BSC2086 A P II Exam 3 You Should Be Able To Questions 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 Pump 1 BSC2086 A P II Exam 3 You Should Be Able To Questions 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 2 BSC2086 A P II Exam 3 You Should Be Able To Questions 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 performance 3 BSC2086 A P II Exam 3 You Should Be Able To Questions 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 Increased carbon dioxide CO2 levels Low tissue oxygen O2 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 receptors that monitor the degree of stretch in the walls of expandable organs Located in the o Carotid sinuses expanded chambers near the bases of the internal carotid arteries of the neck o Aortic sinuses pockets in the walls of the ascending aorta o Wall of the right atrium Function to pressures o Monitor blood pressure o Adjust cardiac output peripheral resistance to maintain normal arterial Describe the chemoreceptor reflexes Chemoreceptor reflexes respond to changes in chemical composition
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