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Questions and Answers
What happens at 0mV in terms of ion channels during repolarization?
What happens at 0mV in terms of ion channels during repolarization?
What prevents premature contractions in the heart?
What prevents premature contractions in the heart?
Which node would fire the fastest without endocrine control?
Which node would fire the fastest without endocrine control?
Which component of the heart's conduction system has the lowest firing rate?
Which component of the heart's conduction system has the lowest firing rate?
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What is the purpose of an electrocardiogram (ECG)?
What is the purpose of an electrocardiogram (ECG)?
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Where is the heart located in the body?
Where is the heart located in the body?
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Which blood vessels attach at the base of the heart?
Which blood vessels attach at the base of the heart?
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What is the function of ventricles in the heart?
What is the function of ventricles in the heart?
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What is unique about the pulmonary vein among all arteries?
What is unique about the pulmonary vein among all arteries?
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Which layer of the heart produces fluid that lubricates the pericardial cavity?
Which layer of the heart produces fluid that lubricates the pericardial cavity?
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What do auricles in the heart do?
What do auricles in the heart do?
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What does the P wave represent in the cardiac cycle?
What does the P wave represent in the cardiac cycle?
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Which phase of the cardiac cycle is associated with 'atrial kick'?
Which phase of the cardiac cycle is associated with 'atrial kick'?
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What is the main function of an artificial pacemaker in the heart?
What is the main function of an artificial pacemaker in the heart?
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In the cardiac cycle, what occurs during ventricular diastole?
In the cardiac cycle, what occurs during ventricular diastole?
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What is the amount of blood pushed out by the ventricles called?
What is the amount of blood pushed out by the ventricles called?
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Which statement is true about the T wave in the cardiac cycle?
Which statement is true about the T wave in the cardiac cycle?
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What is the main function of the endothelium in the heart?
What is the main function of the endothelium in the heart?
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Which structure divides the heart into chambers?
Which structure divides the heart into chambers?
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What is the main role of the atrioventricular valves in the heart?
What is the main role of the atrioventricular valves in the heart?
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Which chamber receives oxygenated blood from the pulmonary veins?
Which chamber receives oxygenated blood from the pulmonary veins?
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What is the function of the moderator band in the heart?
What is the function of the moderator band in the heart?
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What is the significance of valves in the heart?
What is the significance of valves in the heart?
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What is the primary role of coronary circulation in the heart?
What is the primary role of coronary circulation in the heart?
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What is the function of autorhythmicity in cardiac muscle cells?
What is the function of autorhythmicity in cardiac muscle cells?
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What is the main function of Purkinje fibers in the heart?
What is the main function of Purkinje fibers in the heart?
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What is the normal range for cardiac output (CO) in a healthy individual?
What is the normal range for cardiac output (CO) in a healthy individual?
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Which of the following statements about heart murmurs is correct?
Which of the following statements about heart murmurs is correct?
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What is the formula for calculating Stroke Volume (SV) in relation to End-Diastolic Volume (EDV) and End-Systolic Volume (ESV)?
What is the formula for calculating Stroke Volume (SV) in relation to End-Diastolic Volume (EDV) and End-Systolic Volume (ESV)?
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Which factor can decrease heart rate according to the text?
Which factor can decrease heart rate according to the text?
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What is the role of norepinephrine in heart function according to the text?
What is the role of norepinephrine in heart function according to the text?
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Which reflex is triggered by increased blood in the atria according to the text?
Which reflex is triggered by increased blood in the atria according to the text?
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What does S2 correspond to in heart sounds?
What does S2 correspond to in heart sounds?
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Study Notes
Heart Anatomy
- The heart is a muscle that pumps 5.25 L of fluid per minute.
- Located between the lungs in a space called the mediastinum.
- Separated from other structures by the pericardium, a tough membrane.
- The base of the heart is superior and medial to the apex.
Heart Structure
- 4 chambers in the heart: 2 atria and 2 ventricles.
- Atria are superior, collect blood, and push it into lower chambers.
- Ventricles are inferior and pump blood out to the body or lungs.
- 2 circuits: pulmonary and systemic.
- Right ventricle connects to the pulmonary trunk and left ventricle connects to the aorta.
Heart Membranes and Layers
- 2 layers: fibrous and serous pericardium.
- Serous layer has 2 sublayers: parietal and visceral layers separated by pericardial cavity.
