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Questions and Answers
What is the primary function of the Sinoatrial (SA) node in the heart?
What is the primary function of the Sinoatrial (SA) node in the heart?
Which pathway conducts the electrical impulse from the SA node to the AV node?
Which pathway conducts the electrical impulse from the SA node to the AV node?
What happens during the 0.1 second pause at the AV node?
What happens during the 0.1 second pause at the AV node?
Why is the AV node considered the only gateway for electrical signals between the atria and ventricles?
Why is the AV node considered the only gateway for electrical signals between the atria and ventricles?
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What is the typical resting heart rate generated by the sinoatrial node?
What is the typical resting heart rate generated by the sinoatrial node?
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What is one of the learning objectives related to the heart's electrical activity?
What is one of the learning objectives related to the heart's electrical activity?
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Which term refers to the heart's ability to initiate its own contraction without external stimuli?
Which term refers to the heart's ability to initiate its own contraction without external stimuli?
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What does the acronym ECG stand for in the context of heart monitoring?
What does the acronym ECG stand for in the context of heart monitoring?
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What effect does the parasympathetic system have on cardiac automaticity?
What effect does the parasympathetic system have on cardiac automaticity?
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Which receptor is primarily involved in the parasympathetic regulation of cardiac function?
Which receptor is primarily involved in the parasympathetic regulation of cardiac function?
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What effect does the sympathetic system have on heart rate?
What effect does the sympathetic system have on heart rate?
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Which substance is released by the sympathetic system to affect cardiac function?
Which substance is released by the sympathetic system to affect cardiac function?
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Activation of which adrenoreceptors leads to increased cAMP formation in cardiac tissue?
Activation of which adrenoreceptors leads to increased cAMP formation in cardiac tissue?
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What is the role of K+ channel activation by the parasympathetic system?
What is the role of K+ channel activation by the parasympathetic system?
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What happens to Ca2+ channels when M2 receptors are activated?
What happens to Ca2+ channels when M2 receptors are activated?
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Which type of drug would primarily block the sympathetic effect on cardiac rate?
Which type of drug would primarily block the sympathetic effect on cardiac rate?
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What initiates the electrical impulse in the heart?
What initiates the electrical impulse in the heart?
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Which ion is primarily responsible for the rapid depolarization phase of the pacemaker action potential?
Which ion is primarily responsible for the rapid depolarization phase of the pacemaker action potential?
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What is the primary function of the AV bundle (Bundle of His)?
What is the primary function of the AV bundle (Bundle of His)?
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What is the resting membrane potential level in pacemaker cells?
What is the resting membrane potential level in pacemaker cells?
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During which phase of the myocardial action potential does rapid repolarization occur?
During which phase of the myocardial action potential does rapid repolarization occur?
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Which structure ensures that myocardial cells contract as a single unit?
Which structure ensures that myocardial cells contract as a single unit?
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What does the T wave on an ECG represent?
What does the T wave on an ECG represent?
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What is the phase called where the myocardial cell experiences a plateau due to Ca2+ influx?
What is the phase called where the myocardial cell experiences a plateau due to Ca2+ influx?
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Which channel is primarily involved in the funny current (If) of pacemaker cells?
Which channel is primarily involved in the funny current (If) of pacemaker cells?
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The PR segment in an ECG reflects which of the following?
The PR segment in an ECG reflects which of the following?
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Which electrical component connects the atrial and ventricular myocytes facilitating electrical activity?
Which electrical component connects the atrial and ventricular myocytes facilitating electrical activity?
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What is the average heart rate of an adult under normal conditions?
What is the average heart rate of an adult under normal conditions?
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What physiological process does 'automaticity' refer to in pacemaker cells?
What physiological process does 'automaticity' refer to in pacemaker cells?
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Which phase in the myocardial action potential corresponds to the efflux of K+ ions?
Which phase in the myocardial action potential corresponds to the efflux of K+ ions?
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Study Notes
Cardiovascular Physiology & Pharmacology
- Course title: Cardiovascular Physiology & Pharmacology
- Lecturer: Dr Stella Koutsikou
- Module code: MSOP1003
- Office: Anson 307
- Email: [email protected]
Stage 1 Learning Objectives
- Describe the heart's intrinsic electrical conduction system
- Understand the measuring of electrical activity of the heart
- Electrocardiogram (ECG)
- Excitability of the myocardium
- Factors affecting heart excitability
- Pharmacology relating to heart excitability
Heart Anatomy
- Superior Vena Cava
- Right Pulmonary Artery
- Pulmonary Trunk
- Right Atrium
- Right Pulmonary Veins
- Fossa Ovalis
- Pectinate Muscles
- Tricuspid Valve
- Right Ventricle
- Chordae Tendineae
- Trabeculae Carneae
- Inferior Vena Cava
- Aorta
- Left Pulmonary Artery
- Left Atrium
- Left Pulmonary Veins
- Mitral (Bicuspid) Valve
- Aortic Semilunar Valve
- Pulmonary Semilunar Valve
- Atrial Septum
- Left Ventricle
- Papillary Muscles
- Interventricular Septum
- Epicardium
- Endocardium
Blood Flow
- Normal Heart
- Superior Vena Cava to Lungs
- Pulmonary Veins from Lungs
- Aortic to Lungs
- Pulmonary Veins from lungs
- Mitral Valve
- Aortic Valve
- Ventricular Septum
Circulation
- Pulmonary Circulation
- Systemic Circulation
- Arteries
- Veins
- Aorta
- Right Coronary Artery
- Left Main Coronary Artery
- Circumflex Coronary Artery
- Left Anterior Descending Coronary Artery
Coronary Circulation
- Coronary Arteries
- Diagram of the Coronary Arteries showing locations of left main coronary artery, circumflex coronary artery and left anterior descending coronary artery (LAD)
Isolated Hearts
- Question: Will a heart still beat if removed from the body?
