KIB1010 Anatomy and Physiology Self-Reflective Exercise 2 (Cardiovascular System 1) PDF

Department of Biomedical Engineering Faculty of Engineering University Malaya KIB1010 Anatomy and Physiology Sem 1 Session 2024/2025 Self-reflective Exercise 2 (Cardiovascular System 1) Answer ALL questions. 1. What are the...

Department of Biomedical Engineering Faculty of Engineering University Malaya KIB1010 Anatomy and Physiology Sem 1 Session 2024/2025 Self-reflective Exercise 2 (Cardiovascular System 1) Answer ALL questions. 1. What are the main anatomical structures that enclose the heart, and what are their functions? The heart is enclosed by the pericardium, a double-walled sac. The fibrous pericardium provides protection, anchors the heart to surrounding structures, and prevents overfilling. The serous pericardium is a two-layer membrane that reduces friction between the heart and surrounding structures. Between the layers lies the pericardial cavity, filled with lubricating serous fluid. 2. Describe the differences between the pulmonary and systemic circuits of blood circulation. The pulmonary circuit involves the right side of the heart and carries deoxygenated blood to the lungs for gas exchange. The systemic circuit involves the left side of the heart and pumps oxygenated blood to the rest of the body for nutrient and gas exchange with tissues. 3. How do the atrioventricular and semilunar valves function during the cardiac cycle? The atrioventricular (AV) valves (tricuspid and mitral) prevent backflow into the atria when the ventricles contract. The semilunar (SL) valves (aortic and pulmonary) prevent backflow from the arteries into the ventricles after blood is ejected. During ventricular contraction, the AV valves close, and the SL valves open; during relaxation, the AV valves open, and the SL valves close. 4. Explain the role of the sinoatrial (SA) node and atrioventricular (AV) node in regulating the heart's rhythm. The SA node, located in the right atrium, is the heart's primary pacemaker and initiates the electrical impulses that trigger heartbeats. The AV node delays the impulse slightly to allow the atria to contract fully before passing the signal to the ventricles via the bundle of His, bundle branches, and Purkinje fibres, leading to coordinated ventricular contraction. 5. What are the phases of the cardiac cycle, and how does blood flow during each phase? The cardiac cycle has four phases: 1. Ventricular filling: Atria contract, filling the ventricles. 2. Isovolumetric contraction: Ventricles contract, but no blood is ejected as the valves remain closed. 3. Ventricular ejection: Semilunar valves open, and blood is pumped into the aorta and pulmonary artery. 4. Isovolumetric relaxation: Ventricles relax, and pressure decreases without changing the blood volume as the valves are closed. 6. How do preload, contractility, and afterload influence stroke volume and cardiac output? Preload refers to the stretch of cardiac muscle fibres at the end of diastole and directly influences stroke volume based on the Frank-Starling law. Contractility is the strength of contraction at a given preload, increasing stroke volume when higher. Afterload is the pressure the ventricles must overcome to eject blood. Increased afterload can reduce stroke volume. 7. Describe the significance of the P wave, QRS complex, and T wave in an electrocardiogram. The P wave represents atrial depolarisation, triggering atrial contraction. The QRS complex represents ventricular depolarisation, triggering ventricular contraction. The T wave represents ventricular repolarisation, indicating the ventricles are relaxing. 8. What is the Frank-Starling law of the heart, and how does it affect cardiac muscle contraction? The Frank-Starling law states that the heart's stroke volume increases in response to an increase in the volume of blood filling the heart (preload) due to the stretch of cardiac muscle fibres. As the muscle fibres stretch more, they contract with greater force. 9. Explain the ionic basis of action potential in pacemaker cells and its importance in cardiac function. Pacemaker cells have an unstable resting potential, allowing them to depolarise spontaneously. This depolarisation is driven by the closing of potassium channels and the influx of sodium and calcium ions through specialised channels, triggering an action potential and subsequent heart contractions. 