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A&P II > Chapter 18 - The Cardiovascular System - Heart > Flashcards

Chapter 18 - The Cardiovascular System - Heart Flashcards

1
Q

The right side pump of the heart receives:

A

oxygen-poor blood from tissues

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2
Q

The right side pump of the heart pumps to:

A

lungs to get rid of CO2

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3
Q

The right side pump of the heart picks up O2 via ___.

A

the pulmonary circuit

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4
Q

The left side pump of the heart receives:

A

oxygenated blood from lungs

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5
Q

The left side pump of the heart pumps to ___ via ___.

A

body tissues; systemic circuit

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6
Q

The receiving chambers of the heart are:

A
  1. right atrium

2. left atrium

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7
Q

What is the function of the right atrium?

A

Receives blood returning from systemic circuit

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8
Q

What is the function of the left atrium?

A

Receives blood returning from pulmonary circuit

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9
Q

The pumping chambers of the heart are:

A
  1. Right ventricle

2. Left ventricle

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10
Q

What is the function of the right ventricle?

A

Pumps blood through pulmonary circuit

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11
Q

What is the function of the left ventricle?

A

Pumps blood through systemic circuit

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12
Q

The heart is approximately the size of ___.

A

the fist

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13
Q

The location of the heart:

A
  1. in mediastinum between second rib and fifth intercostal space
  2. on superior surface of diaphragm
  3. two-thirds of heart to left of midsternal line
  4. anterior to vertebral column, posterior to sternum
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14
Q

The base (posterior surface) of the heart leans toward ___.

A

the right shoulder

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15
Q

The apex of the heart points toward ___.

A

the left hip

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16
Q

The apical impulse of the heart is located:

A

palpated between fifth and sixth ribs, just below left nipple

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17
Q

What covers the heart?

A

pericardium

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18
Q

What are the characteristics of pericardium?

A
  1. it’s a double-walled sac

2. it has superficial fibrous pericardium

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19
Q

What is the function of fibrous pericardium?

A
  1. protects the heart
  2. anchors to surrounding structures
  3. prevents overfilling
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20
Q

What are the two layers of the serous pericardium?

A
  1. Parietal layer

2. Visceral layer

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21
Q

Where is the parietal layer located within the serous pericardium?

A

It lines the internal surface of fibrous pericardium.

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22
Q

Where is the visceral layer of serous pericardium located in the heart?

A

On the external surface of the heart.

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23
Q

The visceral layer of serous pericardium is also known as:

A

epicardium

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24
Q

The two layers of the serous pericardium are separated by:

A

the fluid-filled pericardial cavity

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25
Q

What is the purpose of the pericardial cavity?

A

decreases friction

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26
Q

Homeostatic imbalance of pericardium can lead to:

A
  1. pericarditis

2. cardiac tamponade

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27
Q

What is pericarditis?

A

inflammation of pericardium

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28
Q

What happens to the membrane surfaces of the pericardium when someone has pericarditis?

A

the surfaces are roughened; the heart has pericardial friction rub (creaking sound) that can be heard with a stethoscope

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29
Q

What is cardiac tamponade?

A

Excess fluid sometimes compresses the heart, which leads to limited pumping ability.

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30
Q

The three layers of the heart wall are:

A
  1. epicardium
  2. myocardium
  3. endocardium
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31
Q

The visceral layer of serous pericardium is:

A

epicardium

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32
Q

Characteristics of the myocardium:

A
  1. spiral bundles of contractile cardiac muscle cells

2. cardiac skeleton; crisscrossing, interlacing layer of connective tissue

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33
Q

What is the function of the cardiac skeleton of myocardium?

A
  1. anchors cardiac muscle fibers
  2. supports great vessels and valves
  3. limits spread of action potentials to specific paths
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34
Q

The endocardium is continuous with:

A

endothelial lining of blood vessels

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35
Q

Where is the endocardium located?

