cardiovascular system: blood vessels, blood flow, blood pressure

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  • Slide 1
  • Cardiovascular system: Blood vessels, blood flow, blood pressure
  • Slide 2
  • Outline 1- Physical laws governing blood flow and blood pressure 2- Overview of vasculature 3- Arteries 4. Capillaries and venules 5. Veins 6. Lymphatic circulation 7. Mean arterial pressure and its regulation 8. Other cardiovascular regulatory processes
  • Slide 3
  • Outline 1- Physical laws governing blood flow and blood pressure 2- Overview of vasculature 3- Arteries 4. Capillaries and venules 5. Veins 6. Lymphatic circulation 7. Mean arterial pressure and its regulation 8. Other cardiovascular regulatory processes
  • Slide 4
  • Physical laws governing blood flow and blood pressure Flow of blood through out body = pressure gradient within vessels X resistance to flow - Pressure gradient: aortic pressure central venous pressure -Resistance: -- vessel radius -- vessel length -- blood viscosity
  • Slide 5
  • Factors promoting total peripheral resistance (TPR) Total peripheral resistance = TPR -- combined resistance of all vessels -- vasodilation resistance decreases -- vasoconstriction resistance increases
  • Slide 6
  • Outline 1- Physical laws governing blood flow and blood pressure 2- Overview of vasculature 3- Arteries 4. Capillaries and venules 5. Veins 6. Lymphatic circulation 7. Mean arterial pressure and its regulation 8. Other cardiovascular regulatory processes
  • Slide 7
  • Vasculature
  • Slide 8
  • Arteries and blood pressure Pressure reservoir Arterial walls are able to expand and recoil because of the pressure of elastic fibers in the arterial wall Systolic pressure: maximum pressure occurring during systole Diastolic pressure: pressure during diastole
  • Slide 9
  • Figure 14.8 Arterial blood pressure
  • Slide 10
  • Blood pressure values: what do they mean? Pulse pressure: PP = SP-DP Mean arterial blood pressure = MABP MABP = SBP + (2XDBP) 3 CO = MABP = SV x HR TPR
  • Slide 11
  • Figure 14.15 Blood flow within each organ changes with body activities Reminder: The ANS controls blood flow to the various organs
  • Slide 12
  • Outline 1- Physical laws governing blood flow and blood pressure 2- Overview of vasculature 3- Arteries 4. Capillaries and venules 5. Veins 6. Lymphatic circulation 7. Mean arterial pressure and its regulation 8. Other cardiovascular regulatory processes
  • Slide 13
  • Capillaries Allow exchange of gases, nutrients and wastes between blood and tissues Overall large surface area and low blood flow Two main types: - continuous capillaries: narrow space between cells permeable to small or lipid soluble molecules - fenestrated capillaries: large pores between cells large molecules can pass
  • Slide 14
  • Local control of blood flow in capillaries Presence of precapillary sphincters on the arteriole and beginning of capillaries Metarteriole: no sphincter continuous blood flow controls the amount of blood going to neighboring vessels
  • Slide 15
  • Movement of materials across capillary walls Small molecules and lipid soluble molecules move by diffusion through the cell membrane Larger molecules, charged molecules must pass through membrane channels, exocytosis or in between 2 cells Water movement is controlled by the capillary hydrostatic and osmotic pressures
  • Slide 16
  • Forces controlling water movement Arterial side of the capillary: High capillary hydrostatic pressure (BHP), lower capillary osmotic pressure (BOP, due to proteins and other molecules in the blood) Net filtration pressure pushes fluid from the blood toward the tissue (but the proteins remain in the capillary Venous side of the capillary: - Lower hydrostatic pressure (due to resistance) and higher capillary osmotic pressure Net filtration pressure moves fluid back toward the capillary Interstitial fluid hydrostatic (IFHP) and osmotic pressures (IFOP) remain overall identical
  • Slide 17
  • Fluid movement in the capillary Arteriole side: fluid moves toward the tissues Venous side: fluid reenters the capillary Overall: for every 1 liter of fluid entering the tissues, only 0.85 l reenter the capillary The remaining 0.15 l is reabsorbed as lymph by lymphatic capillaries and eventually returned back to blood circulation When this system fails: Edema
  • Slide 18
  • Causes of edema Increased hydrostatic blood pressure - heart failure (left or right), - excess fluid in the blood Decreased blood osmotic pressure Liver, kidney diseases, malnutrition (kwashiorkor), burn injuries Increased interstitial hydrostatic pressure (lymphatic capillary blockage) - breast cancer surgery, elephantiasis Leaking capillary wall - histamine release during allergic reaction
