Exchange and Transport in Animals (heart)

Question 1

State flow of blood through chambers of the heart

Answer 1

Right atrium, right ventricle, left atrium, left ventricle

Question 2

What is the purpose of the septum?

Answer 2

Separates oxygenated and deoxygenated blood

Question 3

Name the three major valves and describe where they are.

Answer 3

Bicuspid- between left atrium and left ventricle
Tricuspid- between right atrium and right ventricle

Semi-lunar (aortic and pulmonary) - between ventricles and arteries

Question 4

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

Answer 4

Creates higher pressure so blood can go to extremities. Right side pumps only to the lungs.

Question 5

Which side of the heart contains oxygenated blood?

Answer 5

Left

Question 6

What are the two groups of valves?

Answer 6

Atrioventricular and semi-lunar

Question 7

What is the pericardium?

Answer 7

An inelastic double-walled sac containing the heart and roots of the great vessels

Question 8

What is the role of the pericardium?- 3

Answer 8

Creates closed chamber that aids atrial filling and prevents over distending.
Shields heart by lubricating to reduce external friction
Acts as barrier to infection

Question 9

What does myogenic mean?

Answer 9

Heart has its own intrinsic (spontaneous) rhythm/ innate pacemaker ability.

Question 10

Why do cardiac muscle cells have more mitochondria?

Answer 10

They are more reliant on aerobic respiration than skeletal muscle/ require lots of energy to be released.

Question 11

What connects cardiac muscle cells?

Answer 11

Gap junctions at intercalated discs.

Question 12

Why are cardiac muscle cells branched?

Answer 12

Faster signal propagation and contraction in three dimensions.

Question 13

Why is it important that the heart does not become fatigued?

Answer 13

Allows continuous, life long contractions

Question 14

What stops valves inverting?

Answer 14

Tendons

Question 15

What causes valves to close?

Answer 15

High pressure in front of the valve

Question 16

What are the vessels that supply the heart and what happens if one of these is blocked?

Answer 16

Coronary arteries

Common cause of angina, heart disease, heart attacks and heart failure

Question 17

Three stages of the cardiac cycle

Answer 17

Atrial Systole
Ventricular Systole
Diastole

Question 18

What creates the noise of a heart beat? Specify what causes each part

Answer 18

Valves closing

'lub' = closing of AV valves in ventricular systole
'dub' = closing of semilunar valves in diastole

Question 19

How long is each part of the cardiac cycle?

Answer 19

Atrial systole = 0.1 seconds
Ventricular systole = 0.3 seconds
Diastole = 0.4 seconds

Question 20

Atrial Systole:
Chambers
Blood flow
Valves

Answer 20

Chambers: atrium contract, ventricles are relaxed
Blood flow: atrium to ventricles
Valves: AV open, semilunar closed

Question 21

Ventricular Systole:
Chambers
Blood flow
Valves

Answer 21

Chambers: atria relaxed, ventricles contract
Blood flow: ventricles to arteries/aorta
Valves: AV closed, semilunar open

Question 22

Diastole:
Chambers
Blood flow
Valves

Answer 22

Chambers: all relaxed
Blood flow: from veins through atria into ventricles
Valves: AV open, semilunar closed

Question 23

What do the points on a pressure changes graph where the lines cross show?

Answer 23

Valves opening or closing (caused by pressure difference)

Question 24

What is the bpm of pacemaker cells?

Answer 24

60 bpm

Question 25

Why is heart rate usually 70 bpm?

Answer 25

Cardiomyocytes have slight electrical change across membrane/ are polarized. When charge is revered they are depolarized, causing contraction.

Question 26

Five main parts of network of conduction fibres in heart

Answer 26

``` Sino-atrial node (SAN) Atrio-ventricular node (AVN) Bundle of His Right/left branches of Purkynje tissues Purkynje fibres ```

Question 27

Why is there a delay at the AVN?

Answer 27

So it can empty/refill to the rhythm

Question 28

What is the refractory period and why does it exist?

Answer 28

After contraction, there is a brief period of insensitivity to stimulation. It allows the heart to passively refill between beats and also prevents heart tissue becoming fatigued.

Question 29

What does the SAN contract?

Answer 29

The atrium (atrial systole), forcing blood into ventricles.

Question 30

How do ventricles contract?

Answer 30

AVN sends wave of depolarisation down Bundle of His into the Purkynje fibres. Ventricular walls contract starting at the apex, forcing blood out/upwards.

Question 31

From where does the AVN receive electrical impulses?

Answer 31

the SAN

Question 32

What are the 3 waves/complexes shown on a normal electrocardiogram and what do they represent?

Answer 32

P wave: depolarisation of atria as response to SAN signal QRS complex: depolarisation of ventricles triggered by AVN signal T wave: repolarisation of ventricles and completion of standard heartbeat

Question 33

What are the two intervals that allow for blood flow between the three periods of electrical activity?

Answer 33

PR interval and ST segment

Question 34

What is fibrillation?

Answer 34

Irregular and uncoordinated contraction of the heart muscle after interference of the pacemakers.

Question 35

How can you reestablish normal sinus rhythm when fibrillation occurs?

Answer 35

Defibrillation - a controlled electrical current

Question 36

What heart conditions can be identified via electrocardiography?

Answer 36

Tachycardia (elevated resting heart rate) Bradycardia (depressed resting heart rate) Arrhythmias (irregular heart beats) Fibrillations (unsynchronised contractions of either atria or ventricles)

Question 37

Equation for cardiac output

Answer 37

cardiac output = stroke volume x heart rate

Question 38

What is stroke volume?

Answer 38

Volume of blood pumped in each heart beat

Question 39

What is cardiac output?

Answer 39

Volume of blood pumped around the body per minute