Pupil sheet · The heart and double circulation

One beat, step by step — questions

Name ______________________ Date ____________

Try every question before you use a nudge. Write in full sentences where you are asked to explain.

1. identify

Supplement. The diagram shows a section through a mammal's heart. Which letter shows a semilunar valve?

A section through a mammal's heart, seen from the front, with eleven parts lettered. A: the space at the top left. B: the space at the top right. C: the space below A. D: the space below B, with the thickest wall. E: the wall of muscle down the middle, between C and D. F: the flaps between B and D. G: the pockets at the foot of the large artery that leaves D. H: a vessel running over the outside of the heart muscle. J: the large artery that leaves D and arches over the top. K: the large vein that enters A from above. L: the thick outer wall of muscle around D.

Circle one answer.

Nudge (only if you are stuck): There are two kinds of valve in the heart. Where does each kind sit?

2. sequence

Supplement. The ventricles have just started to contract, and the atrioventricular valves have just shut. Put in order what happens next, until the ventricles are ready to contract again.

Write the number of each step in order.

the atria contract and squeeze their remaining blood into the ventricles
the semilunar valves open and blood leaves the ventricles
the ventricles relax and the semilunar valves shut
the atrioventricular valves open and blood flows into the ventricles

First: ______
Second: ______
Third: ______
Last: ______

Nudge (only if you are stuck): A valve opens when the pressure behind it is higher than the pressure in front of it. Follow the pressure in the ventricles.

3. state

Supplement. Which part of the heart has the thickest muscle wall?

Circle one answer.

the left atrium
the right ventricle
the right atrium
the left ventricle

Nudge (only if you are stuck): Which part pumps blood the furthest?

4. state

Supplement. What does the septum keep apart?

Circle one answer.

the blood inside the heart and the muscle of the heart's own wall
the blood in the atria above and the blood in the ventricles below
the arteries that leave the heart and the veins that come back to it
oxygenated blood on the left and deoxygenated blood on the right

Nudge (only if you are stuck): The septum runs down the middle of the heart. What is on each side of it?

5. identify

Supplement. The ventricles are contracting and blood is leaving the heart. Which row is correct?

Row	Atrioventricular valves	Semilunar valves
A	shut	open
B	open	shut
C	shut	shut
D	open	open

Circle one answer.

Nudge (only if you are stuck): Where is the pressure higher: in the ventricles, or in the atria and the arteries?

6. identify / explain

Supplement. The graph shows the pressures in the right atrium, the right ventricle and the pulmonary artery during one beat. (a) Identify the numbered point at which the semilunar valve at the foot of the pulmonary artery shuts, and explain how the graph shows this. (b) Between points 1 and 2, the pressure in the right ventricle rises steeply, but no blood enters or leaves it. Explain why, using the pressures on the graph.

Pressure against time for three lines: time / s from 0 to 0.8, pressure / kPa from 0 to 5. Grid spacing is 0.05 s horizontally and 0.5 kPa vertically; labels are every 0.1 s and 1 kPa. Right atrium, solid orange: 0.30 kPa at 0 s, rising slowly to 0.45 at 0.30 s, briefly peaking at 0.80 at 0.35 s, then 0.50 at 0.38 and 0.40 s, 0.30 at 0.45 s, rising to 0.50 at 0.70 and 0.75 s, and ending at 0.30 at 0.80 s. Right ventricle, solid maroon: 0.20 at 0 s, 0.35 at 0.30 s, 0.70 at 0.35 s, 0.45 at 0.38 s, 0.50 at 0.40 s, 1.50 at 0.45 s, 3.00 at 0.50 s, a peak of 3.50 at 0.55 s, then 3.30 at 0.60 s, 2.70 at 0.65 s, 2.00 at 0.70 s, 1.00 at 0.73 s, 0.50 at 0.75 s, 0.25 at 0.78 s, and 0.20 at 0.80 s. Pulmonary artery, dashed: decreases from 1.90 at 0 s to 1.50 at 0.40 and 0.45 s, rises to 2.90 at 0.50 s and 3.40 at 0.55 s, then 3.20 at 0.60 s, 2.60 at 0.65 s, 2.00 at 0.70 s, a small rise to 2.10 at 0.72 s, and 2.05 at 0.75 s, ending at 1.95 at 0.80 s. Four numbered dots lie on the right-ventricle line: 1 at 0.40 s and 0.50 kPa; 2 at 0.45 s and 1.50 kPa; 3 at 0.70 s and 2.00 kPa; 4 at 0.75 s and 0.50 kPa.

