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Pathophysiology Cardiac > Modual 3 > Flashcards

Modual 3 Flashcards

1
Q

Name the cardiac layers (from heart –> pericardium)

A

Endocardium

Myocardium

Epicardium

Parietal Space = Pericardial Cavity

Parietal Pericardium

Fibrous Pericardium

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2
Q

Describe the endocardium

A

Similar to endothelial cells that line blood vessels –> smooth “frictionless” surface

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3
Q

What makes up the myocardium?

A

Cardiac Muscle CElls (contractile Tissue)

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4
Q

What is the epicardium (visceral pericardium)?

A

Connective tissue layer

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5
Q

What is contained w/in the parietal space (pericardial cavity)?

A

Pericardial fluid –> reduces friction during heart movement

**clinically –> pericardial effusion (cardiac tamponade)

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6
Q

What is the parietal pericardium?

A

Connective tissue layer insulating the heart

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7
Q

What is the fibrous pericardium?

A

Fibrous sac that “contains” the heart

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8
Q

What are muscle fibers of the myocardial cells made of?

A

Myofibrils

Single Nuclei

Mitochondira

Sarcoplasma Reticulum

Cytoplasm

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9
Q

What is the plasma membrane of myocardial cells called?

A

Sarcolemma

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10
Q

What are T-tubules?

A

Invaginations of sarcolemma into the myofibrils

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11
Q

What does the sarcolemma do?

A

Spreads action potential throughout muscle fiber

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12
Q

How does the action potential spread throughout the myofibril?

A

Lengthwise along the sarcolemma

Penetrates deep into myofibrils via T-tubules

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13
Q

What is the point of the sarcolemma/T-tubule arrangement?

A

Allows for rapid transmission of action potential

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14
Q

What are myofibrils made up of?

A

Myofilaments

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15
Q

What are myofilaments?

A

Protein filaments that provide mechanical shortening/lengthening of the muscle filament

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16
Q

How are myofilaments arranged?

A

In units called sarcomeres

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17
Q

What are sarcomeres?

A

Repeating units arranged in series (end to end) along the length of the myofibril

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18
Q

What do sarcomeres contain?

A

Myofilaments

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19
Q

What are the proteins that make up the myofilaments?

A

Actin

Myosin

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20
Q

How are myosin microfilaments arranged?

A

Chains are wrapped together each w/ protruding globular heads

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21
Q

What do the globular heads of myosin filaments do?

A

Bind to actin and swivel –> mechanical shortening of sarcomere

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22
Q

What do the globular heads of myosin contain?

A

Binding site for actin

Receptor for ATPase

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23
Q

How are actin (thin) microfilaments arranged?

A

2 chains of actin wrap together to form actin microfilaments

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24
Q

Where would you find tropomyosin on the actin microfilament?

