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Physiology > Circulation > Flashcards

Circulation Flashcards

1
Q

Why do we have a heart?

A
  • Pumps blood
  • Move oxygen around the body
  • Take carbon dioxide out
  • Move hormones and waste products around
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2
Q

How does the heart help maintain homeostasis?

A

Provides potential energy and pressure

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3
Q

What is heart failure?

A

When the heart muscle is unable to contract optimally to pump blood at a rate sufficient to meet the requirements of metabolizing organs

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4
Q

When does heart failure occur?

A

When the heart can no longer move blood into the systemic and/or pulmonary circulation at a rate that meets the needs of metabolizing cells

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5
Q

What amount of blood does an adult human need circulated per minute?

A

~ 5L

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6
Q

What are 4 common symptoms of heart failure?

A
  • Congestion in lungs
  • Fatigue
  • Edema
  • Enlarged liver
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7
Q

What is an MI (myocardial infarction)?

A

Loss of heart muscle due to stoppage of blood flow

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8
Q

What causes the stoppage of blood flow in an MI?

A

Plaque build-up in the coronary artery

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9
Q

Do all post-MI patients progress to heart failure?

A

No, only if the initial damage is significant

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10
Q

What are 7 risk factors for an MI?

A
  • Genetics
  • Smoking
  • Gender
  • Diet
  • Personality
  • Stress
  • Alcoholism
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11
Q

What are 5 causes of an MI besides atherosclerosis?

A
  • Essential hypertension
  • Diabetes
  • Idiopathic primary cardiomyopathy
  • Viral infection of the heart
  • Cardiac valve diseases
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12
Q

Why is the heart considered an endocrine organ?

A

It generates a host of hormones and cytokines that may impact on cardiac wound healing and/or growth

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13
Q

What 5 hormones does the heart produce/release?

A
  • Angiotensin 2
  • IL-6
  • Cardiotrophin-1
  • FGF-2
  • TNF-alpha
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14
Q

What are the 3 basic components of the cardiovascular system?

A

1) Heart
2) Blood vessels
3) Blood

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15
Q

What is the broad function of the heart?

A

A pump that serves to pressurize the arterial tree

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16
Q

What direction does blood flow?

A

From high pressure to lower pressure

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17
Q

True or false: blood will flow from an area of higher pressure to an area of lower pressure even if there is a 1 mmHg difference

A

True

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18
Q

Where does major loss of blood pressure occur?

A

Points of restriction within the arterial tree (such as arterioles)

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19
Q

What is the broad function of blood vessels?

A

Delivery mechanisms for blood as it moves from the heart, and for its return to the heart

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20
Q

What are arteries?

A

Vessels that carry blood away from the ventricles to the body

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21
Q

What are veins?

A

Vessels that carry blood from the body to the heart

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22
Q

What is blood?

A

A transport medium within which materials being moved long distances in the body are dissolved or suspended

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23
Q

How does blood flow through the body?

A

Continuously through the closed circulatory system via 2 separate loops, which begin and end at the heart

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24
Q

What is the function of the pulmonary circulation?

A

Carry blood between the heart and lungs

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25
Q

What type of system is the pulmonary circulation?

A

Low pressure & low resistance

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26
Q

What is the function of the systemic circulation?

A

Carry blood from the heart to all peripheral organ systems

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27
Q

What type of system is the systemic circulation?

A

High pressure & high resistance

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28
Q

True or false: the heart functions as a single parallel pump

A

False, it functions as a dual parallel pump

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29
Q

Between what to bones is the heart located and why is the advantageous?

A
  • Sternum and vertebrae
  • Makes it possible to push blood out of the heart when it is not pumping by itself by rhythmically depressing the sternum
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30
Q

What divides the 2 halves of the heart?

A

Interventricular septum

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31
Q

What are atria?

A

The upper chambers of the heart that receive returning blood

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32
Q

What are ventricles?

A

Lower chambers of the heart that receive blood from atria and pump blood into the body

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33
Q

What is the function of the interventricular septum?

A

Prevents mixing of blood from the low oxygenated blood in the right and the highly-oxygenated blood in the left

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34
Q

Describe the pathway of systemic return

A
  • Enters right atrium via the vena cavae
  • Pumped into right ventricle
  • Pumped in pulmonary arteries in each lung, where it is oxygenated
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35
Q

What kind of blood does the systemic return carry?

A

Oxygen poor blood

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36
Q

What is a statement that can be made about the RIGHT side of the heart?

A

It receives blood from the systemic circulation and pumps it into the pulmonary circulation

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37
Q

True or false: each side of the heart needs to pump the same amount of blood

A

True

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38
Q

Which side of the heart is larger and why?

A

Left because it has a longer distance than the right side to pump blood in the same amount of time

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39
Q

Describe the pathway of the pulmonary circulation

A
  • Blood loses CO2 and acquires O2 in the lungs
  • Pumped to the left atrium via the pulmonary veins from each lung
  • Pumped to left ventricle, then to the aorta, and then to the systemic circulation
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40
Q

What kind of blood does the pulmonary circulation carry?

