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BIO 202 Heart, blood pressure, and respiration practice question ANSWERS Heart: 1. The heart is approximately the size of a closed fist and has a conical shape. It is located in the middle mediastinum, slightly to the left side of the thorax. The base of the heart is directed towards the right shoul...

BIO 202 Heart, blood pressure, and respiration practice question ANSWERS Heart: 1. The heart is approximately the size of a closed fist and has a conical shape. It is located in the middle mediastinum, slightly to the left side of the thorax. The base of the heart is directed towards the right shoulder, while the apex points downward and slightly to the left. 2. The coverings of the heart include: - Pericardium: The pericardium is a double-layered sac that surrounds and protects the heart. It consists of an outer fibrous pericardium and an inner serous pericardium. - Epicardium: Also known as the visceral layer of serous pericardium, it covers the surface of the heart. - Myocardium: This thick muscular layer is responsible for contracting and pumping blood. - Endocardium: This smooth inner lining covers the chambers and valves of the heart. 3. The three layers of the heart wall are: - Epicardium: It is composed primarily of connective tissue with some adipose tissue. Its main function is to protect and lubricate the outer surface of the heart. - Myocardium: This middle layer consists mainly of cardiac muscle cells that contract to pump blood throughout the body. It also contains blood vessels, nerves, and connective tissues that support its structure. - Endocardium: A thin layer composed of endothelial cells that line the inside of all four chambers and valves. It provides a smooth surface for blood flow and prevents abnormal clotting. 4. The four heart chambers are: - Right atrium: Receives deoxygenated blood from systemic circulation through the superior and inferior vena cavae. Associated great vessel(s): Superior vena cava, inferior vena cava - Right ventricle: Receives deoxygenated blood from the right atrium and pumps it to the lungs for oxygenation. Associated great vessel(s): Pulmonary artery - Left atrium: Receives oxygenated blood from the lungs through the pulmonary veins. Associated great vessel(s): Four pulmonary veins - Left ventricle: Receives oxygenated blood from the left atrium and pumps it to the systemic circulation. Associated great vessel(s): Aorta 5. The heart valves include: - Tricuspid valve: Located between the right atrium and right ventricle, it prevents backflow of blood when the ventricle contracts. - Pulmonary valve: Positioned between the right ventricle and the pulmonary artery, it controls blood flow from the heart to the lungs. - Mitral (bicuspid) valve: Found between the left atrium and left ventricle, it prevents backflow of blood when the ventricle contracts. - Aortic valve: Situated between the left ventricle and aorta, it regulates blood flow from the heart to the systemic circulation. 6. Pathway of blood through the heart and lungs: Right atrium -> tricuspid valve -> right ventricle -> pulmonary valve -> pulmonary artery -> lungs -> pulmonary veins -> left atrium -> mitral valve -> left ventricle -> aortic valve -> aorta -> systemic circulation 7. The pulmonary circuit carries deoxygenated blood from the heart to the lungs for gas exchange, while the systemic circuit carries oxygenated blood from the heart to all body tissues. The coronary circuit supplies oxygenated blood to the myocardium itself. Gas exchange occurs in capillaries within alveoli in the lungs during respiration. 8. The major branches of coronary arteries are: - Right coronary artery (RCA): Supplies blood to portions of both ventricles, interventricular septum, and sinoatrial (SA) node. - Left main coronary artery (LMCA): Divides into two main branches - left anterior descending (LAD) artery and circumflex artery. - Left anterior descending (LAD) artery: Supplies blood to the anterior portion of the interventricular septum and parts of the left and right ventricles. - Circumflex artery: Supplies blood to the left atrium, lateral walls of the left ventricle, and posterior walls of both ventricles. 9. Cardiac muscle is striated like skeletal muscle but has branching fibers interconnected by intercalated discs. It contains more mitochondria for aerobic respiration due to its continuous contraction. Unlike skeletal muscle, cardiac muscle contracts involuntarily, synchronously, and continuously without fatiguing. 10. Cardiac muscle cell contraction involves a series of events: 1. Depolarization: Sodium ions rapidly enter the cell through voltage-gated sodium channels, causing depolarization. 2. Plateau phase: Calcium ions enter the cell through slow calcium channels, maintaining prolonged depolarization. 3. Repolarization: Potassium ions exit the cell through voltage-gated potassium channels, leading to repolarization. 11. The components of the conduction system include: - Sinoatrial (SA) node: Located in the right atrial wall near the opening of superior vena cava, it initiates each heartbeat and acts as the natural pacemaker. - Atrioventricular (AV) node: Found at the base of the right atrium near the interatrial septum, it receives electrical signals from the SA node and delays them before transmitting them to the ventricles. - Bundle of His (atrioventricular bundle): Divides into two branches called bundle branches that carry electrical impulses down the interventricular septum. - Purkinje fibers: Branches off from bundle branches and transmit electrical signals throughout both ventricles. 12. Autorythmicity means that certain cardiac cells can generate spontaneous electrical impulses without external stimulation. 13. The SA node works by spontaneously generating an electrical impulse that initiates each heartbeat. It is called the pacemaker because it sets the rhythm and rate of the heart's contractions. 14. The AV node functions as a delay system, allowing the atria to contract fully before sending the electrical signals to the ventricles. The pause at the AV node allows time for blood to flow from the atria into the ventricles before ventricular contraction begins. 15. A normal electrocardiogram (ECG) tracing includes waves and intervals: - P wave: Represents atrial depolarization. - QRS complex: Depicts ventricular depolarization. - T wave: Signifies ventricular repolarization. - PR interval: Measures from the beginning of the P wave to the beginning of the QRS complex, representing time taken for electrical conduction through atria and AV node. - QT interval: Measures from beginning of QRS complex to end of T wave, indicating total time for ventricular depolarization and repolarization. 16. Some abnormalities that can be detected on an ECG tracing include: - Arrhythmias: Irregular heart rhythms such as atrial fibrillation, ventricular tachycardia, or bradycardia. - Myocardial infarction: This is indicated by ST-segment elevation or depression and Q waves. - Conduction abnormalities: These can manifest as prolonged PR intervals, bundle branch blocks, or other conduction delays. - Ventricular hypertrophy: Enlargement of the ventricles may be seen as increased amplitude of QRS complexes. - Ischemia: Reduced blood flow to the heart muscle can be indicated by T-wave inversion or ST-segment depression. 