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Physiology > Unit 9: Cardiac Physiology > Flashcards

Unit 9: Cardiac Physiology Flashcards

1
Q

What are the 4 quadrants of the heart?

A

Upper chambers of the heart- receive blood returning to the heart- while the ventricles, the lower chambers- pump blood from the heart.

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2
Q

In which direction to veins carry blood?

A

Veins carry blood BACK TO THE HEART.

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3
Q

In which direction to arteries carry blood?

A

Arteries carry blood TO TISSUES.

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4
Q

Describe the flow of blood, starting from the return of blood from systemic circulation.

A

Blood is circulated from systemic circulation and enters the Superior and Posterior Vena Cavae, where it is direction into the right atrium. This blood is O2 poor. The blood pass the right Atrioventricular Valve (tricupsid value) and passes into the right ventricle. The blood is then pumped through the right ventricle to the pulmonary artery, where it exits to the lungs for oxygenation.

–>In the lungs, the blood drops off the CO2 and picks up fresh O2 before returning to the left atrium. It travels through the left AV valve (bicuspid valve or mitral valve) to the left ventricle, where it leaves the aorta and pumps blood to all the body systems.

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5
Q

During Pulmonary circulation, what are effects of pressure and resistance?

A

Low pressure, low resistance

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6
Q

During systemic circulation, what are effects of pressure and resistance?

A

High pressure, high resistance

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7
Q

What structure fastens down AV valves?

A

Chordae tendinae

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8
Q

Where do the aortic and pulmonary valves lie, and what is another name from these valves?

A

At the entrance of where the pulmonary artery / aortic artery leave.
AKA Semilunar Valves

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9
Q

Do valves exist between the atria and veins?

A

No, different mechanisms such as pressure prevent blood backflow

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10
Q

What is the fibrous skeleton?

A

Seperates the atriums from the ventricles

-provide a fairly rigid structure for attachment to cardiac muslce

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11
Q

The heart wall has 3 layers:

A

Endothelium- inner layer
Myocardium- middle layer- mainly the heart wall
Epicardium- outer layer (covers the heart)

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12
Q

Action potentials in cardiac cells?

A

Cardiac cells have the ability to generate action potentials without nervous stimulation.
-All cardiac muscle contracts as functional syncytium

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13
Q

What is the structure the heart is covered in?

A

The Pericardial Sac

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14
Q

What are the 2 main types of specialized cardiac cells?

A
  1. Contractile Cells- do the mechanical pumping work (99% of cells)
  2. Autorhythmic Cells- generate action potentials (1% of cells)
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15
Q

What kind of contraction do autorhymic cells undergo?

A

Pacemaker potentials! Spontaneously reach threshold and cause action potentials to fire.

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16
Q

What leads to pacemaker potential?

A
  • Constant inward flux of Na, and a decrease outward diffusion of K+ (depolarization)
  • An increase in inward Ca2+
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17
Q

How does an increase in calcium lead to a pacemaker potential?

A

A T type calcium channel opens, allow Ca2+ into the autorhythmic cells, and threshold is reached.

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18
Q

Where are the sites of cardiac rhythmic cells?

A
  1. SA Node (sinoatrial)
  2. AV (atrioventricular)
  3. The Bundle of His
  4. The Purkinge Fibres
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19
Q

Cardiac cells with the fastest rate of action potential initiation are located in ?

A 
The sinoatrial (SA) node
**The Pacemaker of the heart
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20
Q

What 3 criteria must be met for efficient cardiac function to occur?

A
  1. Atrial excitation and contraction MUST be done before ventricular contraction occurs.
  2. Excitation of cardiac cells should occur in functional syncytium
  3. The pair of atria and ventricles should pump simultaneously
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21
Q

What is the Interatrial Pathway?

A

-Extends from the SA node from the right atrium to the left atrium, and pathway termination occurs in the left atrium.

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22
Q

what is The Internodal Pathway?

A
  • Extends from the SA node to the AV node

- THE ONLY WAY AN ACTION POTENTIAL CAN PROPAGATE IS THROUGH THE AV NODE.

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23
Q

What is the AV Nodal Delay?

A

A delay that occurs as action potentials are generated in the AV node, which allows for complete ventricular filling (about 100msec)

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24
Q

What is the purpose of the AV Nodal Delay?

A

-Enables the atria’s to depolarize, contract and empty their contents into the ventricles before ventricular contraction begins.

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25
Q

Where does the impulse travel after the AV Nodal delay?

