Cardio - Physiology (Part 2) Flashcards Preview

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Flashcards in Cardio - Physiology (Part 2) Deck (117)
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1
Q

What type of murmur occurs in late systole after a midsystolic click and is loudest at S2?

A

Mitral prolapse

2
Q

In tricuspid stenosis, the murmur gets louder with _____ (inspiration/expiration) due to increased blood flow into the right atrium.

A

Inspiration

3
Q

Which murmur is often due to age-related calcification?

A

Aortic stenosis

4
Q

What happens during phase 3 of the cardiac myocyte action potential?

A

Rapid repolarization due to increased permeability to potassium

5
Q

During phase 4 of the action potential in a ventricular myocyte, to which ion is the membrane highly permeable?

A

Potassium; as a result, the resting potential of the cell is close to that of potassium

6
Q

What happens during phase 0 of the cardiac myocyte action potential?

A

Rapid depolarization due to increased sodium permeability

7
Q

What happens during phase 1 of the cardiac myocyte action potential?

A

Initial repolarization due to increased potassium permeability

8
Q

What happens during phase 2 of the cardiac myocyte action potential?

A

Electrical plateau due to equivalent calcium influx and potassium efflux

9
Q

What happens during phase 3 of the cardiac myocyte action potential?

A

Rapid repolarization due to potassium efflux that returns the cell to a more negative potential

10
Q

What is the voltage value of the resting potential of a ventricular myocyte?

A

- 85 mV; the value is maintained by the sodium/potassium pump and high permeability to potassium

11
Q

How long does the effective refractory period of the cardiac myocyte last?

A

For the duration of the action potential until the cell returns to resting potential

12
Q

Cardiac myocytes in which locations have pacemaker action potentials?

A

The sinoatrial and the atrioventricular nodes

13
Q

What happens in phase 0 of the pacemaker action potential?

A

Voltage-gated calcium channels open

14
Q

The lack of voltage-gated sodium channels in pacemaker cells results in what effect on cardiac conduction?

A

A slowed conduction velocity through the atrioventricular node to prolong transmission from the atria to the ventricles

15
Q

As compared with the myocardial action potential, which phases are absent from the pacemaker potential?

A

Phases 1 and 2

16
Q

What happens in phase 4 of the cardiac pacemaker action potential?

A

Slow diastolic depolarization due to increased permeability to sodium ion

17
Q

During the pacemaker action potential, the slope of which phase determines the heart rate?

A

Phase 4

18
Q

How does acetylcholine affect the rate of diastolic depolarization and heart rate?

A

It decreases the rate of diastolic depolarization (the slope of phase 4 of the action potential) and thus decreases heart rate

19
Q

What happens in phase 3 of the cardiac pacemaker action potential?

A

Inactivation of the calcium channels and activation of the potassium channels

20
Q

Sympathetic stimulation _____ (decreases/increases)the possibility that If channels are open.

A

Increases; as a result, the pacemaker cell depolarizes more frequently and the heart beats faster

21
Q

Which ion channels in a pacemaker cell are permeable to sodium?

A

If channels

22
Q

On an electrocardiogram, what does the P wave represent?

A

Atrial depolarization

23
Q

On an electrocardiogram, what does the PR segment represent? How long is a normal PR interval?

A

Conduction delay through the atrioventricular node; normally less than 200 msec

24
Q

On an electrocardiogram, what does the QRS complex represent? What is considered a normal QRS duration?

A

Ventricular depolarization; normally less than 120 msec

25
Q

What segment of the electrocardiogram corresponds with the mechanical contraction of the ventricles?

A

The QT interval

26
Q

On an electrocardiogram, ventricular repolarization is represented by what?

A

The T wave

27
Q

In what part of the electrocardiogram is atrial repolarization?

A

Atrial repolarization is masked within the QRS complex

28
Q

On an electrocardiogram, what does the ST segment represent?

A

The isoelectric state after the ventricles have been depolarized and before repolarization

29
Q

What do U waves on an electrocardiogram represent?

A

Hypokalemia or bradycardia

30
Q

What is the physiologic benefit of the atrioventricular delay?

A

It allows time for ventricular filling

31
Q

Define torsades des pointes.

A

A ventricular tachycardia that is characterized by shifting sinusoidal waves on an electrocardiogram; a literal translation is, "twisting of the points"

32
Q

What are the most dangerous sequelae of torsades des pointes?

A

Ventricular fibrillation and death

33
Q

What is the main risk factor for torsades des pointes?

A

Prolongation of the QT interval, usually due to drug adverse effects or genetic syndromes

34
Q

What is the etiology of congenital long QT syndromes?

A

Most often they are due to defects in sodium or potassium channels

35
Q

Congenital long QT syndromes can be associated with what other pathology?