17. Heart sounds are the sounds produced by the closing of the heart valves during the cardiac cycle. The first heart sound (S1) is caused by the closure of the atrioventricular valves (mitral and tricuspid), while the second heart sound (S2) is caused by the closure of the semilunar valves (aortic and pulmonary). A murmur is an abnormal sound caused by turbulent blood flow through a valve that may indicate a valve disorder. Stenosis refers to a narrowing or obstruction of a valve, impairing its ability to open fully, while prolapse refers to when a valve leaflet bulges back into the previous chamber during systole. 18. The cardiac cycle consists of several events: - Atrial systole: Contraction of the atria forces blood into the ventricles. - Isovolumetric contraction: Ventricular contraction begins, but all valves are closed, so no blood leaves yet. - Ventricular ejection: Once pressure in the ventricles exceeds arterial pressure, semilunar valves open and blood is ejected into circulation. - Isovolumetric relaxation: All valves close again briefly before diastole begins. - Ventricular filling: Blood flows from the atria into the ventricles due to pressure differences. 19. Systole refers to the phase of the cardiac cycle when the heart chambers contract, while diastole refers to the phase when the heart chambers relax and fill with blood. Isovolumetric contraction is a brief period during systole when all valves are closed, preventing any change in volume. 20. Cardiac output is the amount of blood pumped by the heart per minute and is calculated by multiplying stroke volume (the amount of blood ejected with each heartbeat) by heart rate. It represents how effectively the heart is delivering oxygenated blood to tissues. 21. Stroke volume (SV) is the amount of blood ejected from the left ventricle with each beat. End-systolic volume (ESV) is the amount of blood remaining in the left ventricle after contraction, while end-diastolic volume (EDV) is the amount of blood in the left ventricle at the end of diastole before contraction. These values can change based on factors such as preload, afterload, and contractility. 22. Heart rate refers to the number of times the heart beats per minute. It can be influenced by factors such as physical activity, stress, or hormonal changes. 23. The contractility of the heart can be changed through various mechanisms such as sympathetic stimulation or certain medications. Preload refers to the degree of stretch on cardiac muscle fibers before contraction, while afterload refers to resistance against which the ventricles must pump blood. 24. Various factors regulate stroke volume and heart rate: - Preload: Increased preload leads to increased stroke volume. - Afterload: Increased afterload decreases stroke volume. - Contractility: Increased contractility increases stroke volume. - Autonomic nervous system: Sympathetic stimulation increases heart rate and contractility, while parasympathetic stimulation decreases heart rate. 25. Tachycardia refers to a rapid heart rate, while bradycardia refers to a slow heart rate. Angina is chest pain caused by reduced blood flow to the heart muscle. Fibrillation refers to chaotic and irregular contractions of the heart muscles. Myocardial infarction is commonly known as a heart attack and occurs when blood flow to the heart muscle is blocked. 26. The autonomic nervous system plays a significant role in regulating cardiac output. Sympathetic stimulation increases heart rate, contractility, and vasoconstriction, leading to increased cardiac output. Parasympathetic stimulation decreases heart rate and contractility. 27. If someone scared you, your body would likely exhibit a stress response, causing an increase in sympathetic activity. This would lead to an increase in cardiac output (CO), heart rate (HR), stroke volume (SV), and contractility due to sympathetic stimulation. 28. The cardioacceleratory center and cardioinhibitory center are regions within the medulla oblongata of the brainstem that regulate cardiovascular function. The cardioacceleratory center stimulates sympathetic activity, increasing heart rate and contractility, while the cardioinhibitory center inhibits parasympathetic activity, reducing heart rate. 29. During development, the heart begins as a simple tube that gradually forms into four chambers: two atria and two ventricles with associated valves. In fetal circulation, there are temporary structures like the foramen ovale and ductus arteriosus that allow blood to bypass certain parts of the immature lungs since oxygenation occurs through the placenta instead of breathing air. 30. Age-related changes in heart function can include decreased elasticity of blood vessels, reduced efficiency of electrical conduction in the heart, thickening or stiffening of heart valves or vessels, and decreased maximum achievable heart rate during exercise. 31. Some common fetal heart defects include atrial septal defect, ventricular septal defect, tetralogy of Fallot, coarctation of the aorta, and transposition of the great arteries. These defects involve abnormalities in the structure or function of the heart during fetal development. Blood Pressure: 1. Blood flow refers to the movement of blood through the circulatory system, delivering oxygen and nutrients to tissues and removing waste products. 2. Blood pressure is the force exerted by circulating blood against the walls of blood vessels. It is generated by the pumping action of the heart, as it pushes blood into the arteries during systole. A pulse is a rhythmic expansion and contraction of arterial walls caused by the ejection of blood from the heart. 3. Systolic pressure is the maximum pressure in the arteries during ventricular contraction, while diastolic pressure is the minimum pressure in the arteries during ventricular relaxation. Mean Arterial Pressure (MAP) represents an average blood pressure throughout one cardiac cycle and is calculated using a formula: MAP = [(2 x diastolic) + systolic] / 3. 4. Peripheral resistance refers to the opposition encountered by blood flow in peripheral arteries. It depends on factors such as vessel diameter, vessel length, blood viscosity, and vessel elasticity. Increased peripheral resistance can be caused by vasoconstriction or narrowing of blood vessels, while decreased resistance can result from vasodilation or widening of blood vessels. 5. Cardiac output (CO), which is the amount of blood pumped by the heart per minute, is determined by heart rate (HR) and stroke volume (SV). Resistance plays a role in determining systemic vascular resistance (SVR), which affects blood pressure. An increase in CO, HR, SV, or resistance can lead to an increase in blood pressure. 6. Blood pressure is highest in arteries due to their proximity to the pumping action of the heart and gradually decreases as it moves through capillaries and veins back towards the heart. 7. Short-term neural controls of BP include baroreceptor reflexes, chemoreceptor reflexes, and hormonal regulation. 8. Baroreceptors are specialized sensory receptors located in certain areas such as carotid sinuses and aortic arch. They monitor changes in blood pressure and transmit signals to the cardiovascular center in the brainstem. Chemoreceptors located in carotid bodies and aortic bodies detect changes in oxygen, carbon dioxide, and pH levels in the blood. If either receptors are stimulated by changes outside normal ranges, they send signals to adjust heart rate, stroke volume, and peripheral resistance. 