8.5 The Heart

Question 1

Function of the heart

Answer 1

Pumps blood around the body

Question 2

Which side of the heart has deoxygenated blood?

Answer 2

Right side

Question 3

Which side of the heart has oxygenated blood?

Answer 3

Left side

Question 4

What muscle makes up the heart?

Answer 4

Cardiac muscle

Question 5

Why is cardiac muscle special?

Answer 5

It doesn’t get tired or fatigued like other muscles

It does require an impulse from the brain to contract/relax

Question 6

What supplies the heart with blood?

Answer 6

Coronary artery - provides oxygenated blood

Question 7

What is the heart surrounded by? Why?

Answer 7

Inelastic pericardial membrane - prevents the heart over distending with blood

Question 8

What is the valve between the RA and RL called?

Answer 8

Tricuspid valve

Question 9

What is the valve between the LA and LV called?

Answer 9

Bicuspid valve

Question 10

Function of vena cava

Answer 10

Brings deoxygenated blood from other parts of the body
Superior vena cava - blood from the head and neck areas
Inferior vena cava - blood from other areas of the body

Question 11

Function of aorta

Answer 11

Pumps oxygenated blood out at high pressure to the rest of the body

Question 12

Function of pulmonary artery

Answer 12

Transports deoxygenated blood from the RV to the lungs

Question 13

Function of pulmonary vein

Answer 13

Brings back oxygenated blood from the lungs to LA

Question 14

Where are the semi lunar valves found?

Answer 14

At the opening to the pulmonary artery

Question 15

What is the septum?

Answer 15

Muscle that separates the two sides of the heart - prevents oxygenated and deoxygenated blood from mixing

Question 16

Function of tendinous cords

Answer 16

Hold the valves in place

Makes sure the valves are not turned inside out by the pressures exerted when the ventricle contracts

Question 17

What is the fat covering the heart called?

Answer 17

Epicardial adipose tissue

Question 18

Why does the LV have a thicker muscle wall than the RV?

Answer 18

Pumps blood out at high pressure, thick walls to withstand the pressure
Blood also has to travel a larger distance

Question 19

Why is the muscle thicker on the left side of the heart than the right side?

Answer 19

Lungs are relatively close to the heart and much smaller than the rest of the body, so right side has to pump blood for a relatively shorter distance and there is only resistance from the pulmonary circulation
The left side has to pump blood to the whole body and overcome the resistance of the arterial system of the body

Question 20

Journey of blood through heart

Answer 20

Deoxygenated blood enters the RA of the heart through the superior and inferior vena cava at a relatively low pressure
As blood flows in, oressure builds up in the RA and the tricuspid valve opens to let blood into the RV
When both RV and RA are full of blood, the RA contracts, forcing all blood into RV and tricuspid valve closes
RV contracts fully and pumps deoxygenated blood through the semi lunar valves into the pulmonary artery
At the same time, oxygenated blood enters the LA from the pulmonary vein
Pressure in the LA builds, causing the bicuspid valve to open between the LA and LV so ventricle fills with blood
When both LA and LV are full of blood, LA contracts, forcing all blood into LV
LV contracts, blood flows through semi lunar valves into the aorta, to be transported around the whole body

Question 21

Cardiac cycle

Answer 21

Events in a single heartbeat - lasts 0.8s

Question 22

Diastole

Answer 22

Heart relaxes
Atria and then ventricles fill with blood
Volume and pressure of blood in the heart build as the heart fills, but pressure in the arteries is at a minimum

Question 23

Systole

Answer 23

Atria contract (atrial systole) followed by the ventricles (ventricular systole)
Pressure in heart increases dramatically, blood forced out of heart
At the end of systole, volume and pressure of blood in the heart are low and blood pressure in the arteries is at a maximum.

Question 24

What are the sounds of heartbeat?

Answer 24

Made by blood pressure closing the heart valves

Question 25

LUB DUB sound

Answer 25

Lub - blood forced against atrioventricular valves as ventricles contract
Dub - semi lunar valves closed in the aorta and pulmonary artery as ventricles relax

Question 26

Myogenic

Answer 26

Has its own intrinsic rhythm

Question 27

How the heart beats

Answer 27

Wave of electrical excitation begins in the pacemaker area (SAN) so that atria contract and initiate heartbeat
This electrical activity is picked up by the AVN and imposes a slight delay before stimulating bundle of His, which penetrate through the septum between the ventricles
Bundle of His splits into 2 branches and conducts wave of excitation to apex of heart
At the apex, Purkyne fibres spread out through the walls of the ventricles on both sides. The spread of excitation triggers contraction of ventricles, starting at the apex

Question 28

Why does contraction start at the apex?

Answer 28

Allows more efficient emptying of the ventricles

Question 29

What is the bundle of His made of?

Answer 29

Purkyne fibres

Question 30

How does an ECG work?

Answer 30

Measures tiny electrical differences in the skin, which are as a result of electrical activity of the heart

Question 31

Tachycardia

Answer 31

Very rapid heartbeat

Question 32

When is tachycardia normal?

Answer 32

During exercise, with a fever, or when frightened/angry

Question 33

Bradycardia

Answer 33

Heart rate slows down below 60 bpm

Question 34

How can severe bradycardia be treated?

Answer 34

Using an artificial pacemaker

Question 35

Ectopic heartbeat

Answer 35

Extra heartbeats out of the heart’s normal rhythm

Question 36

Arrhythmia

Answer 36

Abnormal rhythm of the heart

Question 37

Atrial fibrillation

Answer 37

Rapid electrical impulses are generated in the atria and contract very fast.
However, they do not contract properly and only some impulses are passed onto the ventricles. Therefore, the heart does not pump blood very efficiently.