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Cardiovascular System Flashcards

1
Q

What composes the cardiovascular system?

A

heart and blood vessels

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2
Q

What is perfusion?

A

delivery of blood per time per gram of tissue

mL/min/g

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3
Q

what is the goal of the cardiac system?

A

to provide adequate perfusion to all body tissues

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4
Q

What are the 3 types of blood vessels?

A

arteries
veins
capillaries

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5
Q

What do arteries do?

A

carry blood away from the heart

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6
Q

what do veins do?

A

carry blood back to the heart

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7
Q

what do capillaries do?

A

serve as sites of exchange, either between blood and alveoli in lungs or between blood and body cells

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8
Q

What are the 3 significant anatomical features of the heart?

A

two pump structures
great vessels that lead to and away from heart
2 sets of valves

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9
Q

What does the right side of the heart do?

A

receives deoxygenated blood from the body and pumps it to the lungs

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10
Q

what does the left side of the heart do?

A

receives oxygenated blood from the lungs and pumps it to the body

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11
Q

What is an atrium?

A

the superior chamber of the heart that receives blood

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12
Q

what is a ventricle?

A

the inferior chamber of the heart that pumps blood away from the heart

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13
Q

What are the great vessels?

A

pulmonary trunk
aorta
vena cavae [superior vena cava (sva) and inferior vena cava (iva)]
pulmonary veins

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14
Q

What does the pulmonary trunk do?

A

transports blood from the right side of the heart

splits into the pulmonary arteries

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15
Q

what does the aorta do?

A

transports blood from the left side of the heart

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16
Q

what do the vena cavae do?

A

drain blood into the right side of the heart

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17
Q

what do the pulmonary veins do?

A

drain blood into the left side of the heart

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18
Q

what is the basic pattern of blood flow?

A

right side of the heart -> lungs -> left side of heart -> systemic cells

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19
Q

what are the two sets of valves in the heart?

A

the atrioventricular valves (AV), and the semilunar valves

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20
Q

where are the AV valves located?

A

between the atrium and ventricle of each side of the heart

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21
Q

what is another name for the right AV valve?

A

tricuspid valve

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22
Q

what is the tricuspid valve?

A

the right AV valve

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23
Q

what are other names for the left AV valve?

A

bicuspid valve

mitral valve

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24
Q

what is the mitral valve?

A

the left AV valve

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25
Q

what is the bicuspid valve?

A

the left AV valve

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26
Q

where are the semilunar valves located?

A

between a ventricle and its associated arterial trunk

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27
Q

where is the pulmonary semilunar valve located?

A

between the right ventricle and the pulmonary trunk

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28
Q

where is the aortic semilunar valve located?

A

between the left ventricle and the aorta

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29
Q

What are the 2 circulatory circuits?

A

pulmonary circulation and systemic circulation

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30
Q

what is the basic pattern of blood flow?

A

right side of the heart —> lungs —> left side of heart —> systemic tissues of the body —> right side of the heart

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31
Q

what is ventricular balance?

A

equal amounts of blood pumping by each ventricle through the 2 circulations

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32
Q

what is edema?

A

excess fluid in the interstitial space or within cells

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33
Q

what may happen if the right ventricle is impaired?

A

systemic edema - right ventricle can’t keep up with left ventricle, so fluid remains in systemic circulation

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34
Q

What may happen if the left ventricle is impaired?

A

Pulmonary edema - swelling and fluid accumulation in the lungs - impaired gas exchange

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35
Q

What is the pattern of blood flow through pulmonary circulation?

A

deoxygenated blood enters right atrium from vena cavae (SVC and IVC) and coronary sinus
blood passes through the right AV valve (tricuspid)
blood enters the right ventricle
blood passes through the pulmonary semilunar valve
blood enters the pulmonary trunk
blood continues through the right and left pulmonary arteries to both lungs
blood enters pulmonary capillaries of both lungs for gas exchange
oxygenated blood exits the pulmonary capillaries of the lungs and returns to the heart by right and left pulmonary veins
blood enters the left atrium of the heart

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36
Q

What is the pattern of blood flow through systemic circulation?

A

oxygenated blood enters the left atrium
blood passes through the left AV valve (bicuspid or mitrial valve)
blood enters the left ventricle
blood passes through aortic semilunar valve
blood enters the aorta
blood is distributed by the systemic arteries
blood enters systemic capillaries for nutrient and gas exchange
deoxygenated blood exits systemic capillaries and returns to the heart by systemic veins that drain into the SVC, IVC and coronary sinus
blood enters right atrium

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37
Q

where is the base of the heart?

A

posterior superior surface

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38
Q

Where is the apex of the heart?

A

the inferior conical end

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39
Q

what composes the pericardial sac?

A 
fibrous pericardium (outer layer)
parietal layer of serous pericardium (parietal pericardium)
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40
Q

What is the purpose of the fibrous pericardium?

A

restricts movements of heart and prevents heart from overfilling with blood

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41
Q

what is the fibrous pericardium made of?

A

dense irregular connective tissue

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42
Q

what is the closest membrane to the heart?

A

visceral layer of serous pericardium (epicardium)

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43
Q

What is the pericardial cavity?

A

potential space between the parietal and visceral layers

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44
Q

what is in the pericardial cavity?

A

serous fluid that is secreted by both layers - lubricates membranes and facilitates almost frictionless movement of heart as it beats

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45
Q

What is the deep groove that extends around the circumference of the heart?

A

coronary sulcus

separates atria from ventricles

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46
Q

what is the groove between the ventricles?

A

interventricular sulcus

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47
Q

what is located within the sulci?

A

coronary vessels

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48
Q

which side of the heart is prominent when viewing it anteriorly?

A

right atrium and right ventricles

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49
Q

what is the right auricle?

A

wrinkled, flaplike thing on right atrium (ear)

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50
Q

which side of the heart is most prominent when seen from posterior view?

A

left atrium and left ventricle

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51
Q

what is attached to the left atrium?

A

the pulmonary veins

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52
Q

What can you see from the anterior view of the heart?

A

right atrium and ventricle, right auricle, aorta and pulmonary trunk, small part of left auricle of left atrium, anterior interventricular sulcus and part of coronary sulcus

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53
Q

what can you see from the posterior view of the heart?

A

left atrium and ventricle, pulmonary veins, superior and inferior vena cavae, pulmonary arteries, posterior interventricular sulcus, part of the coronary sulcus that houses the coronary sinus

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54
Q

What is the difference in thickness between chambers of the heart?

A

ventricle walls are thicker than atria walls

left ventricle is typically 3 times thicker than right ventricle

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55
Q

what are the layers of the walls of each chamber of the heart?

A

epicardium
myocardium
endocardium

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56
Q

what is the outermost layer of the heart?

A

epicardium

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57
Q

what is another name for the epicardium?

A

visceral layer of serous pericardium

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58
Q

what is the epicardium?

A

serous membrane composed of simple squamous epithelium and underlying layer of areolar connective tissue

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59
Q

what is the myocardium?

A

middle layer of the heart wall composed of cardiac muscle tissue
thickest of 3 layers

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60
Q

what is the endocardium?

A

internal surface of the heart and external surfaces of the heart valves
simple squamous epithelium (called endothelium) and underlying layer of areolar connective tissue

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61
Q

what separates the right and left atrial chambers?

A

interatrial septum (thin)

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62
Q

what separates the right and left ventricles?

A

the interventricular septum (thick)

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63
Q

what are pectinate muscles?

A

ridges on the internal surface of the atria

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64
Q

what is the fossa ovalis?

A

oval depression in the right atrium interatrial septum

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65
Q

what is the fossa ovalis?

