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From Flashcardlet > 2 A&P Chapter 18 > Flashcards

2 A&P Chapter 18 Flashcards

1
Q

How does the cardiovascular system act like a transport system?

A

It provides the supply of nutrients and prevents the build up of wastes in the body

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2
Q

What role does the heart play in the CV system?

A

It is the transport system’s pump

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3
Q

What role do the blood vessels play in the CV system?

A

They are the delivery routes

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4
Q

What does the right side of the heart receive?

A

Oxygen poor blood from tissues

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5
Q

What does the right side of the heart pump?

A

It pumps blood to the lungs to get oxygen and expel CO2

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6
Q

What does the left side of the heart receive?

A

Oxygen rich blood from the lungs

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7
Q

What does the left side of the heart pump?

A

It pumps blood through the body to supply oxygen and nutrients to tissues

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8
Q

Which atrium and ventricle receive and pump from the pulmonary circuit?

A

Left atrium receives, right ventricle pumps

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9
Q

Which atrium and ventricle receive and pump from the systemic circuit?

A

Right atrium receives, left ventricle pumps

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10
Q

What are the steps to the total heart circuit?

A 
SVC. IVC, CS
RA
Tricuspid
RV
Pulmonary valve
Pulmonary trunk
R and L pulmonary arteries
Pulmonary capillary beds
4 Pulmonary veins
LA
Bicuspid
LV
Aortic valve
Aorta
Great vessels
Systemic arteries
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11
Q

Where is the base of the heart and what body structure does it direct towards?

A

It is superior to the apex and it is directed towards the right shoulder

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12
Q

Where is the apex of the heart and what body structure does it direct towards?

A

Inferior to the base and it directs towards the left hip

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13
Q

Where is the point of maximal intensity?

A

Between the 5th and 6th ribs

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14
Q

Where is the heart located?

A

Between the 2nd and 5th ribs, 2/3 to the left of the sternum

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15
Q

How large is the heart?

A

The size of a fist

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16
Q

What shape is the heart?

A

Cone shaped

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17
Q

What is the weight of the heart?

A

250-350 g

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18
Q

What is the mediastinum?

A

The medial cavity of the thoax

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19
Q

Where is the apical impulse?

A

Between the 5th and 6th ribs below the left nipple

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20
Q

What do you feel when you palpate the apical pulse?

A

The beat of the heart’s apex where it touches the chest

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21
Q

What is the fibrous skeleton?

A

The site for anchoring cardiac muscle, support for great vessels, and an insulator (does not conduct electrically excitable impulses)

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22
Q

What is the pericardium?

A

The double walled sac enclosing the heart

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23
Q

What is the fibrous pericardium?

A

The loosely fitting superficial part, made of dense irregular CT

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24
Q

What are the three functions of the fibrous pericardium?

A
  1. Protect the heart
  2. Anchor the heart to surrounding structures
  3. Prevent the heart from overfilling with blood
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25
Q

What is the serous pericardium?

A

The deeper, thin, slippery, two layers

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26
Q

What are the two layers of the serous pericardium?

A

Visceral and parietal

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27
Q

What is the parietal layer of the serous pericardium?

A

The internal surface the attaches to large arteries exiting the heart

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28
Q

What is the visceral layer of the serous pericardium?

A

The outermost layer of the heart, also part of the heart wall

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29
Q

What is another name for the visceral layer of the serous pericardium?

A

Epicardium

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30
Q

How do the serous and parietal layers continue with one another?

A

The parietal layer folds over and continues over the external surface of the heart as the visceral layer

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31
Q

What are the two parts of the pericardium?

A

Fibrous and serous

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32
Q

How is the myocardium arranged?

A

Spiral or circular

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33
Q

What is the pericardial cavity?

A

Located between the parietal and visceral layers, containing a film of serous fluid

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34
Q

Why are the serous membranes lubricated with fluid?

A

So that the heart can work without friction

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35
Q

What is pericarditis?

A

Inflammation of the pericardium roughens the serous membrane surface, so as the heart beats, it rubs against the sac and creates a creaking sound

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36
Q

What two conditions can result from pericarditis?

A

Adhesions and cardiac tamponade

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37
Q

Why does pericarditis cause adhesions?

A

The visceral and parietal membranes begin to stick to one another and impede heart activity

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38
Q

Why does pericarditis cause cardiac tamponade?

A

Fluid seeps into the cavity and compresses the heart, limiting the ability to pump

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39
Q

What are the layers of the heart?

A
  1. Fibrous pericardium
  2. Parietal layer of serous pericardium
  3. Pericardial cavity
  4. Visceral layer of serous pericardium/epicardium
  5. Myocardium
  6. Endocardium
  7. Heart chamber
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40
Q

What layers include the heart wall?

A

Epicardium, myocardium, and endocardium

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41
Q

What is the myocardium?

A

Composed of cardiac muscle, forming the bulk of the heart

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42
Q

Which layer of the heart contracts?

A

Myocardium

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43
Q

What is the cardiac skeleton?

A

CT fibers form a dense web that reinforces the myocardium and anchors the muscle fibers

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44
Q

Is the cardiac skeleton electrically excitable? Why or why not?

A

No, it limits the spread of action potentials to specific pathways in the heart

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45
Q

What is the endocardium?

A

The white sheet of simple squamous epithelium that rests on the thin CT layer

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46
Q

What does the endocardium line?

A

Lines the valves and the chambers

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47
Q

What is the endocardium immediately adjacent to?

A

The heart chambers

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48
Q

What is the endocardium continuous with?

A

Linings of the blood vessels leaving and entering the heart

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49
Q

What is the intertribal septum?

A

Divides the heart longitudinally, separates the atria

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50
Q

What is the inter ventricular septum?

