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Questions and Answers
Which of the following ions can block action potentials if present in excess?
Which of the following ions can block action potentials if present in excess?
Hypertension leads to increased stroke volume (SV).
Hypertension leads to increased stroke volume (SV).
False
What formula is used to determine maximal heart rate?
What formula is used to determine maximal heart rate?
Maximal hr = 220 bpm - age (years)
Increased ventricular_ pressure requires the heart to generate higher blood pressure to push blood through semilunar valves.
Increased ventricular_ pressure requires the heart to generate higher blood pressure to push blood through semilunar valves.
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Match the following terms with their correct descriptions:
Match the following terms with their correct descriptions:
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What is the primary function of the heart?
What is the primary function of the heart?
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The heart weighs more in males than in females.
The heart weighs more in males than in females.
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What is the scientific study of the heart called?
What is the scientific study of the heart called?
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The pointed tip of the heart is known as the _______.
The pointed tip of the heart is known as the _______.
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Which structure protects the heart from overstretching?
Which structure protects the heart from overstretching?
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Match the part of the pericardium with its characteristics:
Match the part of the pericardium with its characteristics:
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The base of the heart points slightly to the right.
The base of the heart points slightly to the right.
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The heart is found in the ________ of the thoracic cavity.
The heart is found in the ________ of the thoracic cavity.
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What primarily maintains the resting membrane potential in human cells?
What primarily maintains the resting membrane potential in human cells?
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The coronary arteries supply deoxygenated blood to the heart.
The coronary arteries supply deoxygenated blood to the heart.
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What is the main metabolic pathway used by cardiac muscle cells to generate ATP?
What is the main metabolic pathway used by cardiac muscle cells to generate ATP?
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During the relaxation of the heart, blood flows from the ascending aorta into the _______________ arteries.
During the relaxation of the heart, blood flows from the ascending aorta into the _______________ arteries.
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Which part of the cardiac conduction system is known as the 'pacemaker' of the heart?
Which part of the cardiac conduction system is known as the 'pacemaker' of the heart?
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How many signals does the SA node fire per minute on average?
How many signals does the SA node fire per minute on average?
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Cardiac muscle cells are more susceptible to tetanus than skeletal muscle cells.
Cardiac muscle cells are more susceptible to tetanus than skeletal muscle cells.
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Match the following parts of the heart with their primary function:
Match the following parts of the heart with their primary function:
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The coronary veins drain into the coronary _______________, which then empties into the right atrium.
The coronary veins drain into the coronary _______________, which then empties into the right atrium.
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What is a refractory period in cardiac muscle cells?
What is a refractory period in cardiac muscle cells?
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What is primarily used as an energy source by cardiac muscle cells?
What is primarily used as an energy source by cardiac muscle cells?
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Elevation of creatine kinase in the blood can indicate myocardial infarctions.
Elevation of creatine kinase in the blood can indicate myocardial infarctions.
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What does ECG stand for?
What does ECG stand for?
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The period when the heart is contracting is called systole.
The period when the heart is contracting is called systole.
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Match the following heart sounds with their corresponding events:
Match the following heart sounds with their corresponding events:
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What is the average stroke volume (SV) in an average male?
What is the average stroke volume (SV) in an average male?
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Blood pressure decreases during ventricular systole.
Blood pressure decreases during ventricular systole.
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What hormone is released by cardiac accelerator nerves?
What hormone is released by cardiac accelerator nerves?
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Cardiac reserve is the difference between maximum cardiac output and resting cardiac output.
Cardiac reserve is the difference between maximum cardiac output and resting cardiac output.
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During the P wave of an ECG, which process occurs in the atrial muscle cells?
During the P wave of an ECG, which process occurs in the atrial muscle cells?
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What is the primary function of the pericardial cavity?
What is the primary function of the pericardial cavity?
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The myocardium is primarily made of skeletal muscle tissue.
The myocardium is primarily made of skeletal muscle tissue.
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What chamber of the heart receives deoxygenated blood from systemic circulation?
What chamber of the heart receives deoxygenated blood from systemic circulation?
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The left ventricle pumps blood into the _____ through the aortic valve.
The left ventricle pumps blood into the _____ through the aortic valve.
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Match the heart valves with their types:
Match the heart valves with their types:
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Which chamber of the heart is the thickest?
Which chamber of the heart is the thickest?
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The endocardium lines the outside of the heart.
The endocardium lines the outside of the heart.
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What prevents backflow of blood into the atria during ventricular contraction?
What prevents backflow of blood into the atria during ventricular contraction?
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When the atria contract, blood moves into the ventricles due to _____ pressure in the atria.
When the atria contract, blood moves into the ventricles due to _____ pressure in the atria.
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Which of the following arteries branches from the pulmonary trunk?
Which of the following arteries branches from the pulmonary trunk?