A

former location of fetal foramen ovale - shunted blood from right atrium to left atrium to bypass the lungs during fetal life

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66
Q

where is the opening of the coronary sinus

A

inferior to the fossa ovalis in the right atrium

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67
Q

what does the coronary sinus do?

A

drains blood from the heart wall

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68
Q

what are the trabeculae carneae?

A

muscular ridges in the ventricles

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69
Q

what are papillary muscles?

A

cone-shaped projections in the ventricles that anchor the chordae tendineae

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70
Q

what are chordae tendineae?

A

thin strands of collagen fibers that are attached to atrioventricular valves

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71
Q

where is the pulmonary semilunar valve located?

A

between the right ventricle and the pulmonary trunk

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72
Q

what is visible in the left atrium?

A

pectinate muscles, openings of pulmonary veins, left AV valve

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73
Q

how many papillary muscles are there in the right ventricle?

A

usually 3, but between 2-9

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74
Q

how many papillary muscles are there in the left ventricle?

A

2

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75
Q

what is visible in the left ventricle?

A 
trabeculae carneae
2 papillary muscles
chordae tendineae
entrance to the aorta
aortic semilunar valve
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76
Q

where is the aortic semilunar valve located?

A

between the left ventricle and the aorta

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77
Q

what are valves made out of?

A

endothelium-lined fibrous connective tissue flaps called cusps or leaflets

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78
Q

how many cusps do each AV valve have?

A

right AV - 3

left AV - 2

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79
Q

when do the semilunar valves open?

A

when the ventricles contract and the force of the blood pushes the AV valves open and blood enters the arterial trunks

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80
Q

when do the semilunar valves close?

A

when the ventricles relax and the pressure in the ventricle becomes less than the pressure in a great arterial trunk. blood in the arteries begins to fall backward toward the ventricle and is caught in the cusps of the semilunar valves and they close

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81
Q

which valves have chordae tendineae?

A

AV valves

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82
Q

what does cardiac muscle tissue look like?

A

short, branched cells with 1-2 nuclei

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83
Q

what surrounds cardiac cells?

A

endomysium - areolar connective tissue

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84
Q

what is the sarcolemma?

A

plasma membrane of the cardiac muscle

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85
Q

what forms T-tubules?

A

invaginated sarcolemma

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86
Q

what is a sarcomere?

A

the distance from one z disc to another z disc

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87
Q

where are the t-tubules of cardiac muscles

A

overlie the z discs (invaginate once per sarcomere)

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88
Q

what does the sarcoplasmic reticulum (SR) surround?

A

bundles of myofilaments called myofibrils (myofibrils are the bundles of myofilaments)

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89
Q

when does maximum overlap of thick and thin filaments occur in cardiac muscle?

A

when cardiac muscle is stretched as blood is added to a heart chamber (not when cardiac muscle is relaxed - different from skeletal muscles)

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90
Q

what do neighboring cardiac muscle cells have?

A

extensively folded sarcolemma (plasma membranes)

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91
Q

what does the folded sarcolemma of cardiac muscle cells allow?

A

permits adjoining membranes to interconnect - increasing surface area between neighboring cells - facilitates communication between cardiac muscle cells

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92
Q

what are intercalated discs?

A

structures that link cardiac muscle cells together both mechanically and electrically - contain desmosomes and gap junctions

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93
Q

what connects cardiac muscle cells together?

A

intercalated discs

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94
Q

what do desmosomes do?

A

protein filaments that act like glue to prevent cardiac muscle cells from pulling apart

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95
Q

what do gap junctions do?

A

protein pores between sarcolemma of adjacent cardiac muscle cells
allow ion flow - action potential flow across sarcolemma of cardiac muscle cells - making chamber function as single unit

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96
Q

what are the features of intercalated discs?

A

desmosomes and gap junctions

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97
Q

what features of cardiac muscle support its great energy demand?

A

extensive blood supply, numerous mitochondria, + other structures like myoglobin and creatine kinase

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98
Q

how much of cardiac muscle volume is mitochondria?

A

25%

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99
Q

what does cardiac muscle rely almost exclusively on? aerobic or anaerobic cellular respiration?

A

aerobic cellular respiration

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100
Q

what supports the heart internally?

A

fibrous skeleton composed of dense irregular tissue

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101
Q

what are the functions of the fibrous skeleton of the heart?

A

structural support at boundary between atria and ventricles
forms supportive fibrous rings to anchor heart valves
rigid framework for attachment of cardiac muscle tissue
electric insulator (doesn’t conduct AP), so prevents atria from contracting at same time as ventricles

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102
Q

How do muscles work when atria contract?

A

compress walls of chambers inward to move blood into the ventricles

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103
Q

how do the muscles of the ventricle work?

A

like wringing a mop - begins at apex of heart & compresses superiorly, moving blood into the great arterial trunks

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104
Q

how does the heart absorb oxygen and nutrients?

A

coronary circulation system

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105
Q

what are the coronary arteries?

A

vessels that transport oxygenated blood to the wall of the heart

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106
Q

what are the coronary veins?

A

vessels that transport deoxygenated blood away from the heart wall

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107
Q

where are the right and left coronary arteries located?

A

in the coronary sulcus

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108
Q

what are the branches of the ascending aorta?

A

right and left coronary arteries

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109
Q

where do the right and left coronary arteries originate?

A

immediately superior to the aortic semilunar valve in the ascending aorta

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110
Q

what are the branches of the right coronary artery?

A

right marginal artery - supplies the right border of the heart
posterior interventricular artery - supplies the posterior surface of left and right ventricles

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111
Q

what are the branches of the left coronary artery?

A

circumflex artery - supplies the left atrium and ventricle
anterior interventricular artery - (also called left anterior descending artery) - supplies anterior surface of both ventricles and most of the interventricular septum

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112
Q

what does the right marginal artery supply?

A

right border of the heart

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113
Q

what does the posterior interventricular artery supply?

A

posterior surface of both the left and right ventricles

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114
Q

what does the circumflex artery supply?

A

left atrium and ventricle

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115
Q

what does the anterior interventricular artery supply?

A

anterior surface of both ventricles and most of the interventricular septum

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116
Q

what are arterial anastomoses?

A

shared connections between arteries

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117
Q

what are end arteries?

A

arteries that terminate in capillary beds only

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118
Q

what is a functional end artery?

A

arteries that have anastomoses, but anastomoses are too tiny to shunt enough blood from one artery to another to maintain supply

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119
Q

what kind of artery are left and right coronary arteries?

A

functional end arteries

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120
Q

what is atherosclerosis?

A

when coronary arteries become narrowed or occluded with plaques (coronary artery disease)

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121
Q

what is angina pectoris?

A

poorly localized pain sensation on left side of the chest, left arm, shoulder, sometimes jaw and back
sympathetic pathways along T1-T5 spinal cord segments - usually results from strenuous activity

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122
Q

what is infarction?

A

death of tissue due to lack of blood supply

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123
Q

what is myocardial infarction?

A

heart attack - sudden and complete occlusion of a coronary artery

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124
Q

what are the main cardiac veins?

A

great cardiac vein, middle cardiac vein, small cardiac vein - all drain into the coronary sinus

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125
Q

where is the coronary sinus?

A

lies within the posterior aspect of the coronary sulcus

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126
Q

what is the function of the coronary sinus?

A

collects venous blood and drains deoxygenated blood from the heart wall directly into the right atrium of the heart

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127
Q

what are the structures of the heart’s conduction system?

A 
sinoatrial node (SA node)
atrioventricular node (AV node)
atrioventricular bundle (AV bundle)
Purkinje fibers
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128
Q

where is the sinoatrial node located?

A

in the posterior wall of the right atrium, adjacent to the entrance of the superior vena cava

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129
Q

what do the cells of the sinoatrial node do?

A

initiate the heartbeat - commonly referred to as the pacemaker of the heart

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130
Q

conduction system cardiac cells do what?