A
  1. lines heart chambers

2. covers cardiac skeleton of valves

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36
Q

The four chambers of the heart:

A
  1. Two superior atria

2. Two inferior ventricles

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37
Q

separates atria

A

interatrial septum

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38
Q

remnant of foramen ovale of fetal heart

A

fossa ovalis

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39
Q

separates ventricles

A

interventricular septum

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40
Q

The chambers and associated great vessels:

A
  1. coronary sulcus
  2. anterior interventricular sulcus
  3. posterior interventricular sulcus
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41
Q

The coronary sulcus is also known as:

A

atrioventricular groove

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42
Q

This encircles the junction of atria and ventricles.

A

coronary sulcus

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43
Q

This is located in the anterior position of the interventricular septum.

A

Anterior interventricular sulcus

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44
Q

This is a landmark on the posteroinferior surface.

A

posterior interventricular sulcus

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45
Q

appendages that increase atrial volume

A

auricles

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46
Q

The atria are the ___ chambers.

A

receiving

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47
Q

The ventricles are the ____ chambers.

A

discharging

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48
Q

The right atrium has ____.

A

pectinate muscles

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49
Q

The posterior and anterior regions of the right atrium are separated by ____.

A

crista terminalis

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50
Q

The left atrium has pectinate muscles only in ____.

A

auricles

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51
Q

What are the characteristics of atria?

A
  1. small, thin-walled
  2. Contribute little to propulsion of blood
  3. Three veins empty into right atrium
  4. Four pulmonary veins empty into left atrium
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52
Q

What are the three veins that empty into the right atrium?

A
  1. superior vena cava
  2. inferior vena cava
  3. coronary sinus
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53
Q

Most of the volume of the heart is:

A

the ventricles

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54
Q

Where is the right ventricle of the heart located?

A

most of the anterior surface

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55
Q

Where is the left ventricle of the heart located?

A

posteroinferior surface

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56
Q

irregular ridges of muscle on walls

A

trabeculae carneae

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57
Q

The papillary muscles of the ventricles anchor ____.

A

chordae tendineae

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58
Q

What are the characteristics of ventricles?

A
  1. thicker walls than atria

2. they are the actual pumps of the heart

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59
Q

The right ventricle pumps blood into the _____.

A

pulmonary trunk

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60
Q

The left ventricle pumps blood into the ____.

A

aorta

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61
Q

largest artery in the body

A

aorta

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62
Q

What are the characteristics of heart valves?

A
  1. Ensure unidirectional blood flow through the heart
  2. Open and close in response to pressure changes
  3. Two atrioventricular (AV) valves
  4. Two semilunar (SL) valves
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63
Q

What is the purpose of the atrioventricular valves?

A

To prevent backflow into atria when ventricles contract.

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64
Q

What is the purpose of semilunar valves?

A
  1. Prevent backflow into ventricles when ventricles relax.

2. Open and close in response to pressure changes.

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65
Q

Atrioventricular valves are composed of:

A
  1. tricuspid valve (right AV valve)
  2. mitral valve (left AV valve, bicuspid valve)
  3. Chordae tendineae
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66
Q

Chordae tedineae of the atrioventricular valves anchor cusps to _____. What is the purpose of this?

A

papillary muscles; to hold valve flaps in closed position

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67
Q

Semilunar valves are composed of:

A
  1. Aortic semilunar valve

2. Pulmonary semilunar valve

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68
Q

Homeostatic imbalance involving heart valves can lead to:

A
  1. Incompetent valve

2. Valvular stenosis

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69
Q

What happens during incompetent valve?

A

Blood backflows so the heart repumps the same blood over and over.

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70
Q

What happens during valvular stenosis?

A

Stiff flaps; they constrict opening - the heart must exert more force to pump blood

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71
Q

How can heart valve disease be treated?

A

By replacing the valve with a mechanical, animal, or cadaver valve.

