Topic 6: Chpt 14 Flashcards
What is broken heart syndrome, and how can it be fatal?
Broken heart syndrome, also known as stress cardiomyopathy, occurs when sudden, intense emotional stress triggers the release of stress hormones like adrenaline, which can overwhelm the heart. Although typically temporary, in severe cases, this syndrome can lead to heart muscle failure and potentially be fatal due to the acute stress on the cardiovascular system.
What are capillaries and who discovered them?
Capillaries are microscopic blood vessels where exchanges of gases, nutrients, and wastes occur between blood and tissues. They were first observed by Marcello Malpighi, an Italian anatomist, in the seventeenth century using a microscope,
How did William Harvey contribute to the understanding of the cardiovascular system?
William Harvey revolutionized cardiovascular physiology by demonstrating that blood circulates in a closed loop within the body, driven by the heart. He showed that the heart and veins had valves ensuring one-way blood flow, and that the liver was not the source of continuous blood production, debunking longstanding misconceptions about blood circulation and organ functions.
What is the significance of the discovery that blood recirculates in the body?
The discovery that blood recirculates, rather than being continuously consumed and produced, was pivotal. It corrected the fundamental misunderstandings about how blood traveled through the body and the roles of different organs in the circulatory process, laying the groundwork for modern cardiovascular physiology and medical practices.
What is the primary function of the cardiovascular system?
The primary function of the cardiovascular system is to transport nutrients, water, gases, and wastes to and from all parts of the body. It ensures that essential substances like oxygen and nutrients are delivered to cells and metabolic wastes are carried away for excretion.
How does the cardiovascular system contribute to cell-to-cell communication?
The cardiovascular system facilitates cell-to-cell communication by transporting hormones, which are secreted by endocrine glands and travel in the blood to their target cells. It also carries nutrients like glucose and fatty acids to cells, supporting metabolic activities.
What role does the cardiovascular system play in the body’s defense?
It transports white blood cells and antibodies throughout the body, helping to detect and eliminate foreign invaders.
How does the cardiovascular system manage heat distribution in the body?
The cardiovascular system manages heat distribution by carrying heat through the blood from the body core to the surface, where it can dissipate, helping to regulate body temperature. The cardiovascular system
What happens to the brain when blood flow is interrupted, and why?
Interruption of blood flow to the brain leads to loss of consciousness within 5-10 seconds and can cause permanent brain damage if oxygen delivery stops for 5-10 minutes. This is because brain neurons have high oxygen needs that cannot be met through anaerobic metabolism, making them extremely sensitive to hypoxia.
What are the major components of the cardiovascular system?
The cardiovascular system consists of the heart (the pump), blood vessels (tubes), and the blood itself (fluid). It includes arteries that carry blood away from the heart and veins that return blood to the heart.
How is blood flow directed in the cardiovascular system?
Blood flow in the cardiovascular system is directed by a system of valves in the heart and veins, ensuring one-way flow much like turnstiles at an amusement park prevent reverse movement.
What is the role of the heart in the cardiovascular system?
The heart functions as two independent pumps divided by a septum. The right side pumps deoxygenated blood to the lungs for oxygenation, while the left side pumps oxygenated blood to the rest of the body.
Describe the pathway of blood through the cardiovascular system starting from the right atrium.
Blood enters the right atrium, flows to the right ventricle, then to the lungs via the pulmonary arteries (pulmonary circulation). Oxygenated blood returns to the left atrium via pulmonary veins, moves to the left ventricle, and is pumped out through the aorta to the body (systemic circulation).
What is the significance of the color change in cardiovascular diagrams from blue to red?
In diagrams, blue indicates deoxygenated blood and red indicates oxygenated blood. This convention helps visualize the oxygenation process in the lungs and the delivery of oxygen-rich blood to the body.
What is the function of the coronary circulation?
The coronary circulation consists of coronary arteries and veins that supply blood to and drain blood from the heart muscle itself, ensuring it receives the necessary oxygen and nutrients for its functions.
