Physiology II Exam 2 PDF

Chapter 9 How is the pace (heart rate) of the heart controlled by the heart’s conductions system and what other organs can influence the heart rate? Conduction system includes: - sinoatrial (SA) node: the natural pacemaker of the heart and initiates the electrical impulses that cause the heart to be...

Chapter 9 How is the pace (heart rate) of the heart controlled by the heart’s conductions system and what other organs can influence the heart rate? Conduction system includes: - sinoatrial (SA) node: the natural pacemaker of the heart and initiates the electrical impulses that cause the heart to beat. - atrioventricular (AV) node, - bundle of His - Purkinje fibers Heart rate can be influenced by: - Autonomic nervous system - Sympathetic nervous system: increases heart rate by releasing norepinephrine - Parasympathetic nervous system: decreases heart rate by releasing acetylcholine - Hormones - Epinephrine and norepinephrine (released by the adrenal glands) increase HR - Organs: - Lungs: can influence heart rate by regulating the amount of oxygen and carbon dioxide in the blood. - Baroreceptors: can sense changes in blood pressure and send signals to the brain to adjust heart rate accordingly. Understand that action potentials fire down the heart similarly to action potentials firing down neurons. In both cases, the movement of ions creates an electrical signal that travels down the length of the cell. In neurons: - action potentials are initiated by the opening of voltage-gated sodium channels in response to a depolarizing stimulus. - Causes an influx of sodium ions into the cell, which further depolarizes the membrane - Triggers the opening of more sodium channels. - Creates a positive feedback loop that rapidly depolarizes the membrane and generates an action potential. In the heart: - action potentials are initiated by the opening of voltage-gated calcium channels in response to a depolarizing stimulus. - Causes an influx of calcium ions into the cell - Triggers the release of more calcium ions from the sarcoplasmic reticulum. The calcium ions then bind to troponin, which initiates the contraction of the cardiac muscle fibers. The depolarization = slower in cardiac muscle than in neurons - Due to the presence of calcium channels that open more slowly than sodium channels. - This results in a longer duration of the action potential in cardiac muscle cells compared to neurons. Describe the events and channel actions of excitation-contraction coupling. process by which an action potential in the cardiac muscle cell leads to muscle contraction. - AP travels down the T-tubules and triggers the opening of voltage-gated calcium channels in the sarcoplasmic reticulum. - release of calcium ions into the cytoplasm, which binds to troponin - triggers a conformational change in the tropomyosin-troponin complex. - exposes the myosin-binding sites on the actin filaments, allowing myosin heads to bind and initiate muscle contraction. Understand that there are 2 different types of cells in the heart: (a) conduction system cells, which are electrical structures that send commands to contract and (b) muscle cells that obey the command and perform contraction. Name these cells/structures and their locations. Describe the each of their functions and characteristics. The two different types of cells in the heart are: 1) Conduction system cells: specialized cells that make up the heart's electrical conduction system. The main components of the conduction system are: a) Sinoatrial (SA) node: This is the natural pacemaker of the heart and is located in the right atrium. It generates electrical impulses that initiate each heartbeat and set the heart rate. b) Atrioventricular (AV) node: This is located between the atria and ventricles and serves as a gateway for the electrical impulses to pass from the atria to the ventricles. c) Bundle of His: This is a specialized bundle of fibers that conducts the electrical impulses from the AV node to the ventricles. d) Purkinje fibers: These are specialized fibers that spread the electrical impulses throughout the ventricles, causing them to contract. 2) Muscle cells: make up the bulk of the heart muscle and are responsible for performing the contraction of the heart. a) located in the walls of the atria and ventricles b) connected by intercalated discs, which allow for the rapid transmission of electrical impulses between cells. The main characteristics of muscle cells are: - Striated appearance: due to the arrangement of actin and myosin filaments that enable them to contract. - Large number of mitochondria: require a lot of energy to perform contraction, so they have a large number of mitochondria to produce ATP. - Intercalated discs: specialized structures that connect muscle cells and allow for the rapid transmission of electrical impulses between cells. Describe the pathway that electrical signals travel through the conduction, in order. Know where there is a delay in transmission of the signal and why this delay is important. The pathway that electrical signals travel through the conduction system of the heart, in order, is as follows: 1. The electrical signal is generated in the sinoatrial (SA) node, located in the right atrium. 