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Medical Physiology > Cardiovascular system > Flashcards

Cardiovascular system Flashcards

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USMLE® Step 1 flashcards
1
Q

Of what does cardiac muscle consist?

A

Of short, striated muscle fibres (cells).

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2
Q

What do sliding filaments allow?

A

Shortening of the muscle.

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3
Q

Due to which factors’ action are filaments arranged in bundles?

A

Due to the action of actin and myosin.

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4
Q

What is actin?

A

Thin.

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5
Q

What is myosin?

A

Thick.

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6
Q

What are the bundles where filaments are arranged called?

A

Myofibrils.

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7
Q

What are the energy demands on the cell?

A

So high.

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8
Q

What is 40% of cell volume?

A

Mitochondria.

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9
Q

What is the outer layer of the ventricle wall called?

A

The pericardium.

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10
Q

With what does the inner layer or the ventricle make contact with?

A

The blood.

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11
Q

How is the inner layer of the ventricle called?

A

The endocardium.

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12
Q

What is in the middle of the ventricle?

A

The thick myocardium/muscle layer.

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13
Q

Of what is the muscle/myocardium composed?

A

Of myocytes.

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14
Q

Of what is each myocyte composed?

A

Of myofibrils.

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15
Q

What are myofibrils?

A

Cylindrical organelles.

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16
Q

What are the cylindrical organelles of muscles?

A

The contractile unit.

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17
Q

What are the cardiac muscle cells/myocardial cells?

A

Striated.

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18
Q

What do myocardial cells contain?

A

Actin and myosin filaments.

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19
Q

How areactin and myosin filaments arranged?

A

In the form of sarcomeres.

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20
Q

By what do actin and myosin filaments contract?

A

By means of the sliding filament mechanism.

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21
Q

How are myocardial cells characterised?

A

Short.
Branched.
Interconnected.

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22
Q

What is each myocardial cell in structure?

A

Tubular.

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23
Q

To what is each myocardial cell joined?

A

To adjacent myocardial cells.

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24
Q

By what is each myocardial cell joined to adjacent myocardial cells?

A

By electrical synapses/gap junctions.

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25
Q

Where are the gap junctions concentrated?

A

At the ends of each myocardial cell.

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26
Q

What does each myocardial cell permit?

A

Electrical impulses.

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27
Q

Where are electrical impulses of myocardial cells conducted?

A

Along the long axis from cell to cell.

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28
Q

For what do gap junctions in cardiac muscle have an affinity?

A

For stain.

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29
Q

As what does stain make the gap junctions appear in cardiac muscle?

A

As dark lines between adjacent cells.

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30
Q

When do gap junctions appear as dark lines between adjacent cells?

A

When they are viewed in the light microscope.

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31
Q

As what are the dark-staining lines known?

A

As intercalated discs.

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32
Q

Where do action potentials originate?

A

At any point in a mass of myocardial cells.

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33
Q

How are the actions potential from myocardial cells called?

A

Myocardium.

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34
Q

Where is myocardium spread?

A

To all cells in the mass that are joined by gap junctions.

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35
Q

What are all cells in a myocardium?

A

Electrically joined.

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36
Q

As what does a myocardium behave?

A

As a single functional unit.

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37
Q

What do skeletal muscles produce?

A

Contractions.

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38
Q

Depending on what are skeletal muscles graded?

A

On the number of cells stimulated.

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39
Q

To what does a myocardium contract each time?

A

To its full extent.

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40
Q

Why does myocardium contract to its full extend each time?

A

Because all of its cells contribute to the contraction.

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41
Q

What can the ability of the myocardial cells to contract do?

A

Increased by the hormone adrenaline.

By stretching of the heart chambers.

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42
Q

Of what is a myocyte made?

A

Of many myofibrils.

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43
Q

To what does the outer sarcolemma membrane serve?

A

To bundle the fibrils.

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44
Q

To what is the sarcolemma similar?

A

To a typical plasma membrane.

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45
Q

For what does the sarcolemma have specialised functions?

A

For the muscle cell.

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46
Q

By what is the dark and light banding pattern cause?

A

By the regular arrangement of actin and myosin filaments.

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47
Q

Where does depolarisation of the membrane proceed?

A

Down the longitudinal tubules to all the myofibrils.

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48
Q

Across what does depolarisation spread?

A

Across the sarcoplasmic reticulum.

