Download The cardiac cycle is initiated and controlled by the heart itself

AS Biology
Initiation and control of the cardiac cycle- Practice Questions
GROUP PRACTICE QUESTIONS
CLASS SET
1. Read through all of the following passage and then fill in the spaces with the most appropriate
word or words.
The cardiac cycle is initiated and controlled by the heart itself. Cardiac muscle is said to be a).........................
since it will contract and relax of its own accord. The beat is initiated by the b).........................which is
situated in the wall of the c)............... Waves of depolarization travel through the atria causing atrial
d).............. The waves of depolarization can only travel to the ventricles via the e)................... situated at the
top of the ventricular septum. From here the waves travel to the apex of the heart through the
f)..................... which is made of specialized conducting cells called g).......................... These then carry the
waves of depolarization through the ventricle walls causing both ventricles to contract simultaneously. At
this stage the h)..................... are open and the i)........................... are shut so that blood can be forced into the
arches.
2. Explain the roles of the sinoatrial node (SAN), atrioventricular node (AVN) and the Purkyne tissue
during one heartbeat.
3. The diagram shows a normal ECG. The paper on which the ECG was recorded was running at a
speed of 25mm s-1.
a. If this diagram is 10 cm long, calculate the heart rate in beats per minute.
b. The time interval between Q and T is called the contraction time.
i. Suggest why it is given this name.
ii. Calculate the contraction time from this ECG
c. The time interval between T and Q is called the filling time.
i. Suggest why it is given this name.
ii. Calculate the filling time from this ECG
AS Biology
Initiation and control of the cardiac cycle- Practice Questions
CLASS SET
d. An adult male recorded his ECG at different heart rates. The contraction time and filling
time were calculated from the ECGs. The results are shown in the table.
i. Suggest how the man could have increased his heart rate for the purposes of the
experiment
ii. Present these results as a line graph, drawing both curves on the same pair of axes.
iii. Comment on these results
4. During a cardiac cycle, a wave of electrical activity spreads from the sino-atrial node.
Describe how the spread of this wave of electrical activity results in
a. the ventricles only contracting after they have filled with blood;
b. the contraction of the ventricles starting at the apex of the heart.
5. Cardiac muscle is described as myogenic as it naturally contracts and relaxes. With reference to
the structures and tissues within the heart, create a FLOW DIAGRAM to describe how the cardiac
cycle is initiated and coordinated.[5]