A

Through the septum to the Bundle of His and Purkinje Fibers (rapid propagation of action potentials)

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26
Q

What is the resting membrane potential of contractile (mechanical) cardiac cells?

A

-90 mV

During the rising phase of an action potential, the membrane rapidly depolarizes to +30mV, as a result of Na+ influx.

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27
Q

Why does the contractile cell membrane plateau after it reaches +30mV?

A

–>Due to the slower influx of Ca2+

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28
Q

What characterizes the rapid falling phase of contractile cardiac cells?

A
  • Inactivation of Ca2+ gates, and a delayed activation of K+ voltage gated channels.
  • Potassium diffuses out of the membrane, repolarizing the membrane.
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29
Q

What is an Electrocardiogram (ECG)?

A

-Can indicate whether the autorhythmic sequence is correct, whether the heart is enlarged or damaged, and where the damage may be!

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30
Q

What signifies the P wave?

A

–>Artial depolarization

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31
Q

What signifies the QRS Complex?

A

–>Ventricular depolarization

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32
Q

What signifies the T Wave?

A

–>Ventricular polarization

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33
Q

Where does the ECG remain baseline?

A
  • ->At the AV Nodal Delay (PR Segment)
  • ->At the plateau phase (ST Segment)
  • ->When the heart is repolarized the ventricular filling is taking place (TP Interval)
34
Q

What is Tachycardia?

A

A rapid heart rate of over 100 beats/ minute

35
Q

What is Bradycardia?

A

A slow heart rate of less than 60 beats/ minute

36
Q

What is an Arrhythmia?

A

-Any variation from the normal rhythm and sequence of excitation of the heart.

37
Q

What is an Atrial Flutter?

A

-Rapid but regular sequence of atrial depolarizations at rates between 200and 380 beats/ minute.
(Not every atrial impulse reaches the ventricles)

38
Q

What is Atrial Fibrillation?

A
  • Characterized by rapid, irregular, uncoordinated depolarization of the atria with NO definite P waves
  • ->Atrial contractions are chaotic and asynchronized.
  • ->Such a different heart rate and pulse rate is called Pulse deficit!
39
Q

Ventricular Fibrillation?

A
  • A very serious rhythmic abnormality in which the ventricles exhibit abnormal contractions.
  • ->Can be fatal if not reversed!
40
Q

What is Heart Block?

A
  • Arises from defects in the cardiac conducting system

- ->Atrial contractions occur regularly, but ventricles often fail to be stimulated and do not contract.

41
Q

What is Systole?

A

->Contracting (excitation of cells) and emptying

42
Q

What is Diastole?

A

->Dilation (relaxation of cells) and filling

43
Q

What occurs during Mid-Ventricular Diastole?

A
  • Ventricles fill before atrial contraction occurs.

- ->Atrial pressure must be higher than ventricular pressure to push open the AV valve and fill the ventricles.

44
Q

What occurs in Late Ventricular Diastole?

A
  • The SA node reaches threshold and the impulse spreads through the artia (the P wave).
  • Atrial depolarization brings about atrial contractions, raising atrial pressure and squeezing more blood into the ventricles.
45
Q

What occurs at the End of Ventricular Diastole?

A

Ends upon ventricular contraction, and by this time, atrial and ventricular contraction are complete.

46
Q

What is End- Diastolic Volume (EDV) ?

A

-The amount of blood in the ventricle at the end of diastole

–>Usually 135mL

47
Q

What is the isovolumetric ventricular contraction?

A

-A brief period of motionless of blood movement between the opening of the aortic valve and after the closing of the AV value.

48
Q

What promotes the closing of the AV value?

A

Higher ventricular pressure than atrial pressure.

49
Q

What is the stroke volume?

A

The amount of blood that is pumped out of the ventricle, at rest, approximately 70mL.

50
Q

What occurs at the end of Ventricular Systole?

A

-Only about half the blood is ejected out of the ventricle.

51
Q

-The amount of blood left in ventricle after each emptying is called the?

A

The End Systolic Volume (ESV) which is approximately 65 mL

52
Q

What occurs during Ventricular repolarization?

A

-Ventricular pressure drops below aortic pressure, closing the aortic valve, allowing no more blood to exit the ventricle.

53
Q

What is the period called where the aortic valve closes, but the AV valve has not yet opened because ventricular pressure still exceeds atrial pressure?

A

-The Isovolumetric Ventricular Relaxation period- no blood can enter the atria from the ventricle

54
Q

At what rate does typical ventricular filling occur at?

A

75 beats/ minute

55
Q

What is the “lub” sound?

A

-Closing of the AV valves during during ventricular systole

56
Q

What is the “dub” sound?

