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Anatomy and Physiology II > Chapter 19: Heart Powerpoint > Flashcards

Chapter 19: Heart Powerpoint Flashcards

1
Q

The right side of the heart is known as the ______ circuit.

A

pulmonary

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2
Q

What does the pulmonary circuit do?

A

Carries blood to lungs for gas exchange and back to heart

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3
Q

The left side of the heart is known as the ______ circuit.

A

systemic

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4
Q

What does the systemic circuit do?

A

Supplies oxygenated blood to all tissues of the body and returns it to the heart

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5
Q

The pulmonary circuit is on the ____ side of the heart

A

right

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6
Q

Where does blood enter and leave the systemic circuit?

A

Oxygenated blood enters via the pulmonary veins and leave via the aorta

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7
Q

Where does blood enter and leave the pulmonary circuit?

A

Oxygen-poor blood enter via inferior & superior venae cavae

Leave via pulmonary trunk

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8
Q

At any age, the heart is the size of your ______

A

fist

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9
Q

What are the two layers of the sac protecting the heart?

A 
Pericardial sac (outer)
Visceral pericardium/ epicardium (inner)
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10
Q

What are the two layers of the pericardium?

A

1) Superficial fibrous layer of connective tissue

2) Deep, thin serous layer (parietal pericardium)

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11
Q

Describe the visceral pericardium (epicardium)

A

Serous membrane covering heart

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12
Q

What fills the pericardial cavity?

A

5 to 30 mL of pericardial fluid

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13
Q

What are the 3 functions of the pericardium?

A

1) Protects and anchors the heart
2) Allows heart to beat without friction
3) Prevents overfilling of the heart with blood

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14
Q

What are the 3 layers of the heart?

A

Epicardium, myocardium and endocardium

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15
Q

Describe the epicardium (visceral pericardium)

A
  • Serous membrane covering heart
  • Adipose in thick layer in some places
  • Coronary blood vessels travel through this layer
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16
Q

Describe the endocardium

A
  • Smooth inner lining of heart and blood vessels

- Covers the valve surfaces and is continuous with endothelium of blood vessels

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17
Q

Describe the myocardium

A
  • Layer of cardiac muscle proportional to work load; left side has more muscle.
  • Muscle spirals around heart (produces wringing motion)
  • Fibrous skeleton framework of collagenous and elastic fibers
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18
Q

What is the purpose of the fibrous skeleton framework of the myocardium?

A
  • Provides structural support and attachment for muscle and valves
  • Electrical insulation between atria and ventricles (limits spread of action potentials)
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19
Q

Describe the atria of the heart

A
  • Receiving chambers of heart
  • Each atrium has an auricle (seen on surface) to enlarge chamber
  • Pectinate muscles: internal ridges of atria and auricles
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20
Q

Describe the ventricles of the heart

A
  • Discharging chambers of heart

- Trabeculae carneae: internal ridges in both ventricles

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21
Q

What are the two external sulci of the heart?

A

Atrioventricular sulcus and interventricular sulcus

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22
Q

What does the atrioventricular sulcus do?

A

Separates atria and ventricles

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23
Q

What does the interventricular sulcus do?

A

Overlies interventricular septum that divides the right ventricle from the left

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24
Q

What are the two internal septums of the heart?

A

Interatrial septum and interventricular septum

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25
Q

What does the interatrial septum do?

A
  • Wall that separates atria

- There’s a hole in this septum in fetuses

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26
Q

What does the interventricular septum do?

A

Muscular wall that separates ventricles

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27
Q

What do the valves of the heart do?

A

ensure one-way flow of blood

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28
Q

What do the atrioventricular (AV) valves do?

A

Control blood flow between atria and ventricles

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29
Q

The right AV valve is called the _____ valve, and the left AV valve is called the _____ valve (formerly the _____ valve).

A

Tricuspid valve; mitral valve; (bicuspid)

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30
Q

What do the chordae tendineae do?

A
  • Cords connect AV valves to papillary muscles

- Prevent AV valves from flipping (eversion) or bulging into atria when ventricles contract

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31
Q

Describe the semilunar valves

A
  • Located at exit of ventricles (controls flow into great arteries)
  • Open and close because of blood flow and pressure
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32
Q

Pulmonary semilunar valve: ____ side

Aortic semilunar valve: ____side

A

right; left

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33
Q

What happens when the ventricles of the heart contract?