A

Severe congenital sensorineural hearing deficit (Jervell and Lange-Nielsen syndrome)

36
Q

What is the electrocardiogram finding pathognomonic for Wolff-Parkinson-White syndrome and what does it signify?

A

A delta wave, which signifies partial early depolarization of the ventricles via an accessory pathway

37
Q

What is the Bundle of Kent?

A

An accessory conduction pathway from atria to ventricles, which bypasses the atrioventricular node; occurring in Wolff-Parkinson-White syndrome

38
Q

In patients with Wolff-Parkinson-White syndrome, what does the delta wave on electrocardiogram represent?

A

Early depolarization of the ventricle due to the accessory conduction pathway (bundle of Kent), which bypasses the atrioventricular node

39
Q

Patients with Wolff-Parkinson-White syndrome are at higher risk for which type of arrhythmia?

A

Supraventricular tachycardia

40
Q

Which rhythm on electrocardiogram is classically described as having an irregularly irregular pattern with no discrete P waves?

A

Atrial fibrillation

41
Q

Which rhythm on electrocardiogram is described as having a "sawtooth" baseline?

A

Atrial flutter

42
Q

What is the characteristic electrocardiogram finding of first-degree atrioventricular block?

A

Prolonged PR interval (> 200 msec) with no lengthening of the interval and no dropped beats

43
Q

Is first-degree atrioventricular block symptomatic or asymptomatic?

A

Asymptomatic

44
Q

What is the dangerous sequela of atrial fibrillation?

A

Atrial stasis leading to thrombosis, which can embolize and cause stroke

45
Q

A 67-year-old male presents with an irregularly irregular electrocardiogram tracing at a routine doctor's visit. Which drug can decrease his risk of stroke? Which drug can control his heart rate?

A

Warfarin (Coumadin) to prevent thromboembolism and -blockers or calcium channel blockers to control heart rate

46
Q

A 73-year-old female presents with an electrocardiogram tracing with a "sawtooth" pattern. Which three classes of drugs can be given to treat this condition?

A

Class IA, IC, or III antiarrhythmics

47
Q

Which form of second-degree atrioventricular block is more likely to progress to a third-degree block?

A

Mobitz type II

48
Q

Does progressive lengthening of the PR interval take place in Mobitz type I, Mobitz type II, or both?

A

Type I involves progressive lengthening followed by a dropped beat; in type II there are dropped beats without progressive lengthening

49
Q

Given an electrocardiogram showing second-degree Mobitz type II heart block, how can the arrhythmia be further classified?

A

By the ratio of P waves to QRS complexes (eg, 2:1 or 3:1)

50
Q

In what type of heart block do the atria and ventricles beat independently of each other?

A

Third-degree heart block

51
Q

An electrocardiogram shows dropped beats that are not preceded by a change in the length of the PR interval. What is the most likely diagnosis?

A

Second degree atrioventricular block, Mobitz type II

52
Q

An electrocardiogram shows P waves and QRS complexes that have no temporal relation to each other. The atrial rate is faster than the ventricular rate. What is the most likely diagnosis?

A

Third degree (complete) atrioventricular block

53
Q

An electrocardiogram shows no identifiable waves. What is the most likely diagnosis?

A

Ventricular fibrillation

54
Q

In third-degree heart block, the atrial rate is _____ (slower/faster) than the ventricular rate.

A

Faster

55
Q

A 65-year-old male presents with an electrocardiogram tracing that displays P waves and QRS complexes that occur independently of each other. Which therapeutic intervention would be most appropriate?

A

Treatment with an implantable pacemaker

56
Q

An electrocardiogram has an increasing PR interval with each successive beat until a QRS complex does not appear after a P wave. The next beat has a normal PR interval. What is the most likely diagnosis?

A

Second-degree atrioventricular block, Mobitz type I (Wenckebach)

57
Q

Which infectious disease can cause third-degree heart block?

A

Lyme disease

58
Q

By what two mechanisms is a decrease in mean arterial pressure sensed?

A

The medullary vasomotor center detects decreased baroreceptor firing; the juxtaglomerular apparatus in the kidney detects decreased renal perfusion

59
Q

What are the two main regulators that increase mean arterial pressure when it is low?

A

Increased sympathetic tone and activation of the renin-angiotensin system

60
Q

By what mechanism does aldosterone increase cardiac output and mean arterial pressure?

A

Aldosterone works in the kidneys to increase blood volume (and thus cardiac output)

61
Q

By what mechanism does angiotensin II increase blood pressure?

A

Angiotensin II causes vasoconstriction

62
Q

What is atrial natriuretic peptide?

A

It is released from the atria in response to elevated pressure and causes vascular relaxation and diuresis in the kidneys

63
Q

Atrial natriuretic peptide _____ (constricts/dilates) efferent renal arterioles, and _____ (constricts/dilates) afferent arterioles.

