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A+P 2 > Chapter 18 (Lecture) - Heart > Flashcards

Chapter 18 (Lecture) - Heart Flashcards

1
Q

when the mitral valve closes, it prevents backflow from the

A

left ventricle into the left atrium

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2
Q

what is the purpose of the chordae tendineae

A

anchor the AV valves in the closed position

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3
Q

what makes the heart valves open and close?

A

blood pressure

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4
Q

what valve separates the left atrium and left ventricle

A

bicuspid (mitral) valve

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5
Q

valve between the right atrium and right ventricle

A

tricuspid valve

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6
Q

prevents backflow of blood into the left ventricle

A

aortic semilunar valve

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7
Q

where does the blood leave from the left atrium

A

mitral (bicuspid) valve

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8
Q

a condition in which the valve flaps of the heart becomes stiff and consticts the opening

A

stenosis

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9
Q

separates the left ventricle and the aorta

A

aortic semilunar valve

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10
Q

separates the right ventricle and the pulmonary trunk

A

pulmonary semilunar valve

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11
Q

separates the right atrium from the right ventricle

A

tricuspid valve

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12
Q

where does blood leave from the left ventricle

A

aortic semilunar valve

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13
Q

prevents backflow of blood into the right ventricle

A

pulmonary semilunar valve

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14
Q

attached to the AV valve flaps

A

chordae tendineae

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15
Q

where does the blood leave from the right ventricle

A

pulmonary semilunar valve

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16
Q

what prevents the atrioventricular valves from everting during ventricular contraction

A

papillary muscles

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17
Q

which valve is most often faulty in the heart

A

mitral (bicuspid) valve

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18
Q

where does the blood leave from the right atrium

A

tricuspid valve

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19
Q

failure of which heart valve would allow blood to move from the left ventricle to the left atrium

A

mitral (bicuspid) valve

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20
Q

the right side of the heart pumps blood through which circuit

A

pulmonary

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21
Q
  • the left side of the heart pumps blood through which circuit
  • associated with the left ventricle
  • long pathway throughout the entire body and encounters about 5x as much friction, or resistance to blood flow
A

systemic circuit

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22
Q

the right side of the heart receives what type of blood from where

A

oxygen-poor blood from body tissues

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23
Q

the left side of the heart receives what type of blood from where

A

oxygen-rich blood from the lungs

pumps blood to supply oxygen and nutrients to body tissues

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24
Q
  • blood vessels that carry blood to and from the lungs
  • served by the right ventricle
  • short, low pressure circulation
A

pulmonary circuit

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25
Q

the blood vessels that carry blood to and from all body tissues

A

systemic circuit

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26
Q

receives blood returning from the systemic circuit

A

right atrium

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27
Q

receives blood returning from the pulmonary circuit

A

left atrium

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28
Q
  • pumps blood INTO the pulmonary circuit
  • forms most of the anterior surface of the heart
A

right ventricle

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29
Q
  • pumps blood INTO the systemic circuit
  • dominates the inferoposterior aspect of the heart and forms the apex
A

left ventricle

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30
Q

the medial cavity of the thorax containing the heart, great vessels, thymus and parts of the trachea, bronchi, and esophagus

A

mediastinum

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31
Q

posterior surface of the heart that is directed toward the right shoulder

A

base

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32
Q

inferiorly pointed part of the heart that points toward the left hip

A

apex

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33
Q

double-layered sac enclosing the heart and forming its superficial layer; has fibrous and serous layers

A

pericardium

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34
Q
  • loosely fitting part of the pericardium
  • made up of tough, dense CT
  • functions to: protect the heart, anchors the heart to surrounding structures, and prevents the overfilling of the heart with blood
A

fibrous pericardium

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35
Q
  • deep to the fibrous pericardium
  • a thin, slippery, two-layer serous membrane that forms a closed sac around the heart
A

serous pericardium

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36
Q
  • lines the internal surface of the fibrous pericardium
  • attaches to the large arteries exiting the heart and continues over the external heart surface as the visceral layer (epicardium)
A

parietal layer of pericardium

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37
Q
  • located between the parietal and visceral layers of the pericardium
  • contains a film of serous fluid
A

pericardial cavity

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38
Q
  • inflammation of the pericardium
  • roughens surface membrane surfaces
A

pericarditis

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39
Q
  • the visceral layer of the serous pericardium
  • most superficial layer of the heart wall
  • often infiltrated with fat, especially in older people
A

epicardium

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40
Q
  • composed mainly of cardiac muscle and forms the bulk of the heart
  • the layer of the heart that contracts
  • contains CT fibers arranged in circular bundles that link all parts of the heart together
A

myocardium

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41
Q

CT fibers in the myocardium that reinforce it internally and anchors the cardiac muscle fibers