A

do NOT contract, but rather initiate and conduct electrical signals

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131
Q

where is the atrioventricular node located?

A

in the floor of the right atrium between the right AV valve and the opening for the coronary sinus

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132
Q

where is the atriventricular bundle located?

A

extends from the AV node into and through the interventricular septum - it divides into left and right bundles

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133
Q

How does sympathetic innervation of the heart work?

A

cardioacceleratory center sends nerve signals along sympathetic nerves, which results in an increase in both heart rate and force of contraction

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134
Q

where are the Purkinje fibers located?

A

extend from the left and right bundles from the apex of the heart and then continue through the walls of the ventricles

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135
Q

what initiates heart rate?

A

SA node

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136
Q

what regulates heart rate and strength of contraction?

A

autonomic nervous system

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137
Q

where is the cardiac center of the autonomic nervous system?

A

in the medulla oblongata

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138
Q

what does parasympathetic innervation do to heart rate?

A

cardioinhibitory center sends nerve signals along the vagus nerves (CN X) which results in a decrease in heart rate - no direct effect on the force of contraction

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139
Q

what does the right vagus nerve innervate?

A

SA node

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140
Q

what does the left vagus nerve innervate?

A

AV node

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141
Q

where do the neurons that extend to the SA node in the sympathetic nervous system begin?

A

T1-T5 segments of spinal cord

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142
Q

how does sympathetic innervation affect coronary arteries?

A

cause dilation of vessels to support increased blood flow to the myocardium

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143
Q

what controls parasympathetic and sympathetic influence on heart rate?

A

reflexes - chemoreceptors (CO2 and H+ levels) and baroreceptors (blood pressure changes)

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144
Q

what is another name for the atrial reflex?

A

Bainbridge reflex

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145
Q

what does the atrial reflex do?

A

protects the heart from overfilling

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146
Q

How does the Bainbridge reflex work?

A

initiated when baroreceptors (stretch receptors) in atrial walls are stimulated by an increase in venous return. Nerve signals increase along sensory neurons to cardioacceleratory center, increase in nerve signals along sympathetic axons to the heart -> heart rate increases so blood moves more quickly through the heart, decreasing atrial stretch.

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147
Q

what two events result in heart contraction and pumping blood throughout the cardiovascular system?

A

conduction system

cardiac muscle cells

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148
Q

how do cardiac muscle cells cause heart beat?

A

action potential spreads across the sarcolemma of the cardiac muscle cells, causing sarcomeres within cardiac muscle cells to contract. occurs twice during a heart beat - first in the cells of the atria, then in the cells of the ventricles.

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149
Q

what do cells in the SA node generate?

A

action potential

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150
Q

what kind of pumps do nodal cells have?

A

Na+/K+ pumps

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151
Q

what kind of leak channels do nodal cells have?

A

Na+ and K+

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152
Q

where is Na+ ion concentration greatest during resting membrane potential?

A

outside the nodal cells

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153
Q

where is K+ ion concentration greatest during resting membrane potential?

A

inside the nodal cells

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154
Q

what is the Resting membrane potential value for nodal cells?

A

-60 millivolts (mV)

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155
Q

what other kind of ion pumps do nodal cells have?

A

Ca2+ - create Ca2+ concentration gradient with more Ca2+ outside the cell than inside

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156
Q

What kind of voltage-gated channels do nodal cells have?

A

slow voltage-gated Na+ channels
fast voltage-gated Ca2+ channels
voltage-gated K+ channels

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157
Q

what is autorhythmicity?

A

SA nodal cells are capable of depolarizing and firing an action potential spontaneously without any external influence

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158
Q

What are the series of events that occur within SA nodal cells?

A
  1. reaching threshold
  2. depolarization
  3. repolarization
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159
Q

what happens during the reaching threshold step?

A

slow voltage-gated NA+ channels open. Na+ flows into nodal cells, changing resting membrane potential from -60mV to -40mV, which is the threshold value. - reached WITHOUT outside stimulation

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160
Q

what happens during depolarization?

A

membrane potential at threshold triggers opening of fast voltage-gated Ca2+ channels, Ca2+ entry into nodal cell causes change in membrane potential from -40mV to just above 0 mV (slightly positive). –> reversal of polarity = depolarization

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161
Q

what happens during repolarization?

A

Ca channels close, voltage-gated K+ channels open; K+ flows out to change membrane potential from + to -60mV = resting membrane potential. triggers opening of slow voltage-gated Na+ channels & process begins again

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162
Q

what is a normal resting heart rate

A

about 75 beats per minute

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163
Q

what does the vagus nerve do?

A

slows heart rate —> vagal tone
SA nodal cells spontaneously depolarize at about 100X/minute, but parasympathetic stimulation of SA node by vagus nerve slows it down.

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164
Q

what is pacemaker potential?

A

ability to reach the threshold without stimulation (nodal cells have it) due to slow Na+ channels opening.

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165
Q

what are differences between nodal cells and neurons?

A
  1. nodal cells do not require stimulation because they don’t have a stable resting membrane potential.
  2. depolarization occurs by entrance of Na+ into neurons but with Ca2+ into nodal cells
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166
Q

what are the steps of initiation and spread of an action potential through the cardiac conduction system

A
  1. action potential initiated in SA node is spread between cardiac muscle cell in the atria by gap junctions - allow almost instantaneous excitation of all muscle cells in the atrial walls. both atria contract at the same time
  2. AP is delayed at the AV node - AV nodes have smaller fiber diameters & fewer numbers of gap junctions so slow conduction rate (bottleneck) helped by insulating fibrous skeleton. Slows conduction by .1 second - allows atria to finish contracting & force blood into ventricles to complete ventricular filling before ventricles are stimulated to contract.
  3. AP travels from the AV node through the AV bundle to the bundle branches to the purkinje fibers.
  4. AP spreads throughout both ventricles via gap junctions - gap junctions allow almost simultaneous stimulation of cardiac muscle cells - usually within 120-200 milliseconds after firing of SA nodal cells
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167
Q

where does stimulation of ventricles begin?

A

at the apex so blood is ejected superiorly toward arterial trunks

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168
Q

what are the 3 types of blood vessels?

A

arteries
capillaries
veins

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169
Q

what are the layers of the vessel walls called?

A

tunics

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170
Q

what is the inside space of the blood vessel called?

A

lumen

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171
Q

what are the 3 tunics called?

A

the tunica intima
tunica media
tunica externa

172
Q

what is the thickest layer of an artery?

A

tunica media

173
Q

what is the thickest layer of a vein?

A

tunica externa

174
Q

which has a larger lumen, an artery or a vein?

A

a vein

175
Q

what is the innermost layer of a blood vessel wall?

A

a tunica intima

176
Q

what are the layers of the tunica intima?

A

endothelium (simple squamous epithelium) that faces lumen

thin layer of areolar connective tissue

177
Q

describe the tunica media

A

smooth muscle cells supported by elastic fibers

contraction here results in vasoconstriction, relaxation causes vasodilation

178
Q

describe the tunica externa

A

outer most layer of blood vessel wall composed of areolar connective tissue that contains elastic and collagen fibers
anchors the vessel to other structures

179
Q

what are companion vessels?

A

arteries and veins that supply the same body region

180
Q

what parts compose capillaries?

A

tunica intima composed of endothelium and underlying basement membrane - NO subendothelial layer

181
Q

what are the 3 basic types of arteries?

A

elastic arteries
muscular arteries
arterioles

182
Q

what are examples of elastic arteries?

A 
aorta
pulmonary trunk
brachiocephalic artery
common carotid artery
subclavian artery
common iliac artery
183
Q

what characterizes elastic arteries?

