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BIOL1412 03 07 2014.docx

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Department
Biological Sciences
Course
BIOL 1412
Professor
Paul Messing
Semester
Winter

Description
BIOL1412 03 07 2014 2) Extrinsic Regulation:  external control by NS and Endo. a. neuronal regulation (SNS)  arteriolar vasoconstriction (except in brain ­ intrinsic regulation only)  vasodilation due to ⇓ SNS signals (only important PSNS effect = dilation) of arterioles off  penis/clitoris  also vasoconstriction (vein constriction) b. hormonal regulation i. epinephrine  vasoconstriction ­ skin, viscera ­ reinforces SNS  vasodilation ­ heart, skeletal muscle, liver ­ opposes SNS ii. other hormones  angiostensin II, ADH ­ vasoconstriction  histamine ­ vasodilation Blood Pressure (bp)  = hydrostatic P exerted by blood on wall of vessel (clinically on the walls of the arteries) ­ results when F is opposed by R  Systolic Pressure = produced by ventricular contraction against vascular resistance  Diastolic Pressure = produced by elastic arteries against vascular resistance (when ventricle are relaxed)  What we measure in an artery: 120/80 = systolic/diastolic pressure  Pulse Pressure = systolic ­ diastolic  Mean Arterial Pressure = regulated by the body ie. what the body measures  = average blood P through cardiac cycle BUT diastole is longer than systole, so:  MAP = diast. P + 1/3 Pulse Pressure  MAP regulation:  F = ?P/R ∴ ?P F x R ?P  =  F  x  R MAP  =             Cardiac Outputx           Total Peripheral                  (HR x SV)                            (Resistance (TPR)                                                                                            ( = resistance in all arterioles)  ?P = MAP ­ venous P (P in veins ~0 ∴ ?P = MAP) (Fig. 19.6)  MAP is regulated by controlling 1) Cardiac Output 2) TPR (arteriolar radius) 3) Blood Volume (affects venous return ∴ SV; also MAP directly)  Extrinsic regulation MAP: 1) Neural Control: a. Baroreceptor Reflexes ­ short term changes eg. standing →  stretch receptors ­ monitor MAP in:  carotid sinus (brain bp)  aortic arch (systemic bp) ⇑ MAP ⇑ Baroreceptor impulses medulla ⇓ SNS impulses                                                            ⇑ PSNS impulses ① ⇓ epi. secretion          ⇓ CO ② ⇓ vasoconstriction (⇓ TPR) (Fig. 19.9)
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