A

Divides the ventricles

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51
Q

What is the coronary sulcus?

A

Encircles the atria and ventricles junction, divides the atria and ventricles

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52
Q

What is another name for the coronary sulcus?

A

Atrioventricular groove

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53
Q

What is the anterior interventricular sulcus?

A

Anterior position of the septum dividing the left and right ventricles

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54
Q

What is the posterior interventricular sulcus?

A

A continuation of the anterior interventricular sulcus

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55
Q

What artery follows the anterior inter interventricular sulcus?

A

Left anterior descending artery

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56
Q

What are auricles?

A

Small, wrinkled protruding appendages the increase the atrial volume

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57
Q

What do the posterior walls of the atria look like?

A

Smooth

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58
Q

What do the anterior walls of the atria look like?

A

Bundles of muscle tissue, pectinate muscles

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59
Q

What is the crista terminals?

A

The crescent shaped ridge where atria walls are separated

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60
Q

What is the fossa ovals?

A

Interatrial septum’s shallow depression that marks where the foramen oval opening existed in the fetal heart

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61
Q

What is the pressure in the right atrium?

A

0-8 mm Hg

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62
Q

What is the pressure in the left atrium?

A

4-12 mm Hg

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63
Q

What is the characteristic of the atria walls and why?

A

Atria walls are thin because they contract minimally to push blood down into the ventricles

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64
Q

What type of blood do systemic arteries carry and what is the exception?

A

Oxygenated blood, but the pulmonary artery carries deoxygenated blood

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65
Q

What type of blood do systemic veins carry and what is the exception?

A

Deoxygenated blood, but the pulmonary veins carry oxygenated blood

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66
Q

Where does blood enter the right atrium?

A
  1. Superior Vena Cava
  2. Inferior Vena Cava
  3. Coronary Sinus
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67
Q

Where does the superior vena cava return blood from?

A

Above the diaphragm

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68
Q

Where does the inferior vena cava return blood from?

A

Below the diaphragm

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69
Q

Where does the coronary sinus collect blood from?

A

Collects blood draining from the myocardium

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70
Q

Where does blood enter the left atrium?

A

4 pulmonary veins

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71
Q

What part of the heart makes up most of its volume?

A

Ventricles

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72
Q

What are trabeculae carneae?

A

Irregular ridges of muscle on internal ventricular walls

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73
Q

What are papillary muscles?

A

Muscle bundles projecting into the ventricular cavity that play a role in valve function

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74
Q

Where does the right ventricle pump to?

A

Pulmonary trunk

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75
Q

Where does the left ventricle pump to?

A

Aorta

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76
Q

What are the systolic and diastolic pressures of the pulmonary artery?

A

15-25 S

8- 15 D

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77
Q

What are the systolic and diastolic pressures of the aorta?

A

100-130 S

70-80 D

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78
Q

What are the systolic and diastolic pressures of the right ventricle?

A

15-25 S

0-8 D

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79
Q

What are the systolic and diastolic pressures of the left ventricle?

A

110-130 S

4-12 D

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80
Q

What type of blood is pumped from the right ventricle into the pulmonary trunk?

A

Deoxygenated

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81
Q

What type of blood is pumped from the left ventricle into the aorta?

A

Oxygenated

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82
Q

How many valves does the heart have?

A

Four

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83
Q

What are the names of the heart valves?

A

2 Atrioventricular

2 Sumilunar

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84
Q

What do the AV valves do?

A

Prevent back flow into the atria when the ventricles contract

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85
Q

What is the right AV valve called?

A

Tricuspid

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86
Q

What is the left AV valve called?

A

Bicuspid or Mitrial

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87
Q

What are chord tendinae?

A

Tiny white collagen cords attached to each AV valve flap that anchor the cusps to papillary muscles

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88
Q

What do the AV valve flaps do when the heart is relaxed?

A

They hang limp into the ventricle chambers and flow can flow through

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89
Q

What happens to the AV valve flaps when the ventricles contract?

A

Blood is compressed in the chamber, causing an increase in pressure, forcing blood against the flaps and forcing them closed

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90
Q

In what position do the chordae tendinae and papillary muscles anchor the valve flaps?

A

Closed position (the flaps never enter the atria)

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91
Q

What are the two semilunar valves?

A

Pulmonary and aortic valves

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92
Q

What is the function of the SL valves?

A

Preventing the back flow of blood into the ventricles during contraction

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93
Q

What do SL valves look like?

A

3 pocketlike cusps, each shaped like a crescent moon

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94
Q

What happens to the SL valves when the ventricles contract?

A

Blood bursts through and the SL valves open

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95
Q

What structure do SL valves lack?

A

No chordae tendinae

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96
Q

What part of the heart lacks valves protecting the opening?

A

No valves guarding the atria opening at the pulmonary trunk and vena cavae

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97
Q

Does blood flow back into the blood vessels when the atria contract if there are no valves there?

A

Small amounts do flow back, but the atria don’t contract forcefully enough

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98
Q

What happens with an incompetent or insufficient valve?

A

The heart rep umps the same blood because the valve doesn’t close properly and blood back flows

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99
Q

What is valvular stenosis?

A

The valve flaps become stiff and contract the opening

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100
Q

What happens to the efficiency of the heart with valvular stenosis?

A

The heart weakens because its workload over time increases

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101
Q

What is the difference between the amount of blood moved by the pulmonary and systemic circuits?

A

No difference

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102
Q

Is the pulmonary circuit under low/high pressure? Short/long?

A

Pulmonary circuit is a short, low pressure circulation

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103
Q

Is the systemic circuit under low/high pressure? Short/long?

A

Systemic circuit is a long, high pressure circulation

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104
Q

Why is the systemic circuit under high pressure?

