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Integrated Control of the Cardiovascular System
Chapter 24
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Integrated Control of the Cardiovascular System
Chapter 24
• CO = SV x HR
• SV = EDV – ESV
• EDV (Pre Load):
• Filling Pressure is determined by rate of venous return
• Muscle Pump and Thoracic pump aid venous return• Heart Rate; SA node
• SNS increases and PSN decreases, Epi of ß1 increases
• Threshold depolarized and Maximum hyperpolarized by PSN
• Slope is Decreases by PSN and Increased by SNS
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• MAP = CO x TPR• Closed system so increasing CO decreases Filling Pressure and visa versa (Red line)
• TPR: Vasoconstriction will increases TPR while Vasodilatation will decreases TPR
• Baroreceptor monitors and regulates MAP
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• Orthostasis, living in Gravity
• Orthostatic Hypotension (OH)
• Myogenic response minimizes OH
• Blood will pool in lower body
• SNS stimulation decreases the dispensability (compliance) of the lower body veins to minimize the pooling of blood
• Muscle Pump prevents pooling
• 1 cm of water is about 1 mmHg pressure
• Standing: capillary pressure in the feet can be at least 100 mmHg an cause fluid movement into the interstitial space, feet swell
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• Fight or Flight Response
• Response from Higher Centers through the ANS
• SNS alfa1, vasoconstriction
• Dogs only
• ß2
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• Vagovagal Syncope, Heart Stops Momentarily
• Increase output of PSN and decrease of SNS
Lower Pressure
• AVP (ADH) increases
• Blood levels high enough to stimulate the V1 receptor of the vascular smooth muscle to constrict
• Explains why after the syncope episode the person may be flushed and pallor, no blood flow to the shin.
• Greatest Stimulus for ADH release• Blood osmolality less of a stimulus but it is the most common regulator
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• Exercise
• Higher brain levels initiate ANS
• Activated immediately on movement
• SNS initially causes constriction of the arterioles in muscle (Alfa1) but this is quickly over ridden by local metabolic control and epinephrine stimulating the ß2 adrenergic receptor
• Exercise Hyperthermia
• Reset in Hypothalamus
• Increase MAP, 120 mmHg
• Reset baroreceptor reflex
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• Set point is increased to about 120 mmHg
• Exercising Muscle Effects
• During exercise TPR decreases
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• Hemorrhage, Reversible• Thirst and Na+ appetite (low pressure receptors)• ADH (Low pressure baroreceptors)• ANP (right atria)• Transcapillary Refilling
• Lower Capillary Pressure
• ADH and AVP are the same
• Hemorrhage greatest stimulus for release
• V1 receptor of vascular smooth muscle, not very sensitive, need > 100 pM, vasoconstrictor
• V2 receptor in kidney, very sensitive, < 15 pM, save water
• Irreversible
• Low AVP
• High NO
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• Transcapillary Refilling
• Low capillary pressure permits High capillary Colloid Osmotic Pressure (25 mmHg) to pull interstitial fluid into blood
• Interstitial fluid is replaced with cellular fluid