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49
Q

Via what does the depolarisation spread across the sarcoplasmic reticulum?

A

Via the transverse/T tubules.

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50
Q

What is the SR?

A

The store of cellular calcium ions.

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51
Q

Thanks to what a more detailed banding pattern can be observed?

A

Thanks to the arrangement of the tubules.

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52
Q

Of what do triads consist?

A

Of two terminal cisterns of the L-system. associated with a central T-tubule segment.

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53
Q

What is the main function of the triads?

A

To translate the action potential from the plasma membrane to the sarcoplasmic reticulum.

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54
Q

What does action potential from the plasma membrane to the sarcoplasmic reticulum affect?

A

Calcium flow into the cytoplasm.

Initiation of muscle contraction.

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55
Q

Where do T tubules project?

A

Into the depths of the myocyte.

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56
Q

Of what id each myofibril composed?

A

Of a thick and thin filaments.

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57
Q

To what do thick and thin filaments of myofibril give rise?

A

To the banding pattern of the muscle.

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58
Q

What do the voltage-gated Ca channels in the plasma membrane and the Ca release?

A

Channels in the sarcoplasmic reticulum.

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59
Q

What do voltage-gated Ca channels and the Ca do not?

A

Directly interact.

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60
Q

To what region do the transverse T tubules come very close to?

A

To the sarcoplasmic reticulum.

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61
Q

During what does depolarization of the T tubules occur?

A

During an action potential.

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62
Q

What does depolarization of the T tubules open?

A

Voltage-gated Ca channels in their plasma membrane.

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63
Q

Where does Ca diffuse?

A

Into the the cytoplasm.

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64
Q

With what does the Ca that diffuses into the cytoplasm interact?

A

With the nearby Ca.

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65
Q

What do Ca diffused into the cytoplasm and the nearby Ca that interact with, release?

A

Channels in the sarcoplasmic reticulum.

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66
Q

What does the release of channels in the sarcoplasmic reticulum causes the Ca channels?

A

To pen and release the stored Ca into the cytoplasm.

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67
Q

What does the release of the stored Ca into the stimulate stimulate?

A

Contraction.

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68
Q

What is contraction?

A

A process termed: calcium-induced calcium release.

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69
Q

As what does Ca serve?

A

As a second messenger.

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70
Q

From where to where does Ca serve as a second messenger?

A

From the voltage-gated Ca channels to the Ca release channels.

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71
Q

Where is excitation-contraction coupling slower as a result of Ca serving as a second messenger?

A

In cardiac than in skeletal muscle.

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72
Q

Through where does Ca diffusion take place?

A

Through the plasma membrane of the transverse tubules.

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73
Q

Where does Ca diffusion serve mainly?

A

To open the channels in the sarcoplasmic reticulum.

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74
Q

Where does Ca release channels?

A

In the sarcoplasmic reticulum.

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75
Q

For what is the Ca release responsible?

A

For the rapid diffusion of Ca into the cytoplasm.

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76
Q

Where does Ca bind to after is diffused into the cytoplasm?

A

To troponin.

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77
Q

What does Ca stimulate after is diffused into the cytoplasm and binds to troponin?

A

Contraction.

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78
Q

What must the Ca in the cytoplasm be in order for the muscular chambers of the heart to relax?

A

They must be actively transported back into the sarcoplasmic reticulum by the Ca ATPase.

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79
Q

What does tropomyosin block in a relaxed muscle?

A

The attachment of cross bridges to actin .

Concentration of Ca.

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80
Q

What is the calcium concentration in the sarcoplasm?

A

Very low.

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81
Q

What happens to the Ca concentration in the sarcoplasm when the muscle cell is stimulated to contract?

A

It rises sharply.

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82
Q

What does some of the Ca attach?

A

Troponin.

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83
Q

What does the Ca attachment to troponin cause?

A

A conformational change.

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84
Q

What does the conformational change caused by Ca and troponin attachment move?

A

The troponin complex –> attached to tropomyosin.

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85
Q

Why does conformational change move troponin complex and its attached it out of the way?

A

So that the cross bridges can attach to actin.

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86
Q

Where do cross bridges bind to once the attachment sites on the actin are exposed?

A

To actin.

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87
Q

What do cross bridges that bind to actin undergo?

A

Power strokes.

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88
Q

What do cross bridges that bind to actin produce?

A

Muscle contraction.

