FSU BSC 2086 - Lesson 10: Blood Vessel Dynamics

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BSC2086 A&P II Exam #3 “You Should Be Able To” Questions 1 Lesson 10: Blood Vessel Dynamics  Explain how blood pressure and resistance impact blood flow Increased pressure promotes blood flow & increased resistance hinders it Blood pressure must overcome resistance for blood flow to occur  Explain how the mean arterial pressure is calculated The mean arterial pressure (MAP) is calculated by adding one-third of the pulse pressure to the diastolic pressure MAP = Diastolic Pressure + 1/3*(Pulse Pressure) Ex) If BP is 120/90… € MAP= 90 + (1/3)(120 − 90) = 90 +10 = 100mmHg  Describe how blood pressure is maintained by elastic arteries Elastic arteries maintain blood flow through elastic rebound – when the already stretched arterial walls recoil to their original dimensions This forces blood toward the capillaries, which maintains blood flow along the arterial network while the left ventricle is in diastole  Explain which vessels provide the most resistance The smallest vessels, capillaries & arterioles, provide the most resistance They are small in diameter, and the diameter of a vessel has a strong effect on resistance (the smaller the diameter, the greater the resistance) Blood pressure falls as it heads toward the capillaries, and blood velocity is lowest in the capillaries  Explain the mechanisms in the venous system that assist the movement of blood back to the heart Venous pressure is low, but it determines venous return – the amount of blood arriving at the atrium each minute • Muscular compression of peripheral veins o Contractions of skeletal muscles near a vein compress it & help push blood toward the heart o Their one-way valves ensure that blood only flows in one direction • Respiratory PumpBSC2086 A&P II Exam #3 “You Should Be Able To” Questions 2 o Inhaling decreases thoracic pressure  Thoracic cavity expands  Pulls air into lungs  Pulls blood into the inferior vena cava & right atrium from the smaller veins of the abdominal cavity & lower body o Exhaling increases thoracic pressure  Thoracic cavity decreases in size  Forces air out of the lungs  Pushes venous blood into right atrium  Explain what happens at the capillaries Capillary exchange moves materials across typical capillary walls & plays a vital role in homeostasis • The important processes are: o Diffusion o Filtration o Reabsorption  Describe the diffusion routes taken by different molecules at capillaries Water, ions, and small organic molecules (i.e. glucose) – diffuse through adjacent endothelial cells or pores of fenestrated capillaries Many ions (sodium, potassium, calcium, chloride) – diffuse across endothelial cells through channels in plasma membranes Large water-soluble compounds – diffuse through fenestrated capillaries only Lipids (fatty acids & steroids) & lipid-soluble materials (O2 & CO2) – diffuse through endothelial plasma membranes Plasma proteins – diffuse through sinusoids  Explain the difference between filtration and reabsorption at the capillaries Filtration involves moving fluid out of the capillaries & occurs primarily at the arterial end, where capillary hydrostatic pressure (CHP) is highest Reabsorption involves moving fluid back into the capillaries & occurs primarily at the venous end, where blood colloid osmotic pressure (BCOP) is highest  Explain how you can determine if filtration is occurring or reabsorption. Describe how the net filtration pressure is calculated.BSC2086 A&P II Exam #3 “You Should Be Able To” Questions 3 Net Filtration Pressure (NFP): The difference between the net hydrostatic pressure and the net osmotic pressure NFP = CHP – BCOP If the value is positive, this indicates that the fluid will tend to move out of the capillary, meaning that filtration is occurring If the value is negative, fluid will tend to move into the capillary, meaning that reabsorption is occurring  What is the CHP, BCOP, IHP, and ICOP? • Capillary Hydrostatic Pressure (CHP) – contributes to net hydrostatic pressure to push fluids out of capillaries (filtration) • Interstitial Fluid Hydrostatic Pressure (IHP) – contributes to net hydrostatic pressure • Blood Colloid Osmotic Pressure (BCOP) – contributes to net capillary colloid osmotic pressure to pull fluids into capillaries (reabsorption) • Interstitial Fluid Colloid Osmotic Pressure (ICOP) – contributes to net capillary colloid osmotic pressure  Describe the factors that can affect tissue perfusion. Which are short-term? Which are long-term? Tissue Perfusion: Blood flow through the tissues Factors that affect tissue perfusion: • Cardiac output • Peripheral resistance • Blood pressure Regulatory mechanisms: • Autoregulation: Local factors change the pattern of blood flow within capillary beds as precapillary sphincters open & close in response to chemical changes in interstitial fluids o Causes immediate, localized homeostatic adjustments • Neural Mechanisms – respond to changes in arterial pressure or blood gas levels sensed at specific sites o Cardiovascular centers of autonomic nervous system adjust cardiac output & peripheral resistance to maintain blood pressure & adequate blood flow o Short-term • Endocrine Mechanisms – endocrine system releases hormones that enhance short-term adjustments & direct long-term changes in cardiovascular performanceBSC2086 A&P II Exam #3 “You Should Be Able To” Questions 4  Describe the various local vasodilators and vasoconstrictors Vasodilators are factors that promote the dilation of precapillary sphincters • Local vasodilators act at the tissue level to accelerate blood flow through their tissue of origin o Examples:  Low tissue oxygen (O2) levels  Increased carbon dioxide (CO2) levels  Low pH (acidity)  Nitric oxide (NO)  High potassium (K+) or hydrogen (H+) ion concentrations in the interstitial fluid  Chemicals released during local inflammation (i.e. histamine & NO)  Elevated local temperature Vasoconstrictors are factors that stimulate precapillary sphincters to constrict • Local vasoconstrictors act at the tissue level to reduce blood flow o Examples:  Prostaglandins & thromboxanes • Released by damaged tissues  Explain the function of the baroreceptors. Where are they located? What are their functions? Baroreceptors are specialized


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FSU BSC 2086 - Lesson 10: Blood Vessel Dynamics

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