A

largest ones - 1-2.5 cm in diameter
large proportion of elastic fibers throughout all 3 tunics
allows stretch during ventricular systole (contraction) and recoil during ventricular diastole (relaxation) - propels blood through arteries

184
Q

what is another name for muscular arteries?

A

distributing arteries - because they distribute blood to specific body regions and organs

185
Q

how are muscular arteries different than other arteries?

A

thicker tunica media
elastic fibers are only in the internal elastic lamina (separating tunica intima from tunica media) and external elastic lamina (separating tunica media from tunica externa)
better ability to vasoconstrict and vasodilate, lessened ability to stretch compared to elastic arteries

186
Q

what are examples of muscular arteries

A 
brachial
anterior tibial
coronary
inferior mesenteric
most named arteries
187
Q

describe arterioles

A

smallest arteries 3mm-10micrometers
fewer than 6 layers of smooth muscle in tunica media
smallest may have a thin endothelium surrounded by single layer of smooth muscle cells

188
Q

what is vasomotor tone?

A

smooth muscle in arterioles that is usually slightly constricted (like skeletal muscles)
regulated by vasomotor center in brainstem

189
Q

what is atherosclerosis?

A

progessive disease of elastic and muscular arteries

presence of atheroma which leads to thickening of tunica intima and narrowing of arterial lumen

190
Q

what is an aneurysm?

A

part of arterial wall thins and balloons out - more prone to rupture - most commonly occur at base of brain or in aorta

191
Q

what are the layers of a capillary?

A

endothelial layer resting on a basement membrane

192
Q

what are the types of capillaries?

A

continuous
fenestrated
sinusoid

193
Q

what are the most common type of capillaries?

A

continuous

194
Q

what are intercellular clefts?

A

gaps between endothelial cells where materials can move in or out of blood

195
Q

where are continuous capillaries found?

A

muscle, skin, lungs central nervous system (most capillaries are continuous)

196
Q

what can pass through vessel walls of continuous capillaries?

A

not large substances like formed elements and plasma proteins
yes fluid containing small substances like glucose, amino acids and ions (some leukocytes)

197
Q

describe fenestrated capillaries

A

complete continuous lining of endothelial cells and complete basement membrane, but some regions of endothelial cells are extremely thin (fenestrations/pores)

198
Q

what passes through fenestrated capillaries?

A

some smaller plasma proteins

large amounts of materials are filtered, released or absorbed

199
Q

where are fenestrated capillaries found?

A 
small intestine (absorbing nutrients)
ciliary process (produce aqueous humor)
choroid plexus (produce cerebrospinal fluid in the brain)
most endocrine glands (permit absorption of hormones into the blood)
kidneys (for filtering blood)
200
Q

describe sinusoids

A

discontinuous capillaries

have incomplete lining of endothelial cells with large openings & basement membrane is discontinuous or absent.

201
Q

where are sinusoids found?

A 
bone marrow (entrance of formed elements into circulation)
liver and spleen (removing aged erythrocytes)
some endocrine glands (movement of hormone molecules into blood)
202
Q

what materials can pass through the walls of sinusoid?

A

large substances (formed elements, large plasma proteins) and plasma

203
Q

what feeds a capillary bed?

A

metarteriole

204
Q

what is the thoroughfare channel?

A

the distal part of the metarteriole that has no smooth muscle cells

205
Q

what does the thoroughfare channel connect to?

A

a postcapillary venule

206
Q

what does the postcapillary venule do?

A

drains the capillary bed

207
Q

what is at the origin of each true capillary?

A

a smooth muscle ring called the precapillary sphincter

208
Q

what is a precapillary sphincter?

A

a smooth muscle ring at the origin of a true capillary that controls blood flow into the true capillaries

209
Q

how does blood bypass a capillary bed?

A

precapillary sphincter contracts, causing blood to flow from metarteriole to thoroughfare channel into postcapillary venule

210
Q

what is vasomotion?

A

precapillary sphincters relaxing and contracting (5-10 cycles/minute)

211
Q

how many capillary beds are open at any given time?

A

about 1/4

212
Q

what are the smallest veins?

A

venules

213
Q

what are the smallest venules called?

A

postcapillary venules

214
Q

what are companion vessels with arterioles?

A

venules

215
Q

what veins are companion vessels to muscular arteries?

A

small and medium-sized veins

216
Q

what veins are companion vessels to elastic arteries?

A

the largest veins

217
Q

what are vein valves formed from?

A

tunica intima and strengthened by elastic and collagen fibers
similar in structure to semilunar valves of heart

218
Q

how much blood is in the pulmonary circulation system at rest?

A

about 18%

219
Q

how much blood is in the heart while at rest?

A

about 12%

220
Q

how much blood is in the systemic circulation system while at rest?

A

about 70%

221
Q

how much blood is in systemic veins while at rest?

A

about 55%

222
Q

how is blood shifted from venous reservoirs into circulation when necessary?

A

vasoconstriction of veins

223
Q

how is blood shifted back to venous reservoirs when necessary?

A

vasodilation of veins

224
Q

what is the purpose of elastic arteries?

A

they stretch to accommodate the pulses of blood ejected from the heart and recoil to help propel blood through the arteries

225
Q

what is the purpose of muscular arteries?

A

they regulate distribution of blood through vasoconstriction and vasodilation
(same with arterioles)

226
Q

what do precapillary sphincters do?

A

regulate blood flow through capillary beds

227
Q

what are the layers of an artery wall?

A 
from outermost to innermost
tunica externa
elastic fibers
tunica media
elastic fibers
tunica intima 
	(subendothelial layer
	endothelium)
lumen
228
Q

what are the layers of a vein wall?

A 
from outermost to innermost
tunica externa (vasa vasorum)
tunica media
tunica intima
	(subendothelial layer	
	endothelium)
lumen
229
Q

what is the vasavasorum?

A

network of small arteries that supply the tunica externa of large blood vessels

230
Q

list the capillaries in order from least permeable to most permeable

A

continuous
fenestrated
sinusoid

231
Q

what is a simple pathway?

A

one artery, capillary bed and vein associated with an organ or a body region

232
Q

what kind of pathway does the spleen have?

A

simple
splenic artery delivers oxygenated blood to spleen, exchange made in capillary bed, splenic vein drains deoxygenated blood from the spleen

233
Q

what are end arteries?

A

arteries that provide only 1 pathway through which blood can reach an organ

234
Q

what are alternative pathways?

A

anastomoses

portal systems

235
Q

what is an anastomosis?

A

joining together of blood vessels

236
Q

what are the different types of anastomoses?

A

arterial anastomoses
venous anastomoses
arteriovenous anastomosis (shunt)

237
Q

what is an arterial anastomosis?

A

2 or more arteries converging to supply the same body region

238
Q

what are functional end arteries?

A

anastomoses that are so tiny the function of the arteries is considered to be an end artery

239
Q

what are end arteries?

A

arteries that terminate in capillary beds only

240
Q

what is a venous anastomosis?

A

2 or more veins draining the same body region

241
Q

what forms more anastomoses? veins or arteries?

A

veins

242
Q

what are the veins that drain the upper limb?

A

basilic, brachial and cephalic veins

example of a venous anastomosis

243
Q

what is an arteriovenous anastomosis?

A

transports blood from an artery directly to a vein

244
Q

where are arteriovenous anastomoses present?

A

fingers
toes
palms
ears

245
Q

what do arteriovenous anastomosis allow?

A

areas to be bypassed if body is becoming hypothermic

246
Q

what is a portal system?

A

blood flows through 2 capillary beds separated by a portal vein

247
Q

what does a portal vein do?

A

delivers blood to another organ before it is sent back to the heart
artery, capillary bed, portal vein, capillary bed, vein

248
Q

what are the 3 exchange processes in capillaries?