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89
Q

What is now the preferred test for detecting myocardial infarction or heart attack?

A

Measurement of cardiac-specific troponin T/troponin I.

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90
Q

What happens to the myocardial cells in the measurement of cardiac-specific troponin T blood test?

A

They die and release troponin T/I proteins into the blood.

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91
Q

Where do blood tests for troponin T/I rely on?

A

Binding to specific antibodies.

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92
Q

What are the blood tests for troponin T/I?

A

Heart specific.

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93
Q

What does an abnormally increased plasma troponin T/I may indictaed?

A

That an myocardial infarction (MI) has occurred.

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94
Q

What has cardiac troponin become?

A

A continuous variable.

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95
Q

What is the accurate measurement of cardiac troponin?

A

Below the 99th percentile.

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96
Q

How many changes do occur in cardiac toponin?

A

Small changes within 1/2 hours.

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97
Q

What does cardiac troponin measurement and changes enable?

A

Development of algorithms for reliable rule-out and rule-in of acute MI within 2 hours.

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98
Q

What is the cardiac muscle?

A

Striated.

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99
Q

What does the cardiac muscle contain?

A

Sarcomeres that shorten.

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100
Q

By what do the sarcomeres in the cardiac muscle shorten?

A

By sliding of thick and thin filaments.

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101
Q

Of what might the detection of elevated troponin be indicative?

A

Of heart damage.

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102
Q

What do the sarcolemma and T-tubules conduct?

A

Electrical impulse to the muscle.

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103
Q

What does the conduction of sarcolemma and T-tubules that conduct electrical impulse to the muscle trigger?

A

Calcium release from SR.

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104
Q

To what does calcium bind?

A

To troponin.

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105
Q

How are the Bundles of cardiac muscle fibres arranged?

A

Spirally around the ventricles.

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106
Q

How are adjacent cardiac muscle cells joined?

A

End to end.

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107
Q

By what are the cardiac muscle cells joined end to end ?

A

By intercalated discs.

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108
Q

What do intercalated discs contain?

A

Two types of specialized junctions.

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109
Q

Which are the 2 types of specialized junctions that are contained in the intercalated discs?

A
  1. Desmosomes.

2. Gap junctions.

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110
Q

How do desmosomes act?

A

Like rivets.

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111
Q

How do desmosomes hold the cells together?

A

Mechanically.

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112
Q

What do gap junctions permit?

A

Action potentials to spread from one cell to adjacent cells.

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113
Q

Of what is the heart composed?

A

Of spiral clockwise and counter clockwise arrangement of muscle fibres.

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114
Q

What does the physiological sequence of ventricular function involve?

A

An isovolumic contraction phase to develop preejection tension.

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115
Q

What does pre-ejection tension mean?

A

The muscle begins to contract without expelling the blood.

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116
Q

What does follow the ejection phase?

A

Post-ejection isovolumic phase.

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117
Q

When does post-ejection isovolumic phase occur?

A

When there is no change in volume.

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118
Q

What do occur after post-ejection phase?

A

Rapid and slow periods for filling.

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119
Q

How does LV volume decrease in systole?

A

Rapidly.

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120
Q

What is systole?

A

The name for contraction.

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121
Q

How does LV volume decrease after contraction?

A

Slowly.

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122
Q

How does the volume increase in early filling?

A

Rapidly.

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123
Q

How does the volume increase during late filling?

A

More slowly.

124
Q

Of what does the heart consist?

A

4 chambers.
2 atria.
2 ventricles.
major vessels.

125
Q

What do inferior and superior venae cavae bring?

A

Deoxygenated blood back to the right atrium.

126
Q

With what does the left atrium fill?

A

With oxygenated blood from the pulmonary vein.

127
Q

Into where id the blood pumped upon simultaneous contraction?

A

Into the ventricles.

128
Q

Through what is the blood pumped into the ventricles upon simultaneous contraction?

A

Through the tricuspid and bicuspid valves.

129
Q

What do the pulmonary semilunar valve and aortic semilunar valves do as the ventricles contract?

A

They open.

130
Q

Into where is the deoxygenated blood pumped?

A

Into the pulmonary artery.

131
Q

To where is the pumped blood into the pulmonary artery be taken?

A

To the lungs.

132
Q

Into where is the oxygenated blood pumped?

A

Into the aorta.

133
Q

Where is the pumped blood into the aorta carried?

A

Around the body.