2. The signal spreads through the atria, causing them to contract. 3. The signal reaches the atrioventricular (AV) node, located at the junction between the atria and ventricles. 4. There is a delay in transmission of the signal at the AV node, which allows time for the atria to finish contracting before the ventricles begin to contract. 5. The signal then travels down the bundle of His, a specialized bundle of fibers that conducts the signal from the AV node to the ventricles. 6. The signal then spreads through the Purkinje fibers, which are specialized fibers that spread the signal throughout the ventricles, causing them to contract. Name the pacemakers of the heart, where each one is located, when each one is in charge of setting the pace, how fast it sets the pace, and how well that pace meets the needs of the body. 1. Sinoatrial (SA) node: This is the primary pacemaker of the heart and is located in the right atrium. - Sets the pace at a rate of 60-100 beats per minute 2. Atrioventricular (AV) node: This is a secondary pacemaker of the heart and is located between the atria and ventricles. - Sets the pace at a rate of 40-60 beats per minute (still adequate to meet the body's needs) 3. Atria: 60-80 BPM 4. Ventricles: 20-40 BPM 5. Purkinje fibers: These are specialized fibers that can act as a pacemaker if both the SA and AV nodes fail to function properly. - Sets the pace at a rate of 20-40 beats per minute (not adequate to meet the body's needs) What does is mean to say that the heart functions as a Functional Syncytium? What structures are unique in the heart that enable it to function this way, and how do they enable this? Understand that, in reality, because there’s a delay in the conduction system, the heart doesn’t function as just one syncytium, but functions as two: Atrial syncytium and Ventricular syncytium. Why is it important for cardiac muscle to function this way, even though skeletal muscle doesn’t need to? Functional syncytium = heart muscle cells (cardiomyocytes) work together as a single unit to contract and pump blood. - Due to the presence of intercalated discs, which are unique to the heart. Intercalated discs: specialized structures that connect cardiomyocytes to each other. - Contain two types of junctions: 1. Desmosomes: strong adhesive junctions that hold the cells together during contraction 2. Gap junctions: channels that allow for the rapid transmission of electrical impulses between cells. a. enables them to contract together as a single unit b. ensures that all of the cells are contracting in a coordinated manner The heart functions as two syncytia (atrial and ventricular). - Although it is still considered a functional syncytium because the cells within each syncytium work together as a single unit to contract and pump blood. Skeletal muscle does not need to function as a syncytium because it is under voluntary control. - Skeletal muscle fibers are innervated by motor neurons, which allow for precise control of muscle contraction. This is not the case in the heart. Describe the events and channel actions of the different phases of the cardiac muscle action potential. Phase Events Channel Actions Phase 0 Rapid depolarization Voltage-gated Na+ channels open, allowing inward Na+ current Phase 1 Early repolarization Some K+ channels open, allowing outward K+ current Phase 2 Plateau L-type Ca2+ channels open, balancing inward Ca2+ current with outward K+ current Phase 3 Repolarization Potassium (K+) channels fully open, allowing increased outward K+ current Phase 4 Resting Membrane Potential Potassium (K+) channels are open, maintaining a negative membrane potential ❖ Phase 0: opening of fast sodium channels ➢ leads to rapid depolarization of the cell membrane. ❖ Phase 1: closing of fast sodium channels and the opening of transient outward potassium channels ➢ leads to partial repolarization of the cell membrane. ❖ Phase 2: opening of slow calcium channels and the closing of transient outward potassium channels ➢ leads to a plateau phase of the action potential. ❖ Phase 3: involves the closing of slow calcium channels and the opening of delayed rectifier potassium channels ➢ leads to rapid repolarization of the cell membrane. ❖ Phase 4: the resting membrane