Cardiac Cycle

Question 1

How is the CARDIAC OUTPUT measured?

Answer 1

The volume of blood pumped by the left ventricle in each heart beat X the number of times the heart beats per minute.

Question 2

What is the cardiac cycle equation?

Answer 2

Stroke volume X heart rate.

Question 3

Describe Atrial Systole.

Answer 3

The atria is filled with blood; contracts forcing blood through the atrioventricular valves into the ventricles.
Ventricles are now full of blood.

Question 4

Describe Ventricular systole.

Answer 4

Ventricles contract forcing blood up through the semilunar valves and into the aorta and pulmonary artery.
The force of contraction closes the AV valves, preventing backflow.

Question 5

Describe Diastole.

Answer 5

Ventricles relax and the drop in blood pressure causes the SL valves to close.
Atria start to fill with blood, and as the pressure increases, blood starts trickling down into the ventricles again.

Question 6

What is the Sinoatrial Node?

Answer 6

Specialised heart tissue in the right atrium- acts as the hearts PACEMAKER setting the base rate of contraction.

Question 7

Wave of depolarization.

Answer 7

A wave of depolarization passes over the SAN and spread over BOTH ATRIA, causing them to contract, reaching the AVN

Question 8

What happens after the wave of depolarization?

Answer 8

Transmitted from the AVN along specialised muscle fibre in the septum called the bundle of His. reaches the APEX of the heart.

Question 9

What happened once the wave of depolarization reached the APEX?

Answer 9

Transmitted through a network of more specialised muscle cells called PURKINJE FIBRES, to myocytes in the walls of the ventricles. the ventricles contract.

Question 10

What happens at the P wave?

Answer 10

Wave of depolarization that spreads from the SAN.

Question 11

What happens at the PR interval?

Answer 11

Time taken for the wave to get from the SAN to AVN. Starts at the P wave and ends at QRS complex.

Question 12

What happens at the QRS complex?

Answer 12

Contraction of the ventricles. Wav spreads across the ventricles which cases ventricular systole.

Question 13

What happens at the ST segment?

Answer 13

Interval between the end of ventricular depolarization and the start of ventricular repolarization.

Question 14

What happens at the T wave?

Answer 14

Repolarization of the ventricles during diastole.

Question 15

Pressure changes in the CC during Atrial systole.

Answer 15

High pressure`

Question 16

Pressure changes in the CC during Ventricular systole.

Answer 16

Highish pressure.

Question 17

Pressure changes in the CC during Diastole.

Answer 17

Low pressure

Question 18

How does the sympathetic system contribute to the regulation of the heart?

Answer 18

Nervous impulses from the cardio-accelerator increase heart rate due to release of neurotransmitter NOREPINEPHRINE.

Question 19

How does the parasympathetic system contribute to the regulation of the heart?

Answer 19

Nervous impulses from cardio-inhibitor centre via parasympathetic nerve.
Decrease in hear rate due to release of neurotransmitter ACETYCHOLINE

Question 20

How does hormonal control contribute to the regulation of the heart?

Answer 20

Sympathetic nervous system acts on adrenal gland, releasing epinephrine.
Stimulates SAN to generate more impulses; increasing heart rate.

Question 21

What is an artificial pacemaker?

Answer 21

Monitors the hearts electrical activity and stimulate the ventricles or atria to contract when necessary.

Question 22

What is an ECG?

Answer 22

Used to diagnose problems with the heart as variations in different components of the trace can indicate a disease or other abnormality.