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CARDIO - RESP BLOCK > Cardiac Physiology > Flashcards

Cardiac Physiology Flashcards

1
Q

The heart pumps from?

A

Low pressure veins to high pressure arteries

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2
Q

Blood pressure in the pulmonary circuit is approximately?

A

28/8 mmHg

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3
Q

Blood pressure in the systemic circuit is approximately?

A

120/80mm Hg

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4
Q

Define heart failure

A

The pathological state in which the heart is unable to pump blood at a rate required by metabolizing tissues or can do so only with an elevated filling pressure

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5
Q

In adults heart failure most frequently results from inability of the left ventricle to?

A

Fill – Diastolic performance

Eject blood – Systolic performance

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6
Q

What is the Cardiac cycle?

A

The cardiac cycle can be described as a coordinated sequence of electrical and mechanical events occurring from the start of one heartbeat to the start of the next

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7
Q

A single cardiac cycle includes?

A

A complete relaxation and contraction of both atria and ventricles

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8
Q

What is the relaxation phase?

A

DIASTOLE

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9
Q

What is the contraction phase?

A

SYSTOLE

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10
Q

What directs movement of blood in the heart?

A

Valves within the heart

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11
Q

Pressure changes are brought about by ?

A

Conductive electrochemical changes within the myocardium that result in contraction of cardiac muscle

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12
Q

Which valve closes during atrial contraction?

A

Mitriai valve closes

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13
Q

Ventricular isovolumetric contraction occurs ?

A

When both valves are closed and aortic valve opens

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14
Q

Ventricular isovolumetric relaxation occurs?

A

When both valves are closed - mistrial valve opens

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15
Q

Phases of the cardiac cycle

A
  1. Atriole systole begins
  2. Ventricular systole - first phase
  3. Ventricular systole - second phase
  4. Ventricular diastole - early
  5. Ventricular diastole - late
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16
Q

Which ECG wave corresponds to when atriole systole begins ?

A

P wave

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17
Q

Which wave corresponds to Atrial depolarisation in ECG?

A

P wave

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18
Q

Which wave corresponds to Ventricle depolarisation in ECG?

A

QRS complex

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19
Q

Which wave corresponds to Ventricular repolarization?

A

T wave

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20
Q

Function of Gap junctions

A

Gap junctions allow passage of action potentials from one cell to the next, very quickly – allows the cardiac muscle to function together as a SYNCTIUM

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21
Q

What structures allow the cardiac muscle to function as a SYNCTIUM?

A

GAP junctions

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22
Q

Function of Intercalated discs

A

Intercalated discs link muscle cells together and contain desmosomes and gap junctions

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23
Q

Function of Desmosomes

A

Desmosomes hold the muscle cells together tightly

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24
Q

What is the name of the process by which Myocardial cells can spontaneously depolarize?

A

Automaticity

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25
Q

Which structures allow action potential to pass to adjacent cells?

A

Intercalated discs

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26
Q

Spontaneous depolarisation generates?

A

Pacemaker potential

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27
Q

How many syncytiums does the heart have?

A

2

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28
Q

Heart composed of two syncytiums

A

Atrial

Ventricular

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29
Q

Atrial syncytium

A

Constitutes the walls of the two atria

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30
Q

Ventricular syncytium

A

Constitutes walls of the two ventricles

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31
Q

Function of fibrous tissue that seat the cardiac valve

A

It lacks gap junctions and electrically isolates atria from ventricles: provides a border

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32
Q

Phases of the cardiac action potential are associated with changes in cell membrane permeability, mainly by which ions?

A

Na + , K + , and Ca ++ ions.

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33
Q

Changes in cell membrane permeability alter the rate of movement of these ions across the membrane and thereby change the membrane voltage (V m ).

True or false?

A

True

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34
Q

Changes in permeability are accomplished by?

A

Opening and closing of ion channels that are specific for individual ions

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35
Q

Why do cells have a Resting potential?

A

Due to distribution of ions across the cell membrane

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36
Q

The resting is ?

A

NEGATIVE- inside the cell relative to the outside

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37
Q

Find the term:

This is the electrical potential difference (voltage) between the inside and the outside of a cell

A

Transmembrane potential =TMP

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38
Q

When there is a net movement of +ve ions into a cell, the TMP becomes?

A

More POSITIVE

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39
Q

When there is a net movement of +ve ions out of a cell, TMP becomes?

A

MORE negative

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40
Q

Two main forces drive ions across cell membranes?

A

Chemical potential

Electrical potential

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41
Q

Name the process when an ion will move down its concentration gradient.

A

Chemical potential

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42
Q

Name the process when an ion will move away from ions/molecules of like charge

A

Electrical potential

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43
Q

Ionic movements or conductances across the myocardial membrane occur in response to?

A

The electrochemical potential gradient

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44
Q

Ionic movements or conductances are controlled by?

A

selective ion permeability

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45
Q

Properties of cardiac ion channels

A
  • Selectivity
  • Voltage- sensitive gating
  • Time-dependence
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46
Q

Name the property of cardiac ion channels:

They are only permeable to a single type of ion based on their physical configuration.

