Module 2

"Describe the role of semilunar valves in the cardiac cycle."

"Semilunar valves prevent blood that has entered the arteries from flowing back into the ventricles during ventricular relaxation."

"Explain the process of ventricular contraction."

"Ventricular contraction is the phase of the cardiac cycle where the ventricles contract to pump blood out of the heart."

"Define hemodynamics in the context of cardiac physiology."

"Hemodynamics refers to the study of blood flow and the forces involved in circulation within the cardiovascular system."

"How is cardiac blood flow organized in the heart?"

"Cardiac blood flow is organized through a series of chambers and valves that ensure unidirectional flow of blood during the cardiac cycle."

"What occurs during ventricle relaxation?"

"During ventricle relaxation, the ventricles fill with blood as the heart prepares for the next contraction."

"Describe the overview of circulation in the cardiovascular system."

"The overview of circulation includes the pathways through which blood travels, including systemic and pulmonary circulation, to deliver oxygen and nutrients to tissues and remove waste."

"Describe the function of the AV valves during ventricular contraction."

"The AV valves remain closed to prevent blood flow backward into the atria."

"Explain the role of chordae tendinae and papillary muscles in the function of AV valves."

"Chordae tendinae and papillary muscles work together to keep the AV valves closed during ventricular contraction."

"Define the structures associated with the mitral and tricuspid valves."

"The chordae tendinae and papillary muscles are structures associated with the mitral and tricuspid valves."

"How do chordae tendinae behave when the atria contract?"

"When the atria contract, the chordae tendinae are slack, resembling hanging threads of connective tissue."

"Describe the mechanism by which AV valves close during ventricular contraction."

"During ventricular contraction, blood pushes up against the bottom of the valve leaflets, causing them to close and balloon up like a parachute."

"What is the role of papillary muscles during ventricular contraction?"

"Papillary muscles contract, pulling on the chordae tendinae to keep the AV valves closed."

"Explain the structure and function of major arteries."

"Major arteries have stiff and springy walls that act as a pressure reservoir, storing pressure generated during systole and releasing it during diastole to maintain constant blood pressure."

"Describe the characteristics of arterioles."

"Arterioles contain no elastic tissue but have smooth muscle that can contract and relax."

"What is the primary function of capillaries?"

"Capillaries are the site of gas and nutrient exchange with tissues."

"How does capillary permeability get regulated?"

"Capillary permeability can be regulated by pericytes that surround the capillaries."

"Explain how blood flow through capillary beds is regulated."

"Blood flow through capillary beds is regulated by pre-capillary sphincters."

"Describe the structure and function of venules and veins."

"Venules and veins have large diameters and thin walls that are easily distensible, acting as a volume reservoir of the body."

"What feature do veins contain to ensure proper blood flow direction?"

"Veins contain valves that ensure blood flows only one way, towards the heart."

"Describe the role of arteries in the circulatory system."

"Arteries act as a pressure reservoir, stretching during ventricular contraction to accommodate the surge of blood and maintaining driving pressure during diastole through elastic recoil."

"Explain how ventricular contraction affects arteries."

"Ventricular contraction pushes blood into the elastic arteries, causing them to stretch and accommodate the increased blood volume."

"What happens to blood flow during ventricular relaxation?"

"During ventricular relaxation, blood flow decreases, leading to elastic recoil in the arteries that helps maintain driving pressure."

"Define the function of capillary beds in the circulatory system."

"Capillary beds facilitate the exchange of nutrients, gases, and waste between blood and tissues."

"How do valves in major veins contribute to blood circulation?"

"Valves in major veins prevent the backflow of blood, ensuring unidirectional flow towards the heart."

"Describe the significance of area and volume in systemic blood vessels."

"The area and volume contained in systemic blood vessels are crucial for regulating blood pressure and ensuring adequate blood flow throughout the body."

"Describe the difference between veins and arteries in terms of volume stress."

"Veins are referred to as unstressed volume, while arteries are considered stressed volume."

"Explain the role of capillaries in the circulatory system."

"Capillaries provide a large area for easier absorption but have a very small volume."

"Define the function of the SA node in cardiac electrophysiology."

"The SA node is the pacemaker of the heart, initiating the action potential."

"How does the action potential spread from the SA node to the AV node?"

