Exam 1 - Learning Goals

Lecture 2: Cardiac Structure and Functions

• Cardiac Structure

  • Describe the anatomy of the heart including chambers, valves, and major vessels.

    • The heart consists of four chambers: the right atrium, right ventricle, left atrium, and left ventricle, each playing a critical role in the circulation of blood. The valves, including the tricuspid, pulmonary, mitral, and aortic valves, ensure unidirectional blood flow, while major vessels such as the aorta, pulmonary arteries, and veins facilitate the transport of oxygenated and deoxygenated blood throughout the body.

  • Discuss the significance of the myocardium layer in facilitating heart contractions.

    • The myocardium, the thick muscular layer of the heart wall, is essential for generating the force needed for heart contractions, allowing for effective pumping of blood to the lungs and the rest of the body. Its unique structure enables the heart to contract rhythmically and efficiently, responding to electrical impulses that signal the heart to beat.

• Myocardium Structure

  • Discuss the muscular arrangement in myocardium, promoting efficient contraction.

    • The myocardium consists of tightly packed cardiac muscle fibers organized in a spiral pattern, which enhances the heart's ability to contract uniformly and forcefully. This arrangement facilitates the coordinated contraction of the heart chambers, ensuring that blood is pumped effectively during each heartbeat. Additionally, the intercalated discs between these muscle fibers allow for rapid transmission of electrical signals, further promoting synchronized contractions and maintaining the heart's rhythm.

  • Explain the role of intercalated discs in synchronizing muscle contractions.

    • Intercalated discs play a crucial role in synchronizing muscle contractions by connecting individual cardiac muscle cells (myocytes) through gap junctions, which allow ions and electrical impulses to pass freely between adjacent cells. This connectivity enables a rapid spread of action potentials across the myocardium, ensuring that all muscle fibers contract simultaneously. As a result, the heart can function as a single, efficient unit, maximizing the force of contraction and optimizing blood flow throughout the circulatory system. This synchronization is essential for maintaining a steady heartbeat and preventing irregular rhythms, which could lead to conditions such as arrhythmias.

• Calcium in Cardiac Muscle Action Potential

  • Importance of calcium ions in initiating muscle contraction.

    • Calcium ions play a pivotal role in cardiac muscle action potentials by facilitating the process of excitation-contraction coupling. When an action potential reaches the cardiac myocyte, calcium channels open, allowing calcium to flow into the cell. This influx of calcium triggers the release of additional calcium from the sarcoplasmic reticulum, leading to an increase in intracellular calcium concentration. The elevated calcium levels then bind to troponin, causing a conformational change that allows actin and myosin filaments to interact, resulting in muscle contraction. Therefore, calcium is not only critical for the initiation of contraction but also for the regulation of the strength and duration of each heartbeat. In summary, understanding the role of calcium ions in cardiac myocyte function is essential for grasping how the heart contracts and maintains its rhythm.

  • Outline the phases of action potential and the role calcium plays in each phase.

    • Phase 0 - Rapid Depolarization: This phase is initiated by the opening of voltage-gated sodium channels, allowing sodium ions to rush into the cell, causing a rapid increase in membrane potential. Although calcium plays a minimal role here, it sets the stage for the subsequent phases.

    • Phase 1 - Initial Repolarization: Following the peak of depolarization, sodium channels close, and potassium channels open, leading to a brief efflux of potassium ions. Calcium channels begin to open during this phase, preparing for the next phase's influx.

    • Phase 2 - Plateau Phase: This phase is characterized by the prolonged opening of calcium channels, allowing calcium ions to enter the cell. This influx is crucial as it maintains depolarization and facilitates muscle contraction by promoting the release of more calcium from the sarcoplasmic reticulum, enhancing the contractile force.

    • Phase 3 - Repolarization: Calcium channels close, and potassium channels continue to open, leading to a significant efflux of potassium ions. This phase restores the membrane potential back to its resting state, and the decrease in intracellular calcium concentration is vital for the cessation of contraction.