A

Due to the increased resistance to blood flow in the systemic arterial vessels

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105
Q

How many more times resistance does the systemic circuit encounter?

A

5 times

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106
Q

Which ventricle walls are thicker? How many more times thicker? Why?

A

Walls of the left ventricle are 3 times thicker because they pump to the systemic circuit, which encounters more resistance

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107
Q

What shape is the left ventricle?

A

Circular

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108
Q

What shape is the right ventricle?

A

Crescent shaped that encloses the left ventricle

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109
Q

Which ventricle can generate more power? Why?

A

Left ventricle because it pumps to the systemic circuit, which encounters more resistance

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110
Q

What is coronary circulation?

A

Functional blood supply of the heart

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111
Q

Why does the heart need its own circulation if it is always full of blood?

A

The myocardium is too thick to diffuse nutrients to the heart

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112
Q

Where do the coronary arteries arise from?

A

The base of the aorta, right after the aortic valve

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113
Q

Where are the coronary arteries found?

A

Encircling the heart in the coronary sulcus, or the atrioventricular groove

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114
Q

Where does the left coronary artery run to?

A

The left side of the heart

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115
Q

What does the left coronary artery divide into?

A
  1. Anterior interventricular artery (Left anterior descending)
  2. Circumflex artery
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116
Q

Where does the LAD supply blood to?

A

The interventricular septum and the anterior walls of the ventricles

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117
Q

Where does the circumflex artery supply blood to?

A

Left atrium and posterior walls of the left ventricle

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118
Q

Where does the right coronary artery run to?

A

The right side of the heart

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119
Q

What does the right coronary artery divide into?

A
  1. Right marginal artery

2. Posterior interventricular artery

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120
Q

What does the right marginal artery supply?

A

Right atrium and right ventricle

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121
Q

What does the posterior interventricular artery supply?

A

Posterior ventricle walls

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122
Q

What does the posterior interventricular artery merge with? Where?

A

LAD at the apex

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123
Q

How does the arterial blood supply vary between people?

A

In 15% of people, the left coronary artery gives rise to both interventricular arteries. In 4% of people, one coronary supplies the whole heart

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124
Q

What is an anastomoses?

A

Junction

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125
Q

Why are there several anastomoses among branches in the arteries?

A

For additional delivery routes

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126
Q

When do coronary arteries deliver blood? Why?

A

When the heart relaxes, because during contraction, the blood vessels are compressed

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127
Q

What fraction of the body’s weight is the heart? What fraction of the body’s blood supply does the heart need?

A

The heart is 1/200 of the body’s weight but needs 1/20 of the blood supply

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128
Q

What chamber of the heart receives the most blood supply?

A

Left ventricle

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129
Q

What path do the coronary veins follow?

A

The path of the coronary arteries

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130
Q

What path does the great cardiac vein follow?

A

The route of the LAD

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131
Q

What do the coronary veins join to form?

A

The coronary sinus

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132
Q

Where does the coronary sinus empty into?

A

The right atrium

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133
Q

What are the four tributaries of the coronary sinus?

A
  1. Great cardiac vein
  2. Middle cardiac vein
  3. Small cardiac vein
  4. Many anterior cardiac veins
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134
Q

What is angina pectoris?

A

Thoracic pain caused by fleeting deficiency in blood delivery to the myocardium

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135
Q

When does angina pain occur?

A

During stress induced spasms of the coronary arteries, or during increased physical demand on the heart

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136
Q

Do cells die with angina pectoris?

A

No, cells are weakened by the lack of oxygen but don’t die

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137
Q

What is a myocardial infarction?

A

Prolonged coronary blockage results in cell death, replaced with scar tissue

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138
Q

Where is myocardial infarction damage the most serious?

A

Left ventricle

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139
Q

What are some characteristics of cardiac muscle?

A
  1. Striated
  2. Short
  3. Fat
  4. Branched
  5. Interconnected
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140
Q

What mechanism does cardiac muscle use to contract?

A

Sliding filaments mechanism

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141
Q

How many nuclei does a cardiac muscle cell have?

A

One, maybe two, centrally-located, large, pale nuclei

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142
Q

What is endomysium?

A

CT matrix filled with capillaries found in intercellular space

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143
Q

What is an intercalated disc?

A

The plasma membrane of adjacent cardiac cells interlock, dark staining

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144
Q

What do intercalated discs contain?

A

Desmosomes and gap junctions

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145
Q

What do desmosomes do for cardiac muscles?

A

Prevent cells from separating during contraction

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146
Q

What do gap junctions do for cardiac muscles?

A

Allow ions to pass from cell to cell, transmitting currents across the heart

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147
Q

What is functional syncytium?

A

Myocardium behaves as a single coordinated unit because gap junctions electrically couple cardiac cells

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148
Q

What percentage of the cardiac cells volume is mitochondria?

A

Many large mito take up 25-35% of the cardiac cell’s volume

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149
Q

Why do cardiac cells have so many mitochondria?

A

Because they need to be highly resistant to fatigue

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150
Q

What makes up the remaining volume of a cardiac cell?

A

Myofibrils with sarcomeres

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151
Q

What is a sarcomere made up of?

A

Z discs, A and I bands, myosin and actin filaments

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152
Q

How are A and I bands of cardiac cells different than skeletal cells?

A

Their banding pattern is not as prominent

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153
Q

Which filaments are the thick and thin filaments?

A

Myosin is the thick filament

Actin is the thin filament

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154
Q

What do the myofibrils in cardiac cells look like?

A

Vary in diameter and branch

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155
Q

What are the T tubules like in cardiac cells?

A

Wider T tubules, fewer, only enter cells once per sarcomere at the Z disc

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156
Q

What are T tubules used for?

