Lecture 4 – Regulation of Blood Pressure

Lecture 4 – Regulation of Blood Pressure -...

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LECTURE 4 – Regulation of Blood Pressure Merrill’s Personal Experience: o more experience measuring BP in experimental animals – less experience measuring BP in humans o recently changed physicians and stopped going to previous one because of carelessness of hiring medical assistants who weren’t careful in measuring bp current personal physician took systems phys and a former RU student graduate o Merrill’s Mother visited from another part of country tried to find her antihypertensive medication but she forgot to bring it so Merrill measured her pressure for a few days to make sure and during those testings, for many days, he never found any pressures that were hypertensive, but found multiple pressures that were normal tensive, and several pressures that were hypotensive thus, they gave her medication for high blood pressure when in reality, she had bp that was either too low or normal Overview: Regulation of Blood Pressure In Mammals o physical and physiological influences on blood pressure o local (metabolic) control of blood flow vs remote (central) control of pressure o the baroreceptor mechanism and systemic arterial pressure Arterial Volume and compliance effects on pressure o 2 direct variables that affect blood pressures directly: arterial blood volume arterial compliance Both affected indirectly by: o blood flow o resistance to blood flow o Synonym for compliance: elasticity stretchability distense ability o Cardiac output : blood flow to the entire systemic circulatory system same principle applies to any other organ o peripheral resistance : generic term that applies to systemic circulation at large Slide 1 Slide 2
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Arterial blood volume and compliance: o in mammals, blood volume = 8% body mass (mean about 5L) if one weighs 175lbs, divide that by 2.2 ( 2.2 lbs = 1 kg) = 82- 83 kg 83 kg = 8300 g, 8% of 8300 g = 6.3 L of blood in circulation o Blood volume can change : subtly blood is 90% water dehydration and hydration precipitously and rapidly (e.g. gradual dehydration, hemorrhagic shock/hypovolemia) example : in a traumatic situation, you lose a lot of blood o compliance : flexibility relates volume and pressures veins more compliant than the arteries large vena cava (superior and inferior) are more compliant than corresponding aorta o vessel compliance can and does change with age (hypertension) part of the reason of hypertension someone can have hypertensity under one condition and normal tensity under other conditions could be reason why Merrill’s Mother was misdiagnosed with having high BP seeing white coat and doctors office can make you nervous, making bp higher emotions can affect blood pressure body position, angle at which the blood pressure was measured wrong cuff sizes **human error is most common cause of incorrect blood pressure—mistakes can be made o one of reasons why malpractice increase –
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Lecture 4 – Regulation of Blood Pressure -...

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