A
  • AV valves close as blood attempts to back up into the atria
  • Pressure rises inside of the ventricles
  • Semilunar valves open and blood flows into great vessels
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34
Q

What happens when the ventricles of the heart relax?

A
  • Pressure drops inside the ventricles
  • Semilunar valves close as blood attempts to back up into the ventricles from the vessels
  • AV valves open
  • Blood flows from atria to ventricles
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35
Q

Describe the flow of blood through the heart (11 steps)

A

1) Blood enters right atrium from superior and inferior venae cavae.
2) Blood in right atrium flows through right AV valve into right ventricle.
3) Contraction of right ventricle forces pulmonary valve open.
4) Blood flows through pulmonary valve into pulmonary trunk.
5) Blood is distributed by right and left pulmonary arteries to the lungs, where it unloads CO2 and loads O2.
6) Blood returns from lungs via pulmonary veins to left atrium.
7) Blood in left atrium flows through left AV valve into left ventricle.
8) Contraction of left ventricle (simultaneous with step 3) forces aortic valve open.
9) Blood flows through aortic valve into ascending aorta.
10) Blood in aorta is distributed to every organ in the body, where it unloads O_2 and loads CO_2
11) Blood returns to right atrium via venae cavae.

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36
Q

_% of blood pumped by heart is pumped to the heart muscle

A

5

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37
Q

Is most blood delivered to the heart muscles when it’s relaxed or contracted?

A

Relaxed

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38
Q

Define the arterial supply

A

right & left coronary arteries branch from the ascending aorta

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39
Q

Define and describe angina pectoris

A
  • Chest pain from partial obstruction of coronary blood flow (ischemia)
  • Obstruction partially blocks blood flow
  • Myocardium shifts to anaerobic respiration/fermentation, producing lactate and thus stimulating pain
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40
Q

Define and describe myocardial infarction (MI)

A
  • Also known as a heart attack
  • Sudden death of a patch of myocardium resulting from long-term obstruction of coronary circulation
  • Obstruction often blood clot or fatty deposit (atheroma)
  • Some protection from MI is provided by arterial anastomoses which provide alternative routes of blood flow (collateral circulation) within the myocardium
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41
Q

Describe cardiomyocytes

A

striated, short, thick, branched cells

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42
Q

Repair of damage of cardiac muscle is almost entirely by what?

A

Fibrosis (scarring)

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43
Q

What do the intercalated discs (cell junctions) of the heart contain?

A
  • Interdigitating folds
  • Desmosomes and fascia adherens
  • Gap junctions (electrical junctions)
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44
Q

Cardiomyocytes have a smaller sarcoplasmic reticulum, which means they must depend on the influx of what?

A

Calcium ions (**)

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45
Q

The heart depends almost exclusively on what kind of respiration to make ATP? Why?

A
  • Aerobic

- Because the heart is rich in myoglobin and glycogen and has huge mitochondria

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46
Q

True or false: The heart is adaptable to different organic fuels

A

True; the heart is more vulnerable to oxygen deficiency than lack of a specific fuel

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47
Q

True or false: cardiac muscle is fatigue resistant

A

True

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48
Q

Describe autorhythmic cells

A
  • Composed of an internal pacemaker and nerve-like conduction pathways through myocardium
  • Initiate and distribute action potentials through the heart
  • Leads to depolarization and contraction of the rest of myocardium
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49
Q

Describe the sinoatrial (SA) node

A
  • Modified cardiomyocytes

- Pacemaker (determines heart rate)

50
Q

Describe the atrioventricular (AV) node

A

Electrical gateway to the ventricles

51
Q

Describe the atrioventricular (AV) bundle (bundle of His)

A

Bundle forks into right and left bundle branches

52
Q

Describe the subendocardial conducting networks (Purkinje fibers)

A
  • Nerve-like processes spread throughout ventricular myocardium
  • Cardiomyocytes then pass signal from cell to cell through gap junctions
53
Q

List the 5 steps of the heart’s conduction system

A

1) SA node fires.
2) Excitation spreads through atrial myocardium.
3) AV node fires.
4) Excitation spreads down AV bundle.
5) Subendocardial conducting network distributes excitation through ventricular myocardium.

54
Q

________ nerves increase heart rate and contraction strength

A

Sympathetic

55
Q

________ nerves slow the heart rate; little or no vagal stimulation of the myocardium

A

Parasympathetic

56
Q

Define systole and diastole

A

Systole: contraction
Diastole: relaxation

57
Q

Systole and diastole usually refer to what?