  • Slide 19
  • Outline 1- Physical laws governing blood flow and blood pressure 2- Overview of vasculature 3- Arteries 4. Capillaries and venules 5. Veins 6. Lymphatic circulation 7. Mean arterial pressure and its regulation 8. Other cardiovascular regulatory processes
  • Slide 20
  • Veins Veins are blood volume reservoir Due to thinness of vessel wall less resistance to stretch = more compliance
  • Slide 21
  • Factors influencing venous return 1- Skeletal muscle pump and valves 2- Respiratory pump 3- Blood volume 4- Venomotor tone
  • Slide 22
  • Outline 1- Physical laws governing blood flow and blood pressure 2- Overview of vasculature 3- Arteries 4. Capillaries and venules 5. Veins 6. Lymphatic circulation 7. Mean arterial pressure and its regulation 8. Other cardiovascular regulatory processes
  • Slide 23
  • Lymphatic circulation Driven by factors similar to venous circulation: - muscle activity - valves - respiration Lymph = plasma-proteins Lymphatic circulation collects fluid not reabsorbed by the capillaries Lymph is filtered in nodes before return to blood circulation
  • Slide 24
  • Outline 1- Physical laws governing blood flow and blood pressure 2- Overview of vasculature 3- Arteries 4. Capillaries and venules 5. Veins 6. Lymphatic circulation 7. Mean arterial pressure and its regulation 8. Other cardiovascular regulatory processes
  • Slide 25
  • Mean arterial pressure and its regulation Regulation of blood flow in arteries - Intrinsic control - Extrinsic control -- Neural control -- Hormonal control * Control of blood vessel radius * Control of blood volume
  • Slide 26
  • Mean arterial pressure and its regulation Regulation of blood flow in arteries - Intrinsic control - Extrinsic control -- Neural control -- Hormonal control * Control of blood vessel radius * Control of blood volume
  • Slide 27
  • Regulation of blood flow in arteries It is important to adjust blood flow to organ needs Flow of blood to particular organ can be regulated by varying resistance to flow (or blood vessel diameter) Vasoconstriction of blood vessel smooth muscle is controlled both by the ANS and at the local level. Four factors control arterial flow at the organ level: - change in metabolic activity - changes in blood flow - stretch of arterial smooth muscle - local chemical messengers
  • Slide 28
  • Intrinsic control of local arterial blood flow Change in metabolic activity Usually linked to CO 2 and O 2 levels ( CO 2 vasodilation blood flow) intrinsic control Changes in blood flow - decreased blood flow increased metabolic wastes vasodilation Stretch of arterial wall = myogenic response - Stretch of arterial wall due to increased pressure reflex constriction Locally secreted chemicals can promote vasoconstriction or most commonly vasodilation - inflammatory chemicals, (nitric oxide, CO 2 )
  • Slide 29
  • Mean arterial pressure and its regulation Regulation of blood flow in arteries - Intrinsic control - Extrinsic control -- Neural control -- Hormonal control * Control of blood vessel radius * Control of blood volume
  • Slide 30
  • Extrinsic control of blood pressure Two ways to control BP: -Neural control -Hormonal control ** Use negative feedback
  • Slide 31
  • Control of blood pressure Importance: Blood pressure is a key factor for providing blood (thus oxygen and energy) to organs. SBP must be a minimum of 70 to sustain kidney filtration and adequate blood flow to the brain CO= HR X SV = MABP/TPR MABP= HRxSVxTPR heart rate, stroke volume and peripheral resistance affect MABP Main factors controlling BP: - Blood volume - Blood vessel radius
  • Slide 32
  • Neural control of BP - 1 Baroreceptors: carotid and aortic sinuses sense the blood pressure in the aortic arch and internal carotid send signal to the vasomotor center in the medulla oblongata Other information are sent from the hypothalamus, cortex
  • Slide 33
  • Neural control of BP - 2 The vasomotor center integrates all these information The vasomotor sends decision to the ANS center: -Both parasympathetic and sympathetic innervate the S/A node can accelerate or slow down the heart rate -The sympathetic NS innervates the myocardium and the smooth muscle of the arteries and veins promotes vasoconstriction
  • Slide 34
  • Hormonal control of BP Hormones can control blood vessel radius and blood volume, stroke volume and heart rate On a normal basis, bl

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