Draw a labelled diagram of the human heart showing the attached blood vessels.

Describe the action of the heart in pumping blood.

Nerves connecting the brain and heart contain neurons that control heart rate.  Explain how a nerve message passes from one neuron to another neuron.

Remember, up to TWO “quality of construction” marks per essay.

NB: Drawings must be correctly proportioned and clearly drawn showing connections between structures. The drawing may show the heart without contraction or in any stage of contraction. Award [1] for any correctly labelled part that has been drawn to the stated standards.
a. atria/right atrium/left atrium – shown above the ventricles and must not be bigger than ventricles;
b. ventricle/left ventricle/right ventricle – shown below the atria, must have thicker walls than atria;
c. vena cava/superior vena cave/inferior vena cava – connected to right atrium;
d. pulmonary artery – shown from right ventricle (to lungs);
e. pulmonary vein(s) – shown (from lungs) to left atrium;
f. aorta – shown as large artery from left ventricle out of heart;
g. AV valves/atrioventricular valves / mitral/bicuspid and tricuspid – named correctly and shown between both atria and ventricles and labelled at least on one side;
h. semilunar valves – shown in aorta/pulmonary artery;
Valves need to open in correct direction.

Remember, up to TWO “quality of construction” marks per essay.

a. (both) atria collect blood (from veins);
b. sinoatrial/SA node sends impulses to muscle/fibres initiating contraction;
c. blood is pushed to ventricles by contraction of atria/atrial systole;
d. AV (atrioventricular) valves are open (as atria contract);
e. semilunar valves are closed so that ventricles fill with blood;
f. ventricles contract / ventricular systole;
g. AV (atrioventricular) valves close (and preventing backflow);
h. blood is pushed out through the semilunar valves/into pulmonary artery and aorta;
i. when ventricles relax/diastole, semilunar valves close preventing backflow of blood;
Do not accept the description of blood flow without a clear action.
Do not accept general statements such as systole = heart contraction and diastole = heart relaxation.

[4 max] if suggests that left and right sides are contracting at different times or simultaneous contraction not indicated.

Remember, up to TWO “quality of construction” marks per essay.

a. nerve impulse reaches the end of the presynaptic neuron;
b. (depolarization causes) calcium channels in membrane (to) open;
c. calcium diffuses into the presynaptic neuron;
d. vesicles of/containing neurotransmitter move to and fuse with presynaptic membrane;
e. (neurotransmitter) released (by exocytosis) into synaptic space/cleft;
f. (neurotransmitter) diffuses across the space/synapse;
g. (neurotransmitter) attaches to receptors on postsynaptic neuron;
h. receptors cause ion channels to open and sodium diffuses into the postsynaptic neuron;
i. the postsynaptic neuron membrane is depolarized;
j. (depolarization) causes a new action potential;
k. (neurotransmitter) on postsynaptic membrane is broken down;
l. (neurotransmitter) is reabsorbed into the presynaptic neuron;

There were some G2 comments that the whole of this question could be answered with only SL knowledge. This is true. However part c proved difficult for all but the top students.

The diagrams of the heart were of very varied quality. A diagram was asked for, i.e. the chambers and correctly positioned blood vessels, not an artistic impression with the blood vessels mysteriously floating outside the heart. Very few showed the atria with thinner walls than the ventricles.

There were some G2 comments that the whole of this question could be answered with only SL knowledge. This is true. However part c proved difficult for all but the top students.

Perhaps it is the fault of descriptions of the heart action in terms of how a blood cell would pass through the heart, but very few were able to explain that both atria contract at the same time etc. Weaker candidates seemed to think that the blood just flowed through the heart, instead of explain the movement in terms of muscle contraction.

The question writer was obviously trying to show the connection between the heart and nerves with the opening sentence. Unfortunately weaker students did not read beyond the first line and did not realise that the question was about synapses. There were many irrelevant essays about nerve impulse propagation and also the action of the SAN and AVN. Well prepared candidates could explain concisely the train of events triggered by the arrival of the nerve impulse at the presynaptic knob. The word "message" was questioned by several teachers. It was presumably used to imply that it does not pass across the synapse as an impulse.