FSU BSC 2086 - Lesson 10: Blood Vessel Dynamics

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BSC2086 A&P II Exam #3 Study Guide 1 Lesson 10: Blood Vessel Dynamics Circulatory Pressure • ∆P = difference in pressure across the systemic circuit o ~ 100 mmHg • Circulatory pressure MUST overcome total peripheral resistance (R) – resistance of entire cardiovascular system • Total Peripheral Resistance: o Vascular resistance o Blood Viscosity o TurbulenceBSC2086 A&P II Exam #3 Study Guide 2 Cardiovascular PressuresBSC2086 A&P II Exam #3 Study Guide 3 • Pressure depends on: o Vessel diameters o Total cross-sectional areas o Pressures o Velocity of blood flow • Arterial Blood Pressure o Systolic Pressure: Peak arterial pressure during ventricular systole o Diastolic Pressure: Minimum arterial pressure during diastole  Why doesn't the diastolic pressure drop to zero when the heart is relaxed at the end of diastole? • Elastic fiber stretching & recoiling o Recoil squeezes blood and provides pressure o Pulse Pressure: Difference between systolic pressure and diastolic pressure o Mean Arterial Pressure (MAP)  MAP = Diastolic Pressure + 1/3 Pulse Pressure • Ex) If BP is 120/90 o MAP = 90 + 1/3(120-90) = 100 mmHg • Normal Blood Pressure = 120/80 (systolic pressure/diastolic pressure) • Abnormal Blood Pressure – Hypertension & Hypotension o Hypertension: Abnormally high blood pressure  Greater than 140/90 o Hypotension: Abnormally low blood pressure  Less common than hypertensionBSC2086 A&P II Exam #3 Study Guide 4  Mostly caused by overly aggressive drug treatment of hypertension • Elastic Rebound o Arterial walls…  Stretch during systole  Rebound (recoil to original shape) during diastole  Keep blood moving during diastole • Pressures in Small Arteries and Arterioles o Pressure & distance  MAP and pulse pressure decrease with distance from heart  Blood pressure decreases with friction  Pulse pressure decreases due to elastic rebound • By time blood reaches precapillary sphincter, NO pressure fluctuations remain • Venous Pressure and Venous Return – Determines the amount of blood arriving at right atrium each minute o Low effective pressure in venous system o Low venous resistance is assisted by:  Muscular compression of peripheral veins • Compression by skeletal muscles pushes blood toward heart (one-way valves)  Respiratory Pump – thoracic cavity action • Inhaling decreases thoracic pressure o Pulls air into lungs & blood into inferior vena cava • Exhaling increases thoracic pressure o Pushes venous blood into right atrium  Why not backwards, away from heart?BSC2086 A&P II Exam #3 Study Guide 5 • Squeezes veins – have one-way valves, so blood goes only one direction (back to the heart) Capillary Pressures and Capillary Exchange o Vital to homeostasis o Moves materials across capillary walls by:  Diffusion  Filtration  Reabsorption o Diffusion: Movement of ions or molecules from high concentration to lower concentration along the concentration gradient  Extra energy NOT required for this process  Diffusion Routes: • Water, ions, and small molecules (i.e. glucose) o Diffuse between adjacent endothelial cells o Or through fenestrated capillaries • Some ions (Na+, K+, Ca2+, Cl-) o Diffuse through channels in plasma membranes • Large, water-soluble compounds o Pass through fenestrated capillaries • Lipids & lipid soluble materials (i.e O2 & CO2) o Diffuse through endothelial plasma membranes  Membrane = made of phospholipids • Plasma proteins o Cross endothelial lining in sinusoids  Ex) Sinusoidal capillaries in liver o Filtration: Water and small solutes forced through capillary wall  Leaves larger solutes in bloodstream  Driven by hydrostatic pressure (from an area of higher pressure to an area of lower pressure) o Reabsorption  Result of osmotic pressure (OP)  Blood Colloid Osmotic Pressure (BCOP) / Oncotic Pressure: Caused by suspended blood proteins that are too large to cross capillary walls • Equals pressure required to prevent osmosis • Draws fluid back into the capillariesBSC2086 A&P II Exam #3 Study Guide 6 o Interplay between filtration and reabsorption  Ensures that plasma & interstitial fluid are in constant communication and mutual exchange  Accelerates distribution of: • Nutrients, hormones, and dissolved gases throughout tissues  Assists in the transport of: • Insoluble lipids & tissue proteins that cannot enter bloodstream by crossing capillary walls  Has a flushing action that carries bacterial toxins and other chemical stimuli to: • Lymphatic tissues & organs responsible for providing immunity to disease  Net Hydrostatic Pressure – ∆P between inside & outside of capillary • Forces water out of solution o Out of capillary into interstitial fluid  Net Osmotic Pressure • Forces water into solution o From outside capillary to inside capillary  Both net hydrostatic pressure AND net osmotic pressure control filtration and reabsorption through capillaries o Factors that contribute to net hydrostatic pressure:  Capillary Hydrostatic Pressure (CHP)  Interstitial Fluid Hydrostatic Pressure (IHP) o Net capillary hydrostatic pressure tends to push water & solutes out of capillaries and into interstitial fluid o Net Capillary Colloid Osmotic Pressure  Is the difference between… • Blood Colloid Osmotic Pressure (BCOP) o and • Interstitial Fluid Colloid Osmotic Pressure (ICOP)  Pulls water and solutes into a capillary from interstitial fluidBSC2086 A&P II Exam #3 Study Guide 7 • Net Filtration Pressure (NFP): The difference between net hydrostatic pressure and net osmotic pressure o NFP = (CHP – IHP) – (BCOP – ICOP) o Under normal conditions, IHP = ICOP, so the equation can be simplified  NFP = CHP – BCOP • Capillary Exchange o At arterial end of capillary: (NFP > 0)  Fluid moves out of capillary & into interstitial fluid o At venous end of capillary: (NFP < 0)  Fluid moves into capillary & out of interstitial fluid o Transition point between filtration and reabsorption is closer to venous end than arterial end o Capillaries filter more than they reabsorb  Excess fluid enters lymphatic vessels • Capillary Dynamics o Hemorrhaging – reduces CHP & NFP  Increases reabsorption of interstitial fluids (recall of fluids) o


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FSU BSC 2086 - Lesson 10: Blood Vessel Dynamics

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