Explain the hepatic portal system.
The hepatic portal system is a unique blood route in which the vein from the digestive tract flows directly to the liver instead of entering the general circulation. This allows the liver to process and detoxify nutrients and substances before they circulate throughout the body.
What is a portal system, and where can it be found in the body?
A portal system involves two capillary networks connected directly by a vein. Examples include the hepatic portal system between the digestive tract and liver, the renal portal system in the kidneys, and the hypothalamic-hypophyseal portal system linking the hypothalamus with the anterior pituitary.
What is the mechanistic explanation for blood flow in the cardiovascular system?
Mechanistically, blood flows because the heart creates a high-pressure area when it contracts, pushing blood into the blood vessels where the pressure is lower. Blood then flows down this pressure gradient, moving from areas of higher pressure to lower pressure.
How is blood pressure maintained throughout the cardiovascular system?
Blood pressure is highest in the aorta and systemic arteries as they receive blood from the left ventricle and decreases throughout the circuit, reaching its lowest just before blood re-enters the heart at the venae cavae. This gradient is due to friction between the blood and the vessel walls.
What physical laws govern the flow of blood in the cardiovascular system?
By laws that describe the interaction of pressure, volume, flow, and resistance. These principles are similar to those governing the flow of any liquid or gas and are crucial for understanding how blood moves through the body.
What is hydrostatic pressure in the context of the cardiovascular system?
Hydrostatic pressure is the force that a fluid in a static state exerts on the walls of its container. In the cardiovascular system, even though the blood is moving, the term hydrostatic pressure is used to describe the pressure exerted by the blood on the vessel walls, measured commonly in mm Hg.
How is pressure measured in the cardiovascular system, and what are the equivalents?
Pressure in the cardiovascular system is typically measured in millimeters of mercury (mm Hg). One mm Hg is equivalent to the pressure exerted by a 1-mm column of mercury. Other units include torr, which is equal to 1 mm Hg, and centimeters of water, where 1 cm H2O equals 0.74 mm Hg.
What happens to pressure in a system where fluid is moving, such as the cardiovascular system?
In a moving fluid system like the cardiovascular system, pressure decreases over distance due to energy loss from friction. The pressure has two components: a dynamic component related to the kinetic energy of moving fluid and a lateral component, which is the hydrostatic (or potential energy) pressure exerted on the walls of the vessels.
Why might textbooks use “hydraulic pressure” instead of “hydrostatic pressure” to describe blood pressure?
Some textbooks prefer “hydraulic pressure” over “hydrostatic pressure” for describing pressure in the cardiovascular system because hydraulics deals with fluids in motion, making it a more accurate term for systems like blood circulation where the fluid (blood) is continuously moving.
What happens when the walls of a fluid-filled container, like a balloon, contract?
When the walls of a fluid-filled container contract, the pressure within the container increases because the fluid (which is minimally compressible like water) transmits the pressure uniformly. This can cause the container to deform or even burst if the pressure is too high, similar to squeezing a water balloon.
How is the contraction of the heart’s ventricles analogous to squeezing a water balloon?
The contraction increases the pressure on the blood within, which is then forced out into the blood vessels, displacing blood with lower pressure. This process is termed the driving pressure and is essential for propelling blood through the cardiovascular system.
How do volume changes in the heart and blood vessels affect blood pressure?
Volume changes in the heart and blood vessels significantly influence blood pressure. When the heart expands during relaxation, the pressure decreases. Similarly, dilation of blood vessels leads to a drop in blood pressure, while constriction increases it, affecting overall circulatory system dynamics.
How is blood flow related to pressure gradients in the cardiovascular system?
Blood flow is directly proportional to the pressure gradient (∆P) across the vascular system, which is the difference in pressure between two points (P1 - P2). This means that higher pressure differences result in greater blood flow, irrespective of the absolute pressures involved.
What does it mean if there is no pressure gradient in a fluid system?