9. The hypothalamus plays a role in regulating blood pressure through its control of the autonomic nervous system. It integrates inputs from various receptors and sends appropriate signals to maintain homeostasis. 10. Norepinephrine causes vasoconstriction and increases heart rate, atrial natriuretic peptide promotes vasodilation and sodium excretion, aldosterone increases sodium reabsorption leading to water retention, anti-diuretic hormone (ADH) promotes water reabsorption by kidneys, Angiotensin II is a potent vasoconstrictor that also stimulates aldosterone release, and nitric oxide causes vasodilation. 11. Long-term regulation of blood pressure involves the kidneys via direct mechanisms (regulating blood volume) or indirect mechanisms (renin-angiotensin-aldosterone system). The kidneys can increase or decrease urine output based on body fluid needs to help maintain optimal blood pressure. 12. Hypertension is defined as persistently high blood pressure above 130/80 mmHg. It often has no noticeable symptoms but can lead to serious complications such as heart disease, stroke, kidney damage, or vision loss if left untreated. 13. Hypotension refers to abnormally low blood pressure below 90/60 mmHg. It can cause dizziness, fainting, blurred vision, fatigue, or confusion. 14. Circulatory shock is a life-threatening condition characterized by inadequate perfusion of tissues due to low blood volume or impaired cardiac function. Causes can include severe bleeding, heart failure, septicemia, or anaphylaxis. Respiration: 1. Cellular respiration refers to the process by which cells convert glucose and oxygen into energy, carbon dioxide, and water, while mechanical respiration refers to the physical act of breathing. We need both processes because cellular respiration provides our cells with the energy they need to function properly, while mechanical respiration ensures that oxygen is brought into the body and carbon dioxide is removed. 2. Internal respiration refers to the exchange of gases (oxygen and carbon dioxide) between the blood and tissues within the body, while external respiration refers to the exchange of gases between the lungs and the external environment. 3. In addition to its primary function of gas exchange, the respiratory system also plays other important roles. It contributes to speech production by regulating airflow through the vocal cords. The olfactory receptors in our nasal cavity allow us to detect smells. The respiratory muscles act as a pump to facilitate breathing. The Valsalva maneuver is a process where breath-holding helps increase pressure in certain parts of the body, such as during childbirth or lifting heavy objects. Lastly, the respiratory system helps regulate pH levels in the body by controlling levels of carbon dioxide. 4. The conducting zone of the respiratory system includes structures like the nose, pharynx, larynx, trachea, bronchi, and bronchioles. Its main function is to warm, humidify, and cleanse incoming air before it reaches the delicate structures of the lungs. 5. Nasal conchae are scroll-like bones located inside each nasal cavity. They help increase surface area within the nasal cavity, which aids in warming, humidifying, and filtering incoming air. 6. The uvula is a small flap of tissue at the back of your throat that prevents food and liquid from entering your nasal cavity when you swallow. The epiglottis is a leaf-shaped cartilage that covers the glottis (opening into the larynx) during swallowing to prevent food from entering the airway. The glottis is the opening between the vocal cords in the larynx. The true vocal folds are responsible for producing sound, while the false vocal folds help protect the true vocal folds and assist in producing a deeper voice. 7. The three different tonsils are the pharyngeal tonsil (adenoids), located in the back of the throat; the palatine tonsils, located on either side of the back of your throat; and the lingual tonsils, located at the base of the tongue. Their function is to help fight off infections by trapping bacteria and viruses that enter through the mouth and nose. 8. The trachea, also known as the windpipe, is a tube made up of C-shaped cartilage rings that provide structural support and prevent collapse while allowing flexibility during breathing. The respiratory zone refers to structures within the lungs where gas exchange occurs, specifically in tiny air sacs called alveoli. Gas exchange occurs across thin walls composed mainly of Type I cells, which are responsible for gas diffusion, and Type II cells, which secrete surfactant to reduce surface tension and prevent alveolar collapse. 9. Type I cells are extremely thin cells that make up most of the alveolar wall and are directly involved in gas exchange. Type II cells secrete pulmonary surfactant, a substance that helps reduce surface tension in alveoli and prevents them from collapsing during exhalation. 10. Oxygen is carried in the blood primarily by binding to hemoglobin molecules within red blood cells. Carbon dioxide is transported in three forms: dissolved in plasma, bound to hemoglobin, or converted into bicarbonate ions. 11. Hyperventilation refers to rapid or deep breathing, while hyperventilation refers to slow or shallow breathing. Dyspnea is difficulty or discomfort in breathing, and apnea is the temporary cessation of breathing. 12. The respiratory center of the brain is located in the medulla oblongata and pons. The pons helps regulate the rate and depth of breathing, while the medulla controls the basic rhythm of respiration. The hypothalamus can influence breathing through emotional responses. 13. Mechanical breathing involves the contraction and relaxation of muscles involved in respiration, such as the diaphragm and intercostal muscles. Nerves like the phrenic nerve and intercostal nerves control these muscles. Breathing does require energy expenditure. 14. Tidal volume is the amount of air inhaled or exhaled during normal breathing at rest. Inspiratory reserve volume is the additional air that can be forcefully inhaled after a tidal breath. Expiratory reserve volume is the additional air that can be forcefully exhaled after a tidal breath. Vital capacity is the total amount of air that can be forcibly exhaled after maximal inhalation. Residual volume is the air remaining in the lungs after maximal exhalation. 15. COPD (Chronic Obstructive Pulmonary Disease) encompasses chronic bronchitis and emphysema, characterized by airflow limitation and difficulty breathing. Asthma involves chronic inflammation and narrowing of airways leading to wheezing and shortness of breath. Tuberculosis (TB) is a bacterial infection that primarily affects the lungs. Lung cancer refers to the uncontrolled growth of abnormal cells in the lung tissue. 16. Smoking damages the respiratory system by causing inflammation, mucous production, and destruction of lung tissues. However, some damage can be reversed when a person quits smoking, such as improved lung function and decreased risk of certain diseases. 