"The action potential spreads from the SA node to the AV node and the left and right atria via intermodal tracts."

"What is the significance of the AV node delay in cardiac conduction?"

"The AV node delay allows time for the ventricles to fill with blood before they are polarized."

"Describe the pathway of the action potential after it leaves the AV node."

"After the AV node, the action potential enters the ventricular conducting system, traveling down the bundle of His and via left and right branches to the Purkinje fibers."

"Explain the speed of conduction through the ventricular conducting system."

"Conduction through the ventricular conducting system is very fast, rapidly distributing depolarization through low resistance gap junctions of the intercalated disks."

"What is required for efficient contraction of the ventricle in terms of conduction speed?"

"Rapid conduction through the ventricular conducting system is required for efficient contraction of the ventricle."

"Describe the role of the SA node in the heart."

"The SA node is the pacemaker of the heart, generating action potentials spontaneously without the need for extrinsic innervation."

"Explain the significance of the unstable resting potential in the SA node."

"The unstable resting potential in the SA node is due to the opening of hyperpolarization-sensitive Na channels (HCN channels), leading to a gradual increase in depolarization."

"How does an action potential get initiated in the SA node?"

"An action potential is initiated in the SA node when the membrane potential reaches threshold, causing the opening of voltage-gated Ca channels."

"What happens during Phase 3 of the cardiac action potential in the SA node?"

"During Phase 3, K channels open, leading to the repolarization of the cell as the Ca channels close at the peak of the action potential."

"Define the role of HCN channels in the SA node action potential."

"HCN channels contribute to the unstable resting potential and are sensitive to cAMP; their opening increases with higher cAMP levels, influencing heart rate."

"How does epinephrine affect heart rate through the SA node?"

"Epinephrine increases heart rate by activating β receptors coupled to adenylate cyclase, which increases cAMP and opens more HCN channels."

"What determines the heart rate in relation to Phase 4 of the SA node action potential?"

"Heart rate is controlled by the slope of Phase 4; a steeper slope, resulting from more open channels, leads to a faster heart rate."

"Describe the effect of ACh on conduction at the AV node."

"ACh slows conduction at the AV node by inhibiting Ca current and increasing K current."

"Explain the relationship between cAMP levels and HCN channel activity in the SA node."

"Higher cAMP levels lead to more HCN channels opening, which increases the rate of depolarization and can elevate heart rate."

"What is the consequence of increased K current at the AV node due to ACh?"

"Increased K current at the AV node due to ACh results in slower conduction of electrical impulses."

"Describe the initial phase of the cardiac action potential in the atria and ventricles."

"The initial phase, known as Phase 0, involves the rapid depolarization caused by the opening of voltage-gated Na channels."

"Explain what happens during Phase 1 of the cardiac action potential."

"During Phase 1, the Na channels close as the membrane potential reaches around +15mV to +20mV, and K channels open, causing a brief repolarization."

"How does the plateau phase occur in the cardiac action potential?"

"The plateau phase occurs during Phase 2 when slow Ca channels open, allowing Ca to enter the cell, balancing K ions moving out, which slows down repolarization."

"Define the role of calcium during the plateau phase of the cardiac action potential."

"Calcium entry during the plateau phase increases Ca release from intracellular stores, facilitating muscle contraction."

"What leads to the repolarization in Phase 3 of the cardiac action potential?"

"In Phase 3, calcium entry slows as Ca channels close, and K ions become dominant again, leading to repolarization until the membrane potential returns to its resting level."

"Describe the resting membrane potential of cardiac cells after repolarization."

"After repolarization, the membrane potential returns to its resting level of around -85mV, which is referred to as Phase 4."

"Explain the significance of the balance between K ions and Ca ions during the cardiac action potential."

"The balance between K ions moving out of the cell and Ca ions moving into the cell during the plateau phase is crucial for maintaining the action potential and ensuring effective cardiac muscle contraction."

"Describe the role of voltage-gated Na channels in the action potential of cardiac muscles."

"Voltage-gated Na channels open, leading to a rapid depolarization (Phase 0) of the cardiac muscle cell. They close when the membrane potential reaches around 15 to 20 mV."

"Explain what happens during Phase 1 of the cardiac action potential."