    • Phase 4 - Resting Membrane Potential: The cell returns to its stable resting state, largely maintained by the sodium-potassium pump and low calcium levels. This phase is crucial for preparing the cardiac myocyte for the next action potential. Understanding these phases is essential for grasping how cardiac muscle cells function and respond to stimuli, which is vital for both physiological and pathological contexts.

Lecture 3: Myocardium Perfusion and Vascular System

• Myocardium Perfusion

  • Mechanisms by which heart muscle receives its blood supply (coronary circulation).

    • The coronary arteries branch off from the aorta and supply oxygen-rich blood to the myocardium, ensuring its metabolic needs are met. In addition, the cardiac veins collect deoxygenated blood from the myocardium and return it to the right atrium, completing the circulatory cycle necessary for efficient heart function. Understanding the dynamics of myocardial perfusion is crucial for diagnosing and treating cardiovascular diseases.

  • Importance of coronary arteries and the aortic root.

    • The health and functionality of these structures are vital, as any obstruction or disease affecting the coronary arteries can lead to ischemia, heart attacks, or other serious cardiovascular conditions. Therefore, recognizing the signs and symptoms of coronary artery disease is essential for early intervention and improved patient outcomes.

• Vascular System Structure and Function

  • Overview of arteries, veins, and capillaries and their roles in circulation.

    • Understanding the differences in structure and function among these vessels is crucial, as arteries carry oxygenated blood away from the heart, veins return deoxygenated blood back to the heart, and capillaries facilitate the exchange of nutrients and waste at the cellular level. Additionally, a thorough comprehension of how these vessels interact within the vascular system is necessary to appreciate their collective impact on overall health and disease processes.

  • Discuss blood flow dynamics and pressure regulation.

    • This includes understanding how blood pressure is generated by the heart's pumping action, the role of the elasticity of arteries in maintaining pressure during diastole, and the mechanisms by which veins return blood to the heart, including the effects of gravity and muscle contractions. Furthermore, it is important to explore how the autonomic nervous system influences these dynamics, affecting heart rate and vascular resistance, which ultimately contribute to the regulation of blood flow and pressure throughout the body.

• Role of Endothelium

  • Functions of endothelial cells in maintaining vascular health.

    • Endothelial cells regulate vascular tone by releasing substances that cause vasodilation or vasoconstriction.

    • They provide a barrier between the blood and surrounding tissues, preventing the leakage of fluids and proteins.

    • Endothelial cells play a key role in inflammation and immune response by mediating the adhesion and migration of leukocytes. Additionally, they contribute to the formation of new blood vessels through a process known as angiogenesis, which is essential for tissue repair and regeneration.

  • Discuss how endothelium controls vasodilation and constriction.

    • The endothelium achieves this control through the release of various signaling molecules, such as nitric oxide (NO), which promotes vasodilation by relaxing smooth muscle cells, and endothelin, which induces vasoconstriction. This dynamic balance between vasodilators and vasoconstrictors allows for precise regulation of blood flow and pressure in response to physiological demands. Furthermore, the endothelium also responds to shear stress and other mechanical stimuli, adjusting its signaling accordingly to maintain vascular homeostasis and respond effectively to changes in blood flow.

Lecture 4: Intrinsic Controls of Heart Rate

• Three Intrinsic Controls

  • Overview of the sinoatrial (SA) node, atrioventricular (AV) node, and Purkinje fibers.

    • These structures work together to generate and conduct electrical impulses that regulate the heart's rhythm, ensuring that the heart beats in a coordinated manner to meet the body's needs.

    • Sinoatrial (SA) node: Acts as the primary pacemaker of the heart, initiating the electrical impulses that trigger each heartbeat.

    • Atrioventricular (AV) node: Serves as a relay station, slowing down the electrical signal before it moves to the ventricles, allowing time for the atria to contract and fill the ventricles with blood.

    • Purkinje fibers: Specialized fibers that distribute the electrical impulse throughout the ventricles, ensuring a synchronized contraction.

