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A&P > Chapter 18 > Flashcards

Chapter 18 Flashcards

1
Q

Where is the heart located and describe its position?

A
  1. ventral, thoracic, mediastinum, pericardial cavity
  2. apex points to left hip and base to right shoulder
  3. two thirds lies left of the midsternal line, between ribs 2 and 5
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2
Q

What is membrane that closes the heart and has 3 layers?

A

pericardium

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3
Q

What is the pericardium made up of?

A
  1. fibrous pericardium
  2. parietal layer
  3. visceral layer (epicardium)
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4
Q

What is the function of the fibrous pericardium?

A

protects, anchors, and prevents overfilling

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5
Q

What is the function of the parietal layer?

A

lines the internal surface of the fibrous pericardium

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6
Q

What do both parietal and visceral layers produce?

A

lubricating serous fluid

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7
Q

What is the purpose of the lubricating serous fluid?

A

reduces fluid

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8
Q

What are the 3 layers of the heart wall?

A
  1. epicardium
  2. myocardium
  3. endocardium
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9
Q

What type of tissue is the epicardium made up of?

A

squamous epithelium and connective tissue

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10
Q

What does epicardium contain?

A

blood, lymph and nerve supply

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11
Q

What is the function of the epicardium?

A

reduces friction

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12
Q

What is the myocardium made up of?

A

spiral bundles of cardiac muscle cells

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13
Q

The myocardium is a fibrous network of collagen and elastin fibers. Name 3 purposes they have.

A
  1. anchors cardiac muscle fibers
  2. supports great vessels and valves
  3. limits spread of action potentials to specific paths
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14
Q

What is the main function of myocardium?

A

pumps blood throughout the body

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15
Q

What is the innermost layer of the heart wall?

A

endocardium

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16
Q

What is the main function of the endocardium?

A

friction free surface for blood to flow over

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17
Q

What do the surface grooves of the heart carry?

A

coronary blood vessels to heart wall

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18
Q

Name the 3 surface grooves.

A
  1. atrioventricular sulcus

2. anterior & posterior interventricular sulcus

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19
Q

Describe the two walls of the atria and what is their function.

A

ridged by pectinate muscles

function: receiving chambers

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20
Q

When the blood is received in a chamber describe how the blood is moved into the ventricles.

A

30% pumped and 70% passive movement

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21
Q

What are the purpose of the auricles?

A

increase atrial volume

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22
Q

Name the 3 vessels that enter the right atrium.

A

superior and inferior vena cava, coronary sinus

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23
Q

Name the 2 vessels that enter the left atrium.

A

right and left pulmonary veins

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24
Q

What do the right and left pulmonary veins carry?

A

oxygenated blood

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25
Q

What is the function of the two ventricles?

A

discharging chambers

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26
Q

What are the two ventricles separated by?

A

interventricular septum

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27
Q

What comprises most of the heart?

A

right and left ventricles

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28
Q

What muscle anchors the chrodae tendonae of valves?

A

papillary muscles

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29
Q

What forms the ridges in the ventrical walls?

A

trabeculae carnae

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30
Q

Describe the function of the left ventricle

A

receives oxygenated blood from pulmonary veins

pumps blood through aorta to systemic unit

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31
Q

Describe the function of the right ventricle.

A

receives deoxygenated blood from vena cava

pumps blood through pulmonary trunk to pulmonary circuit

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32
Q

Do both left and right sides pump the same volume of blood?

A

yes

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33
Q

Describe the pulmonary circuit

A

short, low pressure circulation

moves blood to and from the lungs for gas exchange between air and blood

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34
Q

Name the 9 steps of the pulmonary circuit

A
  1. right ventricle
  2. pulmonary semilunar valve
  3. pulmonary trunk
  4. pulmonary arteries
  5. capillaries of lungs
  6. pulmonary veins
  7. left atrium
  8. left AV valve
  9. left ventricle
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35
Q

Describe the systemic unit

A

long, high pressure circuit

moves oxygenated blood to and from tissue for gas exchange between blood and tissue cells

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36
Q

Name the 10 steps of the systemic unit

A
  1. left ventricle
  2. aortic semilunar valve
  3. aorta
  4. systemic arteries
  5. tissue capillary beds
  6. systemic veins
  7. vena cava
  8. right atrium
  9. right AV valve
  10. right ventricle
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37
Q

What is the coronary circuit?