- Answer: Heart transplants and lab experiments can isolate hearts and show if they continue to beat
Intrinsic Conduction System of the Heart (Autorhythmic System)
- Internal regulating system controlling rhythmic heart contraction
- Specialized myocardial tissue: Includes
- Sinoatrial (SA) node (Sinus rhythm)
- Internodal pathways
- Atrioventricular (AV) node
- AV bundle (a.k.a. bundle of His)
- Bundle branches
- Purkinje fibers
Intrinsic Conduction System (Sinoatrial Node)
- Pacemaker of the heart
- Spontaneously depolarizes and fires at regular intervals
- Generates sinus rhythm
- Heart beats 60-70 bpm
Pacemaker (SA Node) Action Potential
- Slow depolarization (excitation) due to influx of Na+ ions (slow Na+ currents)
- Slow depolarization leads to a non-true resting membrane potential around -60mV
- Rapid depolarization (excitation) due to influx of Ca2+ ions (fast Ca2+ currents)
- Repolarization (return to resting membrane level) due to outflow of K+ ions (K+ currents).
Ion Channels on Pacemaker (Autorhythmic) Cells
- Key ion channels for pacemaker action potential
- Ca = Voltage-gated Calcium channel
- K = Voltage-gated Potassium channel
- NCX = Sodium-Calcium exchanger
- Hcn = Hyperpolarization-activated cyclic nucleotide-gated channel
- I₁ = funny current (Hcn)
- SR = sarcoplasmic reticulum
- Other relevant cell components: Fibroblasts, Fibronectin, Collagen, Laminin
Electrical Conduction through the Heart
- Summary diagram of the electrical impulse conduction through the heart. Includes steps:
- SA node activity and atrial activation begin
- Stimulus spreads across atrial surfaces and reaches AV node
- AV node delay (100-msec)
- Impulse travels through AV bundle and bundle branches to Purkinje fibers and papillary muscles
- Impulse distributed by Purkinje fibers and ventricular contraction begins.
- Spread of electrical activity along the myocardium (showing pacemaker cells, contractile cells, and cardiomyocyte action potential)
- Gap junctions: allow ions to flow between cells instantly, making sure myocytes contract collectively.
Electrical Conduction through the Myocardium
- Myocardium is excitable and contractile
- Myocardial cells (myocytes) connected via intercalated discs; myocytes branch to ensure collective contraction.
- Gap junctions between myocytes facilitate instant spread of electrical impulses ensuring myocyte contraction as a single unit.
- Myocardial action potential phases (0, 1, 2, 3, 4)
Electrocardiogram (ECG)
- Recording of cardiac electrical activity that measures atrial and ventricular myocyte depolarization
- 12-lead ECG diagram displaying electrodes on the body surface.
- Normal ECG (Sinus Rhythm) graphical recording.
ECG Waves, Segments, and Intervals
- P wave: atrial depolarization
- PR segment: delay at AV node, isoelectric segment
- QRS complex: ventricular depolarization, atrial repolarization
- ST segment: beginning of ventricular repolarization
- T wave: ventricular repolarization
- TP interval: time for ventricles to relax and prepare to fill with blood
Quiz - Spot the ECG Abnormality
- Diagrams and questions of ECG abnormalities to identify.
Summary of Cardiac Excitation
- Summary diagram showing propagation of excitation throughout the heart with relevant ECG leads and timings.
Factors affecting Cardiac Rate and Rhythm
- Isolated heart beats at ~ 100 bpm; normal adult heart rate 60-70 bpm
- Autonomous Nervous System regulation
- Parasympathetic system: Parasympathetic causes cardiac slowing and reduces automaticity. Also inhibits AV conduction. Activation of M₂ receptors reduces CAMP formation, which prevents opening of Ca2+ channels and leads to decreased excitation
- Sympathetic System: Sympathetic increases heart rate, increases automaticity, and influences SA, AV node, and ventricular myocardium. Release of catecholamines (e.g., norepinephrine or adrenaline) leads to cAMP activation, which opens Ca2+ channels, and increases influx of Ca2+
- Effects of beta blockers (e.g., Bisoprolol). β-Blockers decrease influx of Ca2+ of pacemaker cells, decrease conduction velocity, decrease firing and decrease heart rate.
- Effects of Ca2+ channel blockers
- Effects of Na+ channel blockers
- Effects of K+ channel blockers
Additional Reading
- Rang & Dale's Pharmacology
- Any human physiology textbook
- Mader & Windelspecht's Human Biology
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Description
Test your understanding of the heart's electrical conduction system, electrocardiogram (ECG), and pharmacological factors affecting heart excitability. This quiz covers key anatomical features and intrinsic characteristics of cardiac physiology. Enhance your knowledge in this essential area of cardiovascular science.