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72
Q

Pathway of blood through the heart: Pulmonary Circuit: Right atrium:

A

—> tricuspid valve —> right ventricle

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73
Q

Pathway of blood through the heart: Pulmonary Circuit: Right ventricle:

A

—> pulmonary semilunar valve —> pulmonary trunk —> pulmonary arteries —> lungs

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74
Q

Pathway of blood through the heart: Pulmonary Circuit: Lungs:

A

—> pulmonary veins —> left atrium

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75
Q

Pathway of blood through the heart: Systemic Circuit: left atrium:

A

—> mitral valve —> left ventricle

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76
Q

Pathway of blood through the heart: Systemic Circuit: left ventricle:

A

—> aortic semilunar valve —> aorta

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77
Q

Pathway of blood through the heart: Systemic Circuit: aorta:

A

—> systemic circulation

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78
Q

What is the amount of blood pumped to the pulmonary and systemic circuits?

A

equal amount

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79
Q

Characteristic of the pulmonary circuit:

A

short, low-pressure circulation

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80
Q

Characteristic of the systemic circuit:

A

long, high-friction circulation

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81
Q

What is the size of the left ventricle in comparison to the right?

A

3x thicker; pumps with greater pressure

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82
Q

functional blood supply to heart muscle itself

A

coronary circulation

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83
Q

Blood is delivered via coronary circulation when:

A

the heart is relaxed

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84
Q

Most of the blood supply from the coronary circulation is received in:

A

left ventricle

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85
Q

The coronary circulation contains many of these.

A

anastomoses (junctions)

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86
Q

What are the characteristics of anastomoses?

A
  1. Provide additional routes for blood delivery

2. Can not compensate for coronary artery occlusion

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87
Q

Arteries arise from the base of ____.

A

the aorta

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88
Q

The left coronary artery branches into:

A
  1. anterior interventricular artery

2. circumflex artery

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89
Q

The right coronary artery branches into:

A
  1. right marginal artery

2. posterior interventricular artery

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90
Q

What does the left coronary artery supply to?

A
  1. interventricular septum
  2. anterior ventricular walls
  3. left atrium
  4. posterior wall of left ventricle
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91
Q

What does the right coronary artery supply to?

A
  1. right atrium

2. most of right ventricle

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92
Q

These collect blood from capillary beds.

A

cardiac veins

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93
Q

This empties into the right atrium.

A

coronary sinus

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94
Q

The coronary sinus is formed by merging cardiac veins. Which are they?

A
  1. Great cardiac vein
  2. Middle cardiac vein
  3. Small cardiac vein
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95
Q

Where is the great cardiac vein located?

A

anterior interventricular sulcus

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96
Q

Where is the middle cardiac vein located?

A

posterior interventricular sulcus

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97
Q

Where is the small cardiac vein located?

A

inferior margin

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98
Q

Several _____ empty directly into right atrium anteriorly.

A

anterior cardiac veins

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99
Q

Diseases involving coronary circulation:

A
  1. Angina pectoris

2. Myocardial infarction

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100
Q

Characteristics of angina pectoris:

A
  1. Thoracic pain caused by fleeting deficiency in blood delivery to myocardium
  2. cells are weakened
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101
Q

Characteristics of myocardial infarction:

A
  1. Prolonged coronary blockage

2. Areas of cell death repaired with noncontractile scar tissue

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102
Q

myocardial infarction is also known as

A

heart attack

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103
Q

Physical characteristics of cardiac muscle cells:

A
  1. short
  2. branched
  3. fat
  4. interconnected
  5. 1 (perhaps 2) central nuclei
  6. T tubules are wide, less numerous
  7. SR is simpler than in skeletal muscle
  8. numerous large mitochondria
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104
Q

The connective tissue matrix of cardiac muscle connects to ____.

A

cardiac skeleton

105
Q

Another name for connective tissue matrix of cardiac muscle:

A

endomysium

106
Q

This contains numerous capillaries.

A

endomysium

107
Q

Mitochondria of cardiac muscle cells are what percentage of cell volume?

