-
Physiology
Structure and Function4 Topics - Lymphatics and Edema Formation
- The Microcirculation
- Vascular Control3 Topics
- The Cardiac Cycle
- Determinants of Myocardial Performance7 Topics
- Neuro-Control of Heart and Vasculature4 Topics
- Electro-Mechanical Association4 Topics
- Electrical Side of the Heart4 Topics
- PathophysiologyDefining Heart Failure
- Causes of Heart Failure
- MVO2 and Heart Failure
- Cardiac Output and Heart Failure7 Topics
- Compensation for Circulatory Failure
- Vascular Tone in Heart Failure
Lesson Progress
0% Complete
How do Alpha receptors work?
- Alpha receptors mainly function on the vascular smooth muscle wall and are mainly stimulated by norepinephrine.
- Principally we are concerned with Alpha 1 receptors.
- Alpha 2 receptors are presynaptic inhibiting norepinephrine release from the nerve terminal promoting vasodilation and postsynaptic promoting vasoconstriction.
- Alpha 1 receptor activation on vascular smooth muscle activates a G protein which itself activates phospholipase C (PLC)PLC splits phosphatidylinositol into inositol triphosphate (IP3) and diacylglycerol (DAG)IP3 promotes the release of Ca from the SR secondary to Ca induced Ca release
- The increase in cytosolic Ca binds to the protein calmodulin.
- The Ca-calmodulin complex activates myosin light chain kinase, which enables the interaction of actin and myosin.
- DAG activates a protein kinase C that promotes/augments contraction
- In addition to activating the phosphatidylinositol system, Alpha 1 receptor activation directly opens the Ca channel to promote vasoconstriction.