A

Oxygen rich blood

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41
Q

What is a statement that can be made about the LEFT side of the heart?

A

Receives blood from the pulmonary circulation and pumps it into the systemic circulation

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42
Q

What does the aorta do?

A

Carries blood away from the left ventricle

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43
Q

Which side of the heart pumps blood at a higher pressure?

A

Left

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44
Q

What do cardiac valves allow for?

A

Unidirectional flow of blood for efficient pump action

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45
Q

What is special about the positioning of cardiac valves?

A

They are positioned so that they open and close passively from pressure differences

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46
Q

How do cardiac valves open and close?

A
  • A forward pressure gradient (greater pressure behind the valve) forces the valve open
  • A backward pressure gradient (greater pressure in front of the valve) forces the valve closed
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47
Q

True or false: cardiac valves can open in both directions

A

False, can only open in one direction

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48
Q

Where are the atrioventricular valves found?

A

Between atria and ventricles

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49
Q

What is the function of atrioventricular valves?

A
  • Allow for movement of blood from atria to ventricles during ventricular filling
  • Keep blood in the ventricles when they contract
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50
Q

What forces the closure of AV valves?

A

Rising ventricular pressure

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51
Q

What is another name for the right AV valve?

A

Tricuspid

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52
Q

What is another name for the left AV valve?

A

Bicuspid or mitral

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53
Q

What are AV valves attached to and what does this do?

A

Anchored by fibrous chordae tendinae (which attach to papillary muscles) that prevents leaflet eversion from high pressure

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54
Q

Where are the semilunar valves found?

A

Between ventricles and major arteries

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55
Q

What is the function of semilunar valves?

A

Govern blood flow where major arteries leave the ventricles

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56
Q

How many cusps do semilunar valves have?

A

3

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57
Q

What causing semilunar valves to open?

A

When ventricular pressure exceeds the pressure in the aorta and pulmonary artery

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58
Q

What is the heart wall composed of?

A

Spirally arranged cardiac myocytes forming an electrical syncytium

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59
Q

How are cardiac myocytes connected?

A

At specific junctions (intercalated discs) that feature porosity and electrical connectivity

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60
Q

What populates the heart wall?

A

Gap junctions and desmosomes

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61
Q

What are gap junctions (with respect to the heart wall)?

A

Low resistance regions that allow action potentials to spread

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62
Q

What is the function of desmosomes in the heart wall?

A

Structural anchoring

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63
Q

What are the 3 layers of the heart?

A
  • Endocardium
  • Myocardium (muscle)
  • Epicardium (thin external membrane)
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64
Q

True or false: atria and ventricles behave as a single syncytium

A

False, they are electrically isolated and behave as separate syncytiums

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65
Q

What separates the atria and ventricles?

A

A non-conductive fibrous skeleton

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66
Q

What is the function of the spiral arrangement of myocytes?

A

Allows the heart to wring blood from ventricular cavities with each contraction

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67
Q

True or false: there are a great deal of mitochondra in cardiac myocytes

A

True

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68
Q

What is the pericardial sac?

A

Double walled membrane that holds the heart in position

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69
Q

What helps reduced the resistance to movement in the heart?

A

Pericardial fluid

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70
Q

True or false: the heart is autorhythmic

A

True

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71
Q

What triggers contractions of the heart?

A

Autorhythmic cells / pacemakers

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72
Q

How is cardiac contraction coordination achieved?

A

Through structure

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73
Q

What do ECG’s provide?

A

Information about cardiac performance

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74
Q

What is the normal pacemaker of the heart?

A

The sinoatrial node

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75
Q

Where is the SA node located?

A

In the right atrial wall near the opening of the superior vena cavae

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76
Q

The majority of cardiac cells are _____

A

Contractile (they do not fire spontaneously)

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77
Q

What are autorhythmic cells responsible for?

A

Initiating and conducting cardiac action potentials

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78
Q

Where are autorhythmic cells found?

A

SA node, AV node, Bundle of His, and Purkinje fibres

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79
Q

What are the rates of action potentials that the different autorhythmic cells fire?

A
  • SA node fires at 70-80 bpm
  • AV node fires at 40-60 bpm
  • Bundle of His and Purkinje fibres fire at 20-40 bpm
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80
Q

What are pacemaker cells?

A

Cells with the highest discharge rate (cells in the SA node)

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81
Q

What are latent pacemakers?

A

Cells that fire action potentials at lower rates than pacemaker cells

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82
Q

Describe the spread of cardiac excitation

A
  • An action potential is initiated in the SA node
  • Spread throughout both atria
  • Reaches AV node and spreads hastly through ventricles
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83
Q

What is the spread of an action potential through the atria facilitated by?

A

Interatrial and internodal pathways

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84
Q

The _____ is the only point where an action potential can spread from the atria to the ventricles

A

AV node

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85
Q

Why is there a large AV nodal delay?

A

So the atria can properly fill ventricles before they contract

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86
Q

Does atrial or ventricular contraction occur first?

A

Atrial

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87
Q

Contraction of ____ must occur simultaneously

A

Both atria and then both ventricles

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88
Q

How does excitation occur throughout the atria?