    • Bundle of His: A pathway that carries the electrical impulses from the AV node to the ventricles, further coordinating the heart's contraction.

• Heart Rate Increase During Exercise

  • Mechanisms that elevate heart rate in response to physical activity.

    • These mechanisms include increased sympathetic nervous system activity, which releases norepinephrine, enhancing cardiac output and heart rate, as well as elevated levels of circulating adrenaline that stimulate the heart. Additionally, the increased demand for oxygen during exercise leads to greater venous return, which further stimulates the heart to beat faster and more forcefully. The interplay of these factors ensures that the body can meet the heightened metabolic demands during periods of intense physical exertion. The role of baroreceptors is also crucial, as they sense changes in blood pressure and signal the heart to adjust its rate accordingly, ensuring optimal blood flow to vital organs.

• Hormones Affecting Heart Rate

  • Discuss the role of adrenaline and other hormones in modulating heart rate.

    • Adrenaline: Increases heart rate by stimulating beta-adrenergic receptors in the heart, leading to enhanced contractility and faster conduction of electrical impulses.

    • Norepinephrine: Works alongside adrenaline to increase heart rate and blood pressure, primarily through its action on alpha-adrenergic receptors, which also constrict blood vessels and enhance peripheral resistance.

    • Epinephrine: A hormone produced by the adrenal glands, it increases heart rate and cardiac output by stimulating beta-adrenergic receptors, thereby enhancing the body's fight-or-flight response.

Lecture 5: Cardiac Cycle

• Cardiac Cycle and Wiggers Diagram

  • Describe the phases of the cardiac cycle, as illustrated by the Wiggers diagram.

    • Phase 1: Atrial Systole - The atria contract, pushing blood into the ventricles.

    • Phase 2: Isovolumetric Contraction - The ventricles begin to contract with all valves closed, increasing pressure.

    • Phase 3: Ventricular Ejection - Blood is ejected from the ventricles through the aorta and pulmonary artery.

    • Phase 4: Isovolumetric Relaxation - The ventricles relax with all valves closed, causing pressure to drop.

    • Phase 5: Ventricular Filling - Blood flows from the atria into the ventricles, filling them for the next cycle.

  • Illustrate changes in pressure and volume during systole and diastole.

    • During systole, pressure in the ventricles rises sharply as they contract, while volume decreases as blood is ejected.

    • During diastole, pressure in the ventricles drops as they relax, leading to an increase in volume as blood fills the chambers from the atria.

• SV, EDV, and ESV Relationship

  • Define Stroke Volume (SV), End-Diastolic Volume (EDV), and End-Systolic Volume (ESV).

    • Stroke Volume (SV): The amount of blood ejected by the ventricles with each heartbeat.

    • End-Diastolic Volume (EDV): The total volume of blood in the ventricles at the end of diastole, just before contraction.

    • End-Systolic Volume (ESV): The volume of blood remaining in the ventricles at the end of systole, after contraction.

  • Illustrate how these metrics relate to cardiac efficiency.

    • Cardiac Efficiency: The relationship between stroke volume, end-diastolic volume, and end-systolic volume is critical for understanding cardiac efficiency.

      • Cardiac Output (CO): Defined as the product of stroke volume and heart rate, CO reflects the overall efficiency of the heart in pumping blood.

      • Ejection Fraction (EF): Calculated as EF = (SV/EDV) x 100%, this metric indicates the percentage of blood ejected from the ventricles, providing insight into cardiac function and efficiency.

• Blood Pressure and Cardiac Output Calculation

  • Methodology to calculate blood pressure and cardiac output.

    • Blood Pressure (BP): Measured as the force exerted by circulating blood on the walls of blood vessels, BP is typically expressed in millimeters of mercury (mmHg) and is crucial for assessing cardiovascular health.

    • Cardiac Output (CO): Calculated as CO = SV x HR, where SV is stroke volume and HR is heart rate, this measurement reflects the total volume of blood the heart pumps per minute, which is essential for evaluating heart performance.