potential What are the absolute and relative refractory periods in the cardiac muscle action potential? The absolute refractory period is the period during which the cardiac muscle cell cannot be stimulated to depolarize again, no matter how strong the stimulus is. The relative refractory period is the period during which the cardiac muscle cell can be stimulated to depolarize again, but only by a stronger-than-normal stimulus. It - lasts from the middle of phase 2 to the end of phase 3. Describe the pressures and volumes in each chamber and vessel at each moment of the cardiac cycle, the pressure-volume-time graphs and EKG graph, and the pressure-volume diagram. During the cardiac cycle, the heart goes through a series of events that involve changes in pressure and volume in the different chambers and vessels. These events include atrial systole, ventricular systole, and diastole. Atrial systole: the atria contract and push blood into the ventricles. Ventricular pressure: increase Volume: Increase Ventricular systole: the ventricles contract and push blood out of the heart. Ventricular pressure: Increase Volume: Decrease Diastole: the heart relaxes and fills with blood. Ventricular pressure: Decrease Volume: Increase Chapter 10 Describe the structures in and events in the following: 1. Conduction System There are two types of cells in the heart: Conduction System: responsible for generating and conducting electrical impulses throughout the heart. Includes the: 1. SA node 2. internodal pathways 3. AV node 4. AV bundle 5. LBB (left bundle branch) 6. RBB (right bundle branch) 7. Purkinje fibers Cardiomyocytes/Myocardial cells: responsible for contracting to make the heart beat 2. SA Node Action Potential Graph Describes how the SA node pacemaker cells self-excite (spontaneously fire) to set the Heart rate - shows the electrical activity of the SA node over time. The graph starts with Na+ leaking into SA node cells, which causes a slow rise of the SA node action potential graph up to the threshold of -40 mV. - Activates slow Ca2+ channels to open = causes the graph to shoot up. Pacemaker fires. - After the pacemaker fires, the Ca channels close, and K channels open to let K+ out of the cell - SA node cell becomes negative again = action potential graph goes back down (hyperpolarization). - The K channels close, and the graph stops dropping 3. Delay at AV Node and Bundle The delay allows the atria to contract and empty their blood into the ventricles before the ventricles contract. After the delay at the AV node, the electrical impulse travels down the bundle of His, - A specialized group of cells that conduct the impulse rapidly through the ventricular septum. - The bundle of His divides into the left and right bundle branches, carry the impulse to the Purkinje fibers. - The Purkinje fibers are specialized cells that rapidly conduct the impulse throughout the ventricles, causing them to contract in a coordinated manner and pump blood out of the heart. 4. Pacemakers (normal and ectopic) Normal pacemaker: The normal pacemaker of the heart is the SA node - SA node generates electrical impulses that cause the heart to beat. - The impulses then travel through the internodal pathways to the AV node, where there is a delay to allow the atria to contract before the ventricles. - The impulses then travel through the AV bundle, LBB, RBB, and Purkinje fibers to cause the ventricles to contract and pump blood out of the heart. Ectopic pacemakers: occur when a portion of the heart with a more rapid discharge surpasses the sinus node. - This can also occur when transmission from the sinus node through the AV node is blocked (AV block). When this happens, the sinus node discharge does not get through, and the next fastest area of discharge becomes the pacemaker of the heart. 5. Sympathetic vs Parasympathetic Control of the SA node and AV node The sympathetic and parasympathetic nervous systems control the heart's rhythmicity and impulse conduction by the cardiac nerves. Parasympathetic nervous system: The parasympathetic nerves are distributed to the: - SA and AV nodes - Atria (to a lesser extent) - ventricular muscle (VERY little). The PNS releases acetylcholine (ach), which slows the heart rate by: - decreasing the rate of depolarization of the SA node. - Increasing the delay at the AV node Sympathetic Nervous System: The sympathetic nerves are distributed to: - all parts of the heart (with strong representation in the ventricular muscle) The SNS releases norepinephrine, which increases the heart rate by: - increasing the rate of depolarization of the SA node. - decreases the delay at the AV node - The SNS also increases the force of contraction of the ventricles, which increases the amount of