A

Calcium delivery

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157
Q

What is the SR like in cardiac cells?

A

Very simple

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158
Q

What structures do cardiac cells lack?

A

No terminal cisterns, no triads

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159
Q

What is automaticity? What is another name for it?

A

Autorhythmicity is the ability of cardiac cells to be self excitable - they can initiate their own action potential

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160
Q

How do cardiac cells contract, individually or as a unit?

A

As a unit, all of their fibers contract, or none of them do, because of their gap junctions (functional syncytia)

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161
Q

How is the length of a cardiac cell’s absolute refractory period different than skeletal muscle cells?

A

The ARP is much longer, about as long as the contraction itself

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162
Q

What is the absolute refractory period?

A

Inexcitable period when Na channels are still open

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163
Q

How long is a cardiac cell’s ARP?

A

200+ ms

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164
Q

What percent of cardiac cells are autorhythmic?

A

1%

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165
Q

What percent of cardiac cells are contractile muscle?

A

99%

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166
Q

Which cardiac cells pace the heart?

A

Autorhythmic

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167
Q

What are the three steps to cardiac contraction?

A
  1. Depolarization opens Na channels
  2. Depolarization wave travels down T tubules
  3. Excitation-contraction coupling
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168
Q

What happens in the first step of cardiac contraction?

A

Depolarization opens the fast voltage-gated Na+ channels

169
Q

What happens when Na+ enters the cell?

A

Increases in action potentials and starts a positive feedback cycle

170
Q

What happens to the membrane potential when Na+ enters the cell?

A

Moves from -90 mV to +30 mV

171
Q

How do the Na+ channels close?

A

They inactivate quickly and the influx stops

172
Q

What happens in the second step of cardiac contraction?

A

Depolarization wave travels down T tubules

173
Q

What happens when the depol wave travels down the T tubules?

A

Causes the SR to release Ca2+ into the sarcoplasm

174
Q

What is the third step of cardiac contraction?

A

Excitation contraction coupling

175
Q

When does EC coupling occur?

A

When Ca+2 provides the signal

176
Q

What is the signal?

A

When troponin binds and activates the cross bridge formation

177
Q

What does EC coupling mean?

A

It couples the depol wave to the sliding of myofilaments

178
Q

Describe the process of cardiac contraction

A
  1. Depol due to Na influx - positive feedback rapidly opens many Na channels. Channel inactivation ends the phase
  2. Plateau due to Ca influx through slow channels
  3. Repol due to Ca channels inactivating and K channels opening (K efflux brings MP back to resting voltage)
179
Q

How does the SR release Ca?

A

20% of the cell’s Ca enters from the ECF, which triggers the remaining 80% to be released by the SR

180
Q

When do the Ca channels open?

A

When Na dependent membrane depolarization occurs

181
Q

Why are they called slow Ca channels?

A

Because their opening is delayed

182
Q

How do Ca channels exhibit positive feedback?

A

The opening of one Ca channel triggers the opening of more Ca channels

183
Q

What is the plateau?

A

Na channels are inactivated and repolarization is occurring, but Ca surge prolongs it

184
Q

Why is the action potential much longer in cardiac cells?

A

Because of the plateau

185
Q

Why does tension development need to last longer in cardiac cells?

A

Because they need sustained contraction ability for the heart to eject blood

186
Q

What does repolarization result from?

A

K+ channels opening, restoring the RMP

187
Q

What happens to Ca+2 during repol?

A

Ca channels close and Ca returns to the SR or ECF

188
Q

Where does K+ move to and from during repol?

A

From inside of the cell to the ECF

189
Q

What are cardiac cells more dependent on since they have more mitochondria? What type of respiration do they use?

A

More dependent on oxygen, because they use aerobic respiration

190
Q

What happens if there is little oxygen available for the heart?

A

Cardiac muscle is adaptable and readily switches to different metabolic pathways

191
Q

What other fuel molecules can cardiac cells use besides oxygen?

A

Glucose, fatty acids, lactic acid

192
Q

What does ischemia mean?

A

Blood deprived

193
Q

What happens to the mitochondria when the heart uses other fuel molecules besides oxygen?

A

The heart uses anaerobic respiration when it is starved of oxygen, producing lactic acid, which eventually damages the mitochondria

194
Q

Does the ability of the heart to depolarize and contract depend on the nervous system?

A

No!

195
Q

What is the activity of the heart a result of (2)?

A
  1. Gap junctions

2. The heart’s own conduction system

196
Q

What is the intrinsic cardiac conduction system?

A

Noncontractile cardiac cells are specialized to initiate and distribute impulses through the heart

197
Q

What results from the intrinsic cardiac conduction system?

A

The heart depolarizes and contracts in an orderly, sequential manner

198
Q

What are cardiac pacemaker cells?

A

Make up the intrinsic cardiac conduction system and have an unstable RMP that continues depolarization

199
Q

What is another name for cardiac pacemaker cells?

A

Autorhythmic cells

200
Q

What are pacemaker potentials?

A

Spontaneously changing membrane potentials; they initiate the action potential that spreads through the heart to trigger its rhythmic contractions

201
Q

What is another name for pacemaker potentials?

A

Prepotentials

202
Q

What are pacemaker potentials a result of?

A

K+ permeability

203
Q

What happens when threshold is reached?

A

Ca enters the cell

204
Q

What kind of cells have a stable RMP?

A

Unstimulated contractile cells

205
Q

What kind of cells have an unstable RMP?

A

Pacemaker cells

206
Q

What are the three steps to the intrinsic cardiac conduction system?

A
  1. Pacemaker potential
  2. Depolarization
  3. Repolarization
207
Q

What happens during the pacemaker potential?