A

25-35%

108
Q

Cardiac muscle also contains:

A
  1. intercalated discs
  2. desmosomes
  3. gap junctions
109
Q

junctions between cells that anchor cardiac cells

A

intercalated discs

110
Q

These prevent cardiac muscle cells from separating during contraction.

A

desmosomes

111
Q

These allow ions to pass from cell to cell; they also electrically couple adjacent cells.

A

gap junctions

112
Q

Gap junctions allow the heart to be:

A

functional syncytium

113
Q

What is functional syncytium?

A

Behaves as a single coordinated unit.

114
Q

What are the three differences between cardiac muscle and skeletal muscle?

A
  1. ~1% of cardiac muscle cells have automaticity (autorhythmicity)
  2. All cardiomyocytes contract as a unit, or none do
  3. Long absolute refractory period
115
Q

Automaticity (authorhythmicity) in cardiac muscle cells allow for:

A
  1. not needing nervous system stimulation

2. can depolarise the entire heart

116
Q

What is the time length of the absolute refractory period in cardiac muscle cells?

A

250 ms

117
Q

Why do cardiac muscle cells have a long absolute refractory period?

A

To prevent tetanic contractions.

118
Q

What are the three similarities between cardiac muscle and skeletal muscle?

A
  1. Depolarisation opens few voltage-gated fast Na+ channels in sarcolemma
  2. Depolarisation wave down T tubules
  3. Excitation-contraction coupling occurs
119
Q

When depolarisation opens voltage-gated fast Na+ channels in sarcolemma of cardiac muscle cells, what happens?

A
  1. The membrane potential is reversed from -90mV to +30 mV

2. It is brief; Na channels close rapidly

120
Q

After depolarisation wave goes down T tubules in cardiac muscle cells, what happens?

A

SR releases Ca2+

121
Q

When excitation-contraction coupling occurs in cardiac muscle cells, what happens?

A

Ca2+ binds troponin —> filaments slide

122
Q

More differences between cardiac muscle cells and skeletal muscle cells:

A
  1. Depolarisation wave also opens slow Ca2+ channels in sarcolemma —> SR to release its Ca2+
  2. Ca2+ surge prolongs the depolarisation phase
  3. Action potential and contractile phase last much longer
  4. Repolarisation is a result of inactivation of Ca2+ channels and opening of voltage-gated K+ channels
123
Q

When Ca2+ surge prolongs the depolarisation phase of cardiac muscle cells, what is it known as?

A

plateau

124
Q

The action potential and contractile phase of cardiac muscle cells lasts much longer. What does this allow for?

A

Blood ejection from heart

125
Q

After Ca2+ channels are inactivated and repolarisation results of cardiac muscle cells, what happens?

A

Ca2+ is pumped back to SR and extracellularly

126
Q

Cardiac muscle has many ____.

A

mitochondria

127
Q

Cardiac muscle energy requirements:

A
  1. Mitochondria have great dependence on aerobic respiration
  2. Mitochondria have little anaerobic respiration ability
  3. Cardiac muscle readily switches fuel source for respiration
  4. Cardiac muscle even uses lactic acid from skeletal muscles
128
Q

Homeostatic imbalance of cardiac muscle:

A
  1. Ischemic cells
  2. —>anaerobic respiration
  3. —>lactic acid
  4. —> High H+ concentration
  5. —> high Ca2+ concentration
  6. —> mitochondrial damage
  7. —>decreased ATP production
  8. —>gap junctions close
  9. —> fatal arrhythmias
129
Q

The heart depolarises and contracts without:

A

nervous system stimulation

130
Q

Heart rhythm can be altered by:

A

the autonomic nervous system

131
Q

Coordinated heartbeat is a function of:

A
  1. presence of gap junctions

2. intrinsic cardiac conduction system

132
Q

What are the characteristics of the intrinsic cardiac conduction system?