blood pumped out of the heart with each beat. Chapter 13 What are the causes of cardiac arrhythmias? the causes of cardiac arrhythmias include: 1. abnormal rhythmicity of the pacemaker 2. shift of pacemaker from sinus node 3. blocks at different points in the transmission of the cardiac impulse 4. abnormal pathways of transmission in the heart 5. spontaneous generation of abnormal impulses from any part of the heart (ectopic) When shown an EKG strip from my lecture powerpoint, recognize what pattern it shows (for example, tachycardia, third-degree block, VTach, etc). Just to the extent that I described in the powerpoint slides that discuss those strips: describe what is causing each pattern and how the timing/numbers (for example, PR interval) are affected Know causes of tachycardia and AV block Tachycardia can be caused by: 1. Exercise 2. Increased body temperature 3. Sympathetic stimulation (such as from loss of blood and the reflex stimulation of the heart) 4. Toxic conditions of the heart AV block can be caused by: 1. ischemia of A-V nodal or A-V bundle fibers (can be caused by coronary ischemia) 2. compression of A-V bundle (by scarred or calcified tissue) 3. A-V nodal or A-V bundle inflammation 4. Excessive vagal stimulation 5. Excess digitalis. Name 2 cases in which bradycardia is seen - athletes with a large stroke volume excessive vagal stimulation (e.g., carotid sinus syndrome) What is paroxysmal atrial tachycardia, what causes it, and what stops it? Type of arrhythmia characterized by a series of rapid heartbeats that suddenly start and then suddenly stop. - Occurs by re-entrant pathways - the P wave is inverted if the origin is near the A-V node - It can be stopped with a vagal reflex or drugs. What causes VTach? Know that it can it lead to VFib. What is VFib and name 2 causes. You don’t need to know about circus movements. Ventricular tachycardia (V-tach) usually does not occur unless there has been ischemic damage. - V-tach may lead to ventricular fibrillation (V-fib). Ventricular fibrillation is a type of arrhythmia in which some parts of the ventricle contract while others relax, thus little blood flows out of the heart. What is AFib? How does it affect heart pumping efficiency? Atrial fibrillation (AFib) is an irregular, fast heart rate that occurs because of irregular arrival at the AV node of cardiac impulse from multiple re-entries. The most frequent cause is atrial enlargement, which causes a long pathway of conduction that is favorable for circus movements. - There is no P wave - QRS is frequently of normal duration-voltage-shape - The normal or high ventricular response is irregular in rhythm The efficiency of heart pumping is decreased by 20–30%. Chapter 14 What are physical characteristics of arteries, veins, and capillaries? Arteries: - strong vascular walls to withstand high blood pressure - High-velocity blood flow capillaries: - walls are thin to exchange fluid, nutrients, electrolytes, and hormones Veins: - Walls are thin and muscular enough to contract or expand to serve as a major reservoir of extra blood, such as during hemorrhage - Low blood pressure because the veins are so far away from the source of pressure What is the Poiseuille’s law and its importance? Equation that describes the relationship between the pressure gradient, flow rate, and resistance in a cylindrical vessel. The law states that the flow rate is proportional to the fourth power of the radius of the vessel and the pressure gradient, and inversely proportional to the viscosity of the fluid and the length of the vessel. Poiseuille's law is important because it helps to explain how: - changes in the diameter of blood vessels can affect blood flow and pressure - viscosity and length can also impact the function of the circulation. In the systemic circulation, about two thirds of the total systemic resistance to blood flow is resistance in the small arterioles Arterioles respond with only small changes in diameter to nervous or chemical signals, either to turn off blood flow to the tissue almost completely or cause a vast increase in flow How do pressure, flow, and resistance relate to each other? Blood flow through a blood vessel is determined by the pressure gradient and vascular resistance. - Pressure gradient = difference of the blood between the two ends of the vessel - vascular resistance = the impediment to blood flow through the vessel The pressure gradient determines flow rate Ohm’s law states that F (flow) = ∆P (pressure gradient)/R (vascular resistance). Therefore, pressure, flow, and resistance are all interrelated in determining blood flow through the circulation. What are laminar and turbulent flows? Laminar flow occurs when blood flows smoothly through a long, straight