A

diffusion
vesicular transport
bulk flow

249
Q

what kind of exchange do systemic capillaries use?

A

diffusion
way to exchange oxygen, hormones, carbon dioxide
diffuse through endothelial cells, intercellular clefts, fenestrations or gaps in sinusoids

250
Q

what is vesicular transport?

A

when endothelial cells use pinocytosis to fuse fluid-filled vesicles with plasma membrane & transport their contents either from the blood to the IF or from the interstitial fluid to the blood.
certain hormones & fatty acids are transported across the endothelial cells this way

251
Q

what is bulk flow?

A

movement of large amounts of fluids & their dissolved substances in one direction down a pressure gradient

252
Q

what is filtration & where does it occur?

A

occurs on the arterial end of the capillaries, bulk flow out of blood through openings in capillaries - large solutes are usually blocked

253
Q

what is reabsorption?

A

bulk flow of fluid back into the blood

254
Q

what determines filtration vs. reabsorption?

A

hydrostatic pressure and colloid osmotic pressure (mmHg)

255
Q

what is hydrostatic pressure?

A

physical force exerted by a fluid on a structure

256
Q

what is blood hydrostatic pressure?

A

force exerted per unit area by the blood as it presses against the vessel wall.

257
Q

what is interstitial fluid hydrostatic pressure?

A

force of interstitial fluid on the external surface of the blood vessel

258
Q

what is osmotic pressure?

A

pull of water into an area by osmosis due to higher concentration of solutes
pressure is the pull from the inside

259
Q

what is blood colloid osmotic pressure?

A

force that pulls fluid back into the blood due to proteins in the blood

260
Q

what is net filtration pressure (NFP)?

A

difference between the net hydrostatic pressure (difference between blood and interstitial fluid hydrostatic pressures) and the net colloid osmotic pressure

261
Q

what is net filtration pressure typically at the arterial end?

A

14mmHg

262
Q

what does a positive value for NFP mean?

A

hydrostatic pressure pushing fluids out of blood is greater than osmotic pressure pulling fluid back into the capillaries

263
Q

How much fluid do capillaries typically reabsorb?

A

85% of the fluid that has passed into the interstitial fluid

264
Q

what is local blood flow?

A

blood delivered locally to the capillaries of a specific tissue

265
Q

the blood delivered to a specific organ is dependent upon what?

A

degree of vascularization of the tissue
local regulatory factors that alter blood flow
total blood flow

266
Q

what is angiogenesis?

A

formation of new blood vessels in tissues that require them

i.e. skeletal muscles in response to aerobic training

267
Q

what is regression?

A

return to previous state of vessels (vessels go away)

268
Q

what do vasodilators do?

A

dilate arterioles and relax precapillary sphincters

269
Q

what do vasoconstrictors do?

A

constrict arterioles and cause contraction of precapillary sphincters

270
Q

what is autoregulation?

A

tissue itself regulates or controls local blood flow in response to changing metabolic needs

271
Q

what is reactive hyperemia?

A

marked increase in blood flow when local blood flow is restored - i.e. coming back into a warm building after being in the cold - red cheeks initially

272
Q

what are short-term vasodilators?

A

histamine and bradykinin and nitric oxide

released in response to trauma, allergic reaction, infection or exercise

273
Q

what are short term vasoconstrictors?

A

prostaglandins and thromboxanes

274
Q

what hormones are vasodilators?

A

atrial natriuretic peptide (ANP)

epinephrine

275
Q

what hormones are vasoconstrictors?

A

angiotensin II
aldosterone
antidiuretic hormone (ADH)
norepinephrine

276
Q

what is total blood flow?

A

amount of blood transported throughout the entire vasculature in a given period of time
average at rest is 5.25L/min.
equal to cardiac output

277
Q

what are 3 specialized features associated with ventricles?

A

purkinje fibers are larger in diameter than other conduction fibers, so AP is spread immediately throughout ventricular myocardium - cardiac muscle cells of both ventricles contract at the same time
papillary muscles contract just before pressure increase in ventricles - pull on chordae tendineae to brace AV valves & prevent backflow of blood to atria
stimulation of ventricles begins at apex of heart

278
Q

describe the sarcolemma of cardiac muscle cells

A

Na+/K+ pumps and Na+ and K+ leak channels more Na+ outside and more K+ inside
RMP value of cardiac muscle cells is -90mV (compared to -60mV for nodal cells)
also have Ca2+ pumps that form concentration gradient with more Ca2+ outside cell than in
have fast voltage-gated Na+ channels (depolarization) and K+ voltage-gated channels (repolarization)
slow voltage-gated Ca2+ channels

279
Q

what are the electrical events as the heart contracts?

A
  1. depolarization (AP triggers opening of fast voltage-gated Na+ channels)RMP goes from -90mV to 30 mV, Na+ channels close
  2. plateau - depolarization triggers opening of voltage-gated K+ channels. slight change in MP, Ca2+ slow-voltage gated channels open. Ca2+ stimulates sarcoplasmic reticulum to release more Ca2+ (more than 80% of calcium is from SR) - K+ leaving & Ca2+ entering balance each other & stays depolarized
  3. repolarization - voltage gated Ca2+ channels close, K+ stay open, MP goes back to -90mV. allows muscle cell to propogate a new AP when cardiac muscle is stimulated again.
280
Q

what are the mechanical event as the heart contracts?

A

crossbridge cycling
Ca2+ binds to troponin to begin crossbridge cycling w/in sarcomere
closing of voltage-gated Ca2+ channels, reuptake of Ca2+ by SR & removal of Ca2+ by plasma membrane pumps cause Ca to be released from troponin –> decrease in cross bridges between thin and thick filaments, sarcomeres return to resting length as cardiac muscle cell relaxes

281
Q

what is the refractory period?

A

time between depolarization and repolarization when muscle cannot be restimulated to contract

282
Q

what is the difference in refractory period between cardiac muscle and skeletal muscles?

A

skeletal muscles can be restimulated to contract prior to complete relaxation (tetany - sustained contraction - is possible)
cardiac muscle cells have extended plateau so refractory period is longer - allows heart chambers to contract and relax without locking up - pump can continue

283
Q

what are the 3 primary sections on an electrocardiogram?

A

P wave
QRS complex
T wave

284
Q

what does the P wave reflect?

A

electrical changes of atrial depolarization that originates in the SA node (usually lasts .08-.1 second)

285
Q

what does the QRS complex represent?

A

electrical changes associated with ventricular depolarization (atria are simultaneously repolarizing, but masked by greater electrical activity of ventricles) lasts .06-.1 second

286
Q

what does the T wave represent?

A

ventricular repolarization

287
Q

what is the P-Q segment?

A

atrial plateau at the sarcolemma when cardiac muscle cells within the atria are contracting

288
Q

what is the S-T segment?

A

ventricular plateau when cardiac muscle cells in ventricle are contracting

289
Q

what is the P-R interval?

A

beginning of P wave to beginning of QRS
normally from .12-.2 seconds, time required to transmit and AP through entire conduction system
if P-R interval is longer than .2 seconds, indicate impaired conduction within ventricles – often a heart block

290
Q

what is the Q-T interval?

A

from beginning of QRS to end of T
time required for AP to occur w/in ventricles
depends on heart rate & ranges from .2-.4 seconds

291
Q

what is tachyarrhythmia?

A

fast irregular heart rate

292
Q

What is the cardiac cycle?

A

initiation of one heartbeat to the start of the next

293
Q

what is systole?

A

contraction of a heart chamber

294
Q

what is diastole?

A

relaxation of a heart chamber

295
Q

what are the events in the cardiac cycle?

A 
atrial systole
early ventricular systole
late ventricular systole
early ventricular diastole
late ventricular diastole
296
Q

what happens during atrial systole?