A

function blood supply to the heart muscles itself

muscle has high ATP demand

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38
Q

What does the coronary circuit contain many of?

A

junctions (anastomoses)

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39
Q

Name the 5 coronary arteries

A

right and left cononary, marginal, circumflex, anterior interventricular arteries

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40
Q

Name the 3 coronary veins

A

small cardiac, anterior cardiac, great cardiac veins

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41
Q

What are two hoemostatic imbalances of coronary circulation?

A 
angina pectoris
myocardial infarction (heart attack)
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42
Q

What is agina pectoris

A

acute thoracic pain caused by temporary blockage in blood supply to the myocardium

temporary lack of O2 weakens cells

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43
Q

What is myocardial infarction

A

heart attack

proglonged coronary blockage -> prolonged lack O2 -> cells die -> repaired with non contractile scar tissue

if cells do not repair and all die = death

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44
Q

What is the purpose of a heart valve?

A

ensures one way direction of blood flow through the heart

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45
Q

What instigates the opening and closing of of the heart valves

A

changes in blood pressure

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46
Q

Name the 4 valves of the heart

A

left and right atrioventricular valves

left and right semilunar valves

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47
Q

What are the other names for the right and left atrioventricular valves?

A 
right = tricuspid
left = bicuspid (mitral)
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48
Q

What is the function of the right AV valve?

A

prevents back flow into the right atrium when the right ventricle contracts

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49
Q

What is the function of the left AV valve?

A

prevents back flow into the left atrium when the left ventricle contracts

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50
Q

What is the function of the chordae tendinae?

A

anchors the AV valve cusps to papillary muscles and prevents flaps from being blown into the atria during ventricular contraction

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51
Q

What is the function of the papillary muscles?

A

contracts just before ventricles to take up the slack in the chordae tendonae and prevent the valves from being pushed open backwards into the atria

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52
Q

What is the function of the semilunar valves?

A

to prevent back flow into the ventricles when the ventricle relaxes.

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53
Q

Name the two semilunar valves?

A

right pulmonary SL valve

left aortic SL valve

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54
Q

What does the lub dub pause sound represent

A

closing of heart valves

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55
Q

What does the 1st sound in the heart beat represent

A

closing of AV valves - start of ventricular contraction (systole)

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56
Q

What does the 2nd sound in the heart beat represent

A

closing of the SL valves - start of ventricular relaxation (diastole)

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57
Q

What are heart murmurs

A

abnormal heart sounds representing valve problems

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58
Q

What is auscultation

A

listening to heart sounds - valves closing

can clost a sightly different times
LAV closes before RAV
Aortic SL closes before pulmonary SL

59
Q

What are two homeostatic imbalances in valve function

A
  1. leaky valves - produce murmurs

2. stenosis - narrowing of valves - impedes flow - caused by stiffening of valve flap

60
Q

Describe the cardiac muscle cell

A

striated, short, fat, branched, uninucleate and interconnected by intercalated discs

61
Q

What connects the fibrous skeleton in the muscles cells?

A

connective tissue matrix (endomysium)

62
Q

What is the difference between sarcoplasmic reticulum and t-tubules in cardiac muscle vs. skeletal muscle?

A

in cardiac muscle t-tubles are wide but less numerous and sarcoplasmic reticulum is simpler than in skeletal muscles

63
Q

What makes up 25-35% of the cardiac muscle cell volume?

A

mitochondria

64
Q

What is the difference in the sarcomere between the cardiac and skeletal muscle?

A

they are more irregular in the cardiac muscle

65
Q

What are intercalated discs?

A

junctions between cells

66
Q

What do the intercalated discs contain and what is their function?

A

desmosomes - hold cells together during contraction

gap junctions - ions can pass quickly from cell to cell

67
Q

What does it mean when they say a heart behaves as a functional syncytium unit?