blood vessel. Cx’s: - smooth, orderly flow of fluid - fluid moves in parallel layers or streamlines, with little or no mixing between the layers. Turbulent flow can occur when blood flows through a curved or narrowed vessel, or when the flow rate is very high. Cx’s: - chaotic, irregular flow of fluid - fluid moves in a random, swirling pattern, with mixing between the layers. - Situations that will have turbulent flow - 1) if the rate of blood flow becomes too great - 2) if blood is passing by an obstruction (clot) - 3) if the vessel is making a sharp turn - 4) blood passing over a rough surface What is Reynolds’ number? How does it relate To Turbulent flow? Reynolds’ number is a dimensionless quantity that describes the likelihood of a fluid to undergo turbulent flow. When the Reynolds’ number: < 2000 = flow is usually laminar, 2000 - 4000 = flow may be laminar or turbulent > 4000 = flow is usually turbulent Direct proportion to Velocity increasing, Diameter increasing, Density (P) of blood increasing; inverse relationship to Viscosity (N) - Re = (V x D x P) / N What is The total resistance to blood flow in series and parallel vascular circuits? the total resistance to blood flow in a - series circuit = the sum of the individual resistances of each vessel in the circuit - Parallel circuit = less than the resistance of any individual vessel in the circuit. This is because blood flow can be distributed among multiple parallel vessels, which reduces the overall resistance to flow. The relationship between resistance and flow in a circuit is described by Ohm's law, which states that the flow rate is equal to the pressure difference between the two ends of the circuit divided by the total resistance of the circuit. Total Peripheral Resistance (TPR) Total Peripheral Resistance (TPR) = the resistance of the entire systemic circulation - Pressure difference (from systemic arteries to systemic vein) cardiac output - Aorta (100) – SVC/IVC (0) = 100 → then divide by Cardiac Output (100) - 100/100 = 1; so normally the TPR should be 1 PRU - CO → rate of pumping of blood out of the heart = rate of BF through entire circulatory system - 1 PRU = Pressure difference (100 mm Hg) divided by Cardiac Output (100 mL/sec) - So if the blood vessel is constricted, the TPR rises (up to 4 PRU) - So if the blood vessel is dilated, the TPR decreases (as low as 0.2 PRU) What is Conductance, how does it relate to resistance & diameter Conductance = a measure of blood flow though a vessel for a given pressure difference - Conductance is the exact RECIPROCAL of resistance Slight changes in the diameter of a vessel cause tremendous changes in the vessel’s ability to conduct blood when the blood flow is streamlined Conductance increases in proportion to the fourth power of the diameter Blood Hematocrit and Viscosity (Know slide 18/21); What is Hct & what effects it & how - - The greater the viscosity (thicc) → lower the flow in a vessel - Large numbers of suspended RBCs in the blood makes the blood viscous - Each of RBCs exerts frictional drag against adjacent cells & against the wall of the blood vessel (^ RBC= ^ drag= decrease flow) Hematocrit of 40 = 40% of blood volume is cells, and the remainder is plasma - Affected by anemia, degree of bodily activity, and altitude Increased hematocrit = markedly increased viscosity - Viscosity @ normal hematocrit = 3-4 - Viscocity also affected by plasma protein concentration & types of proteins What is blood flow autoregulation? The ability of each tissue to adjust its vascular resistance and to maintain normal blood flow during changes in arterial pressure between 70 and 175 mm Hg Chapter 15 What is the advantage of vascular distensibility? The advantage of vascular distensibility is that veins can serve as a blood reservoir because they are the most distensible of all the vessels What is vascular compliance and its advantage? Vascular compliance refers to the total quantity of blood that can be stored in a given portion of the circulation for each mm Hg pressure rise. Advantage: - allows the arterial tree to normally reduce pressure pulsations the greater the compliance of each vascular segment, the slower the velocity. What are the effects of sympathetic activity alterations on the volume-pressure relationships of the vascular system? Sympathetic stimulation increases the pressure at each volume of the arteries or veins: - Shifts the graph to the left. Sympathetic inhibition decreases the pressure at each volume: - shifts the graph to the right. What is the delayed compliance (Stress-Relaxation) of Vessels? Refers to the phenomenon where blood vessels can adjust their diameter over time in response to changes in blood pressure. When the pressure inside a blood vessel