A

cardiac skeleton

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42
Q
  • the innermost layer of the heart
  • a glistening white sheet of endothelim (squamous epithelium) resting on a thin CT layer
  • located on the inner myocardial surface and lines heart changers and covers the fibrous skeleton of the valves
A

endocardium

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43
Q

the internal partition that divides the heart longitudinally and separates the atria

A

interatrial septum

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44
Q

the internal partition that divides the heart longitudinally and separates the ventricles

A

interventricular septum

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45
Q
  • also known as the atrioventricular groove
  • encircles the junction of the atria and ventricles like a crown
A

coronary sulcus

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46
Q
  • cradles the anteriorventricular artery (LAD)
  • marks the anterior position of the septum separating the right and left ventricles
  • continues as PI sulcus
A

anterior interventricular sinus

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47
Q

the right ventricle pumps blood into … which routes blood to the lungs where gas exchange occurs

A

pulmonary trunk

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48
Q

the largest artery in the body

A

aorta

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49
Q

returns blood from body regions superior to the diaphragm

A

superior vena cava

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50
Q

returns blood from body areas below the diaphragm

A

inferior vena cava

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51
Q

collects blood draining from the myocardium

A

coronary sinus

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52
Q

irregular ridges of muscle that mark the internal walls of the ventricular chambers

A

trabeculae carneae

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53
Q

muscle bundles that project into the ventricular cavity and play a role in valve function

A

papillary muscles

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54
Q

landmarks the posterior position of the septum that separates the left and right ventricles

A

posterior interventricular sulcus

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55
Q
  • located in the interatrial septum, faces the right atrium
  • marks the location of the fetal foramen ovale in the heart
A

fossa ovalis

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56
Q

small, wrinkled, protruding appendages which increase the atrial volume somewhat

A

auricles

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57
Q
  • located the anterior portion of the right atrium and in the auricle of the left atrium
  • look like the teeth of a comb
A

pectinate muscles

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58
Q

a C-shaped ridge that separates the posterior and anterior regions of the right atrium

A

crista terminalis

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59
Q

tributaries of the coronary sinus

A
  • great cardiac vein
  • small cardiac vein
  • middle cardiac vein
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60
Q

several of these empty directly into the right atrium anteriorly

A

anterior cardiac veins

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61
Q
  • empties the blood into the right atrium
  • cardiac veins form this
A

coronary sinus

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62
Q

after passing through the capillary beds of the myocardium, the venous blood is collected by

A

cardiac veins

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63
Q

artery that courses to the right side of the heart

A

right coronary artery

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64
Q

two branches of the right coronary artery

A
  • right marginal artery
  • posterior interventricular artery (posterior inferior descending artery)
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65
Q

artery that serves the myocardium of the lateral right side of the heart

A

right marginal artery

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66
Q
  • runs to the heart apex and supplies the posterior ventricular walls
  • near the apex of the heart, this artery merges (anastomoses) with the anterior interventricular artery (LAD)
A

posterior interventricular artery

otherwise known as the posterior inferior descending artery

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67
Q
  • runs toward the left side of the heart
  • branches into the anterior interventricular artery (LAD) and circumflex artery
A

left coronary artery

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68
Q
  • known clinically as the left anterior descending artery
  • follows the anterior interventricular sulcus and supplies blood to the interventricular septum and anterior walls of both ventricles
A

anterior interventricular artery

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69
Q

supplies the left atrium and the posterior wals of the left ventricle

A

circumflex artery

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70
Q

which ventricle generates more pressure

A

left ventricle

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71
Q

the functional blood supply of the heart and the shortest circulation in the body

A

coronary circulation

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72
Q
  • located at each atrial-ventricular junction
  • prevent backflow into the atria when the ventricles contract
A

atrioventricular (AV) valves

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73
Q
  • attached to each AV flap
  • tiny white collagen chords that anchor the cusps to the papillary muscles protruding from the ventricular walls
  • also known as the heart strings
A

chordae tendineae

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74
Q

act as tethers that anchor the valve flaps in their closed position

A

chordae tendineae and papillary muscles

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75
Q
  • guard the bases of the large arteries issuing from the ventricles and prevent backflow into the associated ventricles
  • crescent moon cusp shaped
A

aortic and pulmonary semilunar (SL) valves

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76
Q
  • arise from the base of the aorta and encircle the ehart in the coronary sulcus
  • provide arterial supply of coronary circulation
A

left and right coronary arteries

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77
Q

the act of listening to the heart with a stethoscope

A

auscultating

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78
Q

what is happening during the “pause” phase when the heart is resting/relaxing?