A

atria contract
ventricles relax
atrial pressure is greater than ventricular pressure
ventricular pressure is less than arterial trunk pressure
AV valves are open
semilunar valves are closed

297
Q

what happens during early ventricular systole?

A

atria relax
ventricles contract
ventricular pressure is greater than atrial pressure
ventricular pressure is less than arterial pressure
both sets of valves are closed

298
Q

what happens during late ventricular systole?

A

atria relax
ventricles contract
ventricular pressure is greater than atrial pressure
ventricular pressure is greater than arterial trunk pressure
AV valves closed
semilunar valves open

299
Q

what happens during early ventricular diastole?

A

atria relax
ventricles relax
ventricular pressure is greater than atrial pressure
ventricular pressure is less than arterial trunk pressure
AV valves are closed
semilunar valves close

300
Q

what happens during late ventricular diastole?

A

atria relax
ventricles relax
ventricular pressure is less than atrial pressure
ventricular pressure is less than arterial trunk pressure
AV valves open
semilunar valves closed

301
Q

what is happening in the heart just prior to atrial systole?

A

all 4 chambers are at rest
blood continues to return to right atrium through SVC and IVC & coronary sinus, and to left atrium through pulmonary veins
passive filling of ventricles is under way
AV valves are open
semilunar valves are closed

302
Q

what happens to the great veins during atrial systole?

A

openings are compressed so additional blood cannot enter atria and blood backflow cannot occur

303
Q

when is ventricular filling complete?

A

upon termination of atrial systole

304
Q

what is end-diastolic volume?

A

maximum blood volume that ventricles hold - happens at end of atrial systole
in resting adult - about 130 mL

305
Q

what initiates atrial systole?

A

SA node

306
Q

what initiates early ventricular systole?

A

purkinje fibers

307
Q

what is isovolumetric contraction?

A

happens during early ventricular systole

all valves are closed so volume of blood in ventricles remains unchanged while cardiac muscle cells are contracting

308
Q

what is stroke volume?

A

the amount of blood pumped out during ventricular systole

generally about 70 mL

309
Q

is all blood ejected from ventricles during systole?

A

no

310
Q

what is end-systolic volume? (ESV)

A

the amount of blood remaining in a ventricle at the end of systole
usually around 60mL

311
Q

what causes semilunar valves to close?

A

relaxation of ventricles allows blood to fall backward slightly within arterial trunks, pushing semilunar valves closed

312
Q

when does most ventricular filling occur?

A

during late ventricular diastole (about 70%)

313
Q

where on a ECG is atrial systole?

A

from middle of P wave to peak of QRS

314
Q

where on an EKG is early ventricular systole?

A

from peak of QRS to beginning of plateau between QRS and T wave

315
Q

where is late ventricular systole on an EKG?

A

from end of QRS (including plateau) to almost end of T wave

316
Q

where is early ventricular diastole on EKG?

A

almost end of T wave to beginning of plateau between T and P waves

317
Q

where is late ventricular diastole on ekg?

A

from beginning of plateau between P and T waves to middle of P wave

318
Q

what is cardiac output?

A

amount of blood that is pumped by a single ventricle in 1 minute (L/min).
both ventricles eject equal amounts, so either can be used

319
Q

what is heart rate?

A

number of beats per minute

320
Q

what is stroke volume?

A

volume of blood ejected per beat (mL/beat)

321
Q

what is the formula for cardiac output?

A

HR (beats/min) X SV (mL/beat) = CO (mL/min)

322
Q

what is cardiac reserve?

A

increase in cardiac output above its level at rest

CO during exercise - CO at rest = cardiac reserve

323
Q

what are normal levels of cardiac reserve?

A

in a normal healthy person, CO can increase by 4

in an athlete - can increase by 7 times

324
Q

what are factors that change the heart rate called?

A

chronotropic agents

325
Q

what are the primary external factors to increase and decrease the heart rate?

A

autonomic innervation & varying levels of some hormones

326
Q

what do external factors act on to affect heart rate?

A

SA node and AV node

327
Q

what are positive chronotropic agents?

A

cause an increase in heart rate
sympathetic nerve stimulation - norepinephrine and epinephrine
and some hormone stimulation

328
Q

what kind of agent is thyroid hormone?

A

positive chronotropic

makes nodal cells more responsive to norepinephrine and epinephrine

329
Q

what are more chronotropic agents?

A

caffeine (inhibits cAMP breakdown)
nicotine (stimulates release of norepinephrine)
cocaine (inhibits reuptake of norepinephrine)

330
Q

what are negative chronotropic agents?

A 
agents that decrease heartrate
parasympathetic innervation (axons release acetycholine which causes hyperpolarization as K+ channels open)
beta-blockers (interfere with binding of norepinephrine and epinephrine to beta receptors)
331
Q

what variables influence stroke volume?

A 
venous return
inotropic agents (external factors that alter the force of contraction of the myocardium)
afterload (resistance in arteries to the ejection of blood from the heart)
332
Q

what is preload?

A

stretch of the heart wall due to the load to which a cardiac muscle is subjected before shortening

333
Q

Starlings Law is…

A

as volume of blood entering heart increases,

334
Q

what causes venous return (preload) to increase or decrease?

A

increased by increase in venous pressure or an increase in time to fill & decreases by decrease in either of those two factors

335
Q

what are factors that change stroke volume called?

A 
inotropic agents
alter contractility (force of contraction) - usually due to change in Ca2+ available in sarcoplasm (alter number of crossbridges formed)
336
Q

what does a positive inotropic agent do?

A

increases available Ca2+, which results in formation of additional crossbridges

337
Q

what are some positive inotropic agents?

A

norepinephrine release from sympathetic axons (then epinephrine & norepinephrine release from adrenal medulla)
thyroid hormone (increases number of receptors for epinephrine)
some drugs used to treat abnormally low cardiac output

338
Q

what does a negative inotropic agent do?

A

decreases contractility by decreasing available Ca2+ so fewer crossbridges are formed

339
Q

what are some negative inotropic agents?

A 
electrolyte imbalances (increase in K+ or H+)
certain drugs that are given to decrease CO usually in an effort to treat high blood pressure
340
Q

what is afterload?

A

resistance in arteries to the ejection of blood by the ventricles
the pressure that must be exceeded before blood is ejected from chamber

341
Q

what is bradycardia?

A

persistently low resting heart rate (below 60 beats/min)

342
Q

what is tachycardia?

A

persistently high resting heart rate (above 100 beats/min)

343
Q

factors that influence heart rate

A

an increase or decrease in heart rate is dependent upon chronotropic agents that influence the conduction system - stimulate SA node to change its firing rate or the AV node to alter the amount of its delay

344
Q

factors that influence stroke volume

A

generally due to changes in the myocardium
venous return alters stretch of the heart
inotropic agents change Ca2+ levels in sarcoplasm - influence number of crossbridges which alters the force of contraction
exception is afterload - increased resistance in arteries make it more difficult for the heart to pump blood - usually only a factor as we age

345
Q

factors that influence cardiac output

A

heart rate and stroke volume influence cardiac output, so if both increase, CO increases, if both decrease, CO decreases
if they do opposite things, net effect is determined by relative change to both heart rate and stroke volume

346
Q

how is venous return correlated with stroke volume?

A

directly correlated

347
Q

how is afterload correlated with stroke volume?

A

inversely

348
Q

what is blood pressure?

A

force per unit area that blood exerts against the inside wall of a vessel

349
Q

what is blood pressure gradient?

A

change in blood pressure from one end of a blood vessel to its other end

350
Q

where is blood pressure highest?

A

in the arteries

351
Q

when is the highest blood pressure?

A

during ventricular systole when the artery is maximally stretched

352
Q

what is systolic pressure?