A

Selectivity

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47
Q

Name the property of cardia ion channels:

A specific TMP range is required for a particular channel to be in open configuration; at all TMPs outside this range, the channel will be closed and impermeable to ions. Therefore, specific channels open and close as the TMP changes during cell depolarization and repolarization, allowing the passage of different ions at different times.

A

Voltage-sensitive gating

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48
Q

Name the property of cardiac ion channels:

Some ion channels (importantly, fast Na+ channels) are configured to close a fraction of a second after opening; they cannot be opened again until the TMP is back to resting levels, thereby preventing further excessive influx.

A

Time - dependence

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49
Q

The cells of the SAN depolarise over time, with movement of ions causing ?

A

The resting membrane potential to gradually decrease (pacemaker potential)

50
Q

What happens once the membran potential exceeds a threshold?

A

An action potential is triggered

51
Q

An action potential is triggered automatically every?

A

0.8 seconds (approx.) at rest

52
Q

The cells of the AVN depolarise like the cells of the SAN, but more slowly. What does this result into?

A

An action potential is triggered in the AVN cells before they depolarise enough to trigger their own

53
Q

Name the process by which an electrical action potential leads to contraction of cardiac muscle cells

A

Excitation-contraction coupling

54
Q

How is Excitation-contraction coupling achieved?

A

By converting a chemical signal into mechanical energy via the action of CONTRACTILE PROTEINS

55
Q

What is the crucial mediator that couples electrical excitation to physical contraction by cycling in and out of the myocyte’s cytoskeleton during each potential?

A

Calcium

56
Q

At what membran potential do SAN cell membrane ‘funny channels’ open?

A

-60 mV

57
Q

What happens at -60 mV?

A

Sodium enters the cell through the ‘funny channels’, taking a positive charge into the cell

58
Q

What effect does Sodium have once entering the cell?

A

The inside of the cell becomes less negative in relation to the outside

59
Q

Once the inside of the cell becomes less negative in relation to the outside what happens next?

A

A type of voltage – gated calcium channels open, and calcium enters the cell slowly

The cell continues to depolarise gradually (pacemaker potential)

60
Q

What happens when the threshold is reached?

A

Another type of voltage- gated calcium channels opens and calcium enters the cell rapidly

61
Q

What is the result of calcium entering the cell rapidly ?

A

This results in rapid depolarisation – the cardiac action potential

62
Q

Depolarisation is due to?

A

K+

63
Q

The initial influx of Ca2+ into myocytes through L-type Ca2+ channels during phase 2 of the action potential is insufficient to trigger contraction of myofibrils. This signal is amplified by?

A

CICR mechanism

64
Q

What is the purpose of the CICR mechanism

A

It triggers much greater release of Ca2+ from the sarcoplasmic reticulum

65
Q

The cell membrane of cardiomyocytes are called?

A

Sarcolemma

66
Q

Name the specialized Ca2+ release receptors in the sarcoplasmic reticulum (SR)

A

Ryanodine receptors

67
Q

The influx of Ca2+ into mycocytes is through?

A

L-type Ca2+ channels during phase 2 of the action potential

68
Q

What is the name of this mechanism?

The cell membrane of cardiomyocytes, called sarcolemma, contains invaginations (T-tubules) that bring L-type Ca2+ channels into close contact with ryanodine receptors, specialized Ca2+ release receptors in the sarcoplasmic reticulum (SR).
• When Ca2+ enters the cells through L-type channels, ryanodine receptors change conformation and induce a larger release of Ca2+ from abundant SR stores.
• Large levels of intracellular Ca2+ act on tropomyosin complexes to induce myocyte contraction.

A

CICR MECHANISM

69
Q

The trace in EINTHOVENS TRUANGLE depends on?

A

a) The direction of travel
b) Whether the cells are depolarising or repolarising
c) The size of the change in potential

70
Q

Electrical trace resulting from action potentials in all the heart muscle fibres

A

ECG

71
Q

Atrial contraction on ECG

A

P wave

72
Q

Depolarisation of ventricular muscle on ECG

A

QRS complex

73
Q

Repolarization of ventricular muscle on ECG

A

T wave

74
Q

The ECG represents?

A

The electrical vectors of the cardiac cycle

75
Q

The baseline of the ECG is the?

A

Isoelectric line - denotes resting membrane potential

76
Q

What denotes resting membrane potential in the ECG

A

Isoelectric Line

77
Q

Atrial repolarization is too minor in amplitude to be recorded by surface electrodes

True or false

A

True

78
Q

What is the isoelectric point in the QRS complex ?

A

S

79
Q

Contraction commences at PEAK of which portion in the QRS complex?

A

R portion

80
Q

Which interval in ECG starts with atrial muscle depolarization ends with the start of ventricular depolarization ?

A

PR interval- it is assumed that the impulse passes through the AV node into the ventricle during this interval

81
Q

A prolonged PR interval may suggest?

