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Pathophysiology > Heart Structure And Function > Flashcards

Heart Structure And Function Flashcards

1
Q

What is the heart?

A

A four chambered organ, supplied by the coronary circulation, that pumps oxygen-poor blood to the lungs and oxygen-rich blood to the rest of the body

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2
Q

What are the 4 chambers of the heart?

A

Left and right atria and ventricles

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3
Q

Where is the heart located?

A

Located posterior to the sternum, level with the 3rd costal cartilage, down to the 5th costal space, approximately 7.5cm to the left of midline

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4
Q

What is the mediastinum?

A

An area in the chest this is between the lungs and it contains the heart, trachea, oesophagus and major blood vessels

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5
Q

What is the heart surrounded by?

A

The heart is surrounded by the pericardium with about 15-20ml of pericardial fluid in between

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6
Q

What are the two layers of the pericardium?

A

Visceral/epicardial -> a serous membrane that covers the heart, it is in direct contact with the heart
Parietal -> covering over the top of the visceral layer

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7
Q

What are the 4 chambers of the heart separated by?

A

Intratrial and intraventricular septum’s

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8
Q

Name the atrioventricular valves

A

Tricuspid (on right side of heart)
Bicuspid/mitral (on the left side if the heart)

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9
Q

What are the valves of the heart tethered down by?

A

Chordae tendineae which are fibrous connective tissue

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10
Q

Where do the fibres of the chordae tendineae originate from?

A

Parts of the muscle walls of the heart by capillary muscles

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11
Q

Name the semilunar valves

A

Pulmonary valve
Aortic valve

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12
Q

What is the trabecular Carneae of the heart?

A

It is muscular ridges

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13
Q

What is the moderator band of the heart?

A

It is a larger version of a trabeculae carneae but it is heavily involved with the transmission of an impulse to make your heart contract

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14
Q

What are cardiac muscles cells connected by?

A

Intercalated discs

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15
Q

What is the importance of intercalated discs in the heart?

A

At these discs is where two cardiac cells are bound together, this connection means that it stabilises all the cardiac cells. It allows for ions to be transferred and molecules to move from one muscle cell to another

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16
Q

What is a syncytium?

A

A multinucleate mass of cytoplasm resulting from fusion of cells

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17
Q

How many syncytiums does the heart have and what is each one composed of?

A

It has 2
The atria are considered as one syncytium and the ventricles as the other

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18
Q

What is the resting potential of cardiac muscle?

A

It is the same as skeletal muscle (-90mV)

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19
Q

What does the action potential in cardiac muscle pass via?

A

Gap junctions/intercalated discs

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20
Q

How long does cardiac muscle action potential last in comparison to skeletal muscle?

A

0.3 sec (cardiac muscle)
0.001 sec (skeletal muscle)

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21
Q

What is the refractory period of contraction of cardiac muscle?

A

It is the time interval before another contraction can take place

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22
Q

What is the purpose of the refractory period?

A

It means fibres are in relaxation before next contraction can occur
It allows the pumping action of cardiac muscle

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23
Q

Why does the action potential need to be coordinated in the heart?

A

So the heart can act as an effective pump

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24
Q

What slows down the rate of APs per minute in the SAN?

A

Vagus nerve

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25
Q

What is the cardiac cycle?

A

All events associated with one heartbeat

26
Q

What is contraction of the heart called?

A

Systole

27
Q

What is relaxation of the heart called?

A

Diastole

28
Q

When the atria contract how much blood do they force into the ventricles?

A

20-25 mL (30% of ventricles volume as already holding 70%)

29
Q

What is end diastolic volume?

A

It is the amount of blood the ventricle is holding at the end of its relaxation/before it contracts

30
Q

What is the EDV of the ventricles?

A

130mL

31
Q

What is isometric contraction in the heart?

A

An event occurring in early systole during which the ventricles contract with no corresponding volume change

32
Q

What is stroke volume?

A

The amount of blood that is ejected

33
Q

What is end systolic volume?

A

The amount of blood left in the ventricles after contraction

34
Q

What is the ESV?

A

50mL

35
Q

How long does ventricular diastole last?

A

430msec

36
Q

What is isovolumetric relaxation?

A

The part of the cardiac cycle between the time of aortic valve closure and mitral opening

37
Q

What is cardiac output?

A

The total blood volume passing through the lungs and systemic circulation in one minute

38
Q

What is the cardiac output equation?

A

Cardiac output = stroke volume x heart rate

39
Q

What is stroke volume?

A

Volume of blood ejected during ventricular systole

40
Q

What 3 factors govern stroke volume?

A

Preload
Contractility
After load

41
Q

What is preload?

A

The stretch on your heart prior to it contracting

42
Q

What is contractility

A

The strength of the contraction

43
Q

What is afterload?

A

The pressure that you need before blood will be pushed out into vessels

44
Q

What is the Frank-Starling law of the heart?

A

The more the heart is filled in diastole, the greater the stretch and the greater the force of systole

45
Q

What are positive inotropic substances?

A

Certain things that can promote contractility of the heart -> could be drugs or our own internal system

46
Q

What are negative inotropic substances?

A

Certain things that will decrease contractility of the heart -> drugs like beta blockers, Ca ion channel blockers, stimulation of parasympathetic nervous system, lack of oxygen

47
Q

What does increased afterload result in?

A

It results in reduced stroke volume because more blood remains in ventricle at end of systole

48
Q

What are the major coronary arteries?

A

Right coronary
Left coronary
Left anterior descending
Left circumflex

49
Q

What effect does the parasympathetic nervous system have on the heart?

A

It slows heart rate

50
Q

What effect does the sympathetic nervous system have on the heart?

A

It increases heart rate

51
Q

What do adrenaline and noradrenaline do to heart rate and contractility?

A

Increases both

52
Q

What does hyperthyroidism do to the heart?

A

It gives tachycardia

53
Q

What does increase potassium and sodium ions do to heart rate and contractility?

A

It decreases both

54
Q

What does a moderate increase of calcium ions do to heart rate and contractility?

A

Increases both

55
Q

What will happen in the event of SAN disease or damage?

A

AVN can take over at 40-60bpm

56
Q

What will happen to the heart if both the AVN and SAN are suppressed?

A

Ventricles will beat at 20-30 bpm from Purkinje fibres

57
Q

What is an electrocardiogram?

A

A measure of the hearts rhythm and rate through the detection of its electrical activity

58
Q

What causes the P wave on an ECG?

A

Atrial depolarisation, initiated by the SAN

59
Q

What causes the QRS complex of an ECG?

A

Ventricular depolarisation which begins at the apex

60
Q

What causes the T wave?

A

Ventricular repolarisation

Pathophysiology (14 decks)

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