17. Lifespan changes in the respiratory system include decreased cilia function, leading to reduced ability to remove mucus and debris from the airways. Mucus becomes thicker, cough and gag reflexes weaken, macrophage activity decreases, and alveoli lose elasticity and may become distended. Negative Feedback in relation to blood pressure: Baroreflex works to maintain blood pressure the same, ideally 120/80 mm Hg. It is a negative feedback loop because an increase in pressure in the sinus caroticus leads to vasodilation and reduced heart rate, which reduces the blood pressure back to normal. The reversed effect also applies, where a drop in pressure in sinus caroticus leads to vasoconstriction and increased heart rate, which brings the blood pressure to normal. The baroreflex provides a negative feedback loop for controlling blood pressure, such that heart rate falls when blood pressure rises, and vice-versa when blood pressure falls, thus modulating blood pressure fluctuations. Study Guide- Chapter 19- Heart Describe the general function of the cardiovascular system The general function of the cardiovascular system is to transport oxygen, nutrients, hormones, and waste products throughout the body. It consists of the heart, blood vessels, and blood. Differentiate among the three primary types of blood vessels. Arteries carry oxygenated blood away from the heart, veins transport deoxygenated blood back towards the heart, and capillaries facilitate exchange of substances between the bloodstream and surrounding tissues. Describe the general structure and function of the heart. Structure: - Size and shape: Approximately the size of a closed fist, cone-shaped. - Location: Located in the chest cavity, between the lungs, slightly to the left side. - Layers: Consists of three layers - epicardium (outermost layer), myocardium (middle layer composed of cardiac muscle), and endocardium (inner lining). Function: - Pumping action: Contracts and relaxes rhythmically to pump blood throughout the circulatory system. - Circulation: Receives deoxygenated blood from the body via veins and pumps oxygenated blood out to various organs and tissues via arteries. - Valves: Contains four valves - tricuspid valve, pulmonary valve, mitral valve, and aortic valve - that ensure unidirectional flow of blood through the heart chambers. - Electrical impulses: Generates electrical signals that regulate the heartbeat, ensuring coordinated contractions. Compare and contrast pulmonary circulation and systemic circulation of the cardiovascular system. Trace blood flow through both circulations. 1. "Pulmonary circulation focuses on oxygenating blood in order to remove carbon dioxide from it, whereas systemic circulation delivers oxygen-rich blood throughout our entire body." 2. The flow of pulmonary circulation goes from right ventricle → pulmonary artery → alveolar capillaries → pulmonary veins → left atrium. 3. The flow of systemic circulation starts at left atrium → left ventricle → aorta → arteries → arterioles → capillaries → venules → veins → right atrium. Describe the location and position of the heart in the thoracic cavity. The heart is centrally located within the thoracic cavity, in a region known as the mediastinum. It is slightly inclined towards the left side of the chest and occupies an oblique position between the second rib and fifth intercostal space. List the structural components of the pericardium. 1. Fibrous Pericardium: The fibrous pericardium is the tough, outermost layer of the pericardial sac. 2. Serous Pericardium: The serous pericardium consists of two layers - the parietal layer and the visceral layer. 3. Parietal Layer: The parietal layer lines the inner surface of the fibrous pericardium and forms the outer wall of the pericardial cavity. 4. Visceral Layer (Epicardium): The visceral layer, also known as epicardium, covers the heart's surface directly. 5. Pericardial Cavity: The space between the parietal and visceral layers is called the pericardial cavity, which contains a small amount of fluid to reduce friction during heart contractions. 6. Pericardial Fluid: Pericardial fluid is a lubricating fluid found within the pericardial cavity that helps reduce friction between the layers of the pericardium during cardiac movements. Describe the function of the pericardium and the purpose of the serous fluid within the pericardial cavity. The pericardium serves to protect and stabilize" the heart, while "serous fluid reduces friction" between its layers. Compare the superficial features of the anterior and posterior aspects of the heart. Anterior Aspect of the Heart: - Location: The anterior aspect of the heart is located towards the front of the chest, behind the sternum (breastbone). - Surface features: It includes the right atrium and right ventricle, which form the majority of the visible anterior surface of the heart. - Structures: The superior vena cava and inferior vena cava enter into the right atrium, while the pulmonary trunk exits from the right ventricle. - Coronary vessels: The right coronary artery can be seen running along the anterior surface, supplying blood to both ventricles. Posterior Aspect of the Heart: - Location: The posterior aspect of the heart is situated towards the back of the chest cavity. - Surface features: It consists mainly of the left atrium and left ventricle, which are visible from a posterior view. - Structures: The four pulmonary veins enter into the left atrium, while the aorta exits from the left ventricle. - Coronary vessels: The left coronary artery is found on this side, supplying blood to both ventricles. Name the three layers of the heart wall and the tissue components of each. Layer 1: Epicardium - Tissue component: Thin layer of connective tissue and epithelial cells - Function: Provides a protective outer covering to the heart Layer 2: Myocardium - Tissue component: Thick layer of cardiac muscle cells - Function: Responsible for contracting and pumping blood throughout the body Layer 3: Endocardium - Tissue component: Inner lining made up of endothelial cells - Function: Forms a smooth surface for efficient blood flow within the heart chambers Characterize the four chambers of the heart and their functions. Chamber: Right Atrium Function: Receives deoxygenated blood from the body and pumps it to the right ventricle. Chamber: Right Ventricle Function: Receives deoxygenated blood from the right atrium and pumps it to the lungs for oxygenation. Chamber: Left Atrium Function: Receives oxygenated blood from the lungs and pumps it to the left ventricle. Chamber: Left Ventricle Function: Receives oxygenated blood from the left atrium and pumps it to the rest of the body. Compare and contrast the structure and function of the two types of heart valves. Type of Heart Valve: Aortic Valve Structure: - The aortic valve is a tricuspid valve with three leaflets, also known as cusps or flaps. - It consists of fibrous tissue covered by thin layers of endothelial cells. - The leaflets are attached to the annulus, a ring-shaped structure that surrounds the opening of the aorta. Function: - The main function of the aortic valve is to prevent the backflow of blood from the aorta into the left ventricle. - When the left ventricle contracts, it forces blood through the aortic valve and into the systemic circulation. - After systole (contraction phase), when the ventricles relax, the aortic valve closes to prevent blood from flowing back into the heart. Type of Heart Valve: Mitral Valve Structure: - The mitral valve, also known as bicuspid valve, has two leaflets or cusps. - Similar to other heart valves, it consists of fibrous tissue covered by thin layers of endothelial cells. - The leaflets are attached to papillary muscles in the left ventricle via chordae tendineae, which provide support and stability. Function: - The primary function of the mitral valve is to regulate blood flow between the left atrium and left ventricle. - During diastole (relaxation phase), when blood fills up in the left atrium, it passes through an open mitral valve into the left ventricle. - As systole begins (contraction phase), the mitral valve closes tightly to prevent any backflow into the atrium. Describe the location and function of the fibrous skeleton. Location: The fibrous skeleton is located within the heart, specifically in the middle layer known as the myocardium. It surrounds and supports the four chambers of the heart. Function: The fibrous skeleton serves several important functions in the heart: 1. Structural Support: It provides a sturdy framework for the attachment of cardiac muscle fibers, ensuring proper alignment and coordinated contraction of the heart chambers. 