A

The action of the ventricles

58
Q

Define sinus rhythm

A

Normal heartbeat triggered by the SA node

SA node actually about 100 bpm but vagus nerve slows it to ~75 bpm (vagal tone)

59
Q

Define ectopic focus

A

A region firing other than the SA node; may set heart rhythm if SA node is damaged

60
Q

Give an example of ectopic focus

A

Nodal rhythm: if SA node is damaged, heart rate is set by AV node, 40 to 50 bpm

61
Q

Why can ectopic focus typically not sustain life?

A

Other ectopic focal rhythms (excluding nodal rhythm) are 20 to 40 bpm and too slow to sustain life – requires artificial pacemaker

62
Q

True or false: SA node does not have a stable resting membrane potential

A

True

63
Q

Describe the steps of an action potential of the SA node

A

1) Starts at −60 mV and gradually depolarizes due to slow Na^+ inflow; this is called pacemaker potential
2) When it reaches threshold of −40 mV, voltage-gated fast Ca^(2+) and Na^+ channels open, which causes faster depolarization
3) K^+ channels then open and K^+ leaves the cell, causing repolarization
4) Once K^+ channels close, pacemaker potential starts over

64
Q

Signal from SA node stimulates what?

A

Two atria to contract almost simultaneously

65
Q

Signal from the SA node slows when it reaches what part of the heart? Why?

A
  • Signal slows down through AV node
  • This is because it has thin cardiomyocytes with fewer gap junctions
  • This delays signal 100 ms which allows the ventricles time to fill
66
Q

Signals travel very quickly through what two places (after the SA node)?

A

AV bundle and subendocardial conducting network (Purkinje fibers)

67
Q

When signal reaches the AV bundle and subendocardial conducting network (Purkinje fibers), what happens?

A
  • Entire ventricular myocardium depolarizes and contracts in near unison
  • Then ventricular systole progresses up from the apex of the heart, twisting the heart
68
Q

Cardiomyocytes have a stable resting potential of ____ mV, and depolarize only when stimulated

A

−90

69
Q

What are the 3 phases of electrical stimulation (in general)?

A

Depolarization, plateau, repolarization

70
Q

Describe the depolarization phase of myocardium

A
  • Very brief
  • Stimulus opens voltage-regulated Na^+ gates (Na^+ rushes in)
  • Na^+ gates close quickly
71
Q

Describe the plateau phase of myocardium

A
  • Lasts 200 to 250 ms, sustains contraction for expulsion of blood from heart
  • Ca(2+) channels open allowing Ca(2+) to flow in from the ECF
  • This causes Ca(2+) to be released from the SR to trigger contraction
72
Q

Describe the repolarization phase of myocardium

A

Ca^(2+) channels close, K^+ channels open, rapid diffusion of K^+ out of cell returns it to resting potential

73
Q

Describe the refractory period of myocardium after an action potential. What does this prevent?

A
  • Has a long absolute refractory period of 250 ms (compared to 1 to 2 ms in skeletal muscle)
  • Prevents wave summation and tetanus which would stop the pumping action of the heart
74
Q

List the 5 steps of myocardium conducting an action potential

A

1) Voltage-gated Na^+ channels open.
2) Na^+ inflow depolarizes the membrane and triggers the opening of still more Na^+ channels, creating a positive feedback cycle and a rapidly rising membrane voltage.
3) Na^+ channels close when the cell depolarizes, and the voltage peaks at nearly +30 mV.
4) Ca^(2+) entering through slow Ca^(2+) channels prolongs depolarization of membrane, creating a plateau. Plateau falls slightly because of some K^+ leakage, but most K^+ channels remain closed until end of plateau.
5) Ca^(2+) channels close and Ca^(2+) is transported out of cell. K+ channels open, and rapid K^+ outflow returns membrane to its resting potential.