A

AV block is present

82
Q

What is used as a baseline - reference line or isoelectric line of the ECG trace?

A

PR segment

83
Q

Volume of blood In the ventricles at the end of diastole is?

A

End diastolic voluMe = EDV

84
Q

How much is EDV ?

A

130 ml at rest

85
Q

Volume of blood at the end of systole is?

A

End of systolic volume = ESV

86
Q

How much is ESV at rest?

A

60 ml

87
Q

Amount if blood elected from the ventricles in one beat is?

A

Stroke volume= SV

88
Q

Formula for SV (STROKE VOLUME)

A

SV=EDV-ESV

Stroke volume= End of diastolic volume - End of systolic volume

89
Q

Formula for Cardiac Output CO?

A

CO= SV x HR (heart rate)

90
Q

Units for HR

A

bpm = beats per minute

91
Q

The higher the arterial pressure, SV is

A

Lower

92
Q

Regulation of SV

A

Preload

Afterload

Contractility

93
Q

The extent of stretch of the heart muscle is called?

A

PRELOAD

94
Q

The pressure against which the heart need to pump, to expel blood is called?

A

AFTERLOAD

95
Q

The ability of the muscle to produce a force is called?

A

CONTRACTILITY

96
Q

What increases contractility ?

A

Inotropic agents such as adrenalin , and the influence of the sympathetic nervous system

97
Q

Force of contraction is proportional to?

A

The INITIAL fibre length in diastole

98
Q

According to the Starlings Law:

Increased stretch of ventricular muscle results in?

A

Increased overlap of actin and myosin filaments so that a greater number of cross bridges are formed

99
Q

Le get tension relationship states that ?

A

There is an optimal sarcomere length for maximum contraction

100
Q

Intracellular calcium required to generate 50 % max tension is lower when?

A

Muscle fibres is stretched

101
Q

Why is Frank-Starling effect important?

A
  • Allows the heart to adapt its pumping capacity to changes in venous return and to changes in arterial blood pressure
  • Helps to match the output of right and left sides of the heart
102
Q

The cardiovascular center in the medulla oblongata controls?

A

Sympathetic and parasympathetic nerves that innervate the heart

103
Q

Which system:

  • Decreases rate of influx of Na+ through the funny channels, and slow Ca2+ influx
  • This means it takes longer for the pacemaker potential to reach the threshold for an action potential
A

Parasympathetic NS (slows heart rate)

104
Q

Which system:

Increases rate of influx of Na+ and Ca2+

This means that pacemaker potentials develop quickly, so cardiac action potentials

A

Sympathetic NS (increases heart rate)

105
Q

What represents the pressure of the blood as it moves through the arterial system?

A

Systemic hypertension

SVR

106
Q

Formula for Blood pressure BP

A

BP=COxSVR

With CO= SV x HR
107
Q

Systolic BP is largely determined by?

A

Characteristics of SV being ejected by the heart and the ability of aorta to stretch to accommodate the SV

108
Q

Diastolic pressure is determined by?

A

The energy that is stored in the elasticity of fibres that are stretched during systole

109
Q

Withouttheelasticrecoil,pressure would?

A

Fall dramatically between beats, as would blood flow

110
Q

Blood pressure is regulated by?

A

A baroreceptor reflex

111
Q

Longtermbloodpressureismaintainedmainlythroughthe?

A

Renin-angiotensin- aldosterone mechanism

112
Q

Stretch - sensitive sensory nerve roots endings are located in the?

A

Carotid sinuses and aortic arch

113
Q

As arterial pressure decreases what happens to HR?

A

HR decreases

114
Q

What happens is blood pressure remains elevated?

A

It can reset or down regulate the reflex to a higher set point

115
Q

Name the process:

  • Contraction of smooth muscle in the vessel walls, also precapillary sphincters in arterioles
  • Causes narrowing of the diameter of the blood vessel
  • Caused by sympathetic nerve activity and the hormone angiotensin II
  • Increases the resistance of blood vessels to blood flow
A

Vasoconstriction

116
Q

Name the process:

  • relaxation of smooth muscle in the vessel walls, also precapillary sphincters in arterioles
  • Causes widening of the diameter of the blood vessel
  • Caused by withdrawal of sympathetic nerve activity and locally released chemicals e.g. nitrous oxide and lactic acid
  • decreases the resistance of blood vessels to blood flow
A

Vasodilation

117
Q

Arterial pressure I’d the product if ?

A

Cardiac output and peripheral resistance

118
Q

Pressure receptors are called?

A

Baroreceptors

119
Q

The response to injury hypothesis states that the initial event in the pathogenesis of atherosclerosis is?

A

Injury to epithelium

120
Q

Atherosclerosis development

A
  • Injury to vascular endothelium
  • Lipoprotein deposition
  • Inflammatory reaction
  • Cap formation
121
Q

Time between atrial depolarisation and ventricular depolarisation in ECG is defined by?

A

PR interval

CARDIO - RESP BLOCK (13 decks)

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