The Heart

Question 1

What are the components of the heart?

Answer 1

Vena cava (superior and inferior), right and left pulmonary artery, cardiac muscle, right and left atrium, tricuspid valve, right and left ventricle, very thick left muscular wall, bicuspid valves, semilunar valves, pulmonary veins, aorta

Question 2

Where does blood enter/leave the heart?

Answer 2

Deoxygenated enters the right side of the heart via the vena cava and leaves to the lungs via the pulmonary artery, oxygenated blood enters the left side of the heart via the pulmonary vein and leaves to the rest of the body via the aorta

Question 3

What happens in the cardiac cycle?

Answer 3

Diastole and systole (atrial and ventricular)

Question 4

What is diastole?

Answer 4

When the entire heart relaxes so the atria and ventricles fill with blood

Question 5

What is atrial systole?

Answer 5

Atrium contracts so blood flows into the ventricles

Question 6

What is ventricular systole?

Answer 6

Ventricles contract so blood flows into the arteries

Question 7

What are the atrioventricular valves?

Answer 7

Bicuspid and tricuspid valves

Question 8

What valves are open in diastole?

Answer 8

Atrioventricular valves are open and semi lunar valves are closed

Question 9

What valves are open in atrial systole?

Answer 9

Atrioventricular valves are open and semi lunar valves are closed

Question 10

What valves are open in ventricular systole?

Answer 10

Atrioventricular valves are closed and semi lunar valves are open

Question 11

How long is the cardiac cycle?

Answer 11

~0.8 seconds

Question 12

How does pressure effect valves in the heart?

Answer 12

High pressure behind causes valves to open, high pressure in front causes valves to close

Question 13

Define the term myogenic

Answer 13

Contraction and relaxation not controlled by the brain

Question 14

What is the beats per minute of the pacemaker cells?

Answer 14

60 bpm

Question 15

What is the beats per minute of the heart? (usually)

Answer 15

70 bpm

Question 16

Why is the bpm higher in the heart than the pacemaker cells?

Answer 16

Because other factors like exercise, excitement and stress also effect our heart rate

Question 17

What are the factors used in the electrical conduction in the heart?

Answer 17

Sino-atiral node (SAN), atrio-ventricular node (AVN), Purkyne fibres, bundle of His, right and left bundles of Purkyne tissues

Question 18

How is the rhythm of the heart maintained via electrical excitation?

Answer 18

• wave of electrical excitation begins in pacemaker area called the sino-atrial node (SAN)
• this causes the atria to contract, but a layer of non-conductive tissue prevents the excitation effecting the ventricle
• electrical activity in the SAN is picked up in the atrio-ventricular node (AVN). There is a slight delay before the signal stimulates the bundle of His
• this penetrates the septum between the ventricles
• the bundle of his splits into two branches and carries wave of excitation to the apex (bottom) of the heart
• the wave of excitation spreads through the Purkyne fibers at the apex up, causing a contraction of the ventricles starting from the bottom up

Question 19

Why is it important the wave of excitation starts at the apex then travels up?

Answer 19

So the blood is emptied from the ventricles efficiently

Question 20

What is an electrocardiogram?

Answer 20

A measure of electrical differences in your skin which result from the activity in the heart to measure the spread of electrical excitation

Question 21

What are electrocardiograms used for?

Answer 21

Diagnosing heart conditions/recognising irregular heart patterns

Question 22

In electrocardiography, what is the P wave?

Answer 22

Depolarisation of the atria in respone from signalling at the SAN

Question 23

In electrocardiography, what is the QRS complex?

Answer 23

Depolarisation of ventricles triggered by signals at the AVN

Question 24

In electrocardiography, what is the T wave?

Answer 24

Repolarisation of the ventricles and completion of a heart beat

Question 25

What are pacemaker cells?

Answer 25

Specialised muscle tissue that sets a rhythm of contraction and relaxation in the heart

Question 26

What is fibrillation?

Answer 26

When an irregular (often fast) heart rate that occurs when the two upper chambers of your heart experience chaotic electrical signals (100-175 bpm)

Question 27

What is fibrillation caused by?

Answer 27

Interference at the pacemaker cells

Question 28

How can fibrillation be corrected?

Answer 28

Defibrillation (controlled electrical current)

Question 29

Name some examples of heart conditions

Answer 29

Tachycardia, bradycardia, ectopic heartbeat, atrial fibrillation (arrhythmia)

Question 30

What is tachycardia?

Answer 30

When the heart beat is very rapid (over 100 bpm). Usually very normal and caused by exercise, but may be irregular if caused by complications of the electrical control in theheart

Question 31

What is bradycardia?

Answer 31

When the heart beat is very slow (below 60 bpm). Usually very normal in athletes, but may very serious and could be fixed with an artificial pacemaker

Question 32

What is an ectopic heartbeat?

Answer 32

Extra heartbeats that are out of the normal rhythm. Most people have one per day, but if frequent could be linked to serious conditions