A

Via gap junctions and the interatrial pathway

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89
Q

How is the AV node excited?

A

Through the internodal pathway and by cell-to-cell contact

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90
Q

Where does the interatrial pathway extend?

A

From the SA node with the right atrium to the left atrium

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91
Q

Where does the internodal pathway extend?

A

From SA node to AV node

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92
Q

What cause the AV nodal delay?

A

Slow conduction through the AV node

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93
Q

Ventricular conduction system is highly ______

A

Organized

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94
Q

Where do the majority of Purkinje fibres terminate?

A

On ventricular muscle cells near the endocardial surface

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95
Q

What is an electrical signal converted to in cardiac muscle?

A

A contractile signal

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96
Q

What is the signal for contraction?

A

An elevation of cytosolic calcium

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97
Q

What can cause cardiac failure?

A

Too much or too little calcium

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98
Q

Where is calcium derived from?

A

The ECF and the sarcoplasmic reticulum

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99
Q

What does elevated calcium lead to?

A

Cross-bridge cycling between actin and myosin

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100
Q

What is tetanus?

A

When the muscle fibre does not have a chance to relax before more stimulation occurs, resulting in a sustained, maximal contraction

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101
Q

How does the brain control the heart?

A
  • Length-tension
  • Increase heart rate
  • Calcium change
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102
Q

What does an ECG measure?

A
  • Overall spread of electrical activity in the heart

- Electrical signals from the heart conducted by body fluids

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103
Q

True or false: an ECG is a direct measure of cardiac electrical activity

A

False, it is not

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104
Q

How does an ECG measure electrical signals?

A

Measures the difference in electrical potential between 2 different points on the body

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105
Q

How many leads/electrodes are used in a typical ECG?

A

12

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106
Q

What does the P wave represent?

A

Atrial depolarization

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107
Q

Is the P wave or QRS complex smaller and why?

A

P wave is much smaller because the atria muscle mass is much smaller than the ventricle, so it generates less electrical activity

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108
Q

What does the QRS complex represent?

A

Ventricular depolarization

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109
Q

What does the T wave represent?

A

Ventricular repolarization

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110
Q

What does the PR segment show?

A

AV nodal delay

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111
Q

What does the ST segment show?

A

When ventricles are completely depolarized

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112
Q

What does the TP interval show?

A

When the heart is at rest and ventricles are filling

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113
Q

What are ECG’s useful at diagnosing?

A
  • Abnormal heart rates
  • Arrhythmias
  • Damage to heart muscle
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114
Q

What is a flutter?

A

When the heart is beating too fast, leaving little time to contract

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115
Q

What are extrasystoles?

A

When pacemaker is in the wrong spot, causing a premature beat

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116
Q

How can an extrasystole be recognized on an ECG?

A

Slow & long-lasting, therefore wide on the ECG

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117
Q

What is a complete heart block and what does it cause?

A
  • Dysfunctional AV node

- Causes no coordination between the top and bottom of the heart, usually causing the ventricles to contract slowly

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118
Q

What are the 3 types of AV block?

A

1) First degree
2) Second degree
3) Third degree

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119
Q

How can a first degree AV block be diagnosed on an ECG?

A

Delay becomes longer after P segment

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120
Q

How can a second degree AV block be diagnosed on an ECG?

A

No QRS with every P wave

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121
Q

What is a third degree AV block?

A

No communication at all between top and bottom of heart

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122
Q

What is atrial fibrillation characterized by?

A

Rapid, irregular, uncoordinated depolarizations of the atria with no definite P waves

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123
Q

What is complete heart block characterized by?

A

Complete dissociation between atrial and ventricular activity, with impulses from the atria not being conducted to the ventricles at all

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124
Q

What does the cardiac cycle consist of?

A

2 alternating phases

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125
Q

What are the 2 phases of the cardiac cycle?

A

1) Systole

2) Diastole

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126
Q

What is systole?

A

Contraction and emptying of the heart and ejection of blood

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127
Q

What causes systole?

A

Depolarization of the cardiac muscle

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128
Q

What is diastole?

A

Relaxation and refilling of the heart

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129
Q

What causes diastole?

A

Repolarization of the cardiac muscle

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130
Q

True or false: atria and ventricles go through separate cycles of systole and diastole

A

True

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131
Q

Does the atria or ventricle contract first and why?

A

Atria, to help move blood into the ventricles

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132
Q

True or false: the left and right atria contract at the same time, same with the left and right ventricles

A

True

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133
Q

What happens to the cardiac cycle in patients with heart block (arrhythmias)?

A

Automatic rhythm is disrupted, leading to fainting and dizziness

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134
Q

What is the first step of the cardiac cycle?

A

Atrial pressure increases due to continuous passive filling of blood into atria

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135
Q

What part of an ECG represent the increase of atrial pressure?

A

TP interval

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136
Q

What occurs after atrial pressure increases in the cardiac cycle?

A

AV valves open

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137
Q

What occurs after AV valves open in the cardiac cycle?

A

Ventricular volume increases as blood flows into ventricles from atria

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138
Q

What occurs after ventricular volume increases in the cardiac cycle?