A

Hyperpol at the end of the AP closes K+ channels and opens Na+ channels
When Na+ influx occurs, the membrane interior becomes more positive

208
Q

What is the rising phase of the action potential due to?

A

Calcium

209
Q

What happens during depolarization in the intrinsic cardiac conduction system?

A

Ca+2 channels open at threshold, resulting in the explosive entry of Ca+2, producing rising AP and reversing MP

210
Q

What value is threshold?

A

-40 mV

211
Q

What happens during repolarization in the intrinsic cardiac conduction system?

A

Falling AP and depolarization from opening K+ channels

212
Q

Where are cardiac pacemaker cells found?

A
  1. SA node
  2. AV ode
  3. AV bundle
  4. Right and Left bundle branches
  5. Purkinje fibers (Subendocardial conducting network)
213
Q

What is the sequence of excitation?

A
  1. Sinoatrial Node
  2. Atrioventricular node
  3. Atrioventricular bundle (Bundle of His)
  4. Right and Left bundle branches
214
Q

Where is the SA node located?

A

Right atrial wall

215
Q

At what rate does the SA node generate impulses?

A

75 per minute

216
Q

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

A

Because no other conduction region has a faster depolarization rate

217
Q

What is the characteristic rhythm of the heart?

A

Sinus rhythm

218
Q

What does the sinus rhythm do?

A

Determines the heart rate

219
Q

At what rate does the AV node generate impulses?

A

50 beats per minute

220
Q

How does the depolarization wave spread from the SA node? What pathway does it use?

A

Via gap junctions through the internodal pathway

221
Q

Where is the AV node located?

A

Interatrial septum above the tricuspid valve

222
Q

How long is the impulse delayed at the AV node?

A

.1 sec

223
Q

Why is the impulse delayed at the AV node?

A

So the atria can complete their contraction before the ventricles contract

224
Q

What does the AV bundle serve as?

A

The ONLY electrical connection between the atria and ventricles

225
Q

At what rate does the AV bundle generate impulses?

A

30 beats per minute

226
Q

What immediately happens once an impulse hits the AV bundle?

A

The bundle splits into left and right bundle branches

227
Q

At what rate do the Purkinje fibers generate impulses?

A

30 beats per minute

228
Q

What does the subendocardial conducting network look like?

A

Long strands of barrel shaped cells with few myofibrils

229
Q

Where do the Purkinje fibers penetrate?

A
  1. Interventricular septum
  2. Heart apex
  3. Ventricle walls
230
Q

How do the ventricles depend on Purkinje fibers?

A

Ventricular depolarization depend on Purkinje fibers and on cell to cell transmission of the impulse via gap junctions

231
Q

How long does it take for an impulse to travel from the SA node to the depolarization of the ventricles?

A

.22 seconds

232
Q

What is an arrhythmia?

A

Irregular heart rhythm

233
Q

What is fibrillation?

A

The condition of rapid and irregular or out of phase contractions

234
Q

What happens to the control of the heart rhythm during fibrillation?

A

Control of heart rhythm is taken from the SA node by rapid activity in other heart regions

235
Q

What happens to the body during fibrillation?

A

Circulation stops and brain death occurs

236
Q

What is defibrillation?

A

Shocking the heart, depolarization of the myocardium

237
Q

What is ectopic focus?

A

Result of a defective SA node, abnormal pacemaker, taking over, or the AV node may become the pacemaker

238
Q

What is junctional rhythm?

A

Pace set by AV node, slower, but still adequate

239
Q

What is the average rate of the junctional rhythm?

A

40-60 bpm

240
Q

When might an ectopic pacemaker appear even when the heart has a good SA node?

A

Excessive caffeine intake or smoking

241
Q

What does an ectopic focus lead to?

A

Premature contraction, or extrasystole

242
Q

What happens during extrasystole?

A

The heart has a longer time to fill on the next contraction

243
Q

What is heart block?

A

Damage to the AV node interferes with the ability of the ventricles to receive pacing impulses

244
Q

What is total heart block?

A

No impulses get through and ventricles beat at an intrinsic rate, which is too slow for adequate circulation

245
Q

What is partial heart block?

A

Some atrial impulses reach the ventricles

246
Q

How can we treat heart block?

A

Artificial devices can be implanted to connect the atria and ventricles

247
Q

How do fibers of the autonomic nervous system affect the circulatory system?

A

The fibers modify the heart beat

248
Q

What two nervous systems influence heart beat?

A

Sympathetic and parasympathetic

249
Q

What is the nick name for the sympathetic nervous system?

A

“accelerator”

250
Q

What does the sympathetic nervous system do to the heart rate?

A

Increases heart rate and force of the heart beat

251
Q

What is the nick name for the parasympathetic nervous system?

A

“Brakes”

252
Q

What does the parasympathetic nervous system do to the heart rate?

A

Slows down heart rate

253
Q

Where is the cardiac center?

A

Medulla

254
Q

Where does the cardioacceleratory center project sympathetic neurons?

A

T1-T5

255
Q

What happens to impulses from sympathetic neurons once they hit T1-T5?

A

Preganglionic, postganglionic, cardiac plexus, heart

256
Q

Where does the cardioinhibitory center project parasympathetic neurons?

A

Through vagus nerves to the SA/AV nodes

257
Q

What is an electrocardiogram?

A

Graphic record of heart activity, a composite of all AP generate by nodal and contractile cells

258
Q

What equipment is needed to do an ECG?

A

12 lead

259
Q

How many leads for an ECG are bi/unipolar?

A

3 bipolar, 9 unipolar

260
Q

What are the waves of an ECG called?

A

Deflections

261
Q

What are the three deflections of an ECG?

A
  1. P wave
  2. QRS wave
  3. T wave
262
Q

What is the P wave?