A

Constricts; dilates; as a result, glomerular filtration rate is increased

64
Q

By what mechanism does activation of the renin-angiotensin system cause an increase in mean arterial pressure?

A

By production of angiotensin II and aldosterone, which cause increased total peripheral resistance and increased blood volume, respectively

65
Q

By what mechanism does activation of the sympathetic nervous system cause an increase in mean arterial pressure?

A

By activation of -1 and α-1 receptors, which cause an increase in cardiac output and total peripheral resistance, respectively

66
Q

By what mechanism does activation of -1 receptors cause an increase in cardiac output?

A

Activation of -1 receptors causes an increase in heart rate and contractility

67
Q

By what mechanism does activation of α-1 receptors cause an increase in mean arterial pressure?

A

α-1 Receptor activation causes venoconstriction, which increases venous return and thus cardiac output; and arterial vasoconstriction, which causes an increase in total peripheral resistance

68
Q

An 80-year-old woman is in shock in the intensive care unit. The attending physician orders the determination of a pulmonary capillary wedge pressure. What instrument is used to perform this study?

A

A Swan-Ganz catheter

69
Q

Pulmonary capillary wedge pressure is a good approximation of the pressure of which chamber?

A

The left atrium

70
Q

What is the normal pressure for the right atrium?

A

<5 mmHg

71
Q

What is the normal pressure for the right ventricle during systole and diastole?

A

<25 / <5 mmHg

72
Q

What is the normal pressure for the pulmonary artery during systole and diastole?

A

<25 / 10 mmHg

73
Q

What is the normal pressure for the left atrium?

A

<12 mmHg

74
Q

What is the normal pressure for the left ventricle during systole and diastole?

A

<130 / 10 mmHg

75
Q

What is the normal pressure for the aorta during systole and diastole?

A

<130 / 90 mmHg

76
Q

What is the normal pulmonary capillary wedge pressure?

A

<12 mmHg

77
Q

A 75-year-old male with congestive heart failure presents with worsening shortness of breath. On physical exam he has a 3/6 diastolic murmur best heard in the fifth intercostal space in the midclavicular line and crackles in the bases of the lungs. What c

A

This patient has mitral stenosis and one would expect the pulmonary capillary wedge pressure to be greater than the left ventricular diastolic pressure

78
Q

The pulmonary vasculature is unique in that _____ causes vasoconstriction whereas in other organs it causes vasodilation.

A

Hypoxia

79
Q

Which local metabolite(s) govern autoregulation of perfusion of the heart?

A

Oxygen, adenosine, and nitric oxide

80
Q

Which local metabolite(s) determine autoregulation of perfusion of the brain?

A

Carbon dioxide (or pH)

81
Q

Which factors govern autoregulation of perfusion of the kidneys?

A

Myogenic and tubuloglomerular feedback

82
Q

Which local metabolites govern autoregulation of perfusion of the skeletal muscles?

A

Lactate, adenosine, and potassium

83
Q

Which factor governs autoregulation of perfusion of the skin?

A

Sympathetic stimulation

84
Q

Sympathetic stimulation alters perfusion of the skin to control which aspect of homeostasis?

A

Temperature control

85
Q

What is meant by autoregulation of blood flow?

A

The method by which blood flow to an organ remains constant over a wide range of blood pressures

86
Q

In the lungs, what is the physiologic advantage of vasoconstriction in response to hypoxia?

A

The mechanism allows for only well-ventilated areas to remain perfused, optimizing gas exchange

87
Q

What is the equation for net filtration pressure?

A

Net filtration pressure = [(capillary pressure - interstitial fluid pressure) - (plasma colloid osmotic pressure - interstitial fluid colloid osmotic pressure)]

88
Q

The filtration constant for capillary permeability is denoted by what symbol?

A

Kf

89
Q

How is net fluid flow calculated?

A

Net fluid flow = (net filtration pressure) × (filtration constant for capillary permeability)

90
Q

What would a patient with excess fluid outflow into the interstitium present with?

A

Swelling (edema)

91
Q

Which pressures, when increased, have a tendency to cause fluid to move out of the capillaries and into tissue?

A

Capillary fluid pressure and interstitial fluid colloid osmotic pressure

92
Q

Which pressures, when increased, have a tendency to cause fluid to move into the capillaries and out of tissue?

A

Interstitial fluid pressure and plasma colloid osmotic pressure

93
Q

An 80-year-old male with a history of right-sided heart failure presents with bilateral ankle edema. In terms of capillary fluid exchange, what is the mechanism by which he developed his edema?

A

Heart failure results in increased capillary pressure, which causes fluid to move out of the capillaries and into the interstitial space

94
Q

A 55-year-old male with long-standing alcoholic cirrhosis presents with bilateral pedal edema and ascites. In terms of capillary fluid exchange, what is the mechanism by which he developed his edema?