A
  1. network of noncontractile (autorhythmic) cells

2. initiates and distributes impulses —> coordinated depolarisation and contraction of heart

133
Q

Characteristics of autorhythmic cells:

A
  1. Have unstable resting membrane potentials (pacemaker potentials or prepotentials) due to opening of slow Na+ channels
  2. At threshold, Ca2+ channels open
134
Q

Because autorhythmic cells have unstable resting membrane potentials due to opening of slow Na+ channels, what happens?

A

They continuously depolarise.

135
Q

After autorhythmic cells reach threshold and Ca2+ channels open, what happens?

A

Explosive Ca2+ influx produces the rising phase of the action potential.

136
Q

Repolarisation of autorhythmic cells results from what?

A

Inactivation of Ca2+ channels and opening of voltage-gated K+ channels.

137
Q

What are the three parts of action potential by pacemaker cells?

A
  1. pacemaker potential
  2. depolarisation
  3. repolarisation
138
Q

When the pacemaker potential of pacemaker cells initiates, what happens?

A

Repolarisation closes K+ channels and opens slow Na+ channels —> ion imbalance

139
Q

After ion imbalance due to pacemaker potential of pacemaker cells, depolarisation occurs; what happens?

A

Ca2+ channels open —> huge influx —> rising phase of action potential

140
Q

After rising phase of action potential of pacemaker cells, repolarisation occurs. What happens?

A

K+ channels open —> efflux of K+

141
Q

Cardiac pacemaker cells pass impulses across heart in what speed?

A

~220 ms

142
Q

What is the sequence of cardiac pacemaker cell impulses?

A
  1. Sinoatrial node
  2. —> Atrioventricular node
  3. —> Atrioventricular bundle
  4. —> Right and left bundle branches
  5. —> Subendocardial conducting network (Purkinje fibres)
143
Q

Heart Physiology: Sequence of Excitation:

A
  1. Sinoatrial node
  2. Impulse spreads across atria, and to AV node
  3. Atrioventricular Node
  4. Atrioventricular Bundle
  5. Right and left bundle branches
  6. Subendocardial conducting network
  7. Ventricular contraction immediately follows from apex toward atria
144
Q

Pacemaker of heart in right atrial wall

A

Sinoatrial (SA) node

145
Q

Characteristics of SA node:

A
  1. Depolarises faster than the rest of myocardium
  2. Generates impulses about 75X/minute
  3. Inherent rate of 100X/minute tempered by extrinsic factors
146
Q

The Sinoatrial node generates impulses at about 75X/minute. What is this known as?

A

sinus rhythm

147
Q

Where is the AV node located?

A

In inferior interatrial septum

148
Q

Characteristics of AV node:

A
  1. delays impulses approximately 0.1 second

2. Inherent rate of 50X/minute in absence of SA node input

149
Q

Why does the AV node delay impulses by approximately 0.1 second?

A
  1. Because fibres are smaller diameter, and have fewer gap junctions
  2. It allows atrial contraction prior to ventricular contraction
150
Q

Where is the AV bundle located?

A

In superior interventricular septum

151
Q

AV bundle has only electrical connection between:

A

atria and ventricles

152
Q

Why does AV bundle only have electrical connection between atria and ventricles?

A

Because atria and ventricles are not connected via gap junctions

153
Q

Characteristics of right and left bundle branches:

A
  1. Two pathways in interventricular septum

2. Carry impulses toward apex of heart

154
Q

Characteristics of subendocardial conducting network:

A
  1. Complete pathway through interventricular septum into apex and ventricular walls
  2. More elaborate on left side of heart
155
Q

The AV bundle and subendocardial conducting network depolarise at:

A

30X/minute in absence of AV node input

156
Q

Defects in intrinsic conduction system may cause:

A
  1. Arrhythmias

2. Fibrillation

157
Q

irregular heart rhythms

A

arrythmias

158
Q

What happens with arrythmias?

A

Uncoordinated atrial and ventricular contractions.

159
Q

rapid, irregular contractions

A

fibrillation

160
Q

When fibrillation leads to rapid, irregular contractions, what happens?