"During Phase 1, as the Na channels close, K channels open, causing a brief repolarization."

"How do slow Ca channels affect the cardiac action potential during Phase 2?"

"Slow Ca channels open during Phase 2, allowing Ca to enter the cell, which slows down the repolarization process."

"Define the plateau phase in the context of cardiac muscle action potential."

"The plateau phase is characterized by a balance between K ions moving out of the cell and Ca ions moving into the cell, which allows for sustained contraction of the muscle."

"What is the significance of calcium entry during the plateau phase of cardiac action potential?"

"Calcium entry during the plateau phase increases Ca release from intracellular stores, facilitating muscle contraction."

"Describe the events that occur during Phase 3 of the cardiac action potential."

"During Phase 3, calcium entry slows down, and the K current becomes dominant again, leading to repolarization."

"Explain the state of the membrane potential during Phase 4 of the cardiac action potential."

"At rest, the inward Na and Ca currents balance the outward K current, resulting in a stable membrane potential."

"What are refractory periods in the context of cardiac muscle action potentials?"

"Refractory periods refer to the times during which the cardiac muscle cannot be re-excited, ensuring proper timing of contractions."

"Describe the excitability of a cardiac muscle cell during the action potential."

"The excitability of a cardiac muscle cell varies throughout the action potential, which is reflected in the different refractory periods."

"Define the absolute refractory period (ARP) in cardiac muscle cells."

"The absolute refractory period (ARP) is the time during which the Na channels are closed, and the cell cannot fire another action potential, regardless of the stimulus size, lasting until the cell repolarizes to approximately -50mV."

"Explain the effective refractory period (ERP) in cardiac muscle cells."

"The effective refractory period (ERP) includes the time when Na channels begin to recover along with the ARP. During this period, there is some inward Na current, but it is insufficient to conduct an action potential to the next site."

"What is the relative refractory period (RRP) in cardiac muscle cells?"

"The relative refractory period (RRP) is when more Na channels have recovered, allowing for the possibility of generating a second action potential, but a greater than normal stimulus is required, resulting in a shorter plateau phase."

"Describe the supranormal period (SNP) in cardiac muscle cells."

"The supranormal period (SNP) occurs when the cell membrane is more excitable than normal, as most Na channels have recovered, making it possible to generate an action potential with a smaller stimulus than usual."

"Explain how an ECG reflects the electrical activity of the heart."

"An ECG measures differences in skin potentials that reflect the electrical activity in the heart, representing the sum of multiple action potentials occurring in various heart cells."

"What is the typical electrical change associated with a ventricular action potential in a heart cell?"

"The ventricular action potential in a heart cell is associated with an electrical change of approximately 110mV, but this voltage change is reduced to about 1mV by the time it reaches the skin."

"Describe the components of an ECG."

"The ECG consists of waves, segments, and intervals that correspond to the individual events occurring in the heart."

"How are electrical recording leads positioned to obtain a simple ECG?"

"To obtain a simple ECG, electrical recording leads are placed on the wrists, left leg, and across the chest, with the recorded waveform depending on the lead's position relative to the heart."

"Describe the components of an electrocardiogram (ECG)."

"An electrocardiogram is divided into waves (P, Q, R, S, T), segments between the waves (such as P-R and S-T segments), and intervals that consist of a combination of waves and segments (like PR and QT intervals)."

"Explain the significance of the P wave in an ECG."

"The P wave represents atrial depolarization."

"Define the P-R segment in the context of an ECG."

"The P-R segment indicates conduction through the AV node and AV bundle."

"What does the QRS complex represent in an ECG?"

"The QRS complex represents ventricular depolarization."

"How is the T wave characterized in an ECG?"

"The T wave represents ventricular repolarization."

"Describe the P-R interval and its components."

"The P-R interval is the time from the initial depolarization of the atria to the initial depolarization of the ventricles, including the P wave and P-R segment."

"Explain the Q-T interval and what it includes."

"The Q-T interval is the time from the first ventricular depolarization to the last ventricular depolarization, including the QRS complex, ST segment, and T wave."

"What is the S-T segment and its significance in an ECG?"

"The S-T segment is an isoelectric portion of the QT interval that correlates with the plateau phase of the ventricular action potential."

"Define heart rate (HR) in the context of an ECG."