A

Liver failure results in decreased plasma proteins, which decreases plasma colloid oncotic pressure, and in turn causes fluid to move out of the capillaries and into the interstitial space

95
Q

A 43-year-old female presents with bilateral pitting leg edema and lab results remarkable for high low-density lipoprotein, low albumin, and proteinuria (likely nephrotic syndrome). In terms of capillary fluid exchange, what is the mechanism by which she developed her edema?

A

Nephrotic syndrome results in proteinuria and subsequent hypoalbuminemia, which decreases plasma colloid oncotic pressure, and in turn causes fluid to move out of the capillaries and into the interstitial space

96
Q

What is the mechanism by which toxins, infections, and burns can cause edema?

A

Any insults (eg, toxins, infections, or burns) that cause increased capillary permeability can cause an increase in the filtration constant (Kf) and subsequently cause fluid to move out of the capillaries and into the interstitial space

97
Q

A 50-year-old Ethiopian male presents with severe bilateral leg and scrotal edema due to Elephantiasis (lymphatic obstruction caused by filarial nematodes). In terms of capillary fluid exchange, what is the mechanism by which he developed his edema?

A

Lymphatic obstruction causes increased interstitial fluid colloid osmotic pressure, which causes fluid to move out of the capillaries and into the interstitial space

98
Q

During what phase of the cardiac myocyte action potential does extracellular calcium enter the cell?

A

The plateau phase

99
Q

What is the effect of extracellular calcium entering the cardiac myocyte?

A

Calcium release from the cardiac muscle sarcoplasmic reticulum (calcium-induced calcium release); and the resulting muscle contraction

100
Q

The plateau in cardiac muscle action potential is caused by what?

A

Calcium influx

101
Q

Which ion channels cause the automaticity of cardiac nodal cells?

A

If channels cause the cells to spontaneously depolarize

102
Q

How is cardiac muscle different from skeletal muscle?

A

Cardiac muscle action potential has a plateau due to calcium ion influx; cardiac nodal cells display automaticity by spontaneously depolarizing; and cardiac mycytes are electrically coupled via gap junctions

103
Q

The aortic arch receptors transmit impulses to the medulla via which nerve? In response to which stimulus?

A

Aortic receptor afferents travel via the vagus in response to only high blood pressure

104
Q

The carotid sinus receptors transmit impulses to the medulla via which nerve? In response to which stimuli?

A

Carotid sinus receptor afferents travel via the glossopharyngeal nerve in response to both high and low blood pressure

105
Q

Changes in which two parameters of brain interstitial fluid affect the response of central chemoreceptors?

A

pH and the partial pressure of carbon dioxide

106
Q

Central chemoreceptors respond to changes in the pH and the partial pressure of carbon dioxide of the brain interstitial fluid, which in turn are influenced by what?

A

Arterial carbon dioxide

107
Q

Are peripheral or central chemoreceptors responsible for the Cushing reaction?

A

Central chemoreceptors

108
Q

What is Cushing's triad?

A

Cushing's triad is the triad of hypertension, bradycardia, and respiratory depression in response to ischemia in the brain

109
Q

Which type of receptors are most important in causing the bodys response to severe hemorrhage?

A

Baroreceptors

110
Q

Why does carotid massage cause bradycardia?

A

Carotid massage causes increased pressure/stretch on the carotid artery, which causes the afferent baroreceptors to fire, which results in a decrease in heart rate

111
Q

Describe the bodys response after baroreceptors sense hypotension.

A

Hypotension causes decreased arterial pressure/stretch, which decreases afferent baroreceptor firing, increases efferent sympathetic firing, and decreases efferent parasympathetic stimulation, all of which cause vasoconstriction, increased heart rate, contractility, and blood pressure

112
Q

What chemical changes of blood elicit a response from peripheral chemoreceptors? How do central chemoreceptors differ?

A

Low PO2, (< 60 mmHg), high PCO2, and low pH of blood; central chemoreceptors are not sensitive to oxygen

113
Q

What is Cushings reaction?

A

The chain reaction that occurs in response to increased intracranial pressure. Increased intracranial pressure leads to arteriolar vasoconstriction, which causes cerebral ischemia, leading to a sympathetic response of hypertension, and ultimately resulting in reflex bradycardia

114
Q

Which internal organ gets the largest share of the systemic cardiac output?

A

The liver

115
Q

Which organ has the highest blood flow per gram of tissue?

A

The kidney

116
Q

A 25-year-old athlete begins training for the Olympics. As she runs her standard 3 miles, is the increased oxygen demand of the heart met by increased coronary blood flow or increased extraction of oxygen?

A

Increased coronary blood flow; the heart always operates with maximal oxygen extraction

117
Q

Which organ has the greatest arteriovenous oxygen concentration difference and why?

A

The heart, because oxygen extraction is always approximately 100%