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Anatomy > Myocardial Anatomy and Phys > Flashcards

Myocardial Anatomy and Phys Flashcards

1
Q

6 characteristics of cardiac muscle cells

A 
Rectangular to elongated
Branching
Contains actin and myosin (Striated)
1-2 nuclei per cell 
Many mitochondria
Very extensive capillary network
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2
Q

Intercalated disks

A

Connect cardiac cells and allow for cell-to-cell communication

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3
Q

Conduction system

A

Made of modified myocardial cells that are larger in diameter with few myofibrils with well-developed intercalated discs to conduct action potentials

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4
Q

SA node

A

Pace-maker, generates the first action potential located in the superior aspect of the right atrium

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5
Q

AV node location

A

Ventral aspect of the right atria at the junction of the atria and ventricle

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6
Q

Purkinje fibers

A

Extensions of the right and left bundle branches found in lateral myocardial wall

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7
Q

Pathway of action potential

A 
SA node
AV node
AV bundle
Right and left bundle branches 
Purkinje fibers
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8
Q

Auto-rhythmicity

A

All myocardial cells have the capacity to generate spontaneous action potentials

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9
Q

Ectopic foci

A

Area of myocardium other than SA node that sets the heart rate that results in the action potential following a different pathway and reducing cardiac output

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10
Q

Where does the action potential slow down at?

A

AV node to allow for atrial contraction and ventricle filling before ventricle contraction

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11
Q

Cardiac muscle duration of action potential

A

200-500msec, longer than skeletal to prohibit tetany

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12
Q

Why does myocardium have long refractory period?

A

To ensure that the muscle will be nearly totally relaxed before accepting another ap

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13
Q

Pre-potential

A

Sodium ions leak into the cell through ion channels that bring the cell to threshold

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14
Q

What is the primary ion responsible for depolarization of SA node cells?

A

Calcium

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15
Q

Plateau phase

A

Sodium channels close, potassium channels begin to open, calcium channels stay open, causes prolongation of AP transmission

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16
Q

Electrocardiogram

A

Detection and measurement of electrical currents generated by ap in the myocardium

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17
Q

P wave

A

Atrial depolarization

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18
Q

P-Q segment

A

Atrial contraction, not detected by the EKG

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19
Q

QRS wave

A

Ventricular depolarization

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20
Q

S-T segment

A

Ventricular contraction, not detected by EKG

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21
Q

T wave

A

Ventricular repolarization

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22
Q

Why check the EKG?

A

Tells the conditon of the heart muscle

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23
Q

Elevated P wave

A

Enlarged atria

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24
Q

Elevated R wave

A

Enlarged ventricles

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25
Q

Elongated Q-T segment

A

Acute myocardial infarction of ventricles that causes ischemia and abnormal conduction of AP

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26
Q

Elongation of PR interval

A

Ischemia of AV nodal region, dilation of atria, ischemia of atria due to blocked blood supply

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27
Q

What is the cardiac cycle?

A

Repetitive pumping process of the heart that begins with the onset of contraction and ends with the beginning of the next contraction

28
Q

What does the cardiac cycle cause?

A

Increase in pressure in one area over another and the movement of blood

29
Q

What is the normal duration of the cardiac cycle?

A

0.7-0.8 seconds

30
Q

Pulmonary pump

A

Moves blood to the luungs and back to the beart, causes oxygenation of the blood

31
Q

Systemic pump

A

Moves blood to the systemic circulation and back to the heart

32
Q

Systole

A

Contraction

33
Q

Diastole

A

Dilation or relaxation

34
Q

Why is diastole critcally important?

A

To allow for filling of the ventricles

35
Q

Period of isovolumic contraction

A

At the completion of the QRS complex when the AV valves close, pressure rises in the ventricle, and no blood flows from ventricle

36
Q

Period of ejection

A

Pressure within the ventricles exceeds that within the aorta and pulmonary trunk causing semilunar valves to open and blood ejection, pressure increases in left ventricle to 120mmHg

37
Q

At what pressure does the aortic semilunar valve open?

A

80mmHg

38
Q

At what pressure does the pulmonary semilunar valve open?

A

8mmHg

39
Q

Period of isovolumic relaxation

A

At the completion of the T wave when ventricles begin to relax, pressure drops, semilunar valves close, and no blood flows back into the ventricles

40
Q

Passive ventricular filling

A

Occurs during ventricular diastole when pressure drops below atrial, AV valves open to allow blood flow into the ventricles without atrial contraction

41
Q

What percent filled are the ventricles after apssive ventricular filling?

A

70%

42
Q

Active ventricular filling

A

Atrial systole when blood is pushed into ventricles to complete ventricular filling

43
Q

When is active ventricular filling most important?

A

Diuring excerise to increase heart rate and cardiac output

44
Q

Lubb

A

Closure of the AV valves

45
Q

Dubb

A

Closure of the semilunar valves

46
Q

Heart murmur

A

Abnormal heart sound that usually causes reduction in cardiac output and increase in work for the heart

47
Q

What can cause a heart murmur?

A

Leaky valves or blockage of a vessel

48
Q

Stenosis

A

Narrowing of blood vessels that causes turbulence of blood flow, more common in young people and congenital

49
Q

Leakage of valves

A

Common in older people that is characterized by a roughness of valve edges or improper closure

50
Q

Mitral valve disease

A

Most common and most serious type of leaky valve

51
Q

Abnormal openings

A

Non-closure of vessels between the aorta and pulmonary trunk that forces blood from left side to the right side causing oxygenated blood to return to the lungs

52
Q

Cardiac output

A

A measure of the ability of the heart to pump blood

Stroke volume in mL x heart rate

53
Q

Average cardiac output

A

5,000mL/min

54
Q

Sympathetic stimulation’s affect on cardiac output

A

Faster depolarization of the SA node, faster heart rate, greater force of contraction

55
Q

Parasympathetic stimulation’s affect on cardiac output

A

Hyperpolarization of the neurons and a slower heart rate

56
Q

Bradycardia

A

Slower heart rate

57
Q

Tachycardia

A

Faster heart rate

58
Q

Frank starling law

A

Stretching of the muscle cells causes increased efficiency of contraction and a stronger contraction

59
Q

Will increasing or decreasing venous return increase the cardiac output?

A

Increasing like moving body parts or inhaling deeply

60
Q

What will decrease venous return?

A

Exhalation, standing still, decrease sympathetic stimulation, decrease in CO2

61
Q

Why is the resistance in skeletal muscle arterioles high?

A

Low CO2 levels at rest, precapillary sphincters are closed and blood flow is reduced

62
Q

How much does blood flow to skeletal muscles increase when exercising?

A

20 fold

63
Q

How can you increase blood flow to the viscera?

A

Eating a meal

64
Q

Ischemia

A

Any condition resulting in insufficient blood flow to the myocardium and therefore O2 deficiency

65
Q

3 causes of ischemia

A

Athersclerosis
blood clot
spasms of coronary arterioles

66
Q

Angina pectoris

A

Pain produced by ischemia

67
Q

Myocardial infarction

A

Complete blockage of blood vessel to myocardium

Anatomy (11 decks)

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