Lecture 6: Blood Flow Dynamics

• Factors Affecting Arterial Blood Flow

  • Discuss resistance, blood viscosity, and vessel diameter factors.

    • Resistance: The opposition to blood flow primarily influenced by the diameter of blood vessels; narrower vessels increase resistance, leading to decreased flow.

    • Blood Viscosity: The thickness of blood, which can be affected by factors such as dehydration or increased red blood cell count, impacting the ease with which blood flows through vessels.

    • Vessel Diameter: Larger diameters allow for easier blood flow, while smaller diameters restrict flow, making this a crucial factor in regulating arterial blood flow.

• Blood Flow Distribution

  • Explain blood flow changes during rest versus exercise, emphasizing redirecting blood to active muscles.

    • During rest, blood flow is primarily directed towards the digestive organs and less active tissues, whereas during exercise, the body redistributes blood to meet the demands of active muscles, increasing flow to the heart, lungs, and skeletal muscles while reducing flow to non-essential areas. This adaptation ensures that oxygen and nutrients are efficiently delivered to the muscles, enhancing performance and endurance during physical activity.

• Three Intrinsic Controls of Blood Flow

  • Explain metabolic, endothelial, and myogenic controls of blood flow.

    • Metabolic Control: This mechanism involves the regulation of blood flow based on the metabolic activity of tissues. When tissues become more active, they produce metabolic byproducts such as carbon dioxide and lactic acid, which lead to vasodilation, increasing blood flow to meet the heightened oxygen and nutrient demands.

    • Endothelial Control: Endothelial cells lining the blood vessels release various substances that influence vascular tone. For instance, nitric oxide is released in response to shear stress from blood flow, promoting vasodilation and thus enhancing blood flow to areas requiring increased perfusion.

    • Myogenic Control: This refers to the inherent ability of vascular smooth muscle to respond to changes in pressure. When blood pressure increases, the smooth muscle cells in the vessel walls constrict to prevent excessive blood flow; conversely, when pressure decreases, they relax to allow more blood to enter the capillary beds.

Lecture 7: Extrinsic Control of Vascular System

• Extrinsic Control Overview

  • Discuss the autonomic nervous system (ANS) components involved in vascular regulation.

    • The sympathetic nervous system plays a crucial role by releasing norepinephrine, which causes vasoconstriction, while the parasympathetic nervous system can induce vasodilation through the release of acetylcholine.

• Physiology of Venous Return

  • Explain mechanisms supporting venous return to the heart and its significance.

    • Venous return is facilitated by several mechanisms, including the skeletal muscle pump, respiratory pump, and venous valves. The skeletal muscle pump operates when muscles contract during movement, compressing veins and propelling blood towards the heart. The respiratory pump enhances venous return by creating pressure changes in the thoracic cavity during inhalation and exhalation, which helps draw blood back to the heart. Additionally, venous valves prevent backflow, ensuring unidirectional blood flow. Together, these mechanisms are vital for maintaining adequate cardiac output and ensuring efficient circulation.

• Basics of Blood Composition

  • Outline the main components of blood: red blood cells, white blood cells, plasma, and platelets.

    • Red Blood Cells (Erythrocytes): Responsible for transporting oxygen from the lungs to the body's tissues and returning carbon dioxide to the lungs for exhalation.

    • White Blood Cells (Leukocytes): Play a crucial role in the immune system by defending the body against infections and foreign invaders.

    • Plasma: The liquid component of blood that carries cells, nutrients, hormones, and waste products; it constitutes about 55% of blood volume.

    • Platelets (Thrombocytes): Small cell fragments essential for blood clotting and wound healing.

Lecture 8: Acute Responses to Exercise

• Acute Exercise Responses

  • Describe immediate changes in Heart Rate (HR), Stroke Volume (SV), Cardiac Output (CO), Blood Pressure (BP), and blood flow.

    • Heart Rate (HR): Increases rapidly to supply more oxygen to muscles.