A

the ventricles are filling

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79
Q

what causes the abnormal swishing or whooshing sound that is heard as blood regurgitates back into an atrium from its associated ventricle

A

blood turbulence

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80
Q

which chamber of the heart has the highest probability of being the site of a myocardial infarction (MI)

A

left ventricle

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81
Q

the presence of an incompetent tricuspid valve would have the direct effect of causing

A

reduced efficiency in the delivery of blood to the lungs

The tricuspid valve separates the right atrium and the right ventricle. It must remain tightly closed during ventricular contraction so blood can be pumped out of the ventricle and into the pulmonary arteries.

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82
Q

if the mitral valve is unable to close properly,

A

blood could flow back into the left atrium

83
Q

Failure in a particular structure of the heart tends to cause a backup of blood in the lungs, known as pulmonary congestive heart failure. Failure of which structure of the heart would lead to such a backup?

A

left ventricle

Failure in the left ventricle can cause increased blood hydrostatic pressure in the lungs, causing fluid buildup in the alveoli.

84
Q

the left ventricular wall of the heart is thicker than the right wall in order to

A

pump blood w/ greater pressure

85
Q

the source of blood carried to the capillaries in the myocardium

A

coronary arteries

86
Q

what separates the parietal and visceral pericardium

A

pericardial cavity

87
Q

excessive amount of fluid in the pericardial cavity

A

prevents the heart from filling properly with blood

88
Q

true or false:

the left side of the heart pumps the same volume of blood as the right

A

true

89
Q

lines the internal surface of the fibrous pericardium

A

parietal pericardium

90
Q

true or false:

the role of the chordae tendineae is to open the AV valves at the appropriate time

A

false

Chordae tendineae anchor the cusps of the AV valves to the papillary muscles protruding from the ventricular walls. The chordae tendineae and the papillary muscles act as tethers that anchor the valve cusps in their closed position. If the cusps were not anchored, they would be blown upward (everted) into the atria, in the same way an umbrella is blown inside out by a gusty wind. The papillary muscles contract with the other ventricular musculature so that they take up the slack on the chordae tendineae as the full force of ventricular contraction hurls the blood against the AV valve cusps.

91
Q

heart sounds are caused by

A

heart valve closure

92
Q

what receives blood during ventricular systole

A

both the aorta and pulmonary trunk

93
Q

the AV valves are closed when

A

the ventricles are in systole

94
Q

during the period of ventricular filling,

A

blood flows mostly passively from the atria through the atrioventricular (AV) valves into the ventricles

95
Q

what BP is necessary to force blood through vessels and effect cellular exchange of gases, wastes, and nutrients

A

120/80

96
Q

what is responsible for the Lub sound

A

closure of the AV valves

97
Q

what is responsible for the Dup sounds

A

closure of the semilunar valves

98
Q

what does the QRS wave of the ECG represent

A

ventricular depolarization

99
Q

cardiac temponade results in ineffective pumping of blood by the heart; because the excessive amount of fluid in the pericardial cavity will

A

prevent the heart from filling properly with blood

100
Q

why are gap junctions a vital part of the intercellular connection of cardiac muscles?

A

gap junctions allow action potentials to spread to connected cells

Gap junctions are a form of electrical synapse that allow action potentials to spread to connected cells. This property allows the signal to spread efficiently through the heart.

101
Q

pathway of the stimulation through the heart

A
  1. AV node
  2. AV bundle
  3. interventricular septum
  4. subendocardial conducting network
102
Q

Suppose a patient develops a myocardial infarction that disables the sinoatrial node. Would the heart still pump blood to the aorta and the pulmonary trunk?

A

Yes, because the atrioventricular node will still stimulate ventricular systole.

The atrioventricular node spontaneously depolarizes similarly to the sinoatrial node, but more slowly. It can lead to the ventricles pumping blood to the aorta and pulmonary trunk around 50 times per minute.

103
Q

Which portion of the electrocardiogram represents the wave-like change in charge in the positive direction received by the atria from the sinoatrial (SA) node?