A

Movement of the depolarization wave from the SA node to the AV node

263
Q

What is the QRS wave?

A

Ventricular depolarization, preceding ventricular contraction

264
Q

What is the T wave?

A

Ventricular repolarization

265
Q

Which wave is the slowest, so it is more spread out?

A

T wave

266
Q

How long does the P wave last?

A

.08 seconds

267
Q

How long does the QRS wave last?

A

.08 seconds

268
Q

How long does the T wave last?

A

.16 seconds

269
Q

What is the PR interval?

A

Atrial excitation, depolarization, contraction, to ventricular excitation

270
Q

Which wave is not always visible?

A

Q wave

271
Q

What does the Q wave mark?

A

The beginning of ventricular excitation

272
Q

What is the ST segment?

A

Entire myocardium is depolarized, plateau phase

273
Q

What is the QT interval?

A

The beginning of ventricular depolarization to ventricular repolarization

274
Q

How long is the QT interval?

A

.38 seconds

275
Q

Explain the PQRST waves (6 steps)

A
  1. P = atrial depol initiated by SA node
  2. Q = Atrial depol complete, impulse delayed at AV node
  3. R = Ventricular depot begins at apex, Atrial repol
  4. S = Ventricular depol complete
  5. T = Ventricular repel begins
  6. Before next P = ventricular repol complete
276
Q

What does an enlarged R wave indicate?

A

Enlarged ventricles

277
Q

What does the ST segment indicate if it is elevated or depressed?

A

Cardiac ischemia

278
Q

What does the QT interval indicate if it is prolonged?

A

Repol abnormality that increases the risk of ventricular arrhythmia

279
Q

Auscultation reveals how many sounds in a heart beat?

A

Two

280
Q

What are heart sound associated with?

A

The heart valves closing

281
Q

What is the pause in heart sound associated with?

A

When the heart is relaxing

282
Q

What is the first sound in a heart beat?

A

When AV valves close

283
Q

What is the second sound in a heart beat?

A

When SL valves slap shut

284
Q

Which sound is longer and louder?

A

First, AV valves

285
Q

Which sound is shorter and sharp?

A

Second, SL valves

286
Q

What are the four areas of the thoracic surface you should listen to when auscultating?

A
  1. Aortic valve
  2. Pulmonary valve
  3. Mitrial valve
  4. Tricuspid valve
287
Q

What is a heart murmur?

A

Blood flow is turbulent due to obstructions, causing abnormal heart sounds

288
Q

What demographics are heart murmurs common in?

A

Kids and elderly

289
Q

Why are heart murmurs common in kids and the elderly?

A

Because their heart walls are thin and vibrate with rushing blood

290
Q

Is is somewhat normal for kids and the elderly to have heart murmurs?

A

Yes

291
Q

What do heart murmurs indicate in middle aged patients?

A

Valve problems

292
Q

What is the sound of a heart murmur due to in middle aged patients?

A

The valves do not close properly, creating a swishing sound and blood back flows

293
Q

What is a stenotic valve?

A

Valve fails to open completely and the narrow opening restricts blood flow through the valve

294
Q

What is systole?

A

Period of contraction

295
Q

What is diastole?

A

Period of relaxation

296
Q

What is the cardiac cycle?

A

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

297
Q

What are the four components to the cardiac cycle?

A

Atrial and ventricular systole and diastole

298
Q

What is the cardiac cycle determined by?

A

Pressure and blood volume changes

299
Q

How is the cardiac cycle described, in terms of atrial or ventricular activity?

A

Ventricular, unless atrial activity is specifically noted

300
Q

What are the steps to the cardiac cycle?

A
  1. Ventricular filling, atrial contraction
  2. Isovolumetric contraction phase, ventricular ejection phase
  3. Isovolumetric relaxation
301
Q

What happens during ventricular filling?

A
  1. Blood from circulation is flowing through atria and into the ventricles
  2. Following depot, atria contract
  3. Ventricles have their maximum amount of blood and atria relax
302
Q

What is the pressure level in the heart during ventricular filling?

A

Low

303
Q

What do the heart valves look like at the beginning of ventricular filling?

A

AV open, SL closed

304
Q

What happens to the pressure inside the heart once the atria contract during ventricular filling?

A

Increase in pressure, blood leaves the atria for the ventricles

305
Q

What is it called at the end of ventricular filling when the ventricles have the maximum amount of blood in them?

A

End diastolic volume

306
Q

What is the atrial kick?

A

When the last portion of blood enters the ventricles from the atria, due to the atrial contraction

307
Q

What percentage of blood goes into the ventricles with the atrial kick?

A

20% (80% has already entered)

308
Q

Is ventricular filling during systole or diastole?

A

Mid to late diastole

309
Q

What happens during the second phase of the cardiac cycle?

A

Ventricular systole - atria relax, ventricles contract

310
Q

What happens to the valves of the heart during the second step of the cardiac cycle?

A

AV valves close, and SL valves are forced open as ventricular pressure increases

311
Q

What is the isovolumetric contraction phase?

A

The period when the ventricles are completely closed and blood volume remains constant

312
Q

When do the SL valves open, in terms of pressure?

A

When the ventricular pressure exceeds the pressure in the aortic and pulmonary arteries

313
Q

What is the ejection phase?

A

Pressure begins to build in the aorta and pulmonary arteries, and blood rushes from the ventricles into the aorta and pulmonary trunk

314
Q

What is the ejection fraction, and what is its value?

A

Not all blood is ejected from the ventricles, the amount of blood that is ejected is the ejection fraction, valued at 60%

315
Q

Is isovolumetric relaxation during systole or diastole?