A

the highest blood pressure - during ventricular systole when artery is maximally stretched

353
Q

what is diastolic pressure?

A

lowest pressure - occurs during ventricular diastole when artery recoils no further

354
Q

what is the average adult blood pressure?

A

120/80 mmHg

355
Q

what is pulse pressure?

A

additional pressure on the arteries from when the heart is resting to when the heart is contracting
systolic pressure-diastolic pressure = pulse pressure

356
Q

why is pulse pressure significant?

A

measures the elasticity and recoil of arteries

357
Q

what is mean arterial pressure?

A

average measure of the blood pressure forces on the arteries
not just average though because of difference in length of time for diastolic and systolic pressure
diastolic pressure + 1/3 pulse pressure = MAP

358
Q

what is the significance of MAP?

A

provides numerical value for how well body tissues and organs are perfused.

359
Q

what is a MAP value that indicates good perfusion?

A

70-110mmHg

360
Q

is there pulse pressure in capillaries?

A

nope

361
Q

what is the blood pressure in capillaries?

A

at arterial end about 40 mmHg

at venous end, below 20 mmHg

362
Q

do veins have pulse pressure?

A

no - too far removed from pumping action of heart

363
Q

what is the pressure gradient in veins?

A

goes from 20 mmHg in venules to almost 0 mmHg by the time blood is in inferior vena cava - not enough to move blood through veins under some conditions

364
Q

how is venous return accomplished?

A

valves within veins
skeletal muscle pump
respiratory pump

365
Q

how does the skeletal muscle pump work?

A

as muscles contract, they squeeze veins & move blood, valves prevent back flow

366
Q

how does the respiratory pump work?

A

inspiration increases blood flow into thoracic veins (increased pressure in abdominal cavity as diaphragm contracts
exhalation, thoracic cavity volume decreases, pressure increases, blood moves from vessels in thoracic cavity into the heart.

367
Q

what is the MAP for a person with average blood pressure?

A

93 mmHg
diastolic pressure + 1/3 pulse pressure
because diastolic pressure lasts longer than systolic pressure

368
Q

what is the blood pressure gradient established by the beating of the heart?

A

93 mmHg

because MAP in arteries is 93, and at vena cava, it’s 0, so difference is 93

369
Q

how are changes in the blood pressure gradient related to total blood flow?

A

directly related

increase in pressure gradient = increase in total blood flow

370
Q

how can you change the steepness of the pressure gradient?

A

change cardiac output
increase in CO will increase pressure gradient
decrease in CO will decrease pressure gradient

371
Q

what is resistance?

A

amount of friction the blood experiences as it travels through the blood vessels

372
Q

what is peripheral resistance?

A

resistance of blood in the blood vessels due to contact between blood and the blood vessel wall

373
Q

what factors affect peripheral resistance?

A

blood viscosity
blood vessel length
size of the lumen of blood vessels (vessel radius)

374
Q

how would anemia affect blood viscosity?

A

it would lower the viscosity, because there would be fewer than normal erythrocytes, so blood would have less resistance to flow

375
Q

what is the main way resistance in vessels is regulated?

A

altering vessel lumen radius

376
Q

how does radius influence resistance?

A

blood flows fastest in the middle, and slowest near the vessel walls. flow is directly proportional to the fourth power of a radius

377
Q

what is atherosclerosis?

A

a disease process where a plaque narrows the lumen of blood vessels

378
Q

how is blood flow related to pressure gradient and resistance?

A

blood flow is proportional to pressure gradient (P1-P2)/resistance

379
Q

what increases blood resistance?

A

increase in blood viscosity
increase in blood vessel length
decrease in vessel lumen diameter

380
Q

what happens to individuals with sustained increased resistance (that accompanies significant weight gain or with atherosclerosis?

A

generally exhibit elevated arterial blood pressure readings

greater blood pressure gradient must be produced to overcome higher resistance

381
Q

what is blood pressure dependent upon?

A

cardiac output
resistance
blood volume

382
Q

how does short-term regulation of blood pressure occur?

A

through autonomic reflexes involving nuclei within medulla oblongata

383
Q

which groups of autonomic nuclei in the medulla oblongata participate in the regulation of blood pressure?

A

cardiac center
vasomotor center
collectively called the cardiovascular center

384
Q

what regulatory nuclei are housed in the cardiac center?

A

cardioacceleratory center and the cardioinhibitory center

385
Q

how does sympathetic pathways affect the cardiac center?

A

extend from cardioacceleratory center to both SA node and to myocardium.
increases heart rate and force of contraction –> increasing cardiac output

386
Q

how do parasympathetic pathways affect cardiac center

A

parasympathetic division pathways extend from cardioinhibitory center to SA node and AV node –> decreases heart rate and slows conduction of electrical signals through the heart’s conducting system - decreasing cardiac output

387
Q

how does sympathetic division pathways affect vasomotor center?

A

extend from vasomotor center to blood vessels
blood vessels with alpha receptors contract –> vasoconstriction (most vessels of the body)
blood vessels with beta receptors relax in response to epinephrine –> vasodilation (skeletal muscles and coronary vessels)
sympathetic stimulation constricts blood vessels with alpha receptors and epinephrine dilates blood vessels with beta receptors

388
Q

what does activation of the vaso motor center and increased nerve signals along sympathetic pathway cause?

A

increased peripheral resistance (more vessels stimulated to constrict rather than dilate - raising blood pressure)
larger circulating blood volume (constriction of veins shifts blood from venous reservoirs & circulating blood volume increases, increasing blood pressure)
redistribution of blood flow (more blood flow reaches skeletal muscles & heart, less goes to other structures)

389
Q

what are baroreceptors?

A

specialized sensory nerve endings that respond to stretch in blood vessel walls

390
Q

what are the 2 main baroreceptors for the cardiovascular system?

A

aortic arch baroreceptors

carotid sinuses

391
Q

where are aortic arch baroreceptors located?

A

in the tunica externa of the aortic arch

transmit nerve signals to cardiovascular center through vagus nerve (CN X) - regulate systemic blood pressure

392
Q

where are carotid sinuses located?

A

baroreceptors located in tunica externa of each internal carotid artery - each one transmits nerve signals back to cardiovascular center through glossopharyngeal nerve (CN IX). monitor changes in pressure of head & neck
more sensitive to blood pressure changes than baroreceptors in aortic arch

393
Q

what happens to baroreceptor reflexes if blood pressure decreases?

A

decreased stretch in blood vessel wall is detected by either or both baroreceptors
2. decrease their firing rate along sensory neurons (w/in vagus and glossopharyngeal nerves that extend to cardiac center and vasomotor center)
3.cardioacceleratory center increases nerve signals along sympathetic pathways. SA node increases firing rate, myocardium contracts with greater force
cardioinhibitory center decreases nerve signals along parasympathetic pathways - heart rate and stroke volume increase —> greater cardiac output
4. vasomotor center increases nerve signals along sympathetic pathways to blood vessels, net vasoconstriction, increase in peripheral resistance, shifting of blood from venous reservoirs
increase CO
increase resistance
larger circulating blood volume
quickly elevate blood pressure to maintain sufficient blood pressure to move blood through vasculature

394
Q

what happens to baroreceptor reflexes if blood pressure increases?

A
  1. increased stretch in blood vessel wall detected by baroreceptors in carotid sinues, and/or aortic arch
  2. increase firing rate to both components of cardiovascular center in brainstem
  3. cardioacceleratory center decreases nerve signals along sympathetic pathways to the SA node (slow down heart rate) and myocardium (decrease stroke volume). cardio inhibitory center increases nerve signals along parasympathetic pathway to slow SA node firing rate and AV node to delay nerve signals —> heart rate & stroke volume decrease, CO decreases
  4. vasomotor center decreases nerve signals along sympathetic pathways to blood vessels –> net vasodilation & decrease in resistance, shifting of blood to venous reservoirs
    decrease in cardiac output
    decrease in resistance
    smaller circulating blood volume
    lower blood pressure
    blood flow returns to resting levels
395
Q

are baroreceptors short or long term pressure regulators?

