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Flashcards in MODULE 2 Deck (94):
1

What is the purpose of the cardiovascular system?

to provide adequate blood flow to all tissues/organs

2

The base of the heart is located... and is the...

near the anterior chest wall, entry and exit to the heart

3

The apex of the heart is located...

inferior tip, points towards the left hip, 12-14cm from base

4

The heart sits in a cavity called the

anterior mediastinum

5

Size of the heart

12-14cm long, 9cm wide

6

The pericardium is... and contains

a double walled sac, an outer parietal pericardium and an inner visceral pericardium/epicardium

7

3 layers of the heart wall are

epicardium, myocardium, endocardium

8

Epicardium

covers the heart (visceral pericardium)

9

Myocardium

the thickest layer, muscular wall consisting of cardiac muscle cells, blood vessels, nerves and connective tissue

10

Endocardium

endothelium (epithelium) covers the inner surfaces of the heart, including heart valves. Forms smooth inner lining which reduces friction so blood can move through easily

11

External structures of the heart: 2 superior atria that are...

thin-walled, receiving chambers, expandable regions called auricles, externally separated from ventricles by the coronary sulcus

12

External structures of the heart: 2 inferior ventricles that are...

thick-walled chambers, discharging chambers, externally separated from each other by an interventricular sulcus (anterior and posterior)

13

Right atria receives... from...

deoxygenated blood, from the superior vena cava, inferior vena cava and coronary sinus

14

Left atria receives... from...

oxygenated blood, from right and left pulmonary veins from the lungs

15

Pulmonary trunk

takes blood from the ventricles and delivers to the lungs for oxygen collection

16

Aorta/aortic arch

takes blood from the ventricles and delivers to the body (for oxygen delivery)

17

Internal structures of the heart: atria (right atrium)

the right atrium receives coronary blood (deoxygenated blood) from the superior and inferior venae carvae and coronary sinus

18

Internal structures of the heart: ventricles are...

separated from the atria via atrioventricular valves (AV) which are anchored via chordae tendinae attached to papillary muscles

Right (tricuspid valve)
Left (bicuspid/mitral valve)

19

Trabelculae carnae are

muscular ridges, less likely for walls to stick together, blood moves through easily

20

Blood exits the ventricles via

semilunar (SL) valves:

Right pulmonary semilunar valve
Left aortic semilunar valve

21

Right ventricle

thinner than the left as it does not have to work as hard (5mm thick)

22

Left ventricle

(15mm thick) thick muscles, generates 4-6 x more force than the right ventricle. Contracts from bottom (apex) upwards and constricts diameter. Pushes blood into the systemic circuit therefore requires a lot of force

23

Function of atrioventricular valves (AV)

prevent backflow of blood into the atria when ventricles contract. Chordae tendinae tense, via contraction of the papillary muscles, preventing the AV valves everting into the atria

24

Function of semilunar valves (SL)

pocket-like crescent shaped cusps, forced open when ventricles contract, close when ventricles relax and blood in the arteries tries to flow backwards

25

Valves open or close in response to

pressure changes

26

Valves ensure the

one-way flow of blood through the heart

27

When AV valves open:

atrial pressure > ventricular pressure. As ventricles contract and intraventricular pressure rises, blood is pushed up against SL valves, forcing them to open.

28

Sequence of events once AV valves open

1. blood returning to the heart fills the atria, putting pressure against AV valves, AV valves are forced open. 2. as ventricles fill, AV valve flaps limply into ventricles. 3. atria contract, forcing additional blood into ventricles

29

When AV valves close:

atrial pressure < ventricular pressure. As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of SL valves and forcing them to close.

30

Sequence of events once AV valves close

1. ventricles contract, forcing blood against AV valve cusps. 2. AV valves close. 3. papillary muscles contract, and chordae tendinae tighten, preventing valve flaps from everting into atria.

31

What is coronary circulation?

coronary circulation supplies blood to he myocardium. Left and right coronary arteries arise from the base of the aorta and circle the heart in the coronary sulcus.

32

Coronary circulation: left coronary artery gives rise to...

the anterior inter-ventricular artery - supplies anterior ventricles

33

Coronary circulation: right coronary artery gives rise to...

the posterior inter-ventricular artery - supplies posterior ventricles

34

Blood moves into the coronary arteries when...

the ventricles relax and blood in the aorta attempts to move backwards towards the heart i.e. in between heart beats

35

Function of the great cardiac vein

drains the anterior regions supplies by the anterior inter-ventricular artery

36

Function of the middle cardiac vein

drains the posterior regions supplies by the posterior inter-ventricular artery

37

All veins drain into the...

coronary sinus (then drains into the right atrium)

38

Coronary artery disease: angina pectoris

temporary deficiency in myocardial blood supply (narrowed coronary vessels). Characterised by thoracic pain, myocardial cells weaken but do not die

39

Coronary artery disease: myocardial infarction

prolonged coronary artery blockage, ischaemic myocardial cell death. Myocardium is replaced by non-contractile scar tissue (weakens heart). Left ventricle damage most serious

40

Left side of the heart is what type of pump

systemic pump

41

Right side of heart is what type of pump

pulmonary pump

42

Blood always moves down a pressure gradient from an area of

high pressure to low pressure

43

The pulmonary circuit is supplied by

the right ventricle. Short, low pressure circulation

44

The systemic circuit is supplied by

the left ventricle. Long, high pressure circulation. Encounters 5 x more resistance to blood flow as the pulmonary circuit