A

Closing of the semilunar valves at the end of ventricular systole

57
Q

What is a heart murmur?

A

-Blurs the sound to varying degrees- as a result of improper closure of the valves.

58
Q

What is Cardiac Output?

A

-The volume of blood pumped by each VENTRICLE per minute.

59
Q

What is the formula for Cardiac Output?

A

-Heart Rate x Stroke Volume

60
Q

What is Cardiac Reserve?

A

The difference between stroke volume at rest and at maximal exercise.

61
Q

What is the name of the Parasympathetic nerve to the heart?

A

The vagus nerve

–>Primarily supplies the atrium

62
Q

True or False- Parasympathetic stimulation of the ventricles is sparse.

A

True

63
Q

What is the Sympathetic nervous system responsible for?

A

Cardiac sympathetic nervous system innervates both the atria, as well as the ventricles.

64
Q

Parasympathetic Stimulation on the heart?

A

Slow of heart rate

-Spontaneous action potentials are reduced due to slowing of K+ channels.

65
Q

Sympathetic Stimulation on the heart?

A
  • Increase in heart rate
  • ->Affects pacemaker tissue
  • speed up depolarizations so action potentials are propagated faster
66
Q

Where is the main control center for control of heart rate?

A

-The cardiovascular control center in the medulla of the brain stem.

67
Q

What is the Frank-Stirling Mechanism?

A

-The larger the diastolic filling, the larger the End-Diastolic Volume (EDV) which results in a greater stretch, and therefore a more powerful contraction.

68
Q

What is the effect on stroke volume and sympathetic stimulation?

A

Cardiac sympathetic nerves and epinephrine enhance the hearts contractibility, therefore an increase in stroke volume.

69
Q

What is the Ejection Fraction?

A
  • The volume of blood pumped from the left ventricle with each beat of the heart.
  • ->Approx. 55%
70
Q

What is Coronary Circulation?

A
  • Heart muscle receives blood through blood vessels. The heart can’t extract O2 directly from the surrounding blood it pumps.
  • ->Coronary circulation include coronary arteries that branch from the aorta just beyond the aortic valve, and the coronary veins empty into the right atrium.
71
Q

When does the heart muscle receive most of its blood supply?

A

Diastole

–>During systole, the coronary arterioles only function at about 30%

72
Q

What is Coronary Artery Disease?

A

Refers to pathological changes within the coronary artery walls that DIMINISH blood flow through these vessels
*May be insufficient during exercise or stressful situations

73
Q

What is a Vascular Spasm?

A
  • An abnormal spastic constriction that narrows the coronary vessels.
  • ->Associated with the early stages of CAD and are most often triggered by exposure to cold, physical exertion, or anxiety.
  • ->Reversible and usually does not last long enough to damage the cardiac muscle.
74
Q

What is Atherosclerosis?

A

-A progressive, degenerative arterial disease that gradually leads to blockage of affected vessels, reducing blood flow through them.

Characterized by Plaques forming beneath the vessel lining within arterial walls

  • ->An atherosclerotic plaque consists of a lipid-rich core covered by an abnormal overgrowth of smooth muscle cells, topped off by a collagen-rich connective tissue cap.
  • As plaques form, they bulge into the vessel lumen
75
Q

What is Angina Pectoris?

A
  • Occurs when O2 demands become too great for in relation to the coronary blood flow
  • -> Myocardial ischemia occurs when blood flow to your heart is reduced, preventing it from receiving enough oxygen.
  • Causes extreme pain of the chest
76
Q

What is a thromboembolism?

A

-Obstruction of a blood vessel by a blood clot that has become dislodged from another site in the circulation.

77
Q

What is a thrombus?

A

-An abnormal clot attached to a vessel wall

78
Q

What is embolus (emboli) ?

A

Free circulating clot within a vessel

79
Q

What is/ causes a heart attack?

A

-When a coronary vessel is completely plugged, the cardiac tissue served by the vessel soon dies from O2 deprivation.

80
Q

What is Collateral Circulation?

A

-Exists when small terminal branches from adjacent blood vessels nourish the same area.

81
Q

What occurs during systole that doesn’t allow coronary arteries to be more efficient?

A

The coronary arteries are:

  1. Obstructed by the aortic valve flaps, and
  2. Are compressed by the contracting heart wall.
82
Q

True or False:

Blood flow in the coronary system DECREASES in response to the heart’s oxygen requirements.

A

False.

-Blood flow increases in response to the heart’s oxygen requirements.

Physiology (12 decks)

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