    • Stroke Volume (SV): Initially increases as the heart pumps more blood per beat.

    • Cardiac Output (CO): Rises significantly due to the combination of increased HR and SV.

    • Blood Pressure (BP): May increase, particularly systolic pressure, due to heightened cardiac output.

    • Blood Flow: Redirected towards active muscles while reducing flow to non-essential organs.

• Relationship to Exercise Capacity (VO2)

  • Discuss how HR, SV, CO, BP, and blood flow influence aerobic capacity during exercise.

    • Heart Rate (HR): Increases to meet the oxygen demands of working muscles, facilitating greater aerobic capacity.

    • Stroke Volume (SV): The amount of blood ejected from the heart with each contraction also rises, enhancing cardiac output (CO).

    • Cardiac Output (CO): The combined effect of HR and SV leads to an overall increase in CO, which is crucial for sustaining prolonged aerobic activities.

    • Blood Pressure (BP): Elevated BP helps maintain adequate perfusion pressure, ensuring that active tissues receive sufficient blood supply during exercise.

    • Overall, the interplay between these factors determines the efficiency and endurance of aerobic performance.

• Determinants of Stroke Volume

  • Factors influencing SV at rest and during exercise, including preload and afterload.

    • Preload: The degree of stretch of the heart muscle fibers at the end of diastole, which enhances stroke volume by optimizing the force of contraction.

    • Afterload: The resistance the heart must overcome to eject blood, which can be influenced by arterial pressure and vascular resistance.

Lecture 9: Effect of Posture on Stroke Volume and Cardiac Output

• Explain how body position influences Stroke Volume (SV) and Cardiac Output (CO).

  • When a person is standing, the gravitational pull causes blood to pool in the lower extremities, potentially decreasing venous return and subsequently lowering stroke volume and cardiac output.

  • Conversely, when lying down, venous return is improved due to the horizontal position, leading to an increase in stroke volume and cardiac output as the heart can pump more efficiently.

Lecture 10: Pulmonary Structure and Function

• Pulmonary Structure

  • Describe the anatomy of the lungs and alveoli, highlighting similarities to the vascular structure.

    • The lungs consist of a series of branching airways that culminate in the alveoli, which are tiny air sacs where gas exchange occurs.

    • Similar to the vascular structure, the alveoli are surrounded by a rich network of capillaries that facilitate the exchange of oxygen and carbon dioxide, demonstrating a close relationship between the respiratory and circulatory systems.

• Inspiration Process

  • Explain the mechanics of inhalation, including pressure changes in thoracic cavity.

    • During inhalation, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity. This expansion creates a negative pressure relative to the atmosphere, causing air to flow into the lungs. Additionally, the intercostal muscles assist by raising the rib cage, further enhancing the volume increase and facilitating the inflow of air.

• Expiration Process

  • Explain the mechanics of exhalation, including pressure changes.

    • During exhalation, the diaphragm relaxes and moves upward, decreasing the volume of the thoracic cavity. This reduction in volume increases the pressure within the lungs, causing air to be expelled out of the lungs and into the atmosphere. The intercostal muscles also relax, allowing the rib cage to descend, which aids in the expulsion of air. This process is generally passive during normal breathing but can become active during forceful exhalation.

Lecture 11: Spirometry and Gas Exchange

• Components of Spirometry

  • Define vital capacity and other key spirometry measurements.

    • Vital Capacity (VC): The maximum amount of air that can be exhaled after a maximum inhalation, which reflects the strength and function of the respiratory muscles.

    • Tidal Volume (TV): The amount of air inhaled or exhaled during normal breathing.

    • Inspiratory Reserve Volume (IRV): The additional amount of air that can be inhaled after a normal inhalation.

    • Expiratory Reserve Volume (ERV): The additional amount of air that can be exhaled after a normal exhalation.

    • Total Lung Capacity (TLC): The total volume of air in the lungs after a maximum inhalation, which includes VC and residual volume.

• Blood Flow Between Heart and Lungs

  • Trace the pathway of blood circulation from the heart to lungs and back.

