
atria/ventricles/chambers; *adrenaline.
Describe the role of the SAN in controlling heartbeats. (2)
*The SAN initiates the heartbeat by *starting a wave of excitation/depolarisation. *The SAN also
determines the heart rate.
Describe how the sequence of muscular contraction in the heart is coordinated and how the
movement of blood through the heart is controlled. (6)
*The Sinoatrial node/SAN *initiates depolarisation, the wave of depolarisation *passes through
the wall of the atria * causing atrial systole. After a short (0.13secs) delay (to give time for
ventricles to fill and atria to finish contracting, *the AVN then conducts the impulse to the
ventricles along the *Purkyne fibres that collectively are the bundle of His. *Ventricular systole
follows from the apex up whilst the *atrioventricular valves are closed (to prevent blood flowing
back to atria). The *semilunar valves are opened by the pressure causing the *blood to be forced
into the arteries. The changed pressure in diastole will then *close the semilunar valves.
Describe how the cardiovascular centre, in the medulla oblongata, affects the SAN during
exercise. (2)
*It will increase impulses to the SAN *via the sympathetic nervous system, *stimulating more
frequent depolarisation in SAN and *increasing the heart rate/cardiac output.

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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.…read more

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Absolutists say drugs should not be used at any time and that *athletes should not be allowed to
be pressured into using drugs. *Relativists say that drugs could be used under some circumstances
e.g. they could be used for medication. But *drugs in the body can be difficult to legislate for.
*Risk to health; *gain unfair advantage; *other harmful substances banned: *burden on care
Explain why the governing bodies of sports ban the artificial enhancement of performance.…read more

Page 4

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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 *lower pH
decreases contraction in both. But *lower pH has no effect at high calcium ion concentration in
both fibres.…read more

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Suggest why using material from structure P to repair structure Q after it tore in a sporting
injury will mean that recovery will be quite slow and require careful physiotherapy. (2)
Because *lots of time will be needed to repair Q and P, recovery will be slow. *Physiotherapy may
be required because the composition of P and Q are different, e.g. ligament (Q) has more elastic
fibres than less flexible tendons/P; this means the *repaired tissue will need to be stretched
gradually.…read more

Page 6

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During this race, runner A lost 3.02 kg of water and runner B lost 2.43 kg of water. Using the
information in the question and your own knowledge, suggest reasons for the change in core
temperature of runner A after 120 minutes. (2)
*Runner A may have become dehydrated and so *stopped sweating, this caused *heat production
to become greater than heat loss and the *cooling mechanisms to fail.
The runner may also have *increased their pace.…read more

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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
compound would run short/not be synthesised. *The products T&H would be reduced.
The hydrogen (H) from the Krebs cycle enters the electron transport chain and oxidative
phosphorylation occurs.…read more

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Electrons are passed along the electron transport chain *losing energy. This energy is *used to
add a phosphate to ADP to make ATP with the enzyme *ATPase. *Oxygen is the final acceptor
molecule, it accepts hydrogen. This process is called *chemiosmosis.
Describe how a spirometer trace recorded immediately after a short period of exercise would
differ from this trace.…read more

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Creatine phosphate may also be used to generate short bursts of energy quickly by providing a
phosphate ion for ATP.
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+.…read more

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Explain how a high concentration of hydrogen ions (H+) is maintained in the intermembrane
space during chemiosis. (3)
*H+ ions from reduced NAD are *pumped into inter membrane space *using energy. The
*electrons move along the ETC *inner membrane/cristae to be combined later.
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.…read more



Excellent! Really helpful. 

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