A

Atria become depolarized

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139
Q

What occurs after atrial depolarization in the cardiac cycle?

A

Atria contract and squeeze blood into the ventricles, causing an increase in atrial pressure

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140
Q

What occurs after atrial contraction in the cardiac cycle?

A

Ventricular pressure increases as ventricular blood volume increases

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141
Q

What occurs after ventricular pressure increases in the cardiac cycle?

A

Impulse travels through AV node and causes ventricular depolarization, initiating contraction

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142
Q

What is end-diastolic volume?

A

The volume of blood at the end of ventricular diastole

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143
Q

What occurs after ventricular contraction in the cardiac cycle?

A

Ventricular pressure exceeds atrial pressure, causing AV valves to close

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144
Q

What occurs after AV valve closure in the cardiac cycle?

A

Ventricular pressure exceeds aortic/pulmonary pressure, causing opening of semilunar valves and ejection of blood

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145
Q

What is isovolumetric ventricular contraction?

A

When the ventricular pressure rises after contraction, but volume and muscle fibre length remain constant

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146
Q

What occurs after the semilunar valves open in the cardiac cycle?

A

Aortic/pulmonary pressure increases due to blood forced into the aorta/pulmonary artery

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147
Q

What occurs after aortic/pulmonary pressure increase in the cardiac cycle?

A

Ventricular volume reduces significantly (but not completely)

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148
Q

What is end-systolic volume?

A

Volume of blood at the end of systole

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149
Q

How is stroke volume determined using end-diastolic volume and end-systolic volume?

A

SV = EDV-ESV

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150
Q

What is a normal end-diastolic volume?

A

135 mL

151
Q

What is a normal end-systolic volume?

A

65 mL

152
Q

What is a normal stroke volume?

A

70 mL

153
Q

What is ejection fraction?

A

The proportion of the blood volume ejected by each ventricle with each contraction

154
Q

How is ejection fraction determined?

A

EF = SV/EDV

155
Q

What is a normal ejection fraction?

A

~ 0.52

156
Q

What occurs after ventricular volume reduction in the cardiac cycle?

A

Ventricular repolarization

157
Q

What occurs after ventricular repolarization in the cardiac cycle?

A

Ventricular pressure falls below aortic/pulmonary pressure causing the semilunar valves to shut

158
Q

What occurs after semilunar valve closure in the cardiac cycle?

A

Ventricular pressure falls below atrial pressure and AV valves open

159
Q

What does semilunar valve closure cause?

A

A disturbance that is seen as a dicrotic notch on the aortic/pulmonary pressure curve

160
Q

What is isovolumetric ventricular relaxation?

A

When ventricular pressure falls, but volume and muscle fibre length remain constant

161
Q

What is the pressure-volume loop usually for?

A

Left ventricle

162
Q

What does increased preload cause?

A

Triggers the Frank-Starling mechanisms, resulting in increased stroke volume

163
Q

What does increased afterload cause?

A
  • Increased pressure in the ventricle before the aortic valve opens
  • Ventricle empties less efficiently, resulting in decreased stroke volume
164
Q

What about the pressure-volume loop can change and when will it change?

A
  • Shape and/or area can change

- Will change in characteristic ways in diseases

165
Q

What happens to ventricular diastole during exercise?

A

Since heart rate is increasing dramatically, the length of ventricular diastole is reduced, therefore there is less ventricular filling

166
Q

Does decreased ventricular filling cause a significant drop in CO? Why or why not?

A

It doesn’t because much of the filling of ventricles occurs in the rapid filling phase

167
Q

When would decreased ventricular filling cause a drop in CO?

A

When heart rate exceeds 200 bpm

168
Q

How many heart sounds are audible with a stethoscope?

A

2

169
Q

What does the first heart sound sound like?

A

Low pitch, soft, long duration

170
Q

What is the first heart sound linked to?

A

AV valve closure

171
Q

What does the first heart sound signal?

A

Onset of ventricular systole

172
Q

What does the second heart sound sound like?

A

High pitch, sharp, shorter duration

173
Q

What is the second heart sound linked to?

A

Semilunar valve closure

174
Q

What does the second heart sound signal?

A

Onset of ventricular diastole

175
Q

What are heart sounds caused by?

A

Vibrations inside the walls of the ventricles and arteries

176
Q

What are heart sounds NOT caused by?

A

The shutting of heart valves

177
Q

What causes abnormal heart sounds?

A

When blood flow that is normally laminar becomes turbulent

178
Q

How can you determine the type of valvular defect?

A

Location and timing of the murmur

179
Q

What type of murmur occurs between the first and second heart sounds?

A

Systolic

180
Q

What type of murmur occurs between the second and first heart sounds?

A

Diastolic

181
Q

What is heard from a stenotic murmur?

A

Whistling

182
Q

What is heard from an insufficient murmur?

A

Swishing

183
Q

What is a stenotic murmur?

A

When a valve doesn’t open completely due to stiffness and narrowing

184
Q

What is an insufficent murmur?

A

When a valve is scarred, resulting in poor apposition of the leaflets that prevents complete closure of the valve

185
Q

What does an insufficient valve allow for?

