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CVS > Physiology > Flashcards

Physiology Flashcards

1
Q

What are is the conduction system of the heart made up of?

A

specialised cardiac muscle fibres

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2
Q

Describe the flow of electrical signals

A
  1. The SA node spontaneously discharges an electrical impulse that triggers a wave of depolarisation down the heart
  2. Signals flow through internodal fibres from SA to AV node. The depolarisation contracts both atria.
  3. From the AV nodes, signals travel to the bundle of His, which then splits into the right and left bundles and into purkinje fibres
  4. Depolarisation of the ventricle muscle fibres results in the ventricle to contract.
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3
Q

What is the hierarchy of pacemakers

A

the pacemaker with the fastest rate of depolarisation sets the rhythm of the heart.

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4
Q

How does the atria function as a priming pump?

A

The atria contracts before the ventricles so that the ventricles may be fully filled before they contract.

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5
Q

What is the purpose of the fibrous ring?

A
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6
Q

How to ensure that the atria contract first.

A

The fibrous ring, together with the delay at the AV node ensures the atria contract first, fill the ventricles with blood, followed by the contraction of the ventricles.

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7
Q

Activation of the sympathetic nervous system results in …

A

the heart beating faster and harder.

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8
Q

Activation of the parasympathetic nervous system …

A

reduces the heart rate but does not affect the strength of cardiac contractions

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9
Q

What are the Factors Affecting Heart Rate DIRECTLY Through the SA Node?

A
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10
Q

What are the Factors Affecting Heart Rate through the Vasomotor Centre and Autonomic Nervous System

A
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11
Q

Describe the respective neurotransmitters, receptors and ionic changes for the sympathetic and parasympathetic systems

A
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12
Q

What gradients are involved in establishing resting membrane potential

A

Concentration gradient and electrical gradient

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13
Q

What is phase 2

A

This is phase 2 of the action potential, called as “plateau” phase. At this point the calcium influx (movement of positively charged ions into the cell) and the efflux of potassium from the cell balance each another, hence the action potential is “flat” at this point. These are the calcium ions that are responsible for causing the muscle fibre to contract

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14
Q

What is phase 0

A

voltage-gated sodium channels on the membrane of the ventricular muscle opens. When that happens, sodium, present in much higher concentrations outside the cell than in, rushes into the cell. The cell now becomes positive due to the entry of sodium.

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15
Q

What is phase 3

A

After a certain period, calcium ion influx stops. When this happens, and potassium continues to leave the cell, the cell continues to become more negative. This is phase 3 of the action potential, and the cell soon returns to its original resting membrane potential of -85 mV, while awaiting the next wave of depolarisation.

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16
Q

what is phase 1

A

To begin with, the outward rectifying potassium channels open. This is the initial repolarization, or phase 1. When potassium channels open, both the concentration gradient (potassium higher on the inside) together with the electrical gradient (because the cell is depolarised) both combine to push potassium out. So, the cell loses positive charges, and the inside of the cell becomes more negative.

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17
Q

Why are both pressure and flow are further regulated by the vascular system (especially the arterioles)?

A

so that optimal perfusion pressure and flow occur at the tissues.

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18
Q

What are examples of uncoordinated electrical activity?

A

ventricular tachycardia, ventricular fibrillation, atrial fibrillation and heart blocks.

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19
Q

How many electrodes are placed on the chest and limbs for an ECG recording?

A

10

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20
Q

What are the attributes of standard limb leads

A
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21
Q

What are the attributes of augmented limb leads

A
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22
Q

What are the attributes of precorial/ chest leads?

A
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23
Q

Describe the P wave

A

The P wave is the result of atrial depolarisation.

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24
Q

Describe QRS complex

A

The QRS complex is ventricular depolarisation. The Q wave results from the vector created when electrical signals depolarise the bundle of His. The R and S waves result from the depolarisation of the ventricles.

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25
Q

Describe the T wave

A

The T wave is ventricular repolarisation.

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26
Q

Why cant we see atrial repolarisation in ECG?

A

Atrial repolarisation occurs during the QRS complex. The wave of atrial repolarisation is small and therefore masked by the higher voltage QRS complex, so we do not see it on the ECG.

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27
Q

Describe how electrical signals give rise to P wave

A

an electrical vector directed towards the positive electrode is designated positive. So, you will see a small magnitude, positive wave. This is the P wave.

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28
Q

Describe how electrical signals give rise to Q wave

A

Similarly, from the vantage point of lead II, you will see a small vector caused by the depolarisation of the bundle of His. This vector is going away from you, so it is negative. So, the ECG will record a small negative wave called the Q wave.

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29
Q

Describe how electrical signals give rise to R wave

A

As the wave of depolarisation travels down the septum and depolarises the ventricles, it creates a vector of higher magnitude that is coming towards lead II. This produces a positive R wave on the ECG.

