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Questions and Answers
What physiological event produces the P wave in an electrocardiogram (ECG)?
What physiological event produces the P wave in an electrocardiogram (ECG)?
Which of the following best describes what an ECG segment represents?
Which of the following best describes what an ECG segment represents?
Which of the following leads is classified as an augmented limb lead?
Which of the following leads is classified as an augmented limb lead?
What is the QRS complex indicative of in an ECG?
What is the QRS complex indicative of in an ECG?
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What can cause an arrhythmia?
What can cause an arrhythmia?
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In a normal ECG, what is represented by the T wave?
In a normal ECG, what is represented by the T wave?
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What does the U wave in an ECG represent?
What does the U wave in an ECG represent?
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What is a potential historical sign of tachycardia?
What is a potential historical sign of tachycardia?
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What causes the first heart sound, commonly referred to as 'lub'?
What causes the first heart sound, commonly referred to as 'lub'?
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Which term refers to the pressure in the artery leading from the ventricle during cardiac contraction?
Which term refers to the pressure in the artery leading from the ventricle during cardiac contraction?
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How is cardiac output measured using an electromagnetic flow meter?
How is cardiac output measured using an electromagnetic flow meter?
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What is the average stroke volume for a resting man of average size?
What is the average stroke volume for a resting man of average size?
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What is the average cardiac output for a resting, supine man?
What is the average cardiac output for a resting, supine man?
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What does the cardiac index represent?
What does the cardiac index represent?
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Which factor does NOT contribute to variations in cardiac output?
Which factor does NOT contribute to variations in cardiac output?
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What type of examination is echocardiography primarily used for?
What type of examination is echocardiography primarily used for?
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What is the primary cause of myocardial infarction?
What is the primary cause of myocardial infarction?
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What does reentry of an impulse in the cardiac conduction system typically cause?
What does reentry of an impulse in the cardiac conduction system typically cause?
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How does an increase in extracellular calcium concentration affect the heart?
How does an increase in extracellular calcium concentration affect the heart?
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How does the arterial pulse relate to cardiac contraction?
How does the arterial pulse relate to cardiac contraction?
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In which stage of the cardiac cycle are the mitral and tricuspid valves open?
In which stage of the cardiac cycle are the mitral and tricuspid valves open?
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What happens to the pressure in the ventricles during late diastole?
What happens to the pressure in the ventricles during late diastole?
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What condition is characterized by a protracted QT interval?
What condition is characterized by a protracted QT interval?
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What represents the peak pressure in the vascular system during the cardiac cycle?
What represents the peak pressure in the vascular system during the cardiac cycle?
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What mechanism primarily controls the cardiac rate?
What mechanism primarily controls the cardiac rate?
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What is the effect of sympathetic stimulation on stroke volume?
What is the effect of sympathetic stimulation on stroke volume?
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What phenomenon refers to the relationship between end-diastolic volume and stroke volume?
What phenomenon refers to the relationship between end-diastolic volume and stroke volume?
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What is classified as a positively inotropic factor?
What is classified as a positively inotropic factor?
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What effect do catecholamines have on cardiac muscle function?
What effect do catecholamines have on cardiac muscle function?
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How is the developed tension in cardiac muscle related to initial fiber length?
How is the developed tension in cardiac muscle related to initial fiber length?
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Which statement best describes the role of norepinephrine in myocardial contractility?
Which statement best describes the role of norepinephrine in myocardial contractility?
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What is the effect of vagal stimulation on the atrial muscle?
What is the effect of vagal stimulation on the atrial muscle?
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What characterizes bradycardia?
What characterizes bradycardia?
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Which arrhythmia is characterized by chaotic electrical impulses in the atria and can lead to serious complications such as stroke?
Which arrhythmia is characterized by chaotic electrical impulses in the atria and can lead to serious complications such as stroke?
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What is common between atrial flutter and atrial fibrillation?
What is common between atrial flutter and atrial fibrillation?
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What is Supraventricular tachycardia primarily characterized by?
What is Supraventricular tachycardia primarily characterized by?
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What does sick sinus syndrome involve?
What does sick sinus syndrome involve?
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Which of the following is NOT associated with bradycardia?
Which of the following is NOT associated with bradycardia?
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What distinguishes atrial flutter from atrial fibrillation?
What distinguishes atrial flutter from atrial fibrillation?
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What is a potential outcome of a conduction block?
What is a potential outcome of a conduction block?
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Study Notes
Cardiovascular Physiology (Part 2) - Lecture 4
- Electrocardiogram (ECG): Electrical impulses from the heart spread to surrounding tissues and reach the body surface. Fluctuations in myocardial fiber potentials, recorded extracellularly, form the ECG. Most ECG machines record these fluctuations on a moving strip of paper.
ECG Leads
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Standard Limb Leads (I, II, III): These record potential differences between pairs of limbs.
