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Questions and Answers
What part of the heart initiates the electrical impulse that triggers cardiac contraction?
What part of the heart initiates the electrical impulse that triggers cardiac contraction?
Which wave on an ECG represents atrial contraction?
Which wave on an ECG represents atrial contraction?
What type of heart block is characterized by a delay in conduction from the SA node to the AV node?
What type of heart block is characterized by a delay in conduction from the SA node to the AV node?
Which part of the heart's conduction system transmits impulses directly to the ventricles?
Which part of the heart's conduction system transmits impulses directly to the ventricles?
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What is the normal range for a resting heart rate in beats per minute?
What is the normal range for a resting heart rate in beats per minute?
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Which hormone from the adrenal medulla increases heart rate during the 'fight or flight' response?
Which hormone from the adrenal medulla increases heart rate during the 'fight or flight' response?
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The right coronary artery supplies blood to which part of the heart?
The right coronary artery supplies blood to which part of the heart?
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What is the role of the vagus nerve in heart rate regulation?
What is the role of the vagus nerve in heart rate regulation?
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What is the primary function of the heart's valves?
What is the primary function of the heart's valves?
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Which chamber of the heart is thicker-walled, reflecting its role in systemic circulation?
Which chamber of the heart is thicker-walled, reflecting its role in systemic circulation?
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What is the role of the SA node in the heart?
What is the role of the SA node in the heart?
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Which part of the heart is responsible for receiving deoxygenated blood from the body?
Which part of the heart is responsible for receiving deoxygenated blood from the body?
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What is the primary function of the pulmonary circuit?
What is the primary function of the pulmonary circuit?
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During which phase of the cardiac cycle do the atria contract?
During which phase of the cardiac cycle do the atria contract?
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What structural feature is characteristic of cardiac muscle cells?
What structural feature is characteristic of cardiac muscle cells?
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What is the role of chordae tendineae in the heart?
What is the role of chordae tendineae in the heart?
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What type of tissue primarily composes the myocardium?
What type of tissue primarily composes the myocardium?
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Which part of the heart is directly responsible for pumping blood into the aorta?
Which part of the heart is directly responsible for pumping blood into the aorta?
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What is the primary function of the cardiac skeleton?
What is the primary function of the cardiac skeleton?
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What causes the first heart sound (S1) during the cardiac cycle?
What causes the first heart sound (S1) during the cardiac cycle?
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What is the average heart rate under resting conditions?
What is the average heart rate under resting conditions?
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Study Notes
Cardiovascular System - Heart
- Heart is the central pumping organ of the cardiovascular system, including heart, blood vessels, and blood.
- Heart functions as a "double pump" with systemic and pulmonary circuits (and coronary circuit).
- Heart has 75 contractions/minute, or 108,000 contractions/day.
- With ~70 mL/contraction, the heart pumps ~5.25 L/min or ~14,000 L/day (or roughly 3,698 gallons per day)
- Heart is located in the mediastinum, enclosed by the pericardium (or pericardial sac) within the pericardial cavity.
- Heart's base sits atop great veins (superior and inferior vena cavae) and great arteries (aorta and pulmonary trunk).
- Heart's apex is situated near left side of body, in the cardiac notch of the left lung.
- Heart is roughly a pine-cone shape with a size similar to a fist (250-300g/9-11 oz for females and 300-500g/11-12 oz for males).
- Heart has 4 chambers: 2 atria and 2 ventricles (receiving and pumping).
- Pulmonary circuit: deoxygenated blood picks up oxygen and releases carbon dioxide.
- Systemic circuit: oxygenated blood delivers oxygen and picks up carbon dioxide.
- Blood flows from right ventricle to the pulmonary trunk to the L & R pulmonary arteries to the L & R lungs to the pulmonary veins to the left atrium to the left ventricle to the aorta to systemic veins.
Heart Membranes, Surface Features, & Layers
- Pericardium (= Pericardial sac) consists of dense irregular CT (fibrous pericardium) and serous pericardium (mesothelium & areolar CT).
- Serous pericardium has 2 layers: parietal pericardium and visceral pericardium (= epicardium).
- Visceral pericardium is mesothelium-lined epithelium, filled with serous fluid within pericardial cavity.
- Atria are extended with auricles.
- Coronary sulcus, anterior, and posterior interventricular sulci are major grooves of the heart.
- Heart wall layers include epicardium (= visceral pericardium), myocardium (cardiac muscle), and endocardium (endothelium, SS ET).
- Myocardium has dense irregular CT organized into cardiac skeleton with interwoven, figure 8 patterns for efficient contraction.