134
Q

By what is the eversion of the AV valves prevented?

A

By tension on the valve leaflets.

135
Q

By what are the valve leaflets exert?

A

By the chordae tendineae.

136
Q

When do the valve leaflets exert by the chordae tendineae?

A

When the papillary muscles contract.

137
Q

What happens to the upturned edges of the semilunar valves when they are swept closed?

A

They fit together in a deep, leakproof seam.

138
Q

What does the deep, leakproof seam prevent?

A

Valve eversion.

139
Q

What is the difference between a cyclist and a patient with morphologically mild hypertrophic cardiomyopathy?

A

The cyclist has an enlarged left ventricular cavity.

140
Q

How is cardiac output measured?

A

Volume of blood pumped by the left ventricle + right ventricle per unit time.

141
Q

By what is the cardiac output determined?

A

By the heart rate * stroke volume.

142
Q

By what factors is heart rate influenced?

A

By hormones: adrenaline.
Fitness.
Age.
Autonomic activity.

143
Q

What do fitter people normally have?

A

A lower heart rate.

144
Q

What do older people usually have?

A

A higher heart rate.

145
Q

What happens to the heart rate if parasympathetic activity is high?

A

It is lower.

146
Q

By which factors is stroke volume influenced?

A

By many factors.

147
Q

What can a larger athletic heart pump?

A

A larger volume.

148
Q

What do males usually have?

A

A larger stroke volume.

149
Q

What do a longer duration and stronger contraction increase?

A

SV.

150
Q

What does a larger end diastolic volume increase?

A

SV.

151
Q

What does a lower vessel resistance permit?

A

A larger volume of blood to be ejected.

152
Q

In response to which factor does stroke volume increase according to the Frank-Starling law?

A

To increased EDV.

153
Q

What is diastole?

A

The relaxation of the heart.

154
Q

When does SV increase?

A

As EDV and pressure increase.

155
Q

With what does the slope increase?

A

With sympathetic activity.

156
Q

What does the slope cause when increases?

A

Increased stroke volume.

157
Q

What happens to the slope and stroke volume with parasympathetic activity?

A

They decrease.

158
Q

When is the heart muscle subjected to an increasing degree of stretch?

A

As EDV increases.

159
Q

How does the heart muscle contract s in strecth?

A

More forcefully.

160
Q

What is the sarcomere?

A

A unit of striated muscle tissue.

161
Q

What does the sarcomere do as EDV increases?

A

It stretches.

162
Q

What happens to the actin filaments attached to parallel Z-lines as EDV increases?

A

They are pulled apart.

163
Q

What does the sympathetic activity increase?

A

The strength of myocardial contraction.

164
Q

What effect does the sympathetic activity that increases the strength of myocardial contraction?

A

It has a positive inotropic effect.

165
Q

What happens to the sarcomere beyond a certain volume ?

A

It stretches to a degree.

166
Q

What does the sarcomere degree impair?

A

The amount of force it can generate.

167
Q

Through where does blood flow to reach the organs of the body?

A

Through arteries.

168
Q

By what does is the blood pumped?

A

By action of the heart.

169
Q

What do the arrows indicate?

A

The direction of blood flow.

170
Q

How are all of the heart valves shown to illustrate the direction of blood flow through the heart?

A

Open.

171
Q

What does the right side of the heart receive?

A

Oxygen poor blood from the systemic circulation.

172
Q

Into where does the right side of the heart pump oxygen poor blood?

A

Into the pulmonary circulation.

173
Q

What does the left side of the heart receive?

A

Oxygen rich blood from the pulmonary circulation.

174
Q

Where does the left side of the heart pump oxygen rich blood?

A

Into the systemic circulation.

175
Q

Through where do the parallel pathways of blood flow?

A

Through the systemic organs.

176
Q

What is the difference between the left ventricular wall and the right wall?

A

The left is much thicker.

177
Q

By what side of the heart do the lungs receive all the blood pumped out?

A

By the right side.

178
Q

What do the systemic organs receive?

A

Some of the blood pumped out by the left side of the heart.

179
Q

How is the percentage of pumped blood received by the various organs under resting conditions characterised?

A

Indicated.

180
Q

What can happen to the distribution of cardiac output?

A

It can be adjusted as needed.

181
Q

What are the carotid arteries?

A

The blood vessels that carry oxygenated blood to the head, brain and face.

182
Q

What is the carotid sinus?