A
  1. It’s useless for pumping blood
  2. —>circulation ceases
  3. —> brain death
161
Q

How is fibrillation treated?

A

defibrillation

162
Q

Defective SA node may cause:

A
  1. Ectopic focus
  2. AV node may take over
  3. Extrasystole
  4. To reach ventricles, impulse must pass through AV node
163
Q

abnormal pacemaker

A

ectopic focus

164
Q

Because of a defective SA node, AV node may take over. What happens then?

A

AV node sets junctional rhythm (40-60 beats/min)

165
Q

premature contraction

A

extrasystole

166
Q

What are the characteristics of extrasystole?

A
  1. Ectopic focus sets high rate

2. Can be from excessive caffeine or nicotine

167
Q

Defective AV node may cause:

A

heart block

168
Q

Charactieristics of heart block:

A
  1. Few (partial) or no (total) impulses reach ventricles

2. Ventricles beat at intrinsic rate–too slow for life

169
Q

How does one treat heart block?

A

artificial pacemaker

170
Q

Heartbeat is modified by:

A

autonomic nervous system via cardiac centres in medulla oblongata

171
Q

When the sympathetic nervous system is activated:

A

heartbeat is increased in rate and force

172
Q

When the parasympathetic nervous system is activated:

A

heartbeat is decreased in rate

173
Q

The cardioacceleratory centre is ____.

A

sympathetic

174
Q

The cardioinhibitory centre is ____.

A

parasympathetic

175
Q

What does the cardioacceleratory centre affect?

A
  1. SA
  2. AV nodes
  3. heart muscle
  4. coronary arteries
176
Q

What does the cardioinhibitory centre inhibit?

A

SA and AV nodes via vagus nerves

177
Q

Composite of all action potentials generated by nodal and contractile cells at a given time

A

electrocardiogram (ECG or EKG)

178
Q

The 3 waves of an electrocardiogram are:

A
  1. P wave
  2. QRS complex
  3. T wave
179
Q

A P wave is characteristic of:

A

depolarisation of SA node —> atria

180
Q

A QRS complex is characteristic of:

A

ventricular depolarisation and atrial depolarisation

181
Q

A T wave is characteristic of:

A

ventricular repolarisation

182
Q

A P-R interval of ECG lasts from:

A

beginning of atrial excitation to beginning of ventricular excitation

183
Q

What happens during an S-T segment of ECG?

A

Entire ventricular myocardium is depolarised

184
Q

A Q-T interval of ECG lasts from:

A

Beginning of ventricular depolarisation through ventricular repolarisation

185
Q

Two sounds are associated with the closing of heart valves (lub-dup). What happens during these?

A
  1. First happens as AV valves close
  2. Second happens as SL valves close
  3. Pause indicates heart relaxation
186
Q

When AV valves close, what happens?

A

Systole begins

187
Q

When SL valves close, what happens?

A

Ventricular diastole begins

188
Q

abnormal heart sounds; usually indicate incompetent or stenotic valves

A

heart murmurs

189
Q

Characteristics of the cardiac cycle:

A
  1. Blood flows through heart during one complete heartbeat: atrial systole and diastole followed by ventricular systole and diastole
  2. systole
  3. diastole
  4. Series of pressure and blood volume changes
190
Q

contraction

A

systole

191
Q

relaxation

A

diastole

192
Q

The phases of the cardiac cycle:

A
  1. ventricular filling
  2. ventricular systole
  3. isovolumetric relaxation
193
Q

When does ventricular filling of the cardiac cycle take place?

A

in mid-to-late diastole

194
Q

When does isovolumetric relaxation of the cardiac cycle take place?

A

early diastole

195
Q

Characteristics of ventricular filling in the cardiac cycle:

A
  1. AV valves are open; pressure is low
  2. 80% of blood passively flows into ventricles
  3. Atrial systole occurs, delivering remaining 20%
  4. End diastolic volume (EDV)
196
Q

What is the end diastolic volume (EDV)?