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30
Q

Describe how electrical signals give rise to S wave

A

The late depolarisation of the ventricles produces a vector that is moving away from lead II and hence a negative S wave.

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31
Q

Describe how electrical signals give rise to T wave

A

Finally, ventricular repolarisation produces an electrical vector that is directed towards you, hence a positive T wave.

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32
Q

Each lead records the ___________ between 2 electrodes

A

Potential difference

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33
Q

Normal speed at which ECG run is …

A

25 mm/s

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34
Q

The RR interval is the time taken for …

A

1 cardiac cycle

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35
Q

The PR interval is the time taken for the signal to travel from …

A

SA node into the ventricle (that is, right until the time the signal emerges from the AV node).

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36
Q

What is used as a measure of the AV nodal delay time?

A

PR interval.

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37
Q

In the case of heart block, the PR interval is prolonged to more than _____.

A

0.2s

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38
Q

The QT interval is the time taken for …

A

ventricular depolarisation and repolarisation

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39
Q

What can cause prolongation of QT interval?

A

a mutation in the potassium channel, certain drugs

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40
Q

What does a tall QRS wave indicate

A

Tall QRS waves are related to ventricular depolarisation and may represent an increase in myocardial mass called hypertrophy.

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41
Q

What does a tall T wave indicate

A

Tall T waves may be caused by problems with ventricular repolarisation, hyperkalemia being an example.

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42
Q

What does elevated or depressed ST segment suggest?

A

An elevated or depressed ST segment may indicate a myocardial infarction or ischaemia, respectively.

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43
Q

How to diagnose angina pectoris using ECG

A

ST segment depressions can be seen while exercising

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44
Q

The unit of contraction of the heart is _____

A

sarcomeres

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45
Q

What causes sarcomeres to contract

A

Ca binding to troponin C

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46
Q

What type of troponin is indicative of cardiac muscle damage

A

Troponin I

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47
Q

_____ is the key determinant of the strength of cardiac contaction

A

Calcium

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48
Q

Is ventricular muscle relaxation an active/passive process

A

active

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49
Q

Describe the role of calcium in the contraction process

A
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50
Q

What are the 2 mechanisms that regulate the force of cardiac contractions

A
  1. Starling’s law
  2. contractility
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51
Q

What does Starling’s law state

A

Starling’s Law states that the more the heart is loaded with volume (increase stretch), the greater the strength of contraction (force), up to a limit.

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52
Q

What is contractility

A

strength of contraction for any given stretch

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53
Q

How is contractility affected?

A

Sympathetic nervous system

54
Q

What is the formula of ejection volume?

A
55
Q

what is the normal range ejection volume

A

55%-75%

56
Q

What does low ejection volume mean

A

cardiac pump failure

57
Q

The phase of the cardiac cycle that rapidly builds up of pressure is the …

A

isovolumetric contraction phase

58
Q

The phase of the cardiac cycle that rapidly reduces pressure is the …

A

isovolumetric relaxation phase

59
Q

Describe the pressure volume loop

A
60
Q

What valves gives rise to the first heart sound?

A

Closure of MV at the start of isovolumetric contraction

61
Q

What valves gives rise to the second heart sound?

A

Closure of the AV at the end of the ejection phase

62
Q

How are the changes in pressure within the right atrium measured?

A

JVP

63
Q

What are the 3rd and 4th heart sounds caused by?

A

They are resulted from vibrations from the flow of blood and may be abnormal

64
Q

What does RT in the ECG suggest?

A

Ventricular systole

65
Q

What is ejection fraction

A

the fraction of the end-diastolic volume that is pumped out with each stroke or contraction, expressed as a percentage.

66
Q

How can ejection fractions be determined

A

non-invasively using cardiac echocardiography (estimated), or invasively by putting catheters into the heart (definitive).

67
Q

What wave is atrial contraction?

A

A wave

68
Q

What wave is atrial filling?

A

V wave

69
Q

When is the splitting of the second heart sound heard?

A

Inspiratory cycle

70
Q

What are the 2 components of the split in S2?

A

Aortic and pulmonary valve

71
Q

Explain the physiological splitting of S2

A
72
Q

What type of murmur is a stenosed mitral valve?

A

Diastolic murmur

73
Q

Which blood vessel has high pressure but low resistance?

A

Arteries

74
Q

What is the dual function of arterioles?

A
  1. Control pressure upstream (arterial circulation)
  2. Control blood flow downstream (capillary circulation)
75
Q

Which law governs rate of blood flow (vol of blood per unit time)

A

Ohm’s law

76
Q

Which law governs resistance of blood flow?

A

Poiseuille-Hagen formula

77
Q

State ohm’s law

A
78
Q

State Poiseuille-Hagen formula

A
79
Q

what is cardiac output?

A

Volume of blood pumped by left ventricle into the aorta per minute

80
Q

What is the formula for cardiac output?