A

A dilated area at the base of the internal carotid artery superior to the bifurcation of the internal and external carotid.

183
Q

What does the sinus contain?

A

Many baroreceptors.

184
Q

What do the baroreceptors sense?

A

Change in blood pressure.

185
Q

What is the carotid body?

A

The main peripheral chemoreceptor.

186
Q

What does the carotid body sense?

A

The arterial PO2, PCO2 and pH.

187
Q

What does carotid chemosensory discharge in response to hypoxemia, hypercapnia and acidosis?

A

Reflex respiratory, autonomic and cardiovascular adjustments.

188
Q

Where is carotid chemosensory located?

A

In the adventitia.

In the bifurcation of the common carotid artery.

189
Q

What do the baroreceptor and chemoreceptors constantly monitor?

A

The blood supply.

190
Q

What do the baroreceptor and chemoreceptors send?

A

Signals to the brain.

191
Q

What do the signals sent to the brain from the baroreceptors and chemoreceptors increase?

A

Parasympathetic or sympathetic nervous system output.

192
Q

Why do the signals sent to the brain from the baroreceptor and chemoreceptor increase parasympathetic and sympathetic nervous system output?

A

To regulate heart rate and breathing appropriately.

193
Q

Due to what there might be a decrease in pH?

A

Due to elevated hydrogen ions in circulation from exercise.

194
Q

How does the brain respond if there is a decrease in pH?

A

With increased heart rate, force and breathing rate.

195
Q

What events occur when the baroreceptors sense a decrease in stretching and chemoreceptors sense a decrease in oxygen along with an increase in carbon dioxide and hydrogen ion levels?

A

Homeostatic sequence of events.

196
Q

What happens when parasympathetic stimulation of heart is decreased?

A

There is an increase in HR and SV.

197
Q

Due to which factor is there an increase in blood flow and pressure?

A

Due to increased cardiac output.

198
Q

Due to which factor is there an increase in blood flow and pressure?

A

Due to increased cardiac output.

199
Q

What is the response to chemoreceptor stimulation?

A

Increased sympathetic stimulation of the hear to increase HR and SV.

200
Q

What else does increased HR and SV cause?

A

An increase in blood flow and pressure.

201
Q

What is the heart?

A

One continuous piece of specialised muscle.

202
Q

What is a heart beat?

A

A coordinated relaxation and contraction of atria and ventricles.

203
Q

To what do a series of valves and muscles contribute?

A

To formation of four chambers and compartmentalisation of blood within the heart.

204
Q

By what is cardiac output determined?

A

By stroke volume and heart rate.

205
Q

Under what influence is stroke volume and heart rate?

A

Of various physiological inputs.

206
Q

What does Frank-Starling law explain?

A

The intrinsic contractile behaviour of the heart in response to increased EDV.

207
Q

What are the mechanical events of the heart muscle contraction?

A

Perfectly coordinated in order.

208
Q

Why are the mechanical events of the heart muscle contraction perfectly coordinated in order?

A

For the correct sequence of events to occur.

209
Q

What happens first in the events of heart muscle?

A

Receiving blood into the atria.

210
Q

What happens after the blood is received into the atria?

A

It enters into the ventricles and then out of the heart.

211
Q

What is the hart after the previous ventricular contraction?

A

Relaxed.

212
Q

What does the pressure in the venae cavae and pulmonary artery begin to do when the heart is relaxed?

A

It begins to force blood into the atria.

213
Q

What does the pressure do when blood begins to fill the atria?

A

It builds up.

214
Q

What do the atrio ventricular valves do, as blood begins to fill the atria?

A

They open.

215
Q

What do the ventricles begin to do, as the blood begins to fill the atria?

A

They fill passively.

216
Q

Due to which factor does the atria contract spontaneously?

A

Due to the cardiac pacemaker potential in sinus node.

217
Q

How much time doe the atria contraction take?

A

0.5 seconds.

218
Q

What happens to the muscle, as the blood fills the ventricles?

A

It tightens but don’t shorten.

It is not yet contracting.

219
Q

What does the tightening of the muscle raise?

A

The pressure in the ventricles.

220
Q

Due to which factor do the atrioventricular valves close?

A

Due to the pressure.

221
Q

As what does the closure of the atrioventricular valves heard?

A

As the first heart sound.

222
Q

What does the cardiac action potential cause?

A

The ventricles to contract.