A

p wave

The P wave represents the depolarization of the left and right atria and the beginning of atrial systole

104
Q

Which portion of the ECG cycle overlaps with the expected ventricular contraction (or systole)?

A

Q-T interval

The Q-T interval is the period from the beginning of ventricular depolarization through ventricular repolarization, during which the ventricles are in systole.

105
Q

The plateau phase of an action potential in cardiac muscle cells is due to the

A

influx of Ca2+ through slow Ca2+ channels

106
Q

true or false:

an ECG provides direct information about valve function

A

false

107
Q

at what point in the cardiac cycle is pressure in the ventricles the highest (around 120 mm Hg in the left ventricle)

A

ventricular systole

108
Q

what causes heart sounds

A

heart valve closure

109
Q

which part of the heart receives blood during ventricular systole

A

both the aorta and pulmonary trunk

110
Q

the AV valves are closed when

A

the ventricles are in systole

111
Q

refers to the short period during ventricular systole when the ventricles are completely closed chambers

A

isovolumetric contraction

112
Q

As your skeletal muscles contract during physical activity, more blood is returned to the heart. Which variable would be affected and what would be the outcome of this action?

A

Preload would be increased, which would result in a larger cardiac output.

More blood returning to the heart would increase the volume of blood in the ventricles at the end of their filling phase (called end diastolic volume, or EDV). A larger EDV results in greater stretching of the myocardium, or a greater preload. Stretching (lengthening) the contractile cells brings them closer to their optimal length, allowing them to produce more force when stimulated to contract. The stronger contraction results in a larger stroke volume, and therefore a larger cardiac output.

113
Q

true or false:

increasing end-diastolic volume (EDV) and end-systolic volume (ESV) will increase stroke volume

A

false

Stroke volume (the volume of blood ejected from the ventricle during systole) is equal to the difference between EDV (the volume of blood in the ventricle before it contracts) and ESV (the volume of blood remaining in the ventricle after it contracts). Increasing EDV will result in a larger stroke volume; however, increasing ESV will result in a smaller stroke volume.

114
Q

hypercalcemia could cause

A

prolonged T wave

The T wave on an ECG tracing represents ventricular repolarization. Repolarization requires the net efflux of K+ ions. Recall that changes in normal concentrations of ions (like Ca2+) in the plasma can affect the ability of other ions to move in and out of the cell.

115
Q

which cranial nerve carries efferent parasympathetic motor impulses to the heart and other major organs

A

vagus nerve

116
Q

which part of the intrinsic conduction system is slowed by impulses from the vagus nerve

A

SA node

117
Q

Which term describes an area of the heart conduction system where the impulse is delayed for 0.1 sec?

A

AV node

118
Q

Which of the following factors gives the myocardium its high resistance to fatigue?

A

Large number of mitochondria in the cytoplasm

119
Q

the cells of the myocardium behave as a single, coordinated unit called a

A

functional syncytium

120
Q

the role of the atrioventricular node (AV node) is to

A

slow down impulses so that atria can contract to fill the adjacent ventricles with blood

121
Q

the absolute refractory period refers to the time during which

A

the muscle cell is not in a position to respond to a stimulus of any strength

122
Q

ventricular repolarization is indicated by which wave

A

T wave

123
Q

the ability of some cardiac muscle cells to initiate their own depolarization and cause depolarization of the rest of the haert is called

A

automaticity

124
Q

another term for contraction

A

systole

125
Q

the area of the heart conduction system with the fastest depolarizing pacemaker cells

A

SA node

126
Q

which wave signifies atrial depolarization

A

P wave

127
Q

what is a difference between cardiac muscle and skeletal muscle

A

unlike skeletal muscle cells, cardiac muscle has gap junctions between cells that allow them to be autorhythmic

128
Q

carries parasympathetic fibers to the sinoatrial (SA) node

A

vagus nerve (X)

129
Q

signifies ventricular depolarization

A

QRS complex

130
Q

sequence of current flow through the intrinsic conduction system of the heart

A
  1. SA node
  2. AV node
  3. AV bundle
  4. right and left bundle branches
  5. subendocardial conducting network
131
Q

the P wave of an ECG represents

A

atrial depolarization

132
Q

Given an end diastolic volume (EDV) of 120 ml / beat and an end systolic volume (ESV) of 50 ml / beat, the stroke volume (SV) would be

A

70 ml / beat

133
Q

true or false:

if blood volume decreased dramatically due to massive bleeding, the autonomic nervous system will attempt to maintain cardiac output by increasing the heart rate.

