The Heart 8.5

Front 1

What is the heart made of ?

Which arteries supply it with oxygenated blood ?

Surrounded by

Back 1

Cardiac muscle, contract and relax in regular rhythm

Coronary arteries

Inelastic pericardial membrane prevent heart from overdistending with blood

Front 2

Process of the function of heart in the right side

Back 2

Deoxygenated blood enters right atrium from upper body via superior vena cava and from lower body via inferior vena cava

Atrium fill with blood and pressure rises until atrioventricular valve open to let blood into right ventricle

When both atrium and ventricle are fill with blood, atrium contracts to force blood into ventricle and ventricle expands

Ventricle contract , atrioventricular valve closes to prevent back flow

Ventricle contracts fully to pump blood through semi lunar valve into pulmonary artery

Front 3

Why is the muscular wall of left side of heart much thicker?

Back 3

Because it has to have sufficient force to overcome resistance of aorta and arterial system of whole body and pump blood under pressure to all extremities of body

Front 4

Septum function

Back 4

Inner dividing wall to prevent blood from mixing

Front 5

Sound of the heart beat

Back 5

Produced by blood pressure closing valves

Described as Lub dub

First sound from blood forced against atrioventricular valve as ventricle contract

Second sound from backflow of blood closing semi lunar valves as ventricle relax

Front 6

Cardiac cycle

Back 6

Event of a single heartbeat and last about 0.8 second

Front 7

Atrial systole

Back 7

Atria contract and pressure inside atria increases

Atrioventricular valve opens and blood flows into ventricle

Pressure decreases and last about 0.1 sec

Front 8

Ventricle systole

Back 8

Ventricle contract and pressure increases

Atrioventricular valve closes

Semi lunar valves in aorta and pulmonary artery opens , blood flows into arteries

Pressure decreases and last abt 0.3 sec

Front 9

Diastole

Back 9

Pressure in ventricle decreases

Semi lunar valves in aorta and pulmonary artery close

Heart muscle relax as blood flows into atrium and ventricle

Front 10

Cardiac muscle is

Back 10

Myogenic so it has its own intrinsic rhythm

Maintain heart beat without wasting resources

Front 11

How is the basic heart rate maintained?

Back 11

By the wave of excitation

Wave of excitation starts at pacemaker called sino-atria node cause atria to contract and non conducting tissue prevent excitation passing directly to ventricle

Pick up by atrioventricular node. AVN imposes slight delay before stimulating bundle of His, conducting tissues made of Purkyne fibres, penetrate through septum

Bundle of His separate to two branches and conducts wave of excitation to apex of heart

At apex, purkyne fibres spread through walls of ventricles and spread of excitation triggers ventricle to contract from apex

Front 12

Why AVN imposes a slight delay?

Back 12

Make sure atria stop contracting before ventricle contract

Front 13

P wave of ECG indicates

Back 13

When SAN contracts , before atrial systole

Front 14

QRS wave of ECG indicates

Back 14

Wave of excitation travels down to apex and sweeps upward through ventricle , before ventricle systole

Front 15

T wave indicates

Back 15

Ventricle relax

Front 16

Bradycardia

Back 16

Slow heart rate

Front 17

Tachycardia

Back 17

Fast heat rate

Front 18

Ectopic heart beat

Back 18

Altered rhythm, extra beat followed by a longer gap

Front 19

Atrial fibrillation

Back 19

Abnormal irregular rhythm from atria, ventricle loses regular rhythm

Front 20

Cardiac output

Back 20

Heart rate * stroke volume