223
Q

What does the cardiac action potential generate?

A

Sufficient pressure.

224
Q

Why does the cardiac action potential generate sufficient pressure?

A

To force the blood out through the semilunar valves and into the aorta and pulmonary artery.

225
Q

What does the back pressure in the vessels do, when the ventricles are relaxed?

A

It forces the semilunar valves shut and the cycle begins again.

226
Q

Where does the action potential initiated at the SA first spread?

A

Throughout both atria.

227
Q

By what is the spread of action potential throughout both atria facilitated?

A

By 2 specialised atrial conduction pathways.

228
Q

Which are the 2 specialised atrial conduction pathways that facilitate the spread of the action potential initiated at the SA?

A
  1. Interatrial / Bacmanns bundle.

2. Internodal pathways.

229
Q

What is the AV node?

A

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

230
Q

Where does the action potential from the AV node spread?

A

Throughout the ventricles.

231
Q

How does the action potential from the AV node spread throughout the vetricles?

A

Rapidly.

232
Q

By what is the action potential from the AV node dispatched?

A

By a specialised ventricular conduction.

233
Q

Of what does the ventricular conduction through where the action potential from the AV node is dispatched consist?

A

Of the bundle of His and Purkinje fibres.

234
Q

What is the first half of the pacemaker potential?

A

The result of simultaneous opening of unique funny channels.

235
Q

What does the simultaneous opening of unique funny channels permit?

A

Inward Na+ current..

Closure of K+ channels.

236
Q

What does the closure of K+ channels reduce?

A

Outward K+ current.

237
Q

What is the second half of the pacemaker potential?

A

The result of opening of T-type Ca2+ channels.

238
Q

What is the result, once threshold potential of -40mV is reached?

A

The rising phase of the action potential.

239
Q

What is the result of the rising phase of the action potential?

A

The opening of L-type Ca2+ channels.

240
Q

What is the result of opening of K+ channels and closing of the calcium channels?

A

The falling phase.

241
Q

What does begin once the cell has repolarised to -60mV?

A

Another slow depolarisation.

242
Q

What does the last slow depolarisation restart?

A

The cycle.

243
Q

From what does the action potential in cardiac contractile cells differ?

A

From the action potential in cardiac autorhythmic cells.

244
Q

What is the rapid rising phase of the action potential in contractile cells?

A

The result of Na+ entry on opening of fast Na+ channels at threshold phase 0.

245
Q

About what value is the resting membrane potential?

A

About -90mV.

246
Q

When is the action potential triggered?

A

When depolarisation occurs beyond -70mV.

247
Q

How is the influx of sodium characterised?

A

So great.

248
Q

What happens to the membrane potential during influx of sodium?

A

It depolarised to 30mV.

249
Q

Why does the early, brief repolarization occur after the potential reaches its peak?

A

Because of limited K+ efflux on opening of transient K+ channels.
And chloride ion efflux accompanied with inactivation of the Na+ channels.

250
Q

The result of what is the prolonged plateau phase, phase 2?

A

Of slow Ca2+ entry on opening of L-type Ca2+ channels, coupled with reduced K+ efflux on closure of several types of K+ channels.

251
Q

What is the rapid falling?

A

Phase 3.

The result of K+ efflux on opening of ordinary voltage-gated K+ channels.

252
Q

By what are the ion concentration and membrane potential restored?

A

By the activity of Na/K ATPase and Na/Ca exchanger.

253
Q

By what is resting potential maintained?

A

By opening of leaky K+ channels.

254
Q

Why can the electrical activity of the heart monitored?

A

To check for signs of pathology.

255
Q

What has been developed as monitoring the electrical activity of the heart is not done directly?

A

An indirect method called ‘electrocardiogram’.

256
Q

What is the use of the electrocardiogram?

A

To record the electrical activity of the heart from different angles to identify and locate pathology.

257
Q

Where are electrodes placed?

A

On different parts of a patient’s limbs and chest.

258
Q

Why are electrodes placed on different parts of a patient’s limbs and chest?

A

To record the electrical activity.

259
Q

What does the reading represent?

A

A graph of voltage versus time of the electrical activity of the heart.

260
Q

How many main components to an ECG are there?

A

3.

261
Q

Which are the 3 main components to an ECG?

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

What does the P wave represent?

A

The depolarization of the atria.

263
Q

What does the QRS complex represent?