A

short term

396
Q

what do chemoreceptor reflexes do?

A

negative feedback loops that bring blood chemistry levels back to normal - stimulate chemoreceptor reflexes

397
Q

what are the 2 main peripheral chemoreceptors?

A

aortic bodies and carotid body
aortic bodies are in arch of aorta
carotid body is w/in each external carotid artery

398
Q

what stimulates chemoreceptors?

A

high CO2 levels, low pH, very low O2 levels

399
Q

what happens when chemoreceptors are stimulated?

A

their increased firing stimulates vasomotor center
vasomotor center responds by increasing nerve signals along sympathetic pathways to blood vessels - increase resistance and shifts blood from venous reservoirs to increase venous return.
raises blood pressure
increases blood flow
including blood flow to lungs - change in respiratory gas exchange & return to blood gas normal levels

400
Q

how do higher brain centers affect blood pressure?

A

increased body temp, fight or flight response - hypothalamus increases cardiac output & resistance

401
Q

how does the renin-angiotensin system affect blood pressure?

A

renin (enzyme) is released by kidney in response to low blood pressure - initiates enzymatic chemical reactions w/in blood that ultimately help raise blood pressure
angiotensin II powerful vasoconstrictor
increases peripheral resistance
stimulates thirst center - fluid intake increases blood volume
decreases urine formation
stimulates other hormones (aldosterone & antidiuretic hormone)

402
Q

how does aldosterone affect blood pressure?

A

released from adrenal cortex in response to angiotensin II & other stimuli
increases absorption of Na+ ion & water in kidneys, decreasing loss of uring, helps maintaining blood volume & pressure

403
Q

how does antidiuretic hormone (ADH) affect blood pressure?

A 
released from posterior pituitary in response to nerve signals from hypothalamus due to increased concentration of blood or stimulation of hypothalamus by antiogensin II.
ADH increases absorption of water by kidneys, decreases loss of urine, maintains blood volume & pressure
stimulates thirst center (more fluid intake = more blood volume)
causes vasoconstriction (vasopressin)
404
Q

how does atrial natriuretic peptide affect blood pressure?

A

released from atrium of heart in response to increase in stretch of atrial walls due to increased blood volume & increased venous return - stimulates vasodilation, decreases peripheral resistance, increases urine output, decreases blood volume, decrease in blood pressure

405
Q

what is blood flow velocity?

A

rate of blood transported per unit time (mL/min)

406
Q

what is the relationship of total cross-sectional area and velocity of blood flow?

A

the greater the total cross-sectional area, the slower the blood flow. capillaries have the greatest cross-sectional area & slowest blood flow

407
Q

how does cardiac output change with exercise?

A

at rest, it is about 5.25 L/min
during strenuous exercise - 17.5 L/min
more blood goes to heart, skeletal muscles & skin, less to abdominal organs, kidneys & other less metabolically active tissues

408
Q

what is the general arterial flow out of the left side of the heart?

A

oxygenated blood goes out the left ventricle enters ascending aorta
left & right coronary arteries emerge from wall of ascending aorta & supply heart wall
ascending aorta curves toward left side of the body & becomes aortic arch

409
Q

what are the 3 main arterial branches emerging from the aortic arch?

A
  1. brachiocephalic trunk –> bifurcates into right common carotid artery (supplying right side of head & neck) and right subclavian artery (supplying right upper limb & some thoracic structures)
  2. left common carotid artery - supplies left side of head & neck
  3. left subclavian artery - supplies left upper limb and some thoracic structures
410
Q

what happens after the aortic arch?

A

projects inferiorly & becomes descending thoracic aorta
becomes descending abdominal aorta as it extends inferiorly through diaphragm
at level of 4th lumbar vertebra, descending abdominal aorta bifurcates into left and right common iliac arteries
each further divides into internal iliac artery (to supply pelvic and perineal structures) and an external iliac artery (to supply lower limb)

411
Q

what 3 vessels return blood to the right atrium of the heart?

A

superior vena cava
inferior vena cava
coronary sinus

412
Q

what happens to veins that drain head, neck, upper limbs, thoracic and abdominal walls?

A

merge to form the left & right brachiocephalic veins which merge to form superior vena cava

413
Q

what happens to veins inferior to the diaphragm?

A

merge to form inferior vena cava

414
Q

what does the inferior vena cava do?

A

carries venous blood toward heart from lower limbs, pelvis and perineum, & abdominal structures.

415
Q

where is the inferior vena cava?

A

lies to the right side of the descending abdominal aorta

416
Q

what supplies most of the blood to head & neck?

A

common carotid arteries

417
Q

what do common carotid arteries become?

A

external carotid artery (supplies structures external to the skull)
internal carotid artery (supplies internal skull structures)

418
Q

what is the difference between a cat aorta and a human aorta?

A

humans have 3 branches off aortic arch (brachiocephalic, left common carotid, subclavian artery), cats have straighter aorta & major branches are left subclavian and brachiocephalic trunk - brachiocephalic trunk divides into right subclavian and common carotid arteries (2(

419
Q

what is the difference between origin of internal and external iliac arteries in cats & humans?

A

in humans, aorta branches into right and left common iliac arteries, then continues to external iliac arteries. internal iliac arteris are first to branch off the iliac arteries. In cat, abdominal aorta branches into right & left external iliac arteries & has 3rd branch that forma median sacral artery. off of the median sacral artery are the left & right internal iliac arteries

420
Q

name arteries from heart to thumb

A

aortic trunk to aortic arch to brachiocephalic trunk to right subclavian artery to axillary artery to brachial artery to radial artery to digital arteries

421
Q

arteries from heart to pinky

A

aortic trunk to aortic arch to brachiocephalic trunk to right subclavian artery to axillary artery to brachial artery to ulnar artery to digital arteries

422
Q

veins from thumb to heart (deep)

A

digital veins to radial veins to brachial veins to axillary vein to subclavian vein to brachiocephalic vein to superior vena cava

423
Q

superficial veins from hand to heart

A

dorsal venous network to basilic vein (medially) or cephalic vein (laterally) to median cubital vein to basilic vein to axillary vein to subclavian vein to brachiocephalic vein to superior vena cava

424
Q

heart to foot

A

aortic arch to descending aorta to descending abdominal aorta to left or right common iliac artery to external iliac artery to femoral artery to popliteal artery to posterior tibial artery to lateral plantar artery to plantar arterial arch to digital arteries

425
Q

foot to heart

A

digital veins to medial plantar veins to posterior tibial veins to popliteal vein to femoral vein to external iliac vein to common iliac vein to inferior vena cava

426
Q

what is the pathway of blood circulation in a fetus?

A
  1. oxygenated blood from placenta enters through umbilical vein
  2. blood is shunted away from liver and directly toward inferior vena cava through ductus venous
  3. oxygenated blood in ductus venosus mixes with deoxygenated blood in inferior vena cava
  4. blood from superior and inferior vena cavae empties into right atrium
  5. pressure is greater on right side of heart, so most of blood is shunted from right atrium to left atrium via foramen ovale, blood flows into left ventricle & is pumped out through aorta
  6. small amount of blood enters right ventricle and pulmonary trunk but shunted from pulmonary trunk to aorta through ductus arterioles
  7. blood travels to the rest of the body, deoxygenated blood returns to placenta through umbilical arteries
  8. nutrient and gas exchange occurs at the placenta & cycle repeats

a&p (5 decks)

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