2. Electrical Insulation: The fibrous skeleton acts as an electrical insulator between different regions of the heart. This prevents abnormal electrical impulses from spreading to unwanted areas, thus maintaining a synchronized and efficient heartbeat. 3. Valve Support: It provides support for the heart valves by forming dense connective tissue rings around them. These rings help maintain the shape and integrity of the valves, preventing their prolapse or collapse during blood flow. 4. Separation of Atria and Ventricles: The fibrous skeleton forms a barrier between the atria (upper chambers) and ventricles (lower chambers) of the heart. This separation helps channel blood flow in a specific direction, allowing efficient filling and ejection of blood during each cardiac cycle. Describe the general structure of cardiac muscle. Intercalated Discs: Specialized junctions between adjacent cardiac muscle cells that allow for rapid transmission of electrical signals. They contain desmosomes to provide mechanical strength and gap junctions to facilitate electrical coupling. Branched Fibers: Cardiac muscle fibers are interconnected, forming a network that allows for coordinated contraction. This branching pattern enables efficient distribution of electrical impulses throughout the heart. Striations: Cardiac muscle exhibits a striped appearance under a microscope due to the presence of organized sarcomeres. These repeating units consist of thick myosin filaments and thin actin filaments responsible for muscle contraction. Explain the intercellular structures of cardiac muscle 1. Intercalated Discs: "Intercalated discs are specialized cell-to-cell junctions that connect adjacent cardiac muscle cells." These disc-like structures contain three main components - desmosomes, gap junctions, and fascia adherens. 2. Desmosomes: "Desmosomes provide strong mechanical adhesion between neighboring cardiac muscle cells." They consist of transmembrane proteins called cadherins, which link with the intermediate filaments of adjacent cells, providing structural stability to the tissue. 3. Gap Junctions: "Gap junctions allow for electrical coupling between cardiac muscle cells." These small channels formed by connexin proteins permit the passage of ions and small molecules, facilitating rapid transmission of action potentials and synchronization of contractions throughout the myocardium. 4. Fascia Adherens: "Fascia adherens form a continuous belt-like structure along the intercalated discs." They anchor actin filaments to the plasma membrane, promoting structural integrity and transmitting contractile forces during muscle contraction. Discuss how cardiac muscle meets its energy needs. - Cardiac muscle primarily relies on aerobic metabolism to meet its energy demands. - The main source of energy for cardiac muscle is adenosine triphosphate (ATP). - ATP is produced through the process of oxidative phosphorylation in the mitochondria of cardiac muscle cells. Identify the coronary arteries, and describe the specific areas of the heart supplied by their major branches. 1. Left Main Coronary Artery (LMCA):The left main coronary artery is an important branch of the ascending aorta that supplies oxygenated blood to the left side of the heart. 2. Left Anterior Descending Artery (LAD): "The LAD is a major branch of the left main coronary artery and supplies blood to the anterior wall of the left ventricle, interventricular septum, and apex of the heart." 3. Circumflex Artery (Cx): "The circumflex artery originates from the left main coronary artery and supplies blood to the lateral wall of the left ventricle." 4. Right Coronary Artery (RCA): "The right coronary artery arises from the right sinus of Valsalva and provides blood supply to most of the right atrium, right ventricle, inferior wall of the left ventricle, and part of the interventricular septum." 5. Posterior Descending Artery (PDA): "The PDA is a branch of either the RCA or Cx artery, depending on anatomical variation, and supplies blood to the posterior walls of both ventricles and part of the interventricular septum." Explain the significance of coronary arteries as functional end arteries. The left and right coronary arteries are considered functional end arteries because, although there coronary arteries have anastomoses, if one of the arteries becomes blocked these anastomoses are too tiny to shunt sufficient blood from one artery to the other. As a result, the part of the heart wall that was supplied by one coronary artery branch will die due to lack of blood flow to the tissue. Describe blood flow through the coronary arteries. Blood flow to the heart wall is not a steady stream; it is impeded and then flows, as the heart rhythmically contracts and relaxes. Identify the coronary veins, and describe the specific areas of the heart drained by their major branches. 1. Great Cardiac Vein: The great cardiac vein drains the left atrium, left ventricle, and interventricular septum. 2. Middle Cardiac Vein: The middle cardiac vein drains the posterior surface of the left ventricle. 3. Small Cardiac Vein: The small cardiac vein drains the right atrium and right ventricle. 4. Anterior Cardiac Veins:The anterior cardiac veins drain the right ventricle and open directly into the right atrium. 5. Coronary Sinus: The coronary sinus is a large venous channel that receives blood from most of the coronary veins and empties into the right atrium. Identify and locate the components of the heart’s conduction system. 1. SA Node (Sinoatrial Node): - Located in the right atrium near the superior vena cava. -The SA node is often referred to as the natural pacemaker of the heart. 2. AV Node (Atrioventricular Node): - Located in the lower portion of the right atrium, near the septum. - The AV node acts as a relay station between the atria and ventricles, delaying electrical impulses before transmitting them to ensure proper coordination 3. Bundle of His: - Located in the upper part of the interventricular septum. - The bundle of His divides into left and right branches, which carry electrical signals down each side of the septum towards the ventricles. 