MUSCLE PHYSIOLOGY

Detailed explanation-1: -Like other adrenergic agonