Cardiac Cycle & Conduction System

Question 1

Path of blood through the heart - left Side

Answer 1

Blood is oxygenated at the lungs and brought back to the heart via the pulmonary vein - oxygenated blood moves from the left atrium to the left AV (bicuspid) valve into the left ventricle - it is then forced out of the left side of the heart into the aorta - the aorta carries the oxygenated blood to the muscles and organs

Question 2

Path of blood through the heart - Right Side

Answer 2

Deoxygenated blood from the muscles and organs enter right atrium through the vena cava - from right atrium to the right AV valve (tricuspid) into right ventricle - here it is forced out of the right side of the heart into the pulmonary artery - this carries blood into the lungs for re-oxygenation

Question 3

State what is the cardiac cycle

Answer 3

A process of cardiac muscle contraction and blood moving through the chambers - one complete cardiac cycle represents one full heartbeat

Question 4

How long does one cardiac cycle take ?

Answer 4

0.8 seconds (approx)

Question 5

What are the cardiac cycle stages and how long do they take ?

Answer 5

Diastole - relaxing and filling (0.4 seconds)
Atrial systole - contraction and emptying (0.1 seconds)
Ventricular systole - contraction and emptying (0.3 seconds)

Question 6

Diastole Phase

Answer 6

Relax and fill with blood

Question 7

How does the diastole phase work ?

Answer 7

-Pressure in the atria increases causing the AV valves to open
-Blood passively enters the ventricles
-The SL valves then close to prevent blood leaving the heart
-oxygenated blood enters the left atrium from the pulmonary veins

Question 8

Volume of blood after filling stage is called What ?

Answer 8

End diastolic volume (EDV)

Question 9

Atrial Systole

Answer 9

When the atria contracts, forcing blood into the ventricles - contraction of left and right atria

Question 10

Ventricular Systole

Answer 10

The ventricles contract, increasing pressure closing the AV valves prevent backflow into the atria - increased blood pressure through ventricular contraction forces blood out of both ventricles

Question 11

In the ventricular systole phase where does the right ventricle force blood to ?

Answer 11

Through the pulmonary valve into the pulmonary artery - to the lungs

Question 12

In the ventricular systole phase where does the left ventricle force blood to ?

Answer 12

Through the aortic valve into the aorta - to the body

Question 13

What is the conduction system ?

Answer 13

Heart is myogenic - the impulse is generated and passes through the muscular walls = contracting
The electrical impulse is responsible for stimulating the heart is called the cardiac impulse

Question 14

What does the heart is myogenic mean ?

Answer 14

It generates its own impulse

Question 15

The electrical impulse is responsible for stimulating the heart is called what ?

Answer 15

Cardiac Impulse

Question 16

Steps of the conduction system !

Answer 16

SA node emits an impulse and fires it through the atria walls, causing an impulse - this creates heart rate - the impulse spreads to the adjacent interconnecting fibres of the left atrium - the impulse moves to the specialised cells called the AV nodes (they act as a distributor and passes the AP impulse to the BOH - BOH happens then the impulse then moves down the BOH to the Apex of the heart - yeh impulse then spreads up the Purkinje fibres causing excitation and ventricular systole.

Question 17

What does the SA node stand for ?

Answer 17

Sino-atrial node

Question 18

Where is the SA node located ?

Answer 18

Right atria wall

Question 19

What does the AV node stand for ?

Answer 19

Atria - ventricular node

Question 20

What does BOH stand for

Answer 20

Bundle Of His

Question 21

What is the bundle of his

Answer 21

Delay of 0.1 seconds from the AV node - relay signal which allows full atrial contraction