4. Purkinje Fibers: - Located throughout both ventricles, branching from the bundle branches. - "Purkinje fibers distribute electrical impulses rapidly through specialized muscle cells, allowing coordinated contraction of both ventricles. Compare and contrast parasympathetic and sympathetic innervation of the heart. Parasympathetic innervation of the heart: - Originates from the vagus nerve (cranial nerve X). - Releases acetylcholine as its primary neurotransmitter. - Acts to slow down heart rate and decrease cardiac output. - Stimulates the release of nitric oxide, which causes vasodilation in coronary blood vessels. - Mediates a "rest and digest" response. Sympathetic innervation of the heart: - Originates from preganglionic neurons in the thoracic region of the spinal cord (T1-T4) and releases norepinephrine as its primary neurotransmitter. - Activates the fight or flight response. - Increases heart rate, contractility, and cardiac output. - Causes vasoconstriction in peripheral blood vessels but promotes vasodilation in coronary blood vessels to increase myocardial oxygen supply. Describe a nodal cell at rest At rest, nodal cells have a stable membrane potential called the resting membrane potential. Resting Membrane Potential: - The resting membrane potential of a nodal cell is approximately -60 mV to -70 mV. - This negative charge inside the cell is maintained by a higher concentration of negatively charged ions, such as proteins and organic anions, compared to outside the cell. - It is primarily regulated by potassium (K+) ion channels that allow K+ to flow out of the cell, contributing to its negativity. - The resting membrane potential allows nodal cells to remain electrically stable until stimulated. - It provides a baseline for depolarization, which triggers action potentials necessary for generating electrical signals within the heart. - A stable resting membrane potential ensures regular rhythmic contractions and proper coordination between different parts of the heart. Define autorhythmicity. Autorhythmicity refers to the inherent ability of certain cells or tissues in the body to generate spontaneous electrical impulses at regular intervals without any external stimulation. These cells are capable of initiating and conducting these electrical signals, which play a crucial role in regulating various physiological processes, such as heart rate and contraction. Describe the steps for SA nodal cells to spontaneously depolarize and serve as the pacemaker cells. 1. Reaching threshold as Na+ enters the nodal cells through open voltage-gated Na+ channels 2. depolarization as Ca2+ enters the nodal cells through open voltage-gated Ca2+ channels 3. Repolarization as K+ exits the nodal cells through voltage-gated K+ channels Describe the spread of the action potential through the heart’s conduction system. The action potential originates in the sinoatrial (SA) node, also known as the natural pacemaker of the heart. "The SA node generates an action potential that spreads across both atria, causing them to contract simultaneously." - From the SA node, the action potential travels through specialized conduction pathways called internodal pathways towards the atrioventricular (AV) node. "Internodal pathways conduct the electrical impulse from the SA node to the AV node, facilitating coordinated contraction between the atria and ventricles." - At the AV node, there is a slight delay in order to allow for complete atrial contraction before ventricular contraction begins. "The AV node delays conduction for about 0.1 seconds, allowing time for atrial contraction and filling of blood into ventricles." - After passing through the AV node, the action potential enters into the Bundle of His or atrioventricular bundle. "The Bundle of His fibers rapidly transmit electrical signals from the AV node to the Purkinje fibers." - The Purkinje fibers then distribute the action potential throughout both ventricles, causing them to contract simultaneously. "The fast-conducting Purkinje fibers rapidly spread excitation throughout all regions of both ventricles, resulting in synchronized ventricular contraction." Describe the conditions at the sarcolemma of cardiac muscle cells at rest. 1. RMP is -90 mV. 2. Contains fast voltage-gated Na+ channels for depolarization and K+ voltage-gated channels for repolarization of membrane. 3. Also contains slow voltage-gated Ca+ channels List the electrical events of an action potential that occur at the sarcolemma. 1. Depolarization: An action potential triggers the opening of fast voltage-gated Na+ channels in the sarcolemma. The resulting resting membrane potential changes from -90 mV to +30 mV. Voltage-gated Na+ channels close to inactivated state. 2. Plateau: Depolarization triggers the opening of voltage-gated K+ channels and K+ leave the cardiac muscle cells. Slow voltage-gated Ca+ channels open and Ca+ enters the cell. The exit of K+ and simultaneous entrance of Ca+ results in no electrical change, and the sarcolemma remains in a depolarized state. 3. Repolarization: Voltage-gated Ca+ channels then close and K+ channels remain open to complete repolarization as K+ exits the cells. Membrane potential of -90 mV is then reestablished. Briefly summarize the mechanical events of muscle contraction. The entry of Ca+ into the sarcoplasm from the plateau allows Ca+ to bind to troponin and begin cross-bridge cycling within a sarcomere, similar to skeletal muscle contraction. The closing of voltage-gates Ca+ channels, reuptake of Ca+ into the sarcoplasmic reticulum by Ca+ pumps, and removal of Ca+ from the cell by plasma membrane Ca+ pumps decrease Ca+ levels in the sarcoplasm. Calcium is released from troponin with subsequent decrease in cross-bridges between thin and thick filaments. Sarcomeres return to their original resting length. Define the refractory period. Refractory period is the period of time following an action potential during which a neuron or muscle fiber cannot generate another action potential. It is characterized by a temporary state of reduced excitability, preventing the neuron from being immediately stimulated again. Explain the significance of the plateau phase The plateau phase delays repolarization and allows the sarcomeres of cardiac muscle cells to fully contract and relax before following each stimulation. This prevents cardiac muscle cells from exhibiting tetany which would result in the locking up of heart chambers. Identify the components of the ECG recording components of an ECG recording consist of electrodes, leads, an ECG machine, a paper strip, calibration markers, waves and intervals, measurements, and interpretation software Waves 1. P wave: Reflects atrial depolarization that originates in the SA node. Typically lasts 0.008 to 0.1 seconds. 2. QRS complex: Represents ventricular depolarization 3. T wave: Represents ventricular repolarization. Segments P-Q segment: Associated with atrial plateau when the cardiac muscle cells within the atria are contracting. S-T segment: The ventricular plateau when cardiac muscle cells within the ventricles are contracting. Intervals P-R interval: represents the period of time between the beginning of the P wave to the beginning of the QRS deflection. Q-T interval: time from the beginning of the QRS complex to the end of the T wave. Identify the two processes within the heart that occur due to pressure changes associated with the cardiac cycle. 1. Ventricular Contraction (Systole): "During ventricular contraction, or systole, the pressure within the ventricles increases, causing the blood to be forcefully ejected into the pulmonary artery and aorta. 2. Ventricular Relaxation (Diastole): "During ventricular relaxation, or diastole, the pressure within the ventricles decreases, allowing blood to flow back into the relaxed chambers from the atria. List and describe what occurs during the five phases of the cardiac cycle. 1. Atrial systole is the contraction of atria to finish filling the ventricles, which are in diastole. 2. Early ventricular systole is a time of isovolumetric contraction: Ventricles begin to contract, AV valves are pushed closed, and no blood leaves the ventricles yet. 3. Late ventricular systole is the time of ventricular ejection: Semilunar valves are pushed open, and blood is forced through the semilunar valves into the arterial trunk. 