A

true

134
Q

true or false:

when released in large quanities, thyroxine, a thyroid gland hormone, causes a sustained increase in heart rate

A

true

135
Q

striated and uninuclear; short, and branched

A

cardiac muscle cells

136
Q
  • connects cardiac muscle cells
  • special anchors that hold the cells together and allow them to communicate via gap junctions
A

intercalated discs

137
Q

opening of fast sodium channels

A

rapid depolarization

138
Q

plateau phase is when slow calcium channels open and prevent rapid repolarization

A

rapid partial repolarization

139
Q

calcium channels shut and membrane is again most responsive to potassium

A

repolarization

140
Q

steps to action potential generation in cardiac muscles

A
  1. rapid depolarization
  2. partial repolarization
  3. repolarization
141
Q

how long does it take for skeletal muscles to generate an action potential

A

2 milliseconds

142
Q

how long does it take for cardiac muscle to generate an action potential

A

300-500 milliseconds

143
Q

why is the refractory period of cardiac muscle action potential so prolonged

A

so that fatigue doesn’t set in when the cardiac muscle beats

144
Q

which hormones increase heart rate

A
  • epinephrine
  • norepinephrine
  • thyroid hormone
145
Q

what effect does parasympathetic innervation have on heart rate and cardiac output?

A

decreased heart rate and lower cardiac output

146
Q

what effect does sympathetic innervation have on heart rate and cardiac output

A

increases heart rate and cardiac output, along with increased contractility

147
Q

the degree of stretch in cardiac muscle fibers before they contract

A

preload

148
Q

end diastolic volume - end systolic volume

A

stroke volume

149
Q

cardiac output =

A

stroke volume x heart rate

150
Q

increasing the stretch in the ventricles by increasing what will increase stroke volume

A

increasing venous return

151
Q

nerves run to the heart muscle and to the SA and AV nodes to accelerate the heart

A

sympathetic innervation of the heart

152
Q

travels to the heart mainly via the vagus nerve and impacts the SA and AV nodes

A

parasympathetic innervation of the heart

153
Q

what prevents rapid depolarization

A

slow Ca2+ channels

154
Q

what occurs before contraction

A

depolarization

155
Q

which part of the intrinsic conduction system depolarizes the fastest

A

SA node

156
Q

what ions are the main effectors of cardiac output

A
  • calcium
  • sodium
  • potassium
157
Q

if stroke volume increases and heart rate stays the same, then what happens to cardiac output?

A

cardiac output increases

158
Q

the amount of blood pumped out by each ventricle per minute

A

cardiac output

159
Q

sounds heard in the 2nd intercostal space at the right sternal margin

A

aortic valve

160
Q

sounds heard in the 2nd intercostal space at the left sternal margin

A

pulmonary valve

161
Q

sounds heard over heart apex (in 5th intercostal space) in line with the middle of the clavicle

A

mitral valve

162
Q

sounds typically heard in right sternal margin of 5th intercostal space

A

tricuspid valve

163
Q

diagram that ties electrical and mechanical events together

A

Wigger’s diagram

164
Q

steps to the cardiac cycle

A
  1. ventricular filling (ventricular filling and atrial contraction)
  2. ventricular systole (isovolumentric contraction –> ventricular ejection)
  3. early diastole (isovolumetric relaxation)
165
Q

measures the electrical activity in the heart

A

electrocardiography

166
Q

atrial depolarization initiated by the SA node causes this wave

A

P wave

167
Q

atrial depolarization is complete and the impulse is delayed at the AV node

A

PQ interval

168
Q
  • ventricular depolarization begins at apex, causing this wave
  • atrial repolarization occurs
A

QRS complex

169
Q

ventricular depolarization is complete

A

ST interval

170
Q

ventricular repolarization begins at the apex, causing this wave

A

T wave

171
Q
  • SA node nonfuncitonal
  • P waves are absent
  • heart is paced by AV node at 40-60bpm
A

junctional rhythm

172
Q
  • some P waves are not conducted through the AV node
  • more P than QRS waves seen
  • ratio of P waves to QRS waves is mostly 2:1
A

second degree heart block

173
Q
  • the volume of blood pumped out by one ventricle with each beat
  • correlates with the force of ventricular contraction
A

