Download 6.2 The transport system – summary of mark schemes

6.2 The transport system – summary of mark schemes
6.2.1
Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood
through the heart.
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6.2.3
left ventricle;
right ventricle;
right atrium;
left atrium;
semilunar valves;
atrioventricular valves;
pulmonary artery;
pulmonary vein;
vena cava;
inferior and superior vena cava distinguished;
aorta;
ventricle wall thicker than atria;
left ventricle wall thicker than right ventricle wall;
coronary artery;
chordinae tendinae / chords and septum;
Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves.
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6.2.4
blood is collected in the atria;
blood is pumped from the atria to the ventricles;
opened atrio-ventricular valves allow flow from the atria to the ventricles;
closed semi-lunar valves prevent backflow from the arteries to the ventricles;
blood is pumped out from the ventricles to the arteries;
open semi-lunar valves allow flow from ventricles to arteries;
closed atrio-ventricular valves prevent backflow to the atria;
pressure generated by the heart causes blood to move around the body;
pacemaker (SAN) initiates each heartbeat;
Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of
the brain and epinephrine (adrenaline).
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6.2.5
the heart is myogenic / beats on its own accord;
60-80 times a minute (at rest);
coordination of heartbeat is under the control of pacemaker;
located in the muscle / walls;
sends out signal for contraction of heart muscle;
atria contract followed by ventricular contraction;
fibres / electrical impulses cause chambers to contract;
nerve from brain can cause heart rate to speed up;
nerve from brain can cause heart rate to slow down;
adrenalin (carried by blood) speeds up heart rate;
artificial pacemakers can control the heartbeat;
Explain the relationship between the structure and function of arteries, capillaries and veins.
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arteries
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arteries carry blood away from the heart / to tissues;
thick wall / elastic fibres to help withstand the high(er) pressure;
arteries have muscle fibres to generate the pulse / help pump blood / even out blood flow;
arteries have elastic fibres to help generate pulse / allow artery wall to stretch / recoil;
lumen small compared to wall thickness to maintain high pressure;
except lumen large near the heart to conduct a large volume of blood;
G. valves in aorta and pulmonary artery to prevent back flow into ventricles in diastole;
H. layers of (smooth) muscle to allow arteries to contract / elastic recoil;
I. allows the pressure to be altered (vasoconstriction and vasodilation);
veins
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veins carry blood back to the heart / from the tissues;
lumen always large in relation to diameter;
wide lumen to maintain blood flow / decrease resistance to flow;
thin wall / more collagen and fewer elastic fibres (than arteries) since pressure low(er);
thin so they are able to be pressed by muscles to pump blood;
very little muscle since not needed for constriction;
valves to prevent back flow between pulses;
capillaries
Q. no muscle / elastic tissue since pressure very low;
R. endothelial layer one cell thick to allow permeability / diffusion of chemicals / tissue fluid;
S. no valves since pressure very low;
T. capillaries allow exchange of O2 / CO2 / nutrients / waste products from tissues / cells;
U. capillaries have pores / porous walls to allow phagocytes / tissue fluid to leave;
V. capillaries are narrow so can penetrate all parts of tissues / bigger total surface area;
W. large number resulting in increased surface area;
X. capillaries have narrow lumen / width of single blood cell;