4. Early ventricular diastole is the beginning of ventricular relaxation: AV valves remain closed, and semilunar valves close. 5. Late ventricular diastole is a time to begin ventricular filling as AV valves open and passive filling of the ventricle begins. Explain the significance of ventricular balance. The term "ventricular balance" refers to the equal distribution of blood flow between the left and right ventricles of the heart. Significance: 1. Efficient Pumping: Ventricular balance ensures that both sides of the heart work together effectively, allowing for optimal pumping of oxygenated blood to the body and deoxygenated blood to the lungs. 2. Normal Functioning: Maintaining ventricular balance is crucial for maintaining normal cardiac function and preventing conditions such as congestive heart failure, where an imbalance in ventricular workload can lead to inadequate pumping and fluid accumulation. 3. Hemodynamic Stability: By achieving ventricular balance, the heart can maintain a stable hemodynamic state, ensuring adequate perfusion to vital organs and tissues throughout the body. Define cardiac output. Cardiac output represents the efficiency and effectiveness of the heart's pumping action. It is calculated by multiplying the stroke volume (the amount of blood ejected with each heartbeat) by the heart rate (the number of times the heart beats per minute). Cardiac output provides a measure of how well the heart is able to deliver oxygenated blood to tissues throughout the body. A healthy adult at rest typically has a cardiac output between 4-8 liters per minute, which can increase during exercise or in response to certain physiological conditions or diseases Explain what is meant by cardiac reserve. Cardiac reserve refers to the ability of the heart to increase its output in response to increased demand, such as during physical exertion or stress. It represents the difference between a person's resting cardiac output and their maximum achievable cardiac output. Define chronotropic agents, and describe how they affect heart rate. External variables that operate on the SA node (the pacemaker) and the AV node may change the heart rate. Autonomic nervous system innervation and fluctuating hormone levels are the key extrinsic variables that raise and decrease heart rate. These variables that affect heart rate are chronotropic agents, and they may be classed as either positive or negative chronotropic agents. - Positive chronotropic agents - increase heart rate. - Negative chronotropic agents - decrease heart rate. Discuss how autonomic reflexes alter heart rate. Cardiac center receives sensory input from baroreceptors and chemoreceptors. Cardiac center responds by altering nerve signals that innervate the heart to maintain homeostasis List the three variables that may influence stroke volume. 1. Preload: Preload refers to the degree of stretch on the ventricular muscle fibers just before contraction and is determined by the volume of blood returning to the heart from the venous system. 2. Afterload: Afterload is defined as the force against which the heart must work to eject blood during systole and is influenced primarily by systemic vascular resistance. 3. Contractility: Contractility refers to the inherent ability of cardiac muscle fibers to shorten actively and develop force. Summarize the variables that influence cardiac output Various circumstances influence heart rate, stroke volume, and cardiac output: ● Heart rate - The conduction system is influenced by chronotropic drugs, which cause a rise or decrease in heart rate. The SA node is stimulated to modify its firing rate, while the AV node is stimulated to adjust the degree of delay. Explain how postnatal heart structures develop from the primitive heart tube. The heart develops during the third week of pregnancy when the embryo is too big to obtain nutrients only by diffusion. By day 19, the embryo has formed two heart tubes from the mesoderm. These paired tubes unite on day 21, creating a single primitive heart tube. On day 22 the heart starts to beat, and by the fourth week, this single heart tube has bent and folded in on itself to produce the exterior heart shape. This tube makes expansions, resulting in postnatal cardiac structures: ● sinus venosus ● primitive atrium ● primitive ventricle ● bulbus cordis The five regions of the primitive heart tube develop into recognizable structures in a fully developed heart. The truncus arteriosus will eventually divide and give rise to the ascending aorta and pulmonary trunk. The bulbus cordis develops into the right ventricle. The primitive ventricle forms the left ventricle. Describe septal defects that may occur during development. The postnatal heart with an atrial septal defect retains an opening between the left and right atria. Thus, blood is diverted from the left atrium to the right atrium. This may result in right-sided heart hypertrophy. Ventricular septal defects may emerge due to an incompletely constructed interventricular septum. Tetralogy of Fallot is a frequent abnormality that arises when the aorticopulmonary septum divides the truncus arteriosus unevenly. Consequently, the patient has a ventricular septal defect, a very thin pulmonary trunk, an aorta that crosses both the left and right ventricles, and right ventricle hypertrophy. Study Guide- Chapter 20- Vessels and Circulation Describe the relationship of the total cross-sectional area and velocity of blood flow. The relationship between the total cross-sectional area and velocity of blood flow can be described by the principle of continuity, which states that "the volume flow rate of an incompressible fluid is constant throughout a closed system" Predict the significance of slow blood flow in the capillaries. Slow blood flow in capillaries has significant consequences on various aspects of human physiology. It impairs oxygen and nutrient delivery to tissues, impedes waste removal, disrupts thermoregulation, and increases the risk of blood clot formation. Explain the process of diffusion and vesicular transport between capillaries and tissues. Diffusion allows small molecules and ions to passively move across capillary walls based on their concentration gradients, while vesicular transport mechanisms such as endocytosis and exocytosis play a role in the movement of larger molecules or specific substances between capillaries and tissues. These processes are vital for maintaining homeostasis by ensuring efficient exchange of nutrients, gases, and waste products within the body. Explain the processes of bulk flow, filtration, and reabsorption. Bulk flow is the downward movement of huge quantities of fluids and their dissolved constituents along a pressure gradient. Compare and contrast hydrostatic pressure and colloid osmotic pressure in the capillaries. While hydrostatic pressure pushes fluid out of the capillaries into tissue spaces, colloid osmotic pressure pulls fluid back into the capillaries. These two opposing forces work together to maintain proper fluid distribution between intravascular and extravascular compartments. Define net filtration pressure (NFP). Net filtration pressure (NFP) is the distinction between the net hydrostatic pressure and the net colloid osmotic pressure. Calculate net filtration pressure for both the arterial end and the venous end