45

Summary of blood flow through the heart:

Superior vena cava, inferior vena cava, coronary sinus - right atrium - right AV valve - right ventricle - pulmonary SL valve - pulmonary trunk - lungs - left atrium - left AV valve - left ventricle - aortic SL valves

46

The myocardium includes cardiac...

pacemaker cells (auto rhythmic cells)

47

Pacemaker cells have an

unstable resting membrane potential, and continually depolarise to generate action potentials

48

5 components of the intrinsic conduction system:

1. sinoatrial node 2. atrioventricular node 3. atrioventricular bundle 4. bundle branches 5. purkinje fibres

49

Sinoatrial node

right atrial wall, inferior to entry point of superior vena cava, depolarises the fastest. Acts as a pacemaker and determines heart rate

50

Atrioventricular node

at the junction between the atria and the ventricles

51

Atrioventricular bundle

aka bundle of His, in the upper interventricular septum, only electrical connection between the atria and ventricles

52

Bundle branches

travel in the interventricular septum to the apex

53

Purkinje fibres

subendothelial conducting network, penetrate ventricle walls, depolarise ventricular myodcardium

54

What is extrinsic innervation

ANS modifies the activity of the heart

55

2 functions of the cardiac centres in the medulla oblongata:

1. cardioacceleratory centre increases heart rate and force of contraction (dilation) 2. cardioinhibitory centre decreases heart rate

56

What is electrocardiography?

cardiac electrical events can be detected (action potentials)

57

What is an electrocardiogram?

a graphic record of heart activity

58

P wave

depolarisation of the atria, beginning at the SA node

59

QRS complex

depolarisation of the ventricles, atrial repolarisation is masked by this complex

60

T wave

repolarisation of the ventricles

61

ECG order of events

1. atrial depolarisation causes the P wave 2. the impulse is delayed at the AV node 3. ventricular depolarisation, begins at the apex and causes the QRS complex 4. ventricular depolarisation is complete 5. ventricular repolarisation begins at apex, causing the T wave 5. ventricular repolarisation is complete

62

Systole

periods of contraction

63

Diastole

periods of relaxation (in between heart beats)

64

Atrial systole

atria contract, completely filling the relaxed ventricles with blood

65

Ventricular systole begins (first phase)

ventricular contraction beginning at the apex, pushing blood upwards and closes the AV valves but pressure not great enough to open SL valves = isovolumetric contraction (no change in ventricular blood volume)

66

Ventricular systole begins (second phase)

ventricular pressure increases, forcing SL valves open and pushing blood out of the ventricles = ventricular ejection

67

Ventricular diastole (early)

as the ventricles relax, arterial blood flows backwards and closes the SL valves

68

Isovolumetric relaxation (no change in ventricular blood volume)

blood flows into the relaxed atria but the AV valves remain closed

69

Ventricular diastole (late)

all heart chambers are relaxed, the AV valves are open, blood moves passively from the atria to the ventricles to 70% of their final volume

70

When heart rate increases all phases are..

shortened (less time for passive filling)

71

Auscultation

listening to body sounds

72

Heart beat (S1 and S2) =

"lubb-dupp"

73

Lubb =

closure of the AV valves

74

Dupp =

closure of the SL valves

75

Heart murmur

swishing sound as blood backflows through an incompetent valve

76

Aortic valve

sounds heard in 2nd intercostal space at right sternal margin

77

Pulmonary valve

sounds heard in 2nd intercostal space at left sternal margin

78

Mitral valve

sounds heard over apex in line with middle clavicle

79

Tricuspid valve

sounds typically heard in right sternal margin of 5th intercostal space

80

Electrical + Mechanical Events

P wave = atrial depolarisation = atrial systole

QRS complex = ventricular depolarisation = ventricular systole

T wave = ventricular repolarisation = ventricular diastole

81

Cardiac output is

the volume of blood pumped (into the systemic circuit) by the left or right ventricle in one minute

82

Cardiac output formula

SV x HR

83

Stroke volume is

volume of blood ejected from the left or right ventricle per beat (mL)

84

End diastolic volume (EDV)

the volume of blood in a ventricle at the end of its relaxation period (just before it contracts)

85

End systolic volume (ESV)

the volume of blood remaining in the ventricles after it has contracted

86

Stroke volume =

EDV - ESV

87

EDV is determined by...

1. venous return (the amount of blood returning to the heart from systemic or pulmonary circuits 2. passive filling time (time both the atria and ventricles are in diastole 3. contractility (amount of force produced during a contraction

88

Contractility

amount of force produced during a contraction. Greater contractility = higher SV = lower ESV = higher CO

89

EDV is increased by...

sympathetic stimulation of ventricular myocardium, hormones, high levels of extracellular calcium, exercise

90

EDV is decreased by...

acidosis (low ECF pH) and increased extracellular K+ levels

91

Preload =

the degree the myocardium is stretched before it contracts = determines force of ventricular myocardial contraction = determines SV

92

Afterload (ESV) =

the pressure that the ventricles must overcome to open the semilunar valves to eject blood into the arteries

93

Bradycardia is

a condition in which the heart rate is slower than normal

94

Tachycardia is

a condition in which the heart rate is faster than normal