A

SV x HR

81
Q

What are the factors affecting cardiac output

A
82
Q

What can cause decrease in preload?

A

Hemorrhage

82
Q

What can affect the heart which in turn affects cardiac output?

A

Myocardial infarction, Bradycardia

82
Q

What can affect afterload?

A

Hypertension

82
Q

What is the acute phase of heart failure

A
82
Q

What is the long-term phase of heart failure

A
82
Q

What is the clinical presentation of acute phase of heart failure?

A
  1. Increase Heart rate
  2. Increase strength of cardiac contractions
  3. Sweating
83
Q

What is the clinical presentation of long-term phase of heart failure?

A
  1. Oliguria (less urine)
  2. Edema
  3. Remodelling heart and blood vessels
84
Q

How can fluid in the kidneys become maladaptive

A
85
Q

How is chronically activated levels of Ang II becomes maladaptive

A
86
Q

What is used as treatment for renin angiotensin aldosterone system activation

A

Diuretics and ACE inhibitors

87
Q

What are 2 types of heart failure

A
88
Q

Activation of sympathetic nervous system in heart failure results in …

A
  • Increase heart rate
  • Pallor
  • Sweating
89
Q

What are the “Forward” failure effects

A
  1. Lowish BP
  2. Tiredness
90
Q

What are the “Backpressure” effects

A
  1. Breathlessness on Exertion
  2. Orthopnoea
91
Q

What is the effect of fluid reabsorption

A
  1. Raised JVP
  2. Peripheral Edema
92
Q

How does patients with long term chronic heart failure present?

A
93
Q

How does Ang II maintain blood pressure?

A
  1. Fluid retention
  2. Vasoconstriction
94
Q

How does Ang II lead to heart failure

A
  • increases resistance, inflammation, fibrosis, hypertrophy
  • reduce NO
95
Q

What can cause increased JVP?

A
  • Increased venous pressure due to too much fluid in the venous system
  • RIght-heart failure (not pumping and filling well)

Therefore there is a back-pressure effect on the RA

96
Q

What does a prominent “a” wave of JVP suggest?

A

Increase in pressure to fill right ventricle ( RV hypertrophy, tricuspid stenosis)

97
Q

What does a prominent “v” wave of JVP suggest?

A

Tricuspid regurgitation

98
Q

What condition could result in radial-femoral delay and higher amplitude of arterial pulse in upper limbs compared to lower limbs?

A

Coarctation of the aorta

99
Q

The upstroke of pulse in ______ is delayed and less abrupt.

A

Aortic stenosis

100
Q

What does the apex beat correspond to?

A

Ventricular systole (ejection phase)

101
Q

What can cause absence of apex beat?

A

Right ventricular hypertrophy

102
Q

Why is S3 indicative of congestive heart failure in adults?

A

It is because there is increased blood volume in the vascular system causing increased filling of the ventricle during early diastole

103
Q

Why is maximal cardiac output reduced in elderly?

A
104
Q

What is the arterial pressure formula?

A

CO x TPR

105
Q

How to measure blood pressure?

A

Sphygmomanometer

106
Q

How is arterial pressure generated?

A

Contraction of ventricles in ejecting cardiac output

107
Q

Which factor affects arterial pressure?

A

resistance in arterioles

108
Q

How are high pressures generated?

A
109
Q

Which baroreceptors detect postural hypotension?

A

Carotid baroreceptors, Aortic baroreceptors

110
Q

The signals from the baroreceptors are interpreted by vasomotor centres in the …

A

Brain stem

111
Q

How does the sympathetic system regulate blood pressure

A
112
Q

How does the parasympathetic system regulate blood pressure

A
113
Q

How do kidneys regulate blood pressure?

A

They regulate fluid status, thus blood volume

114
Q

How does the kidney regulate fluid status?

A

Renin-angiotensin aldosterone system

115
Q

What is present in a Juxtaglomerular apparatus?

A

JG cells, Macula densa

116
Q

What do JG cells sense?

A

Pressure

117
Q

What does Macula densa sense?

A

Cardiac output

118
Q

When is renin released?

A

When pressure and CO drops

119
Q

Describe the JGA Action

A
120
Q

What are the drugs that target the RAAS?

A

ACEi, ARBs, Anti-renin drugs

121
Q

What can predispose to hypertension

A
122
Q

Which organs can be damaged by hypertension?

A

heart, kidneys, brain and the eyes

123
Q

What indicates circulatory shock?

A

Systolic BP< 80mmHg, mean Bp < 60 mmHg

124
Q

Types of circulatory shock are …

A

Hypovolemic, cardiogenic, obstructive, distributive

125
Q

What are examples of cardiogenic shock?

A

Myocardial infarction, Arrhythmias, Severe valve defect

126
Q

What are examples of obstructive shock?

A

Significant pulmonary embolus, Tension pneumothorax, Pericardial temponade

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