APK 2105C Lecture Notes - Lecture 35: Adrenal Medulla, Bradykinin Receptor B2, Posterior Pituitary
16 Jun 2018
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Chapter 14, Lecture 6
Vessels & Blood Pressure
• Extrinsic control of BP: arteriolar radius
o Redistribution works only when simultaneous extrinsic mechanisms maintain an
adequate perfusion pressure
o Flow = pressure gradient / resistance
o MAP = CO x TPR
▪ Arranged this way will help us look at extrinsic control more
• Sympathetic control of arteriolar radius
o Sympathetic nerves release NE (norepinephrine)
▪ Catecholamine
▪ Alpha-receptors in arteriolar smooth muscle
• Vasoconstriction
o Adrenal medulla releases epinephrine in blood
▪ B2 receptors = located on arteriolar smooth muscles that are feeding
heart and skeletal muscle
• Vasodilation
▪ Alpha = located on all arteriolar smooth muscle
• Vasoconstriction
• Hormonal control of arteriolar radius
o Vasoconstriction
▪ Vasopressin (ADH)
• Released from neurohypophysis (posterior pituitary)
• Anti-diuresis
o Impacts kidneys to keep water—higher blood volume—
increased BP
▪ Angiotensin II
• Plasma protein
• Derived from another plasma protein (angiotensinogen from liver)
• Very powerful pressor effect
• Capillary anatomy is well-suited for exchange
o 2 types of capillaries
▪ Continuous
• Majority of capillaries
• Narrow intercellular gap (or cleft)
• Loose CT holding capillary to organ its serving
• Basement membrane
• Tight junctions in these capillaries are leaky
▪ Fenestrated
• Wide intercellular gap between the cells
o WBCs can go through
• Fenestrations = pores through the side of the cell
• Seen in areas where large molecule needs to be exchanged
• Seen where fast exchange is needed
▪ Discontinuous
• Bone marrow
• Spleen
• Local control of BF through capillary beds
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