(a) The point, and how the graph shows it

(b) Between points 1 and 2

Nudge (only if you are stuck): For each pair of lines, ask which is higher at each moment, and which way that would push the blood.

7. explain

Supplement. In atrial fibrillation, the muscle of the atria only quivers and no longer contracts properly, yet many people live with it for years. In ventricular fibrillation, the ventricles only quiver, and the person dies within minutes unless treated. Explain, using this information, why the walls of the atria are thinner than the walls of the ventricles.

Nudge (only if you are stuck): What still happens to the blood when the atria only quiver, and what stops when the ventricles do?

8. identify

Supplement. The diagram shows a section through a sheep's heart, seen from the front, with four valves lettered. Which letter shows the atrioventricular valve on the heart's left side?

A front section with four pale spaces, a sloping central partition and the bottom tip pointing down towards the right. The heart's right side is on your left. T: the two flaps that meet between the upper and lower spaces on the left of the picture. U: the two flaps that meet between the upper and lower spaces on the right of the picture. V: pockets pressed against the sides at the foot of the tube that arches from the centre top. W: pockets pressed against the sides at the foot of the front tube leading up from the lower space on the left. Fine cords extend below T and U.

Circle one answer.

Nudge (only if you are stuck): First find the two valves that lie between two chambers. Then decide which side of the page is the heart's left side.

9. explain

Supplement. In a healthy person, the blood in the aorta carries as much oxygen as the blood in the pulmonary vein, and much more than the blood in the vena cava. Explain how the septum makes this possible, and why it matters to the body.

Nudge (only if you are stuck): Which side of the heart does each of the three vessels join?

10. identify

Supplement. Which row is correct for the valve at the foot of the pulmonary artery?

Row	Kind of valve	It is shut when …	It stops blood flowing back into …
A	atrioventricular	the right ventricle relaxes	the right ventricle
B	semilunar	the right ventricle relaxes	the right ventricle
C	semilunar	the right ventricle contracts	the right atrium
D	atrioventricular	the right ventricle contracts	the right atrium

Circle one answer.

Nudge (only if you are stuck): First decide the kind of valve from where it sits. Then ask when blood would try to flow back out of the artery.

11. identify / explain

Supplement. A student measures the thickness of the muscle wall of each of the four chambers of a dog's heart. (a) Identify which chamber, 1, 2, 3 or 4, is the left ventricle. (b) Explain how you know.

Chamber	1	2	3	4
Wall thickness / mm	4.5	1.6	11	1.9

(a) The left ventricle

(b) How you know

Nudge (only if you are stuck): Two walls are much thinner than the other two. Which pair are the atria?

12. suggest

Supplement. In some people, the semilunar valve at the foot of the aorta does not shut properly. Suggest what happens to some of the blood when the left ventricle relaxes, and how this affects the heart.

Nudge (only if you are stuck): After the ventricle relaxes, where is the pressure higher: in the aorta or in the ventricle?

13. suggest

Supplement. A frog's heart has two atria but only one ventricle. Oxygenated blood from the lungs and deoxygenated blood from the body both enter this one ventricle. Suggest a disadvantage of this heart compared with a mammal's.

Nudge (only if you are stuck): What does a mammal's septum do that the frog's single ventricle cannot?