stroke volume

174
Q
  • the difference between resting and maximal CO
  • in nonathletes is typically 20-25 L/min
A

cardiac reserve

175
Q

the degree to which cardiac muscle cells are stretched just before they contract

A

preload

176
Q

the higher the preload,

A

the higher the stroke volum

177
Q
  • the relationship between preload and stroke volume
  • higher preload = higher stroke volume
A

Frank-Starling

178
Q
  • most important factor stretching cardiac muscle
  • the amount of blood returning to the heart and distending its ventricles
A

venous return

179
Q

resting fetal heart rate

A

140-160bpm

180
Q

avg female resting heart rate

A

72-80bpm

181
Q

male resting heart rate

A

64-72 bpm

182
Q
  • raises HR by acting through the sympathetic nervous system
  • increases systemic blood pressure and routes more blood to working muscles
A

exercise

183
Q

what happens when the right side of the heart fails

A

peripheral congestion

blood stagnates in body organs, and pooled fluids in the tissue spaces impair the ability of body cells to obtain adequate nutrients and oxygen and rid themselves of waste

edema in extremities

184
Q

what are common treatments for damaged heart muscle

A
  • removing excess leaked fluid w/ diuretics
  • reducing afterload with drugs that drive down bp
  • increasing contractility w/ digitalis derivatives
  • heart transplants and other surgical remedies
185
Q
  • when the left side of the heart fails
  • right side of the heart continues to propel blood to the lungs but the left side doesn’t adequately eject the returning blood into systemic circulation

causes pulmonary edema due to engorged vessels w/ increased bp, and fluid leaks from vessels into lung tissue

A

pulmonary congestion

186
Q
  • ventricles stretch and become flabby and the myocardium deteriorates, often for unknown reasons
  • drug toxicity and chronic inflammation may be involved
A

dilated cardiomyopathy (DCM)

187
Q
  • a succession of myocardial infarctions (heart attacks) depresses pumping efficiency because noncontractile fibrous (scar) tissue replaces the dead heart cells
A

multiple myocardial infarctions

188
Q
  • fatty buildup that clogs the coronary arteries, impairs blood and oxygen delivery to cardiac cells
  • heart becomes increasingly hypoxic and begins to contract ineffectively
A

coronary athersclerosis

189
Q
  • the heart is such an inefficient pump that blood circulation is inadequate to meet tissue needs
  • a progressively worsening disorder that reflects the weakening of the myocardium by various conditions that damage it in different ways
  • common causes include: coronary atherosclerosis, persistent high bp. multiple MIs, dilated cardiomyopathy (DCM)
A

congestive heart failure (CHF)

190
Q
  • an abnormally fast resting heart rate (>100 bpm) that may result from elevated body temp, stress, certain drugs, or heart disease
  • if persistent, considered pathological because it occasionally promotes fibrillation
A

tachycardia

191
Q
  • a resting heart rate slower than 60bpm
  • may result from low body temperature, certain drugs, or parasympathetic NS activation
  • often a warning of brain edema after head trauma
A

bradycardia

192
Q

increases HR by enhancing the metabolic rate of cardiac cells

A

heat

193
Q
  • an autonomic reflex initiated by increased venous return and increased atrial filling
  • stretching the atrial walls increases heart rate by stimulating both the SA node and the atrial stretch receptors, triggering reflexive adjustments of autonomic output to the SA node, increasing HR
A

atrial (Bainbridge) reflex

194
Q

factors that increase heart rate

A

positive chronotropic factors

195
Q

factors that decrease heart rate

A

negative chronotropic factors

196
Q

exerts the most important extrinsic controls affecting heart rate

A

ANS

197
Q

in what condition is afterload particularly important and why

A

hypertension; reduces ability of the ventricles to eject blood

198
Q
  • the pressure that ventricles must overcome to eject blood
  • essentially the back pressure that arterial blood exerts on the aortic and pulmonary valves (~80 mmHg in the aorta and 10 mmHg in the pulmonary trunk)
A

afterload

199
Q
A
200
Q

the major intrinsic factor influencing stroke volume

A

end diastolic volume

201
Q
  • the contractile strength achieved at a given muscle length
  • rises more when more Ca2+ enters the cytoplasm from the extracellular fluid and the SR
A

contractility

202
Q

what is the effect of enhanced contractility

A

more blood is ejected from the heart (greater SV) and lower ESV

203
Q
  • substances that increase contractility
  • epinephrine, thyroxine, glucagon, the drug digitalis, high levels of extracellular Ca2+
A

positive inotropic agents

204
Q
  • impair or decrease contractility
  • induce acidosis
  • include rising EC K+ levels and also calcium channel blockers
A

negative inotropic agents

A+P 2 (21 decks)

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