A

“wrapped” around the length of the actin filament

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25
Where would you find troponin on the actin microfilament?
Attached intermittently along the length of tropomyosin
26
What is the function of troponin/tropomyosin?
Allows exposing/covering of the binding site on actin for the myosin globular heads
27
What happens if the binding site of the globular head of myosin on actin is covered?
Sacromere/muscle fiber can't contract
28
What happens if the binding site of the globular head of myosin on actin is exposed?
Myosin head can bind to actin --> mechanical contraction of sarcomere/muscle fiber
29
What are the subunits of troponin?
Troponin T Troponin C Troponin I
30
What does the troponin T subunit do?
Binds troponin to tropomyosin and actin
31
What does the troponin C subunit do?
Contains binding site for Ca2+ **Ca2+ = on/off switch for contraction
32
What does the troponin I subunit do?
Inhibits ATPase **ATP is needed fuel for contraction
33
What does the Z line do?
Anchors/connects thin filaments **z-line to z-line = sarcomere
34
Describe the cross-bridge theory of myocardial muscle contraction
Ca2+ binds to troponin --> exposes binding site on actin = trigger Myosin head attaches to actin Myosin head binds to actin --> releases ADP and Pi --> myosin head swivels ATP binds to myosin head ATP --> ADP + Pi --> release of myosin head from actin to relaxed position
35
Describe excitiation-contraction coupling
Action potential travels across sarcolemma down T-tubules Action potential reaches sarcoplasm a reticulum (stores Ca2+) --> release of Ca2+ Ca2+ diffuses into microfilaments and binds to troponin-C --> exposes myosin head binding site on actin
36
Why is it important that cardiac muscle cells have a lot of mitochondria?
Supply ATP for contraction
37
Where are the intercalated discs of cardiac muscle fibers located and what do they do?
Between muscle fibers Allow action potential to travel from cell to cell
38
What do desmosomes do?
Attach each muscle fiber to the next
39
What do gap junctions do?
Allows electrical action potential to spread through intercalated disc from one muscle fiber to the next
40
What is the frank starling law of the heart?
The length-tension relationship between the length of myocardial muscle and force generation
41
What is the length-tension relationship of healthy cardiac muscle?
Length of cardiac muscle fiber (sarcomere) is DIRECTLY related to the force generated by the muscle fiber
42
What is the end-diastolic volume?
The volume that fills the ventricles
43
What does the end-diastolic volume do?
Determines amount of "stretch" on the cardiac muscle fibers, which means: Increase end-diastolic volumes = increase contractility Increase contractility = increase stroke volume/cardiac output
44
What happens to unhealthy cardiac muscle (heart failure)?
Has been dilated/damaged Sarcomeres have been lengthened too far --> Frank Starling Law no longer applies
45
What is LaPlace's Law?
Wall tension (contraction force) is DIRECTLY related to the product of intraventricular pressure x internal radius (ventricular volume) Wall tension (contraction force) is INDIRECTLY related to wall thickness
46
What does LaPlace's Law mean for a dilated thin walled ventricle full of blood?
It requires more time to generate a contraction force (wall tension) strong enough to generate intraventricular pressure needed to eject blood from the heart **poor cardiac output/performance
47
What is left ventricular preload?
Pressure generated in the L ventricle @ the end of diastole (ventricular filling) **Preload = Left end-diastolic pressure
48
What determines preload in a healthy heart?
L end-diastolic volume (Starling's law of the heart)
49
What happens if you increase left end-diastolic volume?
Increase Preload Increase stroke volume/cardiac output
50
What happens to preload in a pt w/ ventricular hypertrophy?
Increases preload BUT less ventricular filling (decreased end diastolic volume) --> output will be reduced
51
What will excessive left end-diastolic filling pressures cause?
Congestive back-up in pulmonary circulation
52
What is afterload?
The voce the left ventricle must generate during systole to overcome aortic pressure to open the aortic valve
53
What happens if there is increased afterload?
Ventricle has to work harder to eject blood: Takes longer contraction time to generate necessary force Increased afterload + insufficient contraction time = reduced stroke volume
54
What could happen clinically with increased afterload?
Elevated systemic BP Aortic Stenosis Dilated ventricle Decreased stroke volume (increased end systolic volume) Hypertrophy to compensate
55
Where are the cardiovascular control centers located in the brain?
Medulla
56
What does the sympathetic nervous system do to the heart?
Increase HR Increase Contractility
57
What does the parasympathetic nervous system do to the heart?
Decrease HR Decrease Contractility
58
Which part of the autonomic nervous system dominates during rest?
Parasympathetic @ SA node
59
What happens to the autonomic nervous system early during exercise?
Removal of parasympathetic influence @ SA node
60
Which part of the autonomic nervous system dominates during intensive exercise?
Sympathetic @ SA node
61
Where are arterial baroreceptors located?
Aortic Arch Carotid Sinus **systemic "stretch" receptors
62
What will increased pressure cause the baroreceptors to do?
Increase parasympathetic nervous system stimulation Decrease sympathetic nervous system stimulation Net Effect = ↓ HR, ↑ vasodilation which ↓ BP
63
What will decreased pressure cause the baroreceptors to do?
Increase sympathetic nervous system stimulation Decrease parasympathetic nervous system stimulation Net Effect = ↑ HR, ↑ vasoconstriction which ↑ BP
64
Where are atrial stretch receptors located?
R and L atria
65
What do atrial stretch receptors control?
Blood Volume
66
What will stimulation of atrial receptors result in?
Stimulate the release of ANP from atria
67
What does ANP do?
Stimulate kidneys to excrete urine and sodium **end result = reduced blood volume
68
What does the stimulation of atrial receptors result in (in terms of HR)?
Increase HR **arterial baroreceptors have dominant role in maintaining HR compared to atrial receptors
69
What stretch receptors are involved in the bainbridge reflex?
Stretch receptors in atria
70
What is the bainbridge reflex do?
↑ HR after IV infusion (increase blood volume)
71
What are the 2 factors that determine contractility?
Sympathetic nervous input Increased stretch of ventricle (healthy heart) Starling's Law of the Heart --> ↑ preload = ↑ contractility
72
What are the factors that determine cardiac output?
CO = HR x SV
73
What happens with increased stroke volume?
↑ venous return --> ↑ blood volume/↑ sympathetic activity on veins ↑ end-diastolic volume ↑ preload

Pathophysiology Cardiac (4 decks)

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