A

contracts as a single unit

68
Q

Describe the physiology and events of contraction in the heart

A

1% made up of pacemaker cells

99% made up of pumping cells (contractile)

gap junctions ensure heart contracts as a single unit

long refractory period enables pumping

69
Q

Describe the process of the pacemaker cells

A
  • > specialized cardiac cells initiate impulses, ensuring heart depolarizes in an orderly fashion
  • > autorhythmic cells have an unstable resting potential that continuously depolarize (pacemaker potential)
  • > slow depolarization from -60mv (resting potential) to -40mv (threshold) happens due to slow sodium channels opening
  • > once -40mv reached fast calcium gates open and calcium rushes in
  • > membrane continues depolarization until an action potential is generated
  • > calcium gates shut and potassium gates open and potassium leaves the cell and repolarization occurs
  • > action potential is transmitted to rest of myocardium via intrinsic conduction system
  • > heart contracts; first the atria then the ventricles
70
Q

What is the intrinsic conduction system

A
  • > coordinates and synchronizes heart activity

- > causes heart to beat faster, without it impulses would move much slower and contraction would not be synchronous

71
Q

Name the 5 autorhythmic cardiac cells in order of impulse transfer

A
  1. Sinoatrial SA Node - primary pacemaker
  2. internodal pathway to…
  3. AV Node node
  4. AV bundle
  5. right and left bundle branches
  6. purkinje fibers
72
Q

What is the rate called that the SA node sets and how fast?

A

sinus rhythm at about 75 bpm

73
Q

Why does the SA node set the pace for the heart?

A

because no other region of the conduction system of the myocardium has a faster depolarization rate

74
Q

Describe the AV node… what makes it delay impulses and for how long, depolarization rates, fibers and junctions

A

smaller diameter fibers and fewer gap junctions

depolarizes at about 60 x per minute and delays impulse approx 0.1 second

75
Q

What is the rhythm called in the AV node?

A

junctional rhythm

76
Q

What is the function of the AV bundle? Where does it branch into? What else can it be called?

A

connects the atria to the ventricle - is the only electrical connection between them

branches into the purkinje fibers

bundle of His

77
Q

What are the right and left bundle branches?

A

two pathways in the interventricular septum that carry the impulses toward to apex of the heart

78
Q

What is the function of the purkinje fibers? how fast do they depolarize?

A

complete the pathway into the apex and ventricular walls

depolarize only 30 x per minute

79
Q

Name the sequence of stimulation and contraction in the intrinsic conduction system

A
  • > SA node develops pacemaker potential
  • > transmitted to walls of atria
  • > atria begin to contract
  • > impulse delayed at AV node - atria completes contraction
  • > impulse transmitted from AV node to walls of ventricles
  • > ventricles contract
  • > produces normal sinus rhythm
80
Q

What are arrythmias?

A

irregular heart rhythms

81
Q

What is fibrillation?

A

rapid, irregular contractions; useless for pumping blood

82
Q

What would happen if the SA node became defective?

A

the AV node would take over and would result in a junctional rhythm of 40-60 bpm.

“Ectopic focus” = abnormal pacemaker takes over

83
Q

What would a defective AV node result in?

A

partial or total heart block

  • > few or no impulses from the SA node would reach the ventricles
  • > ventricles would beat at different rate from atria
84
Q

What is the result of too much coffee or nicotine?

A

premature ventricular contraction - extra systole

85
Q

Describe what happens when initially the membrane is polarized (contraction of contractile cells)

A
  • > inside is more negative than outside
  • > potential difference is maintained by active transport pumps
  • > sodium is pumped out and potassium is pumped in
  • > both ions are positively charged but more sodium is outside than potassium inside
86
Q

Describe what happens in an action potential from the pacemaker cells to the contractile cells.

A
  • > sodium gates open, sodium rushes into cell, positive feedback, depolarization
  • > fast calcium gates open, calcium enters cell, triggers opening of slow calcium gates in SR
  • > sodium gates shut, SR releases calcium into cell
  • > calcium binds to troponin
  • > crossbridges form, myofilaments slide, etc = contraction
  • > slow calcium gates stay open, keeps calcium high, prolongs contraction, depolarization plateau
  • > potassium gates open, potassium moves out of cell = repolarization
  • > long absolute refractory period - maintained by slow calcium gates, prevents tetany
87
Q

Where is calcium store in the cardiac muscle vs. the skeletal muscle?