A

Backwards flow of blood

186
Q

What is another name for an insufficient valve?

A

Leaky valve

187
Q

What is the most common cause of valve malfunction?

A

Rheumatic fever

188
Q

What is rheumatic fever?

A

An autoimmune disease caused by a streptococcal bacterial infection

189
Q

What occurs in rheumatic fever?

A

Antibodies produced against bacterial toxins attack the body’s own tissues, with the heart valves being a main target

190
Q

What damage to heart valves is done from rheumatic fever?

A

Valves become thick, stiff, and scarred because of large hemorrhagic fibrous lesions

191
Q

What is a less common cause of valve defects?

A

Genetics

192
Q

What is cardiac output?

A

The volume of blood pumped by each ventricle per minute

193
Q

What 2 factors determine cardiac output?

A

1) Heart rate

2) Stroke volume

194
Q

What is heart rate?

A

The number of times the heart beats per minute

195
Q

What is the average resting heart rate?

A

70 bpm

196
Q

What is stroke volume?

A

The volume of blood that is pumped per beat

197
Q

If the average cardiac output is 5 L/minute, what does that tell us about how much each side of the heart is pumping?

A

Each side is pumping 5 L/minute

198
Q

What is a consequence of mismatch between cardiac output of each side of the heart?

A

Back-up behind the weaker side

199
Q

What is cardiac reserve?

A
  • The difference between the cardiac output at rest and at its peak
  • The maximum volume of blood that can be pumped by the heart per minute
200
Q

What can cause cardiac reserve to increase?

A

Exercise

201
Q

How can the heart increase its output?

A
  • Increasing heart rate

- Increasing stroke volume

202
Q

What modulates the heart?

A

Autonomic nervous system (sympathetic and parasympathetic)

203
Q

What branch of the ANS supplies the atrium?

A

Parasympathetic nerve (vagus nerve)

204
Q

What branch of the ANS supplies the SA and AV nodes?

A

Parasympathetic

205
Q

What do cardiac sympathetic nerves supply?

A

Atria and ventricles

206
Q

What is the main function of sympathetic nerves on the heart?

A

Increase heart rate

207
Q

What is the main function of parasympathetic nerves on the heart?

A

Slow down heart rate

208
Q

True or false: in a healthy individual, only the sympathetic or the parasympathetic systems are active at any given time, never at the same time

A

False, both systems can be and typically are active at the same time

209
Q

True or false: nervous stimulation is NOT essential for initiating contractions of the heart

A

True

210
Q

True or false: the SA node needs nervous stimulation to regulate heart rate

A

False, the SA node can regulate heart rate independently

211
Q

What are the sodium and potassium levels of pacemaker cells below threshold?

A

High K and low Na

212
Q

What happens in pacemaker cells as the membrane potential passes threshold?

A

Voltage-gated calcium channels open and a rapid influx of Ca occurs, causing an action potential

213
Q

What does the sympathetic NS act on to increase heart rate?

A

SA and AV nodes

214
Q

How does the sympathetic NS increase heart rate?

A
  • Inactivates K ion channels responsible for the normal outward leak, resulting in build-up of K within the cell
  • The net increase in positive charge makes it easier for the cell to reach threshold
215
Q

______ stimulation reduces AV node delay

A

Sympathetic

216
Q

______ stimulation speeds up the spread of action potentials throughout the specialized conduction pathway

A

Sympathetic

217
Q

How does the sympathetic NS increase force of contraction?

A
  • Increases strength of contraction of atrial and ventricular cells
  • Higher intracellular Ca results in more forceful contraction
218
Q

What does the parasympathetic NS act on to decrease heart rate?

A

SA

219
Q

How does the parasympathetic NS decrease heart rate?

A

Releases acetylcholine which reduces SA node depolarization by slowing the closure of K channels

220
Q

_______ stimulation prolongs AV node delay

A

Parasympathetic

221
Q

_______ stimulation slows the spread of action potentials throughout the specialized conduction pathway

A

Parasympathetic

222
Q

How does parasympathetic stimulation decrease the strength of contraction?

A

Reduces Ca influx and intracellular Ca cycling

223
Q

Why does parasympathetic stimluation have little effect on the ventricles?

A

Lack of parasympathetic innervation

224
Q

When is the sympathetic NS needed to control the heart?

A

During emergency situations or when challenged (like during exercise)

225
Q

When does the parasympathetic NS control the heart?

A

Relaxed situations

226
Q

Which branch of the ANS predominates during resting heart rate?

A

Parasympathetic

227
Q

Where and when is epinephrine secreted?

A
  • From adrenal medulla

- Upon sympathetic stimulation

228
Q

What effects does epinephrine have on the heart?

A

Similar to epinephrine; increases heart rate and contractility

229
Q

What 2 factors determine stroke volume?

A

1) Extent of venous return

2) Extent of sympathetic stimulation

230
Q

Is venous return an intrinsic or extrinsic control?

A

Intrinsic

231
Q

Is sympathetic stimulation an intrinsic or extrinsic control?

A

Extrinsic

232
Q

What happens when more blood is returned to the heart from the venous system?