A

Early diastole

316
Q

What happens to the ventricles during isovolumetric relaxation?

A

The ventricles relax

317
Q

What is the end systolic volume?

A

Blood remaining in the ventricles

318
Q

What happens to the pressure in the ventricles during isovolumetric relaxation?

A

Pressure decreases

319
Q

What happens that makes the SL valves close?

A

The pressure in the aorta and pulmonary artery is high, blood in the vessels starts to flow back towards the heart, and the SL valves close

320
Q

What happens in the atria while the ventricles have been contracting?

A

Atria have been filling with blood

321
Q

When do the AV valves open again?

A

When the pressure in the atria exceeds the pressure in the ventricles

322
Q

How long is the cardiac cycle?

A

.8 seconds

323
Q

How long is atrial systole?

A

.1 seconds

324
Q

How long is ventricular systole?

A

.3 seconds

325
Q

How long is the heart relaxed? What is this period called?

A

.4 seconds, quiescent period

326
Q

What kind of phenomenon is the cardiac cycle?

A

Pressure phenomenon

327
Q

What kind of gradient does blood flow through? Does it flow up or down?

A

Blood flows down a pressure gradient through any available opening

328
Q

Is the right side of the heart under high or low pressure?

A

Low

329
Q

Is the left side of the heart under high or low pressure?

A

High

330
Q

What is the pressure in the pulmonary artery?

A

25 mm Hg (S)

8 mm Hg (D)

331
Q

What is the pressure in the aorta?

A

120 mm Hg (S)

80 mm Hg (D)

332
Q

What is cardiac output?

A

The amount of blood pumped out by each ventricle in one minute

333
Q

CO = ? x ?

A

CO = HR x SV

334
Q

What is stroke volume?

A

The volume of blood pumped out by one ventricle in one beat

335
Q

What is the average stroke volume value?

A

70 mL/beat

336
Q

What is the formula for the average cardiac output?

A

Average CO = 75 bpm x 70 mL/beat = 5.25 L/min

337
Q

What is cardiac reserve?

A

The difference between the resting and maximal cardiac output

338
Q

How many times more is the average maximal CO than the average resting CO? What about in athletes?

A

Average maximal CO is 4-5 times higher than the resting CO. In athletes its about 7 times higher

339
Q

What does stroke volume represent?

A

The difference between End Diastolic Volume and End Systolic Volume (the amount of blood that actually gets pumped out each beat)

340
Q

What is EDV?

A

The amount of blood in the ventricles during diastole

341
Q

What is ESV?

A

The amount of blood in the ventricles after contraction

342
Q

What is EDV determined by?

A

Length of ventricular diastole and venous pressure

343
Q

What is ESV determined by?

A

Arterial blood pressure and the force of ventricular contraction

344
Q

What is the average EDV?

A

120 mL

345
Q

What is the average ESV?

A

50 mL

346
Q

What does SVR stand for?

A

Systemic vascular resistance

347
Q

What does blood pressure take into account?

A

Both cardiac output and SVR

348
Q

BP = ? x ?

A 
BP = CO x SVR
BP = (HR x SV) x SVR
349
Q

SV = ? - ?

A

SV = EDV - ESV

350
Q

What three factors affect SV by altering EDV and ESV?

A
  1. Preload
  2. Contractility
  3. Afterload
351
Q

What is preload?

A

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

352
Q

What is Frank Starling’s law of the heart?

A

The heart has a length-tension relationship
As venous return increases, EDV increases
As cells stretch more, stroke volume increases

353
Q

What happens to SV when preload is increased?

A

SV increases

354
Q

What two things happen at an optimal length of muscle fibers?

A
  1. Maximum number of active cross bridge attachments are possible between actin and myosin
  2. Force of contraction is maximal
355
Q

What kind of relationship does cardiac muscle have?

A

Length-tension relationship

356
Q

How long re resting cardiac cells kept at and why?

A

Resting cardiac cells are kept shorter than optimal length so stretching can produce dramatic increases in contractile force

357
Q

What is the most important factor for stretch?

A

Venous return

358
Q

What is venous return?

A

The amount of blood returning to the heart and distending the ventricles

359
Q

What happens to SV and contractility when the speed of venous return increases?

A

SV and contractility increase

360
Q

Why might venous return increase?

A

Due to slow heart rate or exercise

361
Q

Why might venous return decrease?

A

Severe blood loss, rapid heart rate

362
Q

What is contractility?

A

The contractile strength achieved at a given muscle length

363
Q

What two things is contractility independent of?

A

Stretch and EDV

364
Q

What factors increase contractility? (4)

A
  1. Increased Ca
  2. Increased SV
  3. Decreased ESV
  4. Increased sympathetic NS stimulation
365
Q

What are positive inotropic agents?

A

Substances that increase contractility

366
Q

What are some examples of positive inotropic agents? (5)

A
  1. Epi and Norepi
  2. Thyroxine
  3. Glucagon
  4. Digitalis
  5. High levels of extracellular Ca
367
Q

Why do epi and norepi increase contractility?

A

They trigger cyclic AMP second messenger systems, CA entry is enhanced, and actin myosin cross bridge formation is increased

368
Q

What are negative inotropic agents?

A

They impair or decrease contractility

369
Q

What are some examples of negative inotropic agents? (3)

A
  1. Acidosis
  2. Increased extracellular K+ levels
  3. Calcium channel blockers
370
Q

What is afterload?

A

THe pressure that ventricles must overcome to eject blood (The back pressure exerted by arterial blood)

371
Q

With what condition is afterload an important factor?

A

Hypertension

372
Q

Why does hypertension affect afterload?

A

In people with hypertension, after load decreases the ability of the ventricles to eject blood, so more blood remains in the heart, and ESV increases so SV decreases

373
Q

What factors maintain cardiac output if stroke volume is decreased?