A

calcium is stored in the SR and outside the cell

88
Q

Name 3 things the heart depends on

A
  1. aerobic respiration for adequate ATP
  2. good supply of oxygen and fuel
  3. adequate blood supply
89
Q

What is ischemia?

A

blockage of coronary arteries that leads to deficient O2 supply to the myocardium

90
Q

In terms of fuel what is the limiting factor for the heart?

A

oxygen supply = limiting factor

can use glucose, fatty acids, lactic acid - whatever is available

91
Q

What is an ECG

A

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

92
Q

What are the three deflection waves and what do they represent

A

P wave = depolarization of Atria

QRS complex = depolarization of ventricles

T wave = repolarization of ventricles

93
Q

Describe the 3 segments of the ECG

A

PR interval = beginning of atrial excitation to beginning of ventricular excitation

ST segment = complete depolarization of ventricular myocardium

QT interval = beginning of ventricular depolarization to repolarization

94
Q

What is contraction of atria triggered by?

A

depolarization of SA node

95
Q

What is contraction of ventricles triggered by?

A

purkinje fibers

96
Q

How is the cardiac cycle described?

A

all events associated with blood flow through the heart during one complete heartbeat

97
Q

What are contraction and relaxation called?

A

systole = contraction

diastole = relaxation

98
Q

What are the four phases of the cardiac cycle?

A
  1. ventricular filling
  2. ventricular systole
  3. isovolumetric relaxation
  4. quiescent period
99
Q

When does ventricular filling take place?

A

mid to late diastole

100
Q

What happens during ventricular filling?

A
  1. AV valves are open
  2. 70% of blood passively flows into ventricles
  3. 30% of blood is pumped in during atrial systole
  4. EDV (end diastolic volume) occurs: volume of blood in each ventricle at end of ventricular diastole
101
Q

What happens during ventricular systole?

A
  1. atria relax and ventricles begin to contract
  2. rising ventricular pressure results in closing of AV valves
  3. isovolumetric contraction phase - all valves are closed
  4. ejection phase, ventricular pressure exceeds pressure in the large arteries forcing SL valves open
  5. ESV (end systolic volume): volume of blood left in ventricles
102
Q

What happens during isovolumetric relaxation?

A
  1. ventricles relax
  2. backflow of blood in aorta and pulmonary trunk closes SL valves and causes dicrotic notch (brief rise in aortic pressure)
103
Q

What happens during the quiescent period? How long is it?

A

both atria and ventricles are relaxed - lasts for 0.4 sec

104
Q

What is the length of the cardiac cycle with a heart rate of 75bpm?

A

atrial systole: 0.1 sec

ventricular systole: 0.3 sec

quiescent: 0.4 sec

Total: 0.8 sec

105
Q

What is cardiac output?

A

volume of blood pumped by each ventricle in 1 minute

106
Q

What is cardiac output the product of?

A

heart rate and stroke volume

107
Q

define HR, SV and CO

A

heart rate = number of beats per min

stroke volume = volume of blood pumped by one ventricle with each beat

cardiac output = HR x SV

108
Q

At rest what is the average CO?

A

HR 75 bpm x SV 70 ml/beat = CO 5.25 L/min

109
Q

What is cardiac reserve?

A

the difference between maximal CO and resting CO

110
Q

What can maximal CO reach in a trained athlete?

A

35 L/min

111
Q

What is the formula to determine the regulation of stroke volume?

A

SV = EDV - ESV

112
Q

What is EDV?

A

end diastolic volume = maximum volume in the ventricle prior to contraction

113
Q

What is ESV?

A

end systolic volume = volume left in ventricle at the end of a contraction

114
Q

What are the 3 factors affecting SV?

A

Preload

Contractility

Afterload

115
Q

What is preload?

A

the degree of stretch of cardiac muscle cells before they contract

116
Q

What is the Frank-Starling law of the heart

A

the more the heart stretches prior to contraction the harder it will contract

greater the EDV, the greater the force of the contraction

117
Q

What is EDV increased and decreased by?