If there is no pressure gradient in a fluid system, meaning that the pressure at all points is equal, there will be no flow of fluid through the system. This illustrates the necessity of a pressure differential to drive fluid movement within tubes or blood vessels.
What is “resistance” in the context of the cardiovascular system?
In the cardiovascular system, resistance is the force that opposes the flow of blood through the vessels. It is determined by factors such as the viscosity of the blood, the length of the blood vessels, and most importantly, the radius of the vessels. An increase in resistance leads to a decrease in blood flow.
How does the resistance of a blood vessel affect blood flow?
Blood flow through a vessel is inversely proportional to the vessel’s resistance. This means that if resistance increases, blood flow decreases, and vice versa. This relationship is critical in regulating how blood circulates through the body.
What are the primary factors that influence blood vessel resistance according to Poiseuille’s law?
According to Poiseuille’s law, blood vessel resistance is influenced by three main factors: the length of the vessel (L), the viscosity of the blood (η), and the radius of the vessel (r). The most impactful of these is the radius, as resistance changes with the fourth power of the radius.
How does the radius of a blood vessel affect its resistance and consequently blood flow?
The resistance offered by a blood vessel changes inversely with the fourth power of its radius. A small decrease in the radius of a vessel significantly increases resistance, thereby reducing blood flow, while a small increase in the radius can drastically decrease resistance, enhancing flow.
What is the relationship between blood flow, pressure gradient, and resistance in the cardiovascular system?
Blood flow (Flow) in the cardiovascular system is directly proportional to the pressure gradient (∆P) and inversely proportional to resistance (R). Mathematically, this is expressed as Flow ∝ ∆P/R. This formula shows that flow increases with a higher pressure gradient or lower resistance, and decreases with a lower pressure gradient or higher resistance.
How do vasoconstriction and vasodilation affect blood flow?
Vasoconstriction, the narrowing of blood vessels, increases resistance and decreases blood flow through the vessel. Conversely, vasodilation, the widening of blood vessels, decreases resistance and increases blood flow. These mechanisms are vital for regulating blood flow and pressure within the cardiovascular system.
What is “flow rate” in cardiovascular physiology?
Flow rate, often referred to simply as “flow,” is the volume of blood that passes a given point in the cardiovascular system per unit of time. It is typically measured in liters per minute (L/min) or milliliters per minute (mL/min).
How does “velocity of flow” differ from “flow rate” in the cardiovascular system?
Velocity of flow, or simply velocity, is the speed at which blood moves past a given point and is measured by the distance a fixed volume of blood travels in a given period of time. In contrast, flow rate measures the volume of blood that flows past a point in a given period.
What is the relationship between flow rate, velocity, and cross-sectional area in a blood vessel?
The velocity of flow through a blood vessel is determined by the equation
𝑣 = 𝑄/𝐴, where 𝑣 is the velocity, 𝑄 is the flow rate, and 𝐴 is the cross-sectional area. Velocity is directly proportional to flow rate and inversely proportional to the cross-sectional area of the vessel.
How does the velocity of blood flow vary with the diameter of the blood vessel?
In a blood vessel, if the flow rate remains constant, the velocity of flow varies inversely with the diameter. This means that blood flows faster through narrower sections of a vessel and slower through wider sections.
What is the effect of vessel diameter on the velocity of flow, demonstrated by the behavior of a leaf in a stream?
In narrower sections of a stream, where the cross-sectional area is smaller, a leaf will move rapidly due to the higher velocity of the water. Conversely, in wider sections where the area is larger, the velocity decreases and the leaf moves more slowly.
What is Mean Arterial Pressure (MAP) and what factors influence it?
Mean Arterial Pressure (MAP) is the primary driving force for blood flow in the cardiovascular system. It is influenced by cardiac output (the volume of blood pumped by the heart per minute) and peripheral resistance (the resistance offered by blood vessels to blood flow).
Explain the relationship of MAP to cardiac output and peripheral resistance.