    • Deoxygenated blood flows from the right ventricle through the pulmonary arteries to the lungs, where it receives oxygen and releases carbon dioxide.

    • Oxygenated blood then returns to the left atrium via the pulmonary veins, completing the circuit.

• Partial Pressure of Gases and Diffusion

  • Explain how gases diffuse across membranes through partial pressure gradients.

    • Gases diffuse from areas of higher partial pressure to areas of lower partial pressure, allowing for the exchange of oxygen and carbon dioxide across the alveolar membrane in the lungs and the capillary membranes in tissues.

Lecture 12: Altitude Effects on Gas Transport

• Role of Partial Pressure

  • Discuss changes in gas behavior with altitude.

    • As altitude increases, the partial pressure of oxygen decreases, which can lead to reduced oxygen availability for the body, impacting overall physiological function and performance.

• O2 and CO2 Transport in Blood

  • Explain mechanisms of oxygen and carbon dioxide transport in the bloodstream.

    • Oxygen is primarily transported in two forms: bound to hemoglobin in red blood cells and dissolved in plasma, while carbon dioxide is carried in three ways: dissolved in plasma, as bicarbonate ions, and bound to hemoglobin, each playing a crucial role in maintaining acid-base balance and ensuring efficient gas exchange. Understanding these mechanisms is essential for grasping how the body adapts to varying altitudes and oxygen levels, as well as the importance of maintaining homeostasis during physical exertion. Additionally, factors such as temperature, pH, and the concentration of 2,3-bisphosphoglycerate (BPG) can influence the affinity of hemoglobin for oxygen, affecting its release and uptake in tissues.

• Oxyhemoglobin Curve

  • Illustrate the relationship between hemoglobin saturation and partial pressure of oxygen.

    • This curve demonstrates how hemoglobin's oxygen-binding capacity changes with varying levels of oxygen pressure, highlighting the cooperative binding effect where an increase in one oxygen molecule's binding enhances the affinity for subsequent molecules.

Lecture 13: Gas Exchange Mechanisms

• Gas Exchange at Muscles

  • Describe how oxygen and carbon dioxide are exchanged at the muscle level.

    • Oxygen is delivered from the bloodstream to muscle cells, where it is utilized for aerobic respiration, while carbon dioxide, a byproduct of this process, diffuses out of the cells into the blood for transport back to the lungs. This exchange is facilitated by the concentration gradients of these gases, allowing for efficient uptake of oxygen and removal of carbon dioxide. In addition, the presence of myoglobin in muscle tissue enhances oxygen storage and release, further supporting the metabolic demands of active muscles during exercise.

• Myoglobin vs Oxyhemoglobin Curves

  • Compare these curves and explain their physiological significance.

    • Myoglobin curve: The myoglobin dissociation curve is hyperbolic, indicating that myoglobin binds oxygen more tightly than hemoglobin, allowing for efficient oxygen storage and release in muscle tissues, particularly during intense exercise.

    • Oxyhemoglobin curve: The oxyhemoglobin dissociation curve is sigmoidal, reflecting hemoglobin's cooperative binding properties, which enhance oxygen delivery to tissues under varying oxygen concentrations.

    Physiological significance: The distinct shapes of these curves illustrate how myoglobin is crucial for sustaining oxygen supply in muscle cells during high-demand situations, while hemoglobin effectively transports oxygen throughout the body, adapting to different metabolic needs.

• Central Mechanisms of Breathing

  • Explain the physiological control of respiration, including neural mechanisms.

    • The central mechanisms of breathing are primarily regulated by the brainstem, specifically the medulla oblongata and pons, which coordinate the rhythm and depth of respiration in response to changes in carbon dioxide, oxygen, and pH levels in the blood. Additionally, sensory receptors in the carotid and aortic bodies detect changes in blood gas levels, sending signals to the brainstem to adjust the respiratory rate, thereby maintaining homeostasis and ensuring adequate oxygen delivery to tissues during varying levels of activity.