changes, the vessel walls initially respond by stretching or contracting. However, over time, the vessel walls will gradually relax or contract to reach a new equilibrium diameter. This process is known as stress-relaxation and allows blood vessels to maintain a relatively constant blood flow despite changes in blood pressure. How is right atrial pressure regulated? Right atrial pressure is regulated by a balance between: - the ability of the heart to pump blood out of the right atrium and ventricle into the lungs - the tendency for blood to flow from the peripheral veins into the right atrium. If the right heart is pumping strongly, the right atrial pressure decreases. Some factors that can increase the right atrial pressure include: - increased blood volume - increased large vessel tone - dilation of the arterioles (allows rapid flow of blood from the arteries into the veins) What are Korotkoff’s sounds? Sounds heard during the measurement of blood pressure using a sphygmomanometer and a stethoscope. - Produced by the turbulent flow of blood through the compressed artery What physical properties of blood vessels and blood determine hemodynamics (flow of blood through organs/tissues), and how are they defined by Poiseuille’s law? 1. 2. 3. 4. vessel radius vessel length blood viscosity the pressure gradient driving blood flow These factors are defined by Poiseuille's law, which states that blood flow is directly proportional to the fourth power of the vessel radius, the pressure gradient, and the vessel length, and inversely proportional to blood viscosity. This means that small changes in vessel radius can have a large effect on blood flow, and that resistance to blood flow is highest in the smallest vessels. How is arterial compliance related to stroke volume and pulse pressure? How does arterial compliance affect the arterial pulse wave and cardiac work? ↑ arterial compliance = ↓ pulse pressure + ↑ stroke volume This is because a more compliant artery can expand more easily to accommodate the volume of blood ejected from the heart during systole, resulting in a smaller increase in pressure. Arterial compliance affects the arterial pulse wave by smoothing out the pulsatile flow of blood from the heart, resulting in a more continuous flow of blood to the tissues. This reduces the work of the heart by decreasing the need for it to pump against high resistance and pulsatile flow. What are mean, systolic, diastolic, and pulse pressures, and how are they measured? Mean arterial pressure (MAP) is the average pressure in the arteries over the cardiac cycle and is calculated as MAP = DBP + 1/3 (SBP - DBP). - Systolic blood pressure (SBP) is the highest pressure in the arteries during ventricular systole - Diastolic blood pressure (DBP) is the lowest pressure in the arteries during ventricular diastole. - Pulse pressure is the difference between SBP and DBP. The mean pressure in the aorta is high = 100 mm Hg Arterial pressure = 120/80 mmHg Mean blood pressure in SVC/IVC = 0 mm Hg Pulmonary arteries = 25/8 mmHg (mean 16 mmHg) The mean pulmonary capillary pressure averages only 7 mm Hg Venous Pressures – Central vs Peripheral - - - Central Venous Pressure (CVP) = the pressure in the right atrium (0 mmHg) - Regulated by 1) ability of the heart to pump blood out of RA and RV into lungs, and 2) tendency for blood to flow from peripheral veins into RA - Heart pumping strongly or hemorrhage = decrease in RA pressure Inside of heart vs systemic – slide 10 What can cause increase and why - Factors that can increase the right atrial pressure: (1) increased blood volume; (2) increased large vessel tone and (3) dilation of the arterioles - (allows rapid flow of blood from the arteries into the veins) CVP increases (20-30 mmHg) from serious heart failure & massive transfusion of blood What are the effects of hydrostatic pressure on arterial and venous pressures? In the context of the cardiovascular system, hydrostatic pressure can affect blood flow and pressure in the vessels of the body, particularly in the lower extremities. When a person is standing, hydrostatic pressure can cause blood to pool in the veins of the legs: - increased venous pressure - decreased arterial pressure When a person is lying down, hydrostatic pressure is minimized, and blood flow and pressure are more evenly distributed throughout the body. Estimating venous pressure and how its clinically useful - Venous pressure can be estimated by observing distention in the neck In the sitting position, the neck veins are never normally distended When the right atrial pressure becomes increased to: - +10 mm Hg → lower veins of the neck begin to protrude - +15 mm Hg atrial pressure → all the veins in the neck become distended What is the