A

increased: slower heart beat and excercise (increases venous return)
decreased: rapid heart rate and decreased blood volume (eg. blood loss, dehydration)

118
Q

What is contractility?

A

increase in force of contraction independent of muscle stretch and EDV

119
Q

What is contractility caused by?

A

more calcium ions from SR and extracellular fluid: more cross bridges form and more complete ejection of blood increasing SV

120
Q

What increase and decrease contractility?

A

positive inotropic agents and negative inotropic agents

121
Q

What does the sympathetic system release that is a positive inotropic agent?

A

norepinephrine

122
Q

What are a few negative inotropic agents?

A

acidosis increased hydrogen

increased extracellular potassium ions

drugs called calcium channel blockers

123
Q

What is afterload?

A

pressure that must be overcome for ventricles to eject blood

back pressure that arterial blood exerts making it harder for ventricles to empty

124
Q

What is afterload caused by?

A

hypertension

125
Q

What are the factors called that regulate heart rate? and describe

A

positive chronotropic = factors that increase HR

negative chronotropic = factors that decrease HR

126
Q

What is the heart rate modified by?

A

Autonomic Nervous System Regulation (ANS)

127
Q

Where are the cardiac centres located, what are they called and describe.

A

located in medulla oblongata

cardioacceleratory centre = innervates SA and AV nodes, heart muscle and coronary arteries thru sympathetic neurons

cardioinhibitory centre = inhibits SA and AV nodes thru parasympathetic fibers in the vagus nerves

128
Q

What is the sympathetic nervous system activated by and describe

A

activated by emotional or physical stressors “fight or flight”

positive chronotype = increases HR

mediated by norephinephrine = stimulates SA node

129
Q

What is the parasympathetic system and describe

A

opposes the sympathetic effects

negative chronotype = slows heart rate

mediated by acetycholine = inhibits SA node

130
Q

What do the vagus nerves do and what happens if these nerves are cut?

A

carries parasympathetic fibers to the heart

if vagus nerves cut would increase about 25 bpm

131
Q

What are baroreceptors called? and what do they do?

A

atrial bainbridge reflex

stretching of atrial walls stimulates SA node and sympathetic reflexes

increase venous return -> increase atrial pressure -> stimulates stretch receptors -> sympathetic nervous system -> increase HR and force of contraction

132
Q

How does epinephrine regulate heart rate? and where does it come from?

A

enhances heart rate and contractility

comes from adrenal medulla

133
Q

How does thyroxine regulate heart rate?

A

increases heart rate and enhances effects of norepinephrine and epinephrine

134
Q

What effects to hypercalcemia and hypocalcemia have on the heart?

A

hypercalcemia = increase HR

hypocalcemia = decrease HR

135
Q

What effects to hyperkalemia and hypokalemia have on the heart?

A

hyperkalemia - leads to heart bloc and arrest

hypokalemia - feeble heart rate

136
Q

What effect does hypernatremia have on the heart?

A

decreased HR

137
Q

Name 4 other factors that can influence heart rate?

A

age, gender, exercise, body temperature

138
Q

What is tachycardia?

A

abnormally fast heart rate

may lead to fibrillation; decreases venous return -> decreased CO

139
Q

What is bradycardia?

A

heart rate lower than 60 bpm

inadequate blood circulation

140
Q

What is congestive heart failure?

A

progressive condition where CO is so low that blood circulation cannot meet tissue needs

141
Q

What are four factors that cause congestive heart failure? and describe

A
  1. coronary atherosclerosis - blockage of arteries with fatty deposits
  2. persistent high blood pressure - weakens heart; heart has to pump against greater resistance
  3. multiple myocardial infarcts - contractile cells replaced by scar tissue
  4. dilated cardiomyopathy - flabby ventricles; ventricles enlarge but lose the ability to contract
142
Q

What does left sided heart failure cause?

A

pulmonary congestion

blood accumulates around lungs and fluid leaks into lungs

143
Q

What does right sided heart failure cause?

A

system congestion - edema

blood accumulates in extremities; fluid leaks into interstitial spaces in tissues

A&P (11 decks)

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