of a capillary. At the arterial end of a capillary: 1. Hydrostatic Pressure (HPc): This is the force exerted by the blood against the walls of the capillary. It tends to push fluid out of the capillary into the interstitial space. The typical value for HPc is around 35 mmHg. 2. Colloid Osmotic Pressure (OPc): This is the osmotic pressure exerted by plasma proteins in the blood. OPc tends to draw fluid back into the capillary from the interstitial space. The typical value for OPc is around 25 mmHg. 3. Fluid Permeability (Kf): This represents how easily fluid can move across the capillary wall. Kf depends on characteristics such as endothelial cell fenestrations or gaps between cells. Its typical value varies but is generally low compared to other factors. The net filtration pressure (NFP) at the arterial end can be calculated using the following formula: NFP = HPc - OPc Taking typical values, NFP = 35 mmHg - 25 mmHg = 10 mmHg. At the venous end of a capillary: 1. Hydrostatic Pressure (HPc): Due to resistance encountered along its length, hydrostatic pressure decreases from arteriole to venule end of a capillary. At this point, it typically drops to around 15 mmHg. 2. Colloid Osmotic Pressure (OPc): This remains relatively constant throughout a capillary bed and maintains an average value of approximately 25 mmHg. Using similar calculations as above: NFP = HPc - OPc NFP = 15 mmHg - 25 mmHg = -10 mmHg Explain the lymphatic system’s role at the capillary bed. While net filtration happens at the capillary's arterial end and net reabsorption occurs at the capillary's venous end, not all fluid is reabsorbed at the capillary's venous end. Typically, only around 85 percent of the fluid that has flowed from the blood into the interstitial fluid is reabsorbed by the capillary. Collecting and returning this surplus fluid to the circulation is the job of the lymphatic system. This extra fluid is reabsorbed, filtered, and returned to the venous circulation through lymph vessels. Edema may occur as a consequence of abnormal capillary exchange or lymphatic system absorption of excess fluid. Edema is an accumulation of interstitial fluid that results in tissue swelling. Describe what is meant by degree of vascularization. The degree of vascularization refers to the extent and density of blood vessels within a tissue or organ. It is a measure of how well an area is supplied with blood vessels, which are responsible for delivering oxygen and nutrients to cells, as well as removing waste products. Explain the process of angiogenesis and how it aids perfusion. Angiogenesis is how new blood vessels are formed in tissues in need of them. This mechanism assists in maintaining appropriate perfusion across the course of many weeks to months of anatomic changes. In skeletal muscle, aerobic exercise stimulates angiogenesis. Angiogenesis occurs in adipose connective tissue when a person accumulates weight in the form of fat deposits. Angiogenesis may also develop due to the progressive obstruction of coronary arteries, possibly enabling new pathways for blood to reach the heart wall. Describe the myogenic response that maintains normal blood flow through a tissue. The force that propels blood through blood arteries, known as systemic blood pressure, varies depending on the situation. However, because of the myogenic response, which involves the contraction and relaxation of smooth muscle inside blood vessels in response to variations in blood vessel wall stretch, blood flow into tissue may stay relatively constant. Increased systemic blood pressure results in a high blood volume entering the blood artery, stretching the smooth muscle cells lining the channel. This induces the contraction of smooth muscle cells, resulting in vasoconstriction. Therefore, even when systemic blood pressure is increased, which would result in increased blood flow into the blood vessel, the ensuing vasoconstriction reduces the size of the blood vessel lumen, cancelling out the increase in blood flow into the tissue. Reduced systemic blood pressure, on the other hand, causes a reduced amount of blood to enter the blood vessel, resulting in less stretching of the smooth muscle cells inside the blood vessel wall. This causes smooth muscle cells to relax, which causes vasodilation. Compare and contrast a vasodilator and a vasoconstrictor. Vasodilation is the process by which blood vessels, particularly arterioles and precapillary sphincters, relax and expand in response to certain signals or stimuli. This relaxation allows for an increase in the diameter of the blood vessels, resulting in a greater flow of blood through them. Vasoconstriction refers to the contraction or narrowing of blood vessels. This occurs when smooth muscles surrounding the blood vessels contract, leading to a reduction in their diameter. As a result, the flow of blood through these vessels is restricted. Explain how a tissue autoregulates local blood flow based on metabolic needs. Tissues autoregulate local blood flow based on metabolic needs through a process known as metabolic vasodilation. When the metabolic activity of a tissue increases, such as during exercise or in response to injury, metabolites like adenosine and carbon dioxide accumulate in the tissue. These metabolites act as vasodilators, causing the local arterioles to dilate and increase blood flow to meet the increased metabolic demands of the tissue. This mechanism ensures that tissues receive adequate oxygen and nutrients for their ongoing physiological functions. Describe how local blood flow is altered by tissue damage and as part of the body’s defense. - Tissue damage triggers a local inflammatory response. - Injured cells release chemical signals, such as histamine and prostaglandins, which cause blood vessels to dilate. - Dilation of blood vessels increases blood flow to the damaged area. - Increased blood flow brings oxygen, nutrients, and immune cells to the site of injury for tissue repair and protection against infection. - Blood clotting factors are also transported to the damaged tissues via increased blood flow, helping to stop bleeding and promote healing. - The increased blood flow can result in redness, warmth, and swelling at the site of injury. - This localized increase in blood flow is part of the body's defense mechanism to facilitate healing and protect against further damage. Explain the general relationship of total blood flow to local blood flow. Total blood flow - amount of blood transported throughout the entire vasculature in a given period of time and equal cardiac output. As one increases the other does too. Local blood flow is dependent upon total blood flow. Define blood pressure and blood pressure gradient. Blood pressure - the force blood exerts against the inside wall of a vessel Blood pressure gradient - the change in blood pressure from one end of a blood vessel to the other end driving force that moves blood through the vasculature Compare and contrast blood pressure and blood pressure gradients in the arteries,capillaries, and veins. 1. Arterial blood pressure: Blood flow in arteries pulses with cardiac cycle. Have: Systolic pressure (occurs when ventricle contracts); Diastolic (pressure occurs when ventricles relax); Pulse pressure (pressure in arteries added by heart contraction); 2. Capillary blood pressure: Pressure no longer fluctuates between systolic and diastolic. Needs to be high enough for exchange of substances. Needs to be low enough not to damage vessels;