Mean arterial pressure is directly proportional to both cardiac output and peripheral resistance. An increase in either cardiac output or peripheral resistance will lead to an increase in MAP, thereby affecting blood flow throughout the cardiovascular system.
What is the significance of the heart’s structure as an inverted cone?
The heart is structured like an inverted cone with the apex pointing downward and the base facing upward. This orientation is crucial because it positions the heart optimally within the thoracic cavity, with the apex resting on the diaphragm and the base at the level of the sternum.
What is the function of the pericardium?
The pericardium is a tough membranous sac that encases the heart. It contains pericardial fluid, which lubricates the heart’s surface, reducing friction during heartbeats. Inflammation of this sac, known as pericarditis, can lead to decreased lubrication and a friction rub sound.
Describe the myocardium and its significance.
The myocardium is the heart muscle, primarily responsible for the pumping action of the heart. It is composed of cardiac muscle cells that contract to eject blood from the ventricles, and it is regulated by the heart’s electrical conduction system.
How is blood flow directed in the heart?
Blood enters the heart through the atria and flows into the ventricles through one-way valves. The right ventricle pumps blood to the lungs via the pulmonary trunk, while the left ventricle pumps it to the body via the aorta. Valves at the exits of the ventricles prevent backflow.
Explain the relationship between the heart’s anatomy and its contraction pattern.
The heart’s tubular embryonic development causes a twist, positioning arteries near the top of the ventricles. This arrangement necessitates that ventricles contract from bottom to top, efficiently pushing blood out. Four fibrous connective tissue rings around the valves not only provide structural support but also act as electrical insulators, ensuring coordinated contractions.
How does the heart’s electrical insulator system function?
The fibrous connective tissue around the heart valves serves as an electrical insulator, preventing the direct transmission of electrical signals between the atria and ventricles. This ensures that signals are channeled through the heart’s specialized conduction system, leading to efficient, coordinated contractions.
What is the primary function of the atrioventricular (AV) valves in the human heart?
The atrioventricular (AV) valves primarily prevent the backward flow of blood from the ventricles to the atria during ventricular contraction. Located at the opening between each atrium and its corresponding ventricle, these valves ensure unidirectional blood flow within the heart, critical for maintaining efficient cardiac output and pressure dynamics.
Describe the structural components of atrioventricular (AV) valves and their mechanism of operation.
AV valves consist of flaps of fibrous tissue connected at their base to a connective tissue ring. These flaps are tethered to papillary muscles by chordae tendineae, collagenous tendons. When ventricles contract, blood pushes against the flaps, closing the valve. Chordae tendineae prevent the valve from prolapsing (inverting into the atria), thus maintaining proper closure during the high-pressure phase of the cardiac cycle.
What are the differences between the tricuspid and mitral valves in terms of structure and naming?
The tricuspid valve, situated between the right atrium and ventricle, consists of three tissue flaps and is responsible for controlling blood flow on the heart’s right side. The mitral or bicuspid valve, located between the left atrium and ventricle, has two flaps and is named for its resemblance to a bishop’s miter (a type of ceremonial headwear). This structural distinction corresponds with the different physiological pressures and volumes handled by each side of the heart.
Explain the function and structural uniqueness of semilunar valves in the heart.
Semilunar valves, comprising the aortic and pulmonary valves, are located at the exits of the ventricles leading into the aorta and pulmonary artery, respectively. Each valve has three crescent-moon-shaped leaflets that fit together tightly when closed. These valves open to allow blood to exit the heart and snap shut to prevent backflow, operating without the need for chordae tendineae due to their unique shape and the support of arterial pressure.
How does valve prolapse affect heart function, and what are the primary causes?
Valve prolapse occurs when the valve flaps are pushed back into the atrium during ventricular contraction, usually due to malfunction or degradation of the chordae tendineae. This condition disrupts normal blood flow, potentially leading to regurgitation (reverse blood flow), which can decrease cardiac efficiency and increase the heart’s workload, leading to further complications if not managed effectively.