A

volume of blood in each ventricle at the end of ventricular diastole

197
Q

Characteristics of ventricular systole in the cardiac cycle:

A
  1. Atria relax; ventricles begin to contract
  2. Rising ventricular pressure —> closing of AV valves
  3. Isovolumetric contraction phase
  4. In ejection phase, ventricular pressure exceeds pressure in large arteries, forcing SL valves open
  5. End systolic volume (ESV)
198
Q

What happens during the isovolumetric contraction phase of ventricular systole in the cardiac cycle?

A

all valves are closed

199
Q

What is the end systolic volume (ESV)?

A

volume of blood remaining in each ventricle after systole

200
Q

Characteristics of isovolumetric relaxation of the cardiac cycle:

A
  1. Ventricles relax; atria are relaxed and filling
  2. Backflow of blood in aorta and pulmonary trunk closes SL valves
  3. When atrial pressure exceeds that in ventricles –> AV valves open; cycle begins again at step 1
201
Q

The backflow of blood in aorta and pulmonary trunk closes SL valves during isovolumetric relaxation of the cardiac cycle. This causes what?

A

dicrotic notch; ventricles totally closed chambers

202
Q

What is the dicrotic notch?

A

brief rise in aortic pressure as blood rebounds off closed valve

203
Q

the volume of blood pumped by each ventricle in one minute

A

cardiac output

204
Q

What is the formula for cardiac output?

A

CO = heart rate (HR) x stroke volume (SV)

205
Q

number of beats per minute

A

heart rate (HR)

206
Q

volume of blood pumped out by one ventricle with each beat

A

stroke volume (SV)

207
Q

What is the normal cardiac output?

A

5.25 L/min

208
Q

At rest, the CO is:

A

CO (ml/min) = HR (75 beats/min) x SV (70 ml/beat) = 5.25 L/min

209
Q

Cardiac output increases if:

A

either or both SV or HR is increased

210
Q

Characteristics of maximal cardiac output:

A
  1. it is 4-5 times resting cardiac output in nonathletic people
  2. it may reach 35 L/min in trained athletes
211
Q

the difference (-) between resting and maximal CO

A

cardiac reserve

212
Q

Equation for SV:

A

SV = EDV - ESV

213
Q

EDV is affected by:

A

length of ventricular diastole and venous pressure

214
Q

ESV is affected by:

A

arterial BP and force of ventricular contraction

215
Q

What are the three main factors that affect SV?

A
  1. Preload
  2. Contractility
  3. Afterload
216
Q

What is preload?

A

The degree of stretch of cardiac muscle cells before they contract.

217
Q

The degree of stretch of cardiac muscle cells before they contract follows which principle?

A

Frank-Starling law of heart

218
Q

Characteristics of preload:

A
  1. Cardiac muscle exhibits a length-tension relationship
  2. At rest, cardiac muscle cells are shorter than optimal length
  3. Most important factor stretching cardiac muscle is venous return
219
Q

What is venous return?

A

the amount of blood returning to the heart

220
Q

How is venous return increased?

A

slow heartbeat and exercise increase

221
Q

When venous return is increased, what happens?

A

it distends (stretches) ventricles and increases contraction force

222
Q

What is contractility?

A

contractile strength at given muscle length, independent of muscle stretch and EDV

223
Q

Contractility is increased by:

A
  1. Sympathetic stimulation —> increased Ca2+ influx —> more cross bridges
  2. Positive inotropic agents
224
Q

What are the positive inotropic agents that increase contractility?

A
  1. Thyroxine
  2. glucagon
  3. epinephrine
  4. digitalis
  5. high extracellular Ca2+
225
Q

Contractility is decreased by:

A

negative ionotropic agents

226
Q

What are the negative ionotropic agents that decrease contractility?

A
  1. acidosis
  2. increased extracellular K+
  3. calcium channel blockers
227
Q

What is afterload?