A

Heart rate and contractility

374
Q

What are positive chronotropic factors?

A

Increase heart rate

375
Q

What are negative chronotropic factors?

A

Decrease heart rate

376
Q

What part of the body controls heart rate?

A

Autonomic nervous system

377
Q

What factors activate the sympathetic nervous system?

A

Emotional and physical stressors

378
Q

What happens once the sympathetic nervous system fibers release norepi?

A

Norepi binds to B1 adrenergic receptors, causing the SA node to fire more rapidly, causing the heart to beat faster

379
Q

What system decreases the heart rate after the stress is over?

A

Parasympathetic nervous system

380
Q

What does the parasympathetic nervous system do to decrease the heart rate?

A

ACh hyper polarizes the membrane of cells by opening K+ channels, making the cells less likely to reach threshold

381
Q

The parasympathetic nervous system has little affect on what factor?

A

Contractility

382
Q

What influence is dominant when the SNS and PSNS send impulses to the SA node?

A

Inhibitory

383
Q

What does the heart exhibit due to the inhibitory dominance of the PSNS?

A

Vagal tone (the heart rate would be faster if the vagus nerve wasn’t innervating it)

384
Q

What is the atrial (Bainbridge) reflex?

A

Autonomic reflex that increases heart rate, initiated by increased venous return and increased atrial filling

385
Q

Why does the atrial reflex increase heart rate?

A

Stretching the atrial walls increases the heart rate by stimulating the SA node and atrial stretch receptors

386
Q

What chemicals present in the blood influence heart rate?

A

Hormones and ions

387
Q

What hormones influence heart rate?

A
  1. Epi

2. Thyroxine

388
Q

What does epinephrine do to heart rate?

A

Increases HR, increases contractility

389
Q

What does thyroxine do to heart rate?

A

Increases metabolic rate and production of body heat, increasing heart rate

390
Q

How do ions influence heart rate?

A

Heart function depends on normal levels of ions

391
Q

What are some conditions that result from abnormal ion levels?

A
  1. Hypercalcemia
  2. Hypocalcemia
  3. Hyperkalemia
  4. Hypokalemia
  5. Hypernatremia
392
Q

What four factors can effect heart rate?

A
  1. Age
  2. Gender
  3. Exercise
  4. Body temperature
393
Q

What is congestive heart failure?

A

The heart is an inefficient pump so blood circulation is inadequate to meet tissue needs

394
Q

What is coronary atherosclerosis?

A

Fatty build up clogs coronary arteries and impairs blood and oxygen delivery to cardiac cells

395
Q

What is high BP?

A

Myocardium must exert more force to open aortic valve and pump blood, which weakens heart muscle

396
Q

What are multiple MIs?

A

Depresses pumping efficiency because non contractile scar tissue replaces dead heart cells

397
Q

What is dilated cadiomyopathy?

A

Ventricles stretch and become flabby and myocardium deteriorates

398
Q

What is pulmonary congestion?

A

Left side of the heart fails, blood vessels in the lungs are engorged with blood, increasing pressure, and fluid leaks into the lungs causing pulmonary edema

399
Q

What is peripheral congestion?

A

Right side of the heart fails, blood stagnates in the organs, pooled fluid in tissue spaces impair cells ability to obtain oxygen and nutrients, resulting in edema in the hands and feet

400
Q

What happens when one side of the heart fails?

A

It places strain on the other side of the heart

401
Q

How do you treat one sided heart failure (3)?

A
  1. Removal of fluids with diuretics
  2. Decrease after load with drugs that decrease BP
  3. Increase contractility with digitalis
402
Q

What problems result when the right side of the heart fails?

A

Peripheral vascular symptoms

403
Q

What problems result when the left side of the heart fails?

A

Pulmonary problems

404
Q

On what day does the fetal heart start beating?

A

22

405
Q

What does the fetal heart begin as?

A

Two endothelial tubes which eventually fuse to form a chamber

406
Q

What are the four early bulges in the fetal heart?

A
  1. Sinus venosus
  2. Atrium
  3. Ventricle
  4. Bulbus cordis
407
Q

What is the sinus venous? What does it become?

A

Initially receives all venous blood, becomes part of the RA and SA node

408
Q

What does the atrium become?

A

Pectinate muscles and part of the atria

409
Q

What does the ventricle become?

A

LEFT ventricle

410
Q

What does the bulbs cords become?

A

Pulmonary trunk, part of aorta, and RIGHT ventricle

411
Q

Which chamber of the fetal heart is the strongest pump?

A

Ventricle

412
Q

What is the foramen ovale?

A

Connects the two atria and allows blood entering the right side of the heart to bypass the pulmonary circuit and collapsed fetal lungs

413
Q

What is the ductus arteriosus?

A

Located between the pulmonary trunk and aorta, another fetal lung bypass

414
Q

What structure is incomplete in the fetal heart?

A

Interatrial septum

415
Q

What structure is the foramen ovale in the adult heart?

A

Fossa ovalis

416
Q

What structure is the ductus arteriosus in the adult heart?

A

Ligamentum arteriosum

417
Q

What is the most common birth defect in infants?

A

Congenital heart defects

418
Q

What are two congenital heart defects seen in infants?

A
  1. Mixing of oxygen rich and poor blood, resulting in inadequately oxygenated blood reaching the tissues
  2. Narrowed valves and vessels that increase the work load of the heart
419
Q

What four structural changes of the heart are inevitable over time?

A
  1. Valve flaps thicken and become sclerotic
  2. Cardiac serve declines
  3. Cardiac muscle becomes scarred (fibrosed)
  4. Atherosclerosis

From Flashcardlet (133 decks)

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