- Left ventricle is thicker-walled (systemic circuit) than the right ventricle (pulmonary circuit).
Internal Heart Structures
- Septa divide atria and ventricles.
- Interatrial septum has a fossa ovalis (foramen ovale).
- Interventricular septum separates the ventricles.
- Atrioventricular septum separates atria from ventricles.
- Heart also has atrioventricular valves (tricuspid valve on right, bicuspid (=mitral) valve on left) and semilunar valves (pulmonary valve, aortic valve).
Cardiac Skeleton
- Dense irregular CT reinforces the atrioventricular septum and provides attachment for heart valves.
- Also insulates the heart's electrical conducting system.
Heart Chambers
- Right atrium receives blood from the inferior and superior vena cavae and coronary sinus.
- Pectinate muscles are ridges on the inside of the atrium to help spread electrical signals.
- Tricuspid valve is the right atrioventricular valve.
- Right ventricle has chordae tendineae that anchor tricuspid valve to papillary muscles.
- Right ventricle has trabeculae carneae - muscular ridges.
- Moderator band spreads electrical signals from one side of ventricle to another.
- Pulmonary semilunar valve at the entrance of pulmonary trunk.
- Left atrium receives blood from pulmonary veins.
- Pectinate muscles are only on the auricle on the left atrium.
- Bicuspid (= Mitral) valve is the left atrioventricular valve.
- Left ventricle has chordae tendineae that anchor the bicuspid valve and trabeculae carneae
- Left ventricle has a thicker wall than the right ventricle.
- Aortic semilunar valve at the entrance of aorta.
Cardiac Cycle
- Systole is chamber (heart) contraction and diastole is relaxation.
- Cardiac cycle includes ventricular relaxation and contraction, and atrial diastole and systole.
- Blood enters atria passively (during cardiac diastole).
- Atrial systole fills ventricles.
- Ventricular systole ejects blood.
- Ventricular diastole passively fills ventricles again.
Heart Valves
- Valves prevent backflow, ensuring one-way blood movement.
- At cardiac diastole, AV valves are open and semilunar valves are closed.
- In ventricular systole, AV valves close (1st heart sound) and pressure rises, allowing blood flow out through semilunar valves.
- Ventricular diastole causes a drop in pressure, semilunar valves close (2nd heart sound), and AV valves open passively.
Heart Sounds
- Heart sounds (S1 and S2) occur due to valve closures.
- S1 = closure of AV valves while S2 = closure of semilunar valves.
- Murmurs are abnormal sounds due to turbulent blood flow.
Cardiac Muscle & Electrical Activity
- Cardiac muscles (cardiomyocytes) are branched, with one to two nuclei and intercalated discs (composed of desmosomes, fasciae adherens, and gap junctions).
- Myocardial contractile cells (99%) are responsible for chamber contraction.
- Myocardial conducting cells (1%) are autorhythmic generating APs and setting the pace of chamber contractions.
Conduction System of the Heart
- Myocardial conducting cells form the conduction system (SA node, AV node, AV bundle, AV branches, and Purkinje fibers).
- SA node (pacemaker) initiates the heartbeat.
- Impulse travels through internodal pathways to atria, then to AV node, AV bundle (Bundle of His), bundle branches, and Purkinje fibers in ventricles.
Spread of the Conducting Signal through the Heart
- Signal spreads sequentially through the atria and ventricles.
Electrocardiogram (ECG)
- ECG measures electrical activity of the heart.
- The ECG waves represent the heart's electrical activity including the P wave (atrial depolarization), PR interval (atrial depolarization and conduction delay through AV node), QRS complex (ventricular depolarization), ST segment (ventricular plateau phase), QT interval (ventricular depolarization and repolarization), and the T wave (ventricular repolarization).
Disorders of the Conducting System
- Heart block is an interruption of the heart's conduction path, resulting in an irregular heartbeat.
- Degrees of heart block can be varying degrees of severity.
Heart Rates
- Heart rate (HR) varies with exercise, fitness level, age, and hormones.
- Resting HR is 60-100 bpm, maximum HR is 200-220 bpm, with sympathetic and parasympathetic pathways regulating the heart rate.
Coronary Circulation
- Coronary arteries supply oxygenated blood to cardiomyocytes.
- Coronary veins collect deoxygenated blood and return it to the right atrium.
Development of the Heart
- Section about the development of the heart is not included.
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Description
Test your knowledge about the heart and its functions within the cardiovascular system. This quiz covers the heart's anatomy, its role in systemic and pulmonary circulation, and interesting facts about its performance. Get ready to dive into the vital organ that pumps life-sustaining blood throughout the body.