75
Q

Compare and contrast the conduction of an electrical signal in skeletal and cardiac muscle

A

1) Skeletal:
- Requires motor neuron to release ACh.
- Binding of ACh causes depolarization of motor end plate.
- This leads to action potential across sarcolemma of muscle cell.
- Depolarization (Na+ rushes in) leads to contraction of muscle.
- Repolarization (K+ rushes out) “resets” sarcolemma
- Action potential: 1-2ms
- Contraction: 15-100ms
2) Cardiac:
- Have slow depolarization to threshold
- At threshold, have fast depolarization.
- This leads to action potential of rest of conduction system AND any muscle cell connected by gap junctions.
- Depolarization (Na+ rushes in) leads to contraction of muscle.
- Plateau (Ca+ flows in) allows ____(**)
- Repolarization (K+ rushes out) “resets” sarcolemma
- Action potential: 200-250ms
- Contraction: 200ms

76
Q

Define an Electrocardiogram (ECG or EKG)

A

Composite of all action potentials of nodal and myocardial cells detected, amplified and recorded by electrodes on arms, legs, and chest

77
Q

What happens during the P wave of an ECG?

A
  • SA node fires, atria depolarize and contract

- Atrial systole begins 100 ms after SA signal

78
Q

What happens during the QRS complex of an ECG?

A
  • Ventricular depolarization

- Complex shape of spike due to different thickness and shape of the two ventricles

79
Q

What happens during the ST segment of an ECG?

A
  • Ventricular systole

- Corresponds to plateau in myocardial action potential

80
Q

What happens during the T wave of an ECG?

A

Ventricular repolarization and relaxation

81
Q

Deviations of ECG from normal can indicate what?

A

1) Myocardial infarction (MI)
2) Abnormalities in conduction pathways
3) Heart enlargement
4) Electrolyte and hormone imbalances

82
Q

Describe ventricular fibrillation

A
  • Serious arrhythmia caused by electrical signals traveling randomly
  • Heart cannot pump blood; no coronary perfusion
  • Hallmark of heart attack (MI)
  • Kills quickly if not stopped
83
Q

Define the cardiac cycle

A

One complete contraction and relaxation of all four chambers of the heart

84
Q

What are the two main variables that govern fluid movement?

A

Pressure causes flow and resistance opposes it

85
Q

Fluid will only flow if there is a ______ ________

A

pressure gradient (pressure difference)

86
Q

Fluid flows from ____-pressure point to ____-pressure point

A

high; low

87
Q

What unit is pressure measured with, and with what instrument?

A

Pressure is measured in mmHg with a manometer (sphygmomanometer for BP)

88
Q

Increasing volume, ______ pressure

Decreasing volume, _______ pressure

A

Increasing volume, decreases pressure

Decreasing volume, increases pressure

89
Q

Describe how pressure gradients and flow allow the heart to function

A

1) When ventricle relaxes and expands, its internal pressure falls
- This allows AV valves open, blood flows into ventricle
2) When ventricle contracts, internal pressure rises
- This causes AV valves to close; semilunar valves are pushed open and blood flows out of ventricles

90
Q

Define valvular insufficiency and give 3 examples of valvular insufficiency disorders

A

-Defined as any failure of a valve to prevent reflux (regurgitation), the backward flow of blood

Examples:

1) Valvular stenosis: cusps are stiffened and opening is constricted by scar tissue (such as from rheumatic fever)
2) Mitral valve prolapse
3) Heart murmur: abnormal heart sound

91
Q

Define auscultation

A

Listening to sounds made by the body

92
Q

Describe the first heart sound (S1) and the second heart sound (S2)

A

1) First heart sound (𝐒𝟏): louder and longer “lubb,” occurs with closure of AV valves
2) Second heart sound (𝑺𝟐), softer and sharper “dupp,” occurs with closure of semilunar valves

93
Q

List the 4 phases of the cardiac cycle

A

1) Ventricular filling (during diastole)
2) Isovolumetric contraction (during systole)
3) Ventricular ejection (during systole)
4) Isovolumetric relaxation (during diastole)

94
Q

The entire cardiac cycle (all four of these phases) is ___ sec in a heart beating 75 bpm

A

0.8

95
Q

Describe ventricular filling (during diastole)

A
  • Ventricles relax and expand, pressure decreases.
  • Blood flows from atria to ventricles
  • At end of phase, atria contract to finish filling ventricles
  • AV valves are open; semilunar valves are closed
96
Q

Describe the 2 things that happen during ventricular systole (atria in diastole)

A

1) Isovolumetric contraction: ventricles start contracting and AV valves close
2) Ventricular ejection: semilunar valves forced open

97
Q

Describe the 2 things that happen during early diastole

A

1) Isovolumetric relaxation: Both atria and ventricles are relaxed; semilunar valves close
The cycle starts over!
2) Ventricular filling: AV valves now open