A

the pressure ventricles must overcome to eject blood

228
Q

Afterload is increased by:

A

hypertension, resulting in increased ESV and reduced SV

229
Q

Positive chronotropic factors ___ heart rate.

A

increase

230
Q

Negative chronotropic factors ___ heart rate.

A

decrease

231
Q

The sympathetic nervous system is activated by:

A

emotional or physical stressors

232
Q

What happens when the sympathetic nervous system is activated?

A
  1. Norepinephrine causes pacemaker to fire more rapidly (and increases contractility)
  2. Norepinephrine binds to Beta1-adrenergic receptors —> increased HR
  3. increased contractility; faster relaxation
  4. increased contractility offsets lower EDV due to decreased fill time
233
Q

What happens when the parasympathetic nervous system is activated?

A
  1. Acetylcholine hyperpolarises pacemaker cells by opening K+ channels —> slower HR
  2. Little to no effect on contractility
234
Q

Heart at rest exhibits ____.

A

vagal tone

235
Q

What is vagal tone?

A

Parasympathetic nervous system is dominant the influence.

236
Q

How is heart rate chemically regulated?

A
  1. hormones

2. intra and extracellular ion concentrations must be maintained for normal heart function

237
Q

Hormones that regulate heart rate:

A
  1. epinephrine

2. thyroxine

238
Q

Epinephrine is released from the ___.

A

adrenal medulla

239
Q

What does epinephrine do for the heart?

A

increases heart rate and contractility

240
Q

What does thyroxine do for the heart?

A
  1. increases heart rate

2. enhances effects of norepinephrine and epinephrine

241
Q

Homeostatic imbalance of heart rate can lead to:

A
  1. hypocalcemia
  2. hypercalcemia
  3. hyperkalemia
  4. hypokalemia
  5. tachycardia
  6. bradycardia
  7. congestive heart failure (CHF)
242
Q

What does hypocalcemia do?

A

depresses heart

243
Q

What happens in hypercalcemia?

A

increased HR and contractility

244
Q

What happens in hyperkalemia?

A

electrical activity is altered —> heart block and cardiac arrest

245
Q

What happens in hypokalemia?

A

feeble heartbeat; arrhythmias

246
Q

Characteristics of tachycardia:

A
  1. abnormally fast heart rate (>100 beats/min)

2. if persistent, may lead to fibrillation

247
Q

Characteristics of bradycardia:

A
  1. heart rate is slower than 60 beats/min
  2. may result in grossly inadequate blood circulation in nonathletes
  3. may be desirable result of endurance training
248
Q

Characteristics of congestive heart failure:

A
  1. progressive condition
  2. cardiac output is so low that blood circulation is inadequate to meet tissue needs
  3. weakened myocardium
249
Q

Weakened myocardium in congestive heart failure can be caused by:

A
  1. coronary atherosclerosis–clogged arteries
  2. persistent high blood pressure
  3. multiple myocardial infarcts
  4. dilated cardiomyopathy (DCM)
250
Q

The embryonic heart chambers are:

A
  1. sinus venosus
  2. atrium
  3. ventricle
  4. bulbus cordis
251
Q

The fetal heart structures that bypass pulmonary circulation:

A
  1. foramen ovale

2. ductus arteriosus

252
Q

The foramen ovale connects:

A

two atria

253
Q

The remnant of foramen ovale in adults is:

A

fossa ovalis

254
Q

The ductus arteriosus connects:

A

pulmonary trunk to aorta

255
Q

The remnant of ductus arteriosus in adults is:

A

ligamentum arteriosum

256
Q

The foramen ovale and ductus arteriosus close:

A

at or shortly after birth

257
Q

Most congenital heart defects are one of two types:

A
  1. due to mixing of oxygen-poor and oxygen-rich blood, e.g. septal defects, patent ductus arteriosus
  2. narrowed valves or vessels –> increased workload on the heart, e.g. coarctation of aorta
258
Q

In Tetralogy of Fallot:

A

both congenital heart defects are present

A&P II (8 decks)

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