venous pump? And how does it affect venous pressure? Refers to the mechanism by which blood is returned to the heart from the veins of the body. It is composed of: - a series of one-way valves in the veins: prevent blood from flowing backward - skeletal muscle contractions: propel blood toward the heart. Which organs act as the specific blood reservoirs? The liver and spleen are considered specific blood reservoirs in the human body. Liver: holds approximately 10% of the body's total blood volume Spleen: store around 5% of total blood volume Chapter 16 What vessels constitute the microcirculation? - small arterioles Metarterioles Capillaries venules What is vasomotion? And how it controls tissue blood flow? Vasomotion is the rhythmic changes in the diameter of arterioles that occur spontaneously and independently of nerve impulses or hormonal influences. - Local conditions of the tissues control the diameter of arterioles, and thus the amount of blood flow in the area. What is Donnan’s effect? Phenomenon that occurs when there is an unequal distribution of charged particles across a semipermeable membrane, such as a cell membrane or capillary wall Results in a difference in osmotic pressure across the membrane, which can affect the movement of water and other solutes. In the context of capillary function, Donnan's effect can contribute to the movement of fluid and solutes between the blood and interstitial fluid What are the hydrostatic and osmotic factors that underlie Starling’s hypothesis for capillary function? 1. The capillary hydrostatic pressure (Pc) tends to force fluid outward through the capillary membrane. 2. The interstitial fluid hydrostatic pressure (Pif) tends to force fluid inward through the capillary membrane when Pif is positive but outward when Pif is negative. 3. The capillary plasma colloid osmotic pressure (Πp) tends to cause osmosis of fluid inward through the capillary membrane. 4. The interstitial fluid colloid osmotic pressure (Πif) tends to cause osmosis of fluid outward through the capillary membrane. Therefore, the hydrostatic and osmotic factors that underlie Starling's hypothesis are: - capillary hydrostatic pressure - interstitial fluid hydrostatic pressure - capillary plasma colloid osmotic pressure - interstitial fluid colloid osmotic pressure How do interstitial fluid pressure change in tightly encased tissues? In tightly encased tissues, the interstitial fluid pressure may increase due to the limited space available for fluid to accumulate. - This can lead to compression of the surrounding tissues and blood vessels, which can further affect the flow of interstitial fluid and blood. How do intrinsic and extrinsic factors modulate peripheral circulation, and how do these factors affect blood flow in particular organs? intrinsic and extrinsic factors can modulate peripheral circulation and affect blood flow in particular organs. Intrinsic factors include: - oxygen and carbon dioxide levels - pH - adenosine Extrinsic factors include: - sympathetic and parasympathetic nervous system activity - epinephrine - norepinephrine These factors can cause vasoconstriction or vasodilation of arterioles, which can affect blood flow to particular organs. What is the function of lymphatic system? 1) Fluid Balance → picks up lymph (excess water/protein) and returns to bloodstream 2) Immune Defense → pick up WBC & pathogens and send killing stations (lymph nodes) 3) Transport Lipids & Proteins → Lacteals are lymph vessels that absorb large lipids The lymphatic system consists of: - lymphatic vessels - lymph nodes - lymphoid organs Plays a crucial role in maintaining fluid balance in the body. What are the effects of interstitial fluid and oncotic pressures on lymph flow? two main factors that determine lymph flow: 1) interstitial fluid pressure: pressure exerted by the interstitial fluid on the lymphatic vessels. It is influenced by: a) Tissue compression b) Inflammation c) Lymphatic obstruction 2) the activity of the lymphatic pump: the contraction of the smooth muscle of the lymphatic vessel, which propels lymph. Oncotic pressure, which is caused by plasma proteins, also plays a role in lymph flow. The colloid osmotic pressure caused by plasma proteins tends to cause fluid movement by osmosis from the interstitial spaces into the blood - prevents significant loss of fluid volume from the blood into the interstitial spaces. - Helps to maintain the balance of fluid between the blood and interstitial spaces Therefore, interstitial fluid pressure and oncotic pressure can affect lymph flow by influencing the pressure gradient between the interstitial spaces and the lymphatic vessels, and by regulating the movement of fluid and plasma proteins between these compartments