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Additional Leads: Six precordial leads (V1-V6) are placed on the chest, and three limb leads (VR, VL, VF) are augmented (aVR, aVL, aVF).
Components of ECG
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Waves: Parts of the ECG above or below the isoelectric line.
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Segments: Parts located on the isoelectric line.
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Intervals: Include both waves and segments.
Depolarization and Repolarization
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Depolarization: Produces a positive deflection.
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Repolarization: Produces a negative deflection.
Key ECG Waves
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P wave: Represents atrial depolarization.
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QRS complex: Represents ventricular depolarization.
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ST segment: Represents ventricular repolarization.
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T wave: Represents ventricular repolarization.
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U wave: An inconstant wave believed due to slow repolarization of the papillary muscles.
Normal ECG
- The ECG of a normal individual, along with electrode placement and interpretation considerations, is typically shown within the ECG waves.
Cardiac Arrhythmia
- An arrhythmia is an irregular or abnormal heart beat caused by problems with electrical impulses coordinating heartbeats.
Types of Arrhythmias
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Tachycardia: A resting heart rate exceeding 100 beats per minute.
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Bradycardia: A resting heart rate below 60 beats per minute.
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Atrial Fibrillation (AF): Rapid, irregular, and weak atrial contractions due to chaotic electrical signals (rate ~110-160 bpm). Associated with complications like stroke.
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Atrial Flutter: More organized and rhythmic electrical impulses compared to AF. Atrial rates are typically above 250 bpm and up to 320 bpm. Also associated with stroke.
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Supraventricular Tachycardia (SVT): A broad term for arrhythmias originating above the ventricles (atria or AV node). Associated with sudden palpitations.
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Heart Block: Blocks in heart electrical pathways, occurring in or near the AV node or other pathways to each ventricle. Types include first-degree, second-degree (2:1), and third-degree blocks.
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Ventricular Fibrillation (VF): Severe and life-threatening arrhythmia.
Etiological Factors of Arrhythmias
- General heart disease
- Myocardial infarction (MI)
- Systemic hypertension
- Electrolyte imbalances (hyper/hypokalemia)
- Chronic obstructive pulmonary disease (COPD)
Etiopathogenesis of Arrhythmias
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Abnormal Impulse Formation: Decreased automaticity (escape beats, bradycardia) or increased automaticity (premature beats, tachycardia).
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Abnormal Impulse Conduction: Conduction block or delay, reentry (impulse rerouting through previously traveled regions).
Myocardial Infarction
- Myocardial infarction occurs when blood supply to a portion of the myocardium is interrupted.
- This leads to irreversible muscle damage and cell death. ECG changes, such as ST segment elevation, are useful in diagnosis.
Effects of Changes in Ionic Composition of Blood
- Changes in blood concentrations of Na+, K+, and Ca2+ affect myocardial fiber potentials and electrical activity.
- Increases in extracellular Ca2+ enhance contractility.
- Hypocalcemia prolongs the QT interval.
Mechanical Events of Cardiac Cycle
- Systole: Peak pressure during contraction.
- Diastole: Lowest pressure during relaxation.
- Late Diastole: Filling of atria and ventricles.
- Valves (Mitral/Tricuspid/Aortic/Pulmonary): Important for blood flow directions and control.
Cardiac Output (CO)
- The volume of blood pumped by ventricles per minute (liters).
- Important for constant adjustment in transport needs.
Methods to Measure Cardiac Output
- Electromagnetic flow meters (animals)
- Doppler and echocardiography (humans)
Echocardiography
- A non-invasive ultrasound technique to assess cardiac function and wall movement.
Cardiac Output in Various Conditions
- Stroke volume (volume per beat) – approximately 70 mL
- Cardiac output - approximately 5.0 L/min
- Relationship with body surface area (cardiac index).
Factors Controlling Cardiac Output (CO = HR x SV)
- Sympathetic/parasympathetic stimulation effects on heart rate and stroke volume.
- Influence of neural input on contraction strength.
Relation of Tension to Length in Cardiac Muscle (Frank-Starling Law)
- Proportional relationship between end-diastolic volume and stroke volume.
- Curve shape.
Myocardial Contractility
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Impact on stroke volume
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Influence of sympathetic stimulation (positive inotropy)
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Influence of vagal stimulation (negative inotropy).
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Inotropic effects of circulating cathecholamines like norepinephrine and epinephrine
Factors Influencing Cardiac Contractility
- Various factors like circulating cathecholamines, digitalis, etc. that affect Contractile state of the myocardium,
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Description
This quiz focuses on the electrocardiogram (ECG) including its leads, components, and the processes of depolarization and repolarization. Test your understanding of the critical aspects of ECG interpretation and its significance in cardiovascular physiology. It also covers the key waves involved in ECG analysis.