"Heart rate (HR) is the number of cycles per minute, measured from one R wave to the next R wave or from the beginning of one P wave to the beginning of the next P wave."

"Describe hemodynamics and its importance in the cardiovascular system."

"Hemodynamics refers to the dynamics of blood flow through the cardiovascular system and explains the physical laws that govern blood flow in blood vessels."

"What factors affect blood flow in the cardiovascular system?"

"Factors affecting blood flow include the volume of blood flowing through any tissue per minute, pressure differences (blood flows from high to low pressure), and vessel resistance to flow."

"Explain the relationship between cardiac output (CO) and blood flow."

"Total blood flow is equal to cardiac output (CO), which is the volume of blood circulating through systemic or pulmonary vessels each minute, calculated as CO = HR x SV."

"How does pressure difference influence blood flow?"

"Blood flows from areas of high pressure to areas of low pressure, and the greater the pressure difference, the greater the blood flow."

"What is the effect of vessel resistance on blood flow?"

"The higher the resistance in the vessels, the smaller the blood flow."

"Define flow rate in the context of fluid dynamics."

"Flow rate refers to the volume of fluid passing a given point per unit time, typically measured in ml/min."

"Explain the relationship between flow rate and velocity in a tube of fixed diameter."

"In a tube of fixed diameter, velocity is directly related to flow rate; as flow rate increases, velocity also increases."

"Describe how velocity is affected in a tube of variable diameter when flow rate is constant."

"In a tube of variable diameter, if the flow rate is constant, velocity is inversely related to the diameter; narrower tubes result in higher velocity."

"How is flow calculated in relation to velocity and area?"

"Flow is calculated as flow = velocity x area; conversely, velocity can be calculated as velocity = flow/area."

"What is required for fluid to flow through a tube?"

"Fluid flows only if there is a positive pressure gradient."

"Discuss the factors that influence fluid flow in a system."

"Fluid flow depends on the magnitude of the pressure gradient rather than the absolute pressure."

"Explain hydrostatic pressure in the context of static fluids."

"Hydrostatic pressure is the pressure exerted on the walls of a container by the fluid within it."

"What happens to pressure as fluid begins to flow through a system?"

"Once fluid begins to flow, the pressure falls with distance due to energy loss from friction."

"Describe the manifestation of pressure drop in the circulatory system."

"In the circulatory system, pressure drops with distance from the heart as blood flows, primarily due to friction between the blood and vessel walls."

"How does friction affect blood flow in the cardiovascular system?"

"As blood flows through the system, pressure is lost because of friction between the fluid and the walls of the blood vessels."

"Describe the formula for calculating total resistance in a series circuit."

"The total resistance in a series circuit is calculated by summing the individual resistances: R total = R1 + R2 + R3 + R4 + R5."

"Explain how to calculate total resistance in a parallel circuit."

"In a parallel circuit, the total resistance is calculated using the formula: 1/R total = 1/R1 + 1/R2 + 1/R3 + 1/R4."

"Define total peripheral resistance in the context of the human body."

"Total peripheral resistance refers to the cumulative resistance of all the blood vessels in the body, primarily determined by the resistance of the arterioles."

"How does the resistance of arterioles compare to the overall systemic resistance in the body?"

"The resistance of the arterioles is approximately equal to the total peripheral resistance, as they are the chief resistance vessels in the body."

"Explain the significance of the pulmonary system in relation to total peripheral resistance."

"The pulmonary system is a low pressure system, with arterioles in the lungs contributing only about 0.15-0.2 of the whole body systemic resistance."

"Describe the relationship between vessel radius and resistance."

"Resistance is inversely proportional to vessel radius; small changes in vessel size can significantly affect flow rate, with flow increasing 16-fold when the radius is doubled."

"What factors influence resistance in fluid flow?"

"Resistance is influenced by the viscosity of the fluid and the length of the vessel; for example, it is easier to drink through a short straw than a long one, and through water than a smoothie."

"How does flow relate to pressure gradient in a fluid system?"

"Flow is proportional to the pressure gradient; more pressure is required to move a viscous solution through a long vessel."

"State the relationship between resistance and radius according to the formula provided."

"Resistance is calculated as 1/radius^4, indicating that resistance increases dramatically as the radius decreases."