A

More blood must be pumped out of the heart

233
Q

What causes more blood to be returned to the heart?

A

An increase in end-diastolic volume, which means a larger stroke volume

234
Q

What determines the hearts ability to adjust stroke volume?

A

The length-tension relationship of cardiac muscle

235
Q

At rest, is cardiac muscle fibre length longer or shorter than its optimal length?

A

Shorter

236
Q

What is the major factor that determines cardiac muscle fibre length?

A

Amount of blood entering during diastole

237
Q

What does increased filling result in?

A

Increased stretching of the heart, which causes greater tension development, stronger force of contraction and larger stroke volume

238
Q

What helps equalize the output of the right and left sides of the heart?

A

The relationship between venous return and stroke volume

239
Q

What happens when the right side of the heart receives a large volume of blood?

A
  • The EDV increases and causes the right ventricle to contract forcefully, propelling blood into the pulmonary circulation
  • A large volume is pumped to the left side, which increases EDV and causes the left ventricle to conract forcefully, ejecting blood into the systemic circulation
240
Q

How are effects of the sympathetic NS mediated?

A

Through epinephrine and norepinephrine on contractile cells

241
Q

What else does activation of the sympathetic NS cause besides increased cardiac contractility?

A

Constriction of veins, which in turn results in greater return of blood to the heart, causing increased EDV and CO

242
Q

What 2 pathological conditions can increase the workload of the heart?

A

High arterial pressure or a defective valve

243
Q

What is hypertrophy?

A

A short-term compensatory mechanism by which the heart is able to adjust to the increased workload by increasing the number of cardiac muscle cells

244
Q

What is the main difference between a failing heart and a non-failing heart?

A

A failing heart ejects a lower stroke volume for a given EDV

245
Q

What is the hallmark of heart failure?

A

Impaired contractility

246
Q

What are 2 compensatory mechanisms used in the initial stages of heart failure?

A

1) Elevated sympathetic activity

2) Increased EDV

247
Q

How do the kidneys help with heart failure?

A

CO is diminished, so the kidneys retain extra salt and water, increasing blood volume and thus elevating EDV

248
Q

What is backward failure and when does it occur?

A
  • When blood that is unable to enter the heart and blood that is unable to be pumped out builds up in the venous system
  • Occurs in later stages of heart failure
249
Q

What is forward failure and when does it occur?

A
  • When the heart cannot pump sufficient blood as a result of a progressively smaller stroke volume
  • Occurs after backward failure
250
Q

Are blood vessels a closed or open system?

A

Closed

251
Q

What are the 2 portal systems in humans?

A

Hepatic and hypophyseal

252
Q

True or false: blood is evenly distributed through the circulatory system

A

False, different vascular beds receive different amounts of blood depending on the needs of the tissue

253
Q

True or false: each tissue receives only the amount of blood it needs

A

False, some organs receive more blood than they need

254
Q

Why is it advantageous that some organs receive more blood than they need?

A

They can survive large fluctuations in blood flow without damage

255
Q

What are 3 examples of organs that can withstand a decrease in their normal blood flow?

A

1) Kidneys
2) Skin
3) Digestive tract

256
Q

What are arterioles coated with?

A

Smooth muscle

257
Q

What are capillaries the site of?

A

Nutrient and cellular waste exchange

258
Q

What is the function of venules?

A

Drain capillary beds

259
Q

Why are veins highly elastic?

A

They need to constrict

260
Q

How is flow rate determined?

A

delta P/R

261
Q

Why is pressure gradient significant to flow rate?

A

It is the main driving force for flow through the vessel

262
Q

What provides the energy for the pressure gradient?

A

Cardiac pump

263
Q

What is resistance?

A

A measure of hindrance to blood low through a vessel

264
Q

What happens if resistance increases?

A

The pressure gradient must also increase to maintain a steady flow rate

265
Q

With respect to arterioles, at which points is mean arterial pressure higher and lower?

A
  • Higher before blood reaches arterioles

- Lower within the arterioles just before it reaches capillaries

266
Q

What happens if resistance doubles and pressure gradient remains the same?

A

Flow rate will reduce by half

267
Q

What is flow a measure of?

A

Volume per unit time

268
Q

What is velocity a measure of?

A

Linear distance per unit time

269
Q

What is caused by a greater vessel surface area in contact with blood?

A

Greater resistance

270
Q

What is caused by a smaller diameter vessel?

A

Greater resistance

271
Q

How are resistance and vessel radius related?

A

Resistance is inversely related to the 4th power o the vessel radius (r^4/R)

272
Q

What would a 2x increase in radius do to resistance?

A

Decrease resistance by 16-fold

273
Q

What would a 2x increase in radius do to flow rate?

A

Increase flow rate by 16x

274
Q

Why is vessel length ignored?

A

Because we have a closed circulatory system, and length rarely changes

275
Q

What is the most important contributor to resistance?

A

Vessel radius

276
Q

What occurs in atherosclerosis with respect to radius and flow rate?

A

Radius decreases due to plaque, causing flow rate to decrease

277
Q

What is pulse pressure?

A

The difference between systolic and diastolic pressure

278
Q

What is mean arterial pressure?