10. What clinical conditions can lead to congestive heart failure, and how do they affect the cardiovascular system? Coronary artery disease, high blood pressure, multiple myocardial infarctions, and cardiomyopathy can lead to congestive heart failure by impairing the heart's ability to pump blood effectively. This results in fluid accumulation in the lungs (pulmonary congestion) or body tissues (peripheral congestion). PART B 11. What are the structural differences between the left and right ventricles, and how do these differences relate to their functions? The left ventricle has a thicker, more muscular wall because it pumps blood into the systemic circulation, which requires greater force to push blood throughout the body. The right ventricle has a thinner wall because it only pumps blood to the lungs, a shorter and lower- pressure circuit. 12. Explain how the heart maintains unidirectional blood flow and the role of valves in this process. Unidirectional blood flow is maintained by the heart's four valves (tricuspid, mitral, aortic, and pulmonary), which open and close in response to pressure changes in the chambers. This prevents backflow and ensures blood flows in one direction through the heart and circulatory system. 13. Describe the coronary circulation and explain how it supplies blood to the myocardium. Coronary circulation provides oxygen-rich blood to the heart muscle (myocardium) via the right and left coronary arteries, which arise from the base of the aorta. The coronary arteries supply oxygen and nutrients to the heart, and deoxygenated blood is collected by cardiac veins, draining into the coronary sinus. 14. What is the significance of the refractory period in cardiac muscle cells, and how does it differ from skeletal muscle cells? The refractory period in cardiac muscle cells is more extended than in skeletal muscle cells, preventing tetanus (sustained contraction) and ensuring the heart has time to relax and fill with blood between contractions. This ensures rhythmic and effective pumping. 15. How does the autonomic nervous system regulate heart rate, and what are the roles of the sympathetic and parasympathetic divisions? The sympathetic nervous system increases heart rate and contractility via norepinephrine, while the parasympathetic nervous system decreases heart rate via acetylcholine. The balance between these systems controls heart rate in response to physiological needs. 16. Explain the mechanisms involved in the conduction of an action potential through the heart’s conduction system. The SA node generates an action potential, which spreads through the atria, causing contraction. The impulse then travels to the AV node, where it is delayed. From the AV node, the impulse travels through the bundle of His, bundle branches, and Purkinje fibres, leading to coordinated ventricular contraction. 17. How does calcium influx contribute to the contraction of cardiac muscle cells, and what role does calcium-induced calcium release play? Calcium influx from the extracellular space and the sarcoplasmic reticulum triggers the sliding of actin and myosin filaments, leading to muscle contraction. Calcium-induced calcium release amplifies this process by causing more calcium to be released from the sarcoplasmic reticulum, enhancing contraction strength. 18. What are the phases of an action potential in ventricular contractile cells, and how do they contribute to the cardiac cycle? The action potential in ventricular contractile cells has five phases: 1. Phase 0: Rapid depolarisation due to sodium influx. 2. Phase 1: Partial repolarisation as sodium channels inactivate. 3. Phase 2: Plateau phase where calcium influx counteracts potassium efflux, prolonging depolarisation and supporting contraction. 4. Phase 3: Rapid repolarisation as potassium channels open. 5. Phase 4: Resting potential, where the cell is ready for the following action potential. 19. Define stroke volume and explain how changes in end-diastolic volume (EDV) and end- systolic volume (ESV) affect it. Stroke volume (SV) is the volume of blood pumped out by one ventricle per beat. It is calculated as the difference between end-diastolic volume (EDV) (blood in the ventricle at the end of diastole) and end-systolic volume (ESV) (blood remaining after systole). Increased EDV or decreased ESV results in higher stroke volume. 20. What are the causes and consequences of pulmonary and peripheral congestion in congestive heart failure? Pulmonary congestion occurs when the left side of the heart fails, leading to blood backing up in the lungs, causing fluid leakage and pulmonary edema. Peripheral congestion occurs when the right side of the heart fails, causing blood to pool in the systemic circulation, resulting in edema in extremities and organs.