A

The depolarisation of the ventricles.

264
Q

What does the T wave represent?

A

The repolarisation of the ventricles.

265
Q

What does the reading represent?

A

The sum of the electrical activity.

266
Q

Where do depolarisation, repolarisation and maintenance of resting membrane potential happen?

A

In different regions of the heart.

267
Q

What do the ventricles do during atrial systole?

A

They are relaxed and repolarised.

268
Q

What happens when the ventricles are relaxed and repolarised?

A

Inward sodium conductance in the atria.

Outward K conductance in the ventricles.

269
Q

Which are the dominant ion flows during atrial systole?

A

Na+ and K+.

270
Q

What does the cardiac action potential contract?

A

The ventricles.

271
Q

What can the ECG help detect?

A

Arrhythmias.
Coronary heart disease.
Heart attacks.
Cardiomyopathy.

272
Q

What happens in arrhythmias?

A

The heart beats too slowly, too quickly, or irregularly.

273
Q

What happens in coronary heart disease?

A

The heart’s blood supply is blocked or interrupted by a build-up of fatty substances.

274
Q

What happens in heart attacks?

A

The supply of blood to the heart is suddenly blocked.

275
Q

What happens in cardiomyopathy?

A

The heart walls become thickened or enlarged.

276
Q

Which are the 3 main types of ECG?

A
  1. A resting ECG.
  2. A stress or exercise ECG.
  3. An ambulatory ECG.
277
Q

When is a resting ECG carried out?

A

While you’re lying down in a comfortable position.

278
Q

When is a stress or exercise ECG carried out?

A

While you’re using an exercise bike or treadmill.

279
Q

What happens in an ambulatory ECG?

A

The electrodes are connected to a small portable machine worn at your waist so your heart can be monitored at home for 1 or more days.

280
Q

Why do the ventricles depolarise and contract?

A

To eject blood into the aorta.

281
Q

What happens to pressure in the arteries, as the ventricles depolarise and contract?

A

It rises.

282
Q

Where does a slight lab occur?

A

In the initiation of depolarisation.
The initiation of the QRST complex.
The peak arterial pressure.

283
Q

When does the pressure rise in the vessels?

A

When the blood is pumped.

284
Q

What does the parasympathetic stimulation decrease?

A

The rate of SA nodal depolarisation.

285
Q

Why does the parasympathetic stimulation decrease the rate of SA nodal deporisation?

A

So that the membrane reaches threshold more slowly and has a fewer action potentials.

286
Q

What does the sympathetic stimulation increase?

A

The rate of depolarisation of the SA node.

287
Q

Why does the sympathetic stimulation increase the rate of depolarisation of the SA node?

A

So that the membrane reaches threshold more rapidly and has more frequent action potentials.

288
Q

To what does each SA done action potential lead?

A

To a heartbeat.

289
Q

What does increased parasympathetic activity decrease?

A

The heart rate.

290
Q

What does the increased sympathetic activity increase?

A

The heart rate.

291
Q

What does the valve closing produce?

A

2 normal heart sounds.

292
Q

By what is the first heart sound (S1)/ ‘ lub’ caused?

A

By closing of the AV valves.

292
Q

By what is the first heart sound (S1)/ ‘ lub’ caused?

A

By closing of the AV valves.

293
Q

By what is the second heart sound (S2) / ‘dub’ caused?

A

By closing of the aortic and pulmonary valves.

294
Q

What does a defective valve function produce?

A

Turbulent blood flow.

295
Q

As what can the turbulent blood flow be heard?

A

As a heart murmur.

296
Q

What might the abnormal valves be?

A

Stenotic or insufficient.

297
Q

What are the stenotic valves?

A

The do not open completely.

298
Q

What are the insufficient valves?

A

They do not close completely.

299
Q

What is a cardiac arrest?

A

An abnormal electrical event.

300
Q

By what is a heart attack caused?

A

By restriction of the blood supply to the myocardium.

301
Q

Where does the pacemaker potential originate?

A

In the SA node.

302
Q

What does the pacemaker potential determine?

A

The intrinsic heart rate.

303
Q

What does SA node receive?

A

Sympathetic and parasympathetic input.

304
Q

What does coordinated activation of Na+, K+ and Ca2+ channels regulate?

A

The electrical activity of SA node and cardiac muscle.

305
Q

What is ECG?

A

A graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin.

Medical Physiology (12 decks)

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