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Question 1

Describe the cardiac cycle (1/3)

Answer 1

Diastole - the return of blood via the vena cava and pulmonary veins to the atria causes blood in the atria to increase.

Eventually, arterial pressure exceeds that of the ventricles.

AV valves are pushed open and blood begins to enter the ventricles.

Question 2

Describe the cardiac cycle (2/3)

Answer 2

Arterial Systole - the two atria contract simultaneously and send the remainders of the blood into the ventricles through the open AV valves.

The ventricles fill up with blood and the SL valves remain closed.

Question 3

Describe the cardiac cycle (3/3)

Answer 3

Ventricular Systole - 0.1 secs after arterial systole.

The pressure exerted on blood in the ventricles as the cardiac muscles contract soon exceeds the blood pressure in the arteries.

The SL valves are pushed open and blood is pumped out of the heart and into the aorta and pulmonary arteries.

Question 4

What is an electrocardiogram?

Answer 4

Electrical activity in the heart can be detected using electrodes on the skin; this is know as an electrocardiogram (ECG).

Examination of an ECG can detect disease and observe/diagnose abnormal heart activity.

Question 5

Electrocardiogram Stage - P

Answer 5

the wave of contraction across the atria from the SA node (atrial systole)

Question 6

Electrocardiogram Stage - QRS

Answer 6

the wave of contraction in the ventricles (ventricular systole)

Question 7

Electrocardiogram Stage - T

Answer 7

the electrical recovery at the end of ventricular systole (repolarization)

Question 8

Describe CARDIAC OUTPUT formula and components

Answer 8

Cardiac Output = Heart Rate x Stroke Volume

CO = HR x SV

• CO - the volume of blood pumped out of a ventricle per minute
• HR - (pulse) the number of heartbeats that occur per minute
• SV - the volume of blood expelled by each ventricle on contraction.

Question 9

Sino-Atrial Node (1/2)

Answer 9

The pacemaker is the sino-atrial node, situated in the wall of the right atrium.

Cells in the SA node initiate electrical impulses that make the cardiac muscle contract.

Question 10

Sino-Atrial Node (2/2)

Answer 10

The impulse from the SA node spreads across both atria making them contract (atrial systole).

The impulse from the SA node is then picked up by the atrio-ventricular node.

Question 11

Atrio-Ventricular Node (/2)

Answer 11

The atrio-ventricular node is located at the base of the atria.

The impulse from the AV node is relayed into the conducting fibres in the wall between the two ventricles.

Question 12

Atrio-Ventricular Node (/2)