A

The average pressure driving the blood forward into the tissues

279
Q

Why is mean arterial pressure not (systolic + diastolic) / 2?

A

Arterial pressure remains closer to diastolic than systolic pressure for a longer portion of the cardiac cycle

280
Q

How is mean arterial pressure calculated?

A

pp/3 + D

281
Q

What are Korotkoff sounds?

A

The sounds heard when the pressure of the cuff matches the blood pressure

282
Q

What blood pressure is considered hypertension?

A

140/90

283
Q

What blood pressure is considered hypertension for diabetics or those with kidney disease?

A

130/80

284
Q

Arteries are ____ vessels

A

Conductance

285
Q

Arterioles are _____ vessels

A

Resistance

286
Q

Veins are _____ vessels

A

Capacitance

287
Q

What 4 things are arteries composed of?

A

1) Smooth muscle cells
2) Endothelial cells
3) Collagen fibres
4) Elastic laminae

288
Q

What is the function of smooth muscle cells for arteries?

A

Regulate diameter

289
Q

What is the function of endothelial cells for arteries?

A

Regulate smooth muscle function & vessel permeability

290
Q

What are 2 functions of collagen fibres for arteries?

A
  • Impart rigidity to the arterial wall

- Give mechanical strength to withstand pressure and stretching

291
Q

What is the function of elastic laminae for arteries?

A

Impart elasticity to the arterial wall

292
Q

Do arteries offer lots or little resistance to flow and why?

A

Little because of their relatively large diameter

293
Q

True or false: arteries can store energy to force blood movement when the heart relaxes

A

True

294
Q

What is blood pressure a function of?

A

The volume of blood in the vessel and the compliance of the vessel

295
Q

What happens when pressure is changed in a vessel with high compliance?

A

A large change in volume

296
Q

What happens when pressure is changed in a vessel with low compliance?

A

A small change in volume

297
Q

During systole, is there more blood going in or out of the vessel and what does this cause?

A

Volume going in is greater than volume going out, which means the pressure gradient will increase and vessel walls expand

298
Q

During diastole, is there more blood going in or out of the vessel and what does this cause?

A

Volume going in is less than volume going out, which means the pressure gradient decreases and vessel walls contract

299
Q

What is the function of elastic properties of arteries?

A

Allows them to expand and thus store potential energy as blood volume increases with contraction

300
Q

What protein produces the elastic properties of arteries?

A

Elastin

301
Q

Why do arterioles adjust?

A

To determine the distribution of cardiac output and to regulate blood pressure

302
Q

What is another term for flow?

A

Cardiac output

303
Q

What is another term for pressure gradient?

A

Mean arterial pressure

304
Q

What is another term for resistance?

A

Total peripheral resistance

305
Q

If cardiac output increases, what will happen to blood pressure?

A

It will also increase

306
Q

If resistance increases, what will happen to blood pressure?

A

It will also increase

307
Q

If vessels open, what will happen to blood pressure?

A

It will decrease

308
Q

What happens when resistance is increased due to vasoconstriction?

A

Blood flow is decreased

309
Q

What is vascular tone?

A

Partial constriction of the vessel

310
Q

What does vascular tone allow for?

A

Fine control of resistance

311
Q

What would happen if vascular tone did not exist?

A

No vasodilation control

312
Q

What 2 things cause generation of vascular tone?

A

1) Myogenic activity

2) Sympathetic release of norepinephrine

313
Q

True or false: a tissue receives exactly the amount of perfusion required to meet its immediate metabolic needs

A

True

314
Q

What can too little perfusion cause?

A

Impair the tissues ability to function

315
Q

What can too much perfusion cause?

A

Deny valuable resources to other tissues

316
Q

What are 2 important factors for extrinsic control of arteriolar resistance?

A

1) Neural

2) Hormonal

317
Q

True or false: systemic extrinsic effects override local intrinsic adjustments

A

False, intrisic effects override extrinsic effects

318
Q

What supplies all smooth muscle (except in brain tissue)?

A

Sympathetic nerve fibres descending from the cardiovascular control centre of the brain

319
Q

What does elevated sympathetic activity cause?

A

Vasoconstriction

320
Q

What does decreased sympathetic activity cause?

A

Vasodilation

321
Q

What can activation of the motor cortex cause?

A

Regulation of the sympathetic NS and parasympathetic NS, thus affecting cardiovascular regulation

322
Q

What are baroreceptors?

A

Pressure-sensitive receptors

323
Q

Where are baroreceptors located?

A

In the carotid sinus and aortic arch

324
Q

When are baroreceptors activated?

A

In response to high or low BP and act to regulate BP

325
Q

What do baroreceptors influence?

A

PNS and SNS

326
Q

Where are skeletal muscle mechanoreceptors located?

A

In muscle

327
Q

What do skeletel muscle mechanoreceptors sense?

A

Mechanical or metabolic signals associated with muscle contraction

328
Q

What happens when skeletal muscle mechanoreceptors are activated?

A

They influence the SNS to increase blood pressure and heart rate; contribute to the central control of blood flow

329
Q

What 2 things have a significant impact on blood pressure?