How are the atrioventricular and semilunar valves different in terms of their response to pressure changes during the cardiac cycle?
AV valves respond passively to changes in blood pressure: they open when atrial pressure exceeds ventricular pressure during diastole and close when ventricular pressure rises during systole. Semilunar valves also operate passively but are influenced by the pressure in the arteries they feed into; they open when ventricular pressure exceeds arterial pressure and close when it drops below arterial pressure, ensuring efficient ejection of blood from the heart and preventing backflow.
What is the coronary circulation and why is it significant?
The coronary circulation refers to the network of arteries and veins that provide blood supply directly to the heart muscle. It is crucial for delivering oxygen and nutrients to the heart itself, ensuring that the heart maintains the robust function required for its pumping action. The coronary arteries encircle the heart near its base, resembling a crown, which is reflected in the term “coronary.”
Describe the paths of the major coronary arteries.
The right coronary artery (RCA) originates from the aorta and encircles the right side of the heart, supplying the right atrium, most of the right ventricle, some of the left ventricle, and the posterior part of the interventricular septum. The left coronary artery (LCA) also starts at the aorta and branches into the circumflex artery and the anterior interventricular artery (LAD), supplying the left atrium, most of the left ventricle, interventricular septum, and parts of the right ventricle.
How does venous blood return from the coronary circulation to the heart?
Venous blood from the coronary circulation returns mainly through cardiac veins that drain into the coronary sinus located on the posterior aspect of the heart, which then empties directly into the right atrium. Additionally, smaller blood channels within the heart muscle and some veins from the anterior right ventricle also drain directly into the heart chambers.
Why is venous blood from the coronary circulation particularly low in oxygen content?
Cardiac muscle consumes an exceptionally high percentage of the oxygen delivered by the blood, estimated at 70–80%, which is more than double that used by other cells. This high consumption rate reflects the heart’s intense energy demands, particularly during periods of increased activity.
What are the consequences of reduced myocardial blood flow?
Reduced blood flow to the myocardium, often caused by blockage of a coronary artery or extremely low blood pressure, can lead to severe damage or death of heart muscle tissue. This underscores the critical nature of maintaining proper coronary circulation to support the heart’s continuous and demanding function.
What is the composition of the heart and the unique property of its muscle cells?
The heart is mostly made up of cardiac muscle cells, or myocardium. About 1% of these are specialized autorhythmic cells that generate action potentials spontaneously, allowing the heart to contract without external signals. This myogenic property enables the heart to beat even when disconnected from the body.
What are autorhythmic cells and their function in the heart?
Autorhythmic cells, also known as pacemaker cells, are specialized myocardial cells that set the heartbeat rate. They are smaller, contain few contractile fibers, and lack organized sarcomeres, contributing minimally to contractile force but crucially regulating the heart’s rhythm.
How does cardiac muscle differ structurally from skeletal muscle?
Cardiac muscle fibers are smaller than skeletal muscle fibers, generally containing a single nucleus. They form a complex network by branching and joining end-to-end at intercalated disks, which include desmosomes for physical connection and gap junctions for electrical connectivity, facilitating synchronized contraction.
How does cardiac muscle compare to skeletal and smooth muscle?
Unlike skeletal muscle, cardiac muscle has larger t-tubules, a smaller sarcoplasmic reticulum, and relies partially on extracellular calcium for contraction, similar to smooth muscle. It also resembles single-unit smooth muscle in how cells are electrically connected, allowing unified contraction.
What reflects the high energy demand of cardiac muscle cells?
Cardiac contractile fibers have mitochondria occupying about one-third of their cell volume, a reflection of the high energy requirements needed to sustain continuous heart contractions. This dense mitochondrial presence supports the intensive metabolic demands of cardiac tissue.
How does excitation-contraction coupling (EC coupling) initiate in cardiac muscle?
In cardiac muscle, EC coupling begins with an action potential originating spontaneously from the heart’s pacemaker cells. This action potential spreads to contractile cells via gap junctions, triggering the EC coupling process.