- Cavity filled with lubricating fluid.
- Visceral layer is called epicardium and produces fluid.
Heart Features
- 2 auricles: thin-walled structures that can hold blood and empty into atria.
- Sulci: fat-filled grooves that contain coronary blood vessels.
Layers of the Heart
- Epicardium: most superficial layer.
- Myocardium: middle, thickest layer, muscle cells, nerve fibers, and blood vessels.
- Endocardium: innermost layer, lines the chambers filled with blood, covers heart valves.
- Endothelium: cells that line the blood vessels, release endothelins, which are strong vasoconstrictors.
Internal Structures
- Septum: divides the heart into chambers, physical extensions of myocardium, 3 septa in the heart.
- Fossa ovalis: a depression in the interatrial septum, was a foramen ovale (opening) while a fetus.
- Atrioventricular valves: separate atria from ventricles, tricuspid on right and mitral or bicuspid on left.
- Semilunar valves: separate ventricles from blood vessels, pulmonary and aortic valves.
Chambers of the Heart
- Right atrium: receives deoxygenated blood from systemic circulation, contains pectinate muscles.
- Right ventricle: receives deoxygenated blood from the right atrium, has chordae tendineae connected to 3 papillary muscles.
- Left atrium: receives oxygenated blood from the pulmonary veins, no pectinate muscles.
- Left ventricle: thicker muscle, receives oxygenated blood from the left atrium, pushes blood into the aorta.
Valves of the Heart
- Ensure unidirectional blood flow.
- Semilunar valves have no muscular attachments, but make an audible sound as they close.
- Tricuspid and mitral valves close due to papillary muscles.
- Valve disorders are usually caused by inflammation.
Coronary Circulation
- Cyclical and not continuous.
- Arteries branch off the aorta just superior to the semilunar valve.
- Coronary arteries bring blood to the myocardium and other components.
- Anastomosis: blood vessel interconnections to allow blood to flow even if there is a partial blockage in another branch.
Cardiac Muscle and Electrical Activity
- Autorhythmicity: cardiac muscle can initiate an electrical potential at a fixed rate.
- Myocardial conducting cells: initiate and propagate the action potential through the heart.
- Myocardial contractile cells: conduct impulses and contract to pump blood through the body.
Comparative Conduction
- SA node sets normal cardiac rhythm, known as the pacemaker.
- AV node receives impulse from SA node and slows it down.
- Bundle of His receives impulse from AV node and flows down the interventricular septum.
- Purkinje fibers spread the impulse around the ventricles.
Membrane Potentials
- Cardiac conductive cells have Na+ channels that allow a slow influx to create the spontaneous depolarization.
- Cardiac contractile cells depolarize as an impulse reaches them, then they plateau before repolarizing.
Calcium Ions
- Allow for the plateau phase in cardiac contractile cells.
- Bind to troponin to allow the myosin and actin cross-bridge.
Electrocardiogram (ECG)
- Records electrical signals of the heart.
- 3, 5, or 12 leads.
- P wave: depolarization of the atria.
- QRS complex: depolarization of ventricles and it masks the repolarization of the atria.
- T wave: repolarization of ventricles.
Cardiac Cycle
- Begins at atrial contraction and ends with ventricular relaxation.
- Systole: pumping blood into circulation.
- Diastole: chambers are relaxed and filling with blood.
Phases of the Cardiac Cycle
- Atrial systole: atria contract from superior portion following depolarization (P wave).
- Atrial diastole: muscles relax as ventricles begin to contract.
- Ventricular systole: blood in ventricles is the end-diastolic volume (EDV) or preload.
- Ventricular diastole: relaxation, semilunar valves close, and atrioventricular valves are closed too.
Heart Sounds
- Healthy heart has 2 audible sounds: S1 and S2 (lub dub).
- S1: closing of atrioventricular valves.
- S2: closing of semilunar valves.
Murmur
- Caused by turbulent blood flow.
- Inhalation increases blood flow to the right side and may increase the amplitude of a right-sided murmur.
- Expiration partially restricts blood flow to the left side and may increase the amplitude of a left-sided murmur.
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Description
Test your knowledge on the physiological processes of the cardiac muscle, including repolarization, refractory period, ion channels, and conduction pathways. Learn about the role of calcium ions, action potentials, SA node firing, and the function of troponin in muscle contraction.