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Study Notes
Cardiovascular System Overview
- Composed of the heart, blood, and blood vessels
- The heart is a pump, propelling blood throughout the body
- Averages ~100,000 beats/day; ~35 million/year; ~2.5 billion/lifetime
- Cardiology is the study of the heart and its related functions
- Heart size: roughly the size of a clenched fist (~250g in females; ~300g in males)
- Located in the mediastinum of the thoracic cavity
- Apex (pointed tip): rests on the diaphragm, formed by the inferior tip of the left ventricle
- Base (opposite the apex): angled posteriorly, formed by the atria
- Inferior surface sits on the diaphragm
- Right surface faces the right lung
- Left surface faces the left lung
- Anterior surface faces the sternum
Pericardium
- Wraps the heart, a double-layered sac
- Fibrous pericardium: inelastic, dense irregular connective tissue; fused with central tendon; protects from overstretching and anchors the heart in the mediastinum
- Serous pericardium: deep to the fibrous pericardium; more fragile; subdivided into:
- Parietal serous pericardium: fused to fibrous pericardium
- Visceral serous pericardium (epicardium): mesothelium + connective tissue; rich in blood vessels and lymphatics; makes the heart slippery
- Pericardial cavity: space between parietal and visceral layers; filled with pericardial fluid to reduce friction during heart contractions
Heart Wall Layers
- Epicardium (visceral serous pericardium): serous membrane (mesothelium + CT); rich in blood vessels and lymphatics
- Myocardium: bulk (95%) of heart wall; cardiac muscle tissue; responsible for pumping blood forcefully
- Endocardium: made of endothelium; lines the chambers and valves, continuous with blood vessel lining; reduces friction
Heart Chambers and Function
- Four chambers: two atria (superior) and two ventricles (inferior)
- Auricles: anterior “wings” of the atria that increase their volume
- Atria receive blood from veins, ventricles pump blood into arteries
- Right atrium receives deoxygenated blood from the superior vena cava, inferior vena cava, and coronary sinus, then pumps into the right ventricle through the tricuspid valve.
- Right ventricle pumps deoxygenated blood to the pulmonary trunk (via pulmonary valve) to the lungs for oxygenation.
- Left atrium receives oxygenated blood from the lungs via four pulmonary veins, then pumps into the left ventricle through the bicuspid (mitral) valve.
- Left ventricle pumps oxygenated blood into the aorta (via aortic valve) to the body
Heart Valves
- Atrioventricular (AV) valves (tricuspid and mitral): prevent backflow into atria during ventricular contraction. Cusps billow into ventricles during atrial contraction. Papillary muscles contract, pulling on the chordae tendineae, preventing eversion of the cusps and backflow.
- Semilunar valves (pulmonary and aortic): permit blood to leave the heart and travel into arteries. Blood pressure in the ventricles is initially greater than in arteries. After ventricular contraction, blood pressure exceeds pressure in the ventricles and pushes the valves closed.
Coronary Circulation
- Coronary vessels serve the heart by carrying oxygenated blood.
- Coronary arteries receive blood from the ascending aorta when the heart is at rest
- Coronary veins collect deoxygenated blood containing metabolic wastes, which then drain into the coronary sinus and ultimately empty into the right atrium.
Cardiac Muscle Tissue and Conduction System
- Cardiac muscle cells: branching, mononucleated, striated; rich in mitochondria; intercalated discs facilitate coordinated contraction; exhibit autorhythmicity, with T-tubules wider than skeletal muscle, but less numerous
- Cardiac conduction system: 1% of cardiac muscle fibres become autorhythmic during embryonic development.
- Electrical signals follow a specific path to stimulate contraction: SA (sinoatrial) node (pacemaker), AV (atrioventricular) node, AV bundle (bundle of His), Bundle branches, Purkinje fibres.
Cardiac Action Potentials
- Action potentials are electrochemical signals that travel along membranes of electrically-excitable cells.
- Three phases:
- Depolarization: Na+ channels open, reversing membrane potential to positive; plateau: Ca2+ channels open, prolonged depolarization; Repolarization: K+ channels open, restoring resting membrane potential.
- Refractory period: a time when cell cannot respond; longer than cardiac muscle contraction.
Cardiac Cycle
-
Systole: contraction of atria or ventricles
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Diastole: relaxation of atria or ventricles
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ECG (electrocardiogram): recorded change in electrical currents during action potentials
-
Three waves:
- P wave: atrial depolarization, stimulates atrial systole
- QRS complex: ventricular depolarization, stimulates ventricular systole
- T wave: ventricular repolarization, leads to ventricular diastole
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Heart sounds (S1, S2): turbulence due to valve closure
Cardiac Output (CO)
- CO: volume of blood pumped per minute (L/min) = stroke volume (SV, L/beat) x heart rate (HR, beats/min)
- Regulation of cardiac output: CO is regulated by the ANS, higher brain centers, sensory inputs (proprioceptors, baroreceptors, and chemoreceptors), hormones, electrolytes (K+, Na+, and Ca2+) and age, gender, physical fitness, and temperature
- Cardiac accelerator nerves stimulate norepinephrine release (sympathetic), increasing HR, SV, and CO; vagus nerves stimulate acetylcholine release (parasympathetic), decreasing HR and CO
Exercise and the Heart
- Exercise increases maximal cardiac output (average: 5–7 L/min), and strengthens bones and muscles.
- Cardiac hypertrophy (enlarged heart) may be seen in athletes as well as hypertension.
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Description
Explore the key components and functions of the cardiovascular system, including the heart, blood, and blood vessels. Understand the anatomy of the heart, its location, and the protective role of the pericardium. This quiz will test your knowledge of cardiology fundamentals.