98
Q

True or false: Both ventricles must eject same amount of blood

A

True

99
Q

Define congestive heart failure (CHF) and describe its causes

A
  • Results from the failure of either ventricle to eject blood effectively
  • Usually due to a heart weakened by myocardial infarction, chronic hypertension, valvular insufficiency, or congenital defects in heart structure
100
Q

Define left ventricular failure and describe its symptoms

A
  • Blood backs up into the lungs causing pulmonary edema

- Symptoms: Shortness of breath or sense of suffocation

101
Q

Define right ventricular failure and describe its symptoms

A
  • Blood backs up in the vena cava causing systemic or generalized edema
  • Symptoms: Enlargement of the liver, ascites (pooling of fluid in abdominal cavity), distension of jugular veins, swelling of the fingers, ankles, and feet
  • Eventually leads to total heart failure
102
Q

Describe the steps of a pulmonary edema

A

1) Right ventricular output exceeds left ventricular output.
2) Pressure backs up.
3) Fluid accumulates in pulmonary tissue.

103
Q

Describe the steps of a systemic edma

A

1) Left ventricular output exceeds right ventricular output.
2) Pressure backs up.
3) Fluid accumulates in systemic tissue.

104
Q

Define cardiac output

A
  • Amount ejected by each ventricle in 1 minute

- Cardiac output = heart rate x stroke volume

105
Q

What is normal cardiac output at rest? What about during vigorous exercise?

A
  • About 4 to 6 L/min at rest

- Vigorous exercise increases CO to 21 L/min for a fit person and up to 35 L/min for a world-class athlete

106
Q

Define cardiac reserve and state what it’s correlated with

A
  • The difference between a person’s maximum and resting CO

- Increases with fitness, decreases with disease

107
Q

Define heart rate and stroke volume

A

Heart Rate: beats per minute

Stroke Volume: amount of blood pumped out by a ventricle with each contraction

108
Q

Infants have HR of ___ bpm or more
Young adult females average __ to __ bpm
Young adult males average __ to __ bpm
Heart rate rises again in the elderly

A

Infants have HR of 120 bpm or more
Young adult females average 72 to 80 bpm
Young adult males average 64 to 72 bpm
Heart rate rises again in the elderly

109
Q

Define positive and negative chronotropic agents

A

Positive chronotropic agents—factors that raise the heart rate
Negative chronotropic agents—factors that lower the heart rate

110
Q

What does the cardiovascular center of the medulla do, and what influences it?

A

-Sends out sympathetic or parasympathetic signals based on input from cerebral cortex or limbic system

111
Q

What 3 variables affect stroke volume?

A

1) Preload
2) Contractility
3) Afterload

112
Q

1) Increased preload or contractility ______ stroke volume

2) Increased afterload _____ stroke volume

A

1) Increased preload or contractility increases stroke volume
2) Increased afterload decreases stroke volume

113
Q

Define and describe preload

A
  • Defined as the amount of tension in ventricular myocardium immediately before it begins to contract
  • Increased preload causes increased force of contraction
  • Exercise increases venous return and stretches myocardium
114
Q

What does the Frank–Starling law of the heart say?

A
  • Stroke volume is proportional to the end diastolic volume
  • Ventricles eject almost as much blood as they receive
  • The more they are stretched, the harder they contract
115
Q

Define contractility in the context of the heart

A

It refers to how hard the myocardium contracts for a given preload

116
Q

Positive inotropic agents increase __________

A

contractility

117
Q

Give 4 examples of things that are positive inotropic agents

A

1) Hypercalcemia
2) Catecholamines
3) Glucagon
4) Digitalis

118
Q

Give 4 examples of negative inotropic agents

A

1) Hypocalcemia
2) Hyperkalemia
3) Acidosis
4) Drugs such as calcium channel blockers

119
Q

Define and describe afterload

A
  • Defined as the sum of all forces opposing ejection of blood from ventricle
  • Afterload mostly is the blood pressure in aorta and pulmonary trunk
  • Opposes the opening of semilunar valves
  • Limits stroke volume
120
Q

What increases afterload?

A
  • _______(**) increases afterload and opposes ventricular ejection
  • Anything that impedes arterial circulation can also increase afterload
  • Lung diseases that restrict pulmonary circulation (Cor pulmonale) such as: emphysema, chronic bronchitis, and black lung disease

Anatomy and Physiology II (40 decks)

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