A

1) Blood volume

2) Fluid balance

330
Q

Why are hypertension patients often prescribed diuretics?

A

To increase urine output and decrease blood volume, thus decreasing blood pressure

331
Q

What are 2 vasodilator hormones?

A

1) Bradykinin

2) Histamine

332
Q

What does bradykinin cause?

A

Dilation and increased capillary permeability

333
Q

What does histamine cause?

A

Vasodilation of arteriolar smooth muscle

334
Q

Where does histamine arise from?

A

Connective tissue cells or circulating WBC’s

335
Q

What are 3 vasoconstrictor hormones?

A

1) Norepinephrine/epinephrine
2) Angiotensin 2
3) Vasopressin

336
Q

Where is epinephrine released from?

A

Adrenal medulla

337
Q

What does epinephrine cause?

A

Systemic vasoconstriction and increased blood pressure

338
Q

What is a secondary function of epinephrine?

A

Binds to beta-2 adrenoreceptors to cause vasodilation in tissues with a lot of beta-2 receptors

339
Q

What does angiotensin 2 cause?

A

Increase in TPR, thus increasing blood pressure

340
Q

What does angiotensin do at the local level?

A

Can severely limit blood flow by promoting severe vasoconstriction

341
Q

Is vasopressin or angiotensin 2 more potent?

A

Vasopressin

342
Q

Where is vasopressin formed?

A

In nerve cells in the hypothalamus

343
Q

Where is vasopressin stored?

A

Posterior pituitary

344
Q

What does vasopressin do once it is secreted into the blood?

A

Influences blood pressure regulation during severe hemorrhage

345
Q

True or false: intrinsic control can be either chemical or physical in nature

A

True

346
Q

What does high O2 tension mean?

A

Vasoconstriction

347
Q

What does high CO2 tension mean?

A

Vasodilation

348
Q

What happens to oxygen and flow when metabolic demands increase?

A

Oxygen is depleted, so muscle tension cannot be maintained, the vessel dilates, and flow to the tissue increases

349
Q

What is active hyperemia?

A

When blood flow increases in order to meet increased local metabolic demand

350
Q

What is produced by actively metabolizing tissues and what do all of these substances have in common?

A
  • CO2, acids, potassium, and adenosine

- All are vasodilators

351
Q

Lipid-derived prostaglandins are vaso_____

A

Dilators

352
Q

What is prostacyclin produced by and what is it’s function?

A

Produced by endothelial cells to maintain normal flow

353
Q

What is endothelial-derived relaxing factor (EDRF)?

A

A potent vasodilator that has been identified as the soluble gas nitric oxide

354
Q

What does nitric oxide cause?

A

Relaxation of smooth muscle; aka vasodilation

355
Q

What can impaired nitric oxide production cause?

A

Hypertensive disorders

356
Q

What is endothelial-derived hyperpolarizing factor (EDHF)?

A

A vasodilator

357
Q

When is endothelin released?

A

In response to vascular damage caused by physical trauma

358
Q

Where is endothelin found?

A

Endothelial cells of most blood vessels

359
Q

What does endothelin cause?

A

Severe vasoconstriction to help prevent extensive bleeding

360
Q

True or false: endothelin produces a long-term effect

A

False, endothelin produces a short-term immediate effect

361
Q

Heat ____ blood flow

A

Increases

362
Q

Cold ____ blood flow

A

Decreases

363
Q

What does cold cause?

A

Vasoconstriction, resulting in reduced blood flow to the affected tissue

364
Q

What is reactive hyperemia?

A
  • When blood flow to a tissue is totally restriced, myogenic relaxation is coupled with a decrease in O2 levels in that tissue
  • The result is a large increase in blood flow once the occlusion is removed
365
Q

What is shear stress?

A

A longitudinal force induced by the friction of blood flowing over the endothelial cell surface

366
Q

What is a result of shear stress?

A

Endothelial cells release nitric oxide, causing relaxation of underlying smooth muscle

367
Q

What is pressure autoregulation?

A

A means by which tissues resist changes in blood flow, in the fact of changes in mean arterial pressure

368
Q

What does a drop in MAP cause?

A

Reduced blood flow and stretching of arterioles, therefore arterioles dilate to restore blood flow to normal

369
Q

What does an increase in MAP cause?

A

Increased blood flow and stretch of arterioles, resulting in vasoconstriction to restore blood flow back to normal

370
Q

True or false: tissue metabolic demands remain the same most of the time

A

False, they change rapidly

371
Q

What stimulates a change in tissues metabolic needs?

A

A need to quickly alter perfusion

372
Q

What causes a tissues metabolic needs to change (what factors actually cause the change)?

A

Various systemic and local factor changes

373
Q

Skeletal and cardiac muscle have powerful _____ to override ____

A
  • Local control mechanismss

- Sympathetic vasoconstriction and local beta-2 adrenoreceptors to promote vasodilation

374
Q

What happens upon starting exercise?

A

Sympathetic drive increases throughout the body, resulting in generalized vasoconstriction, but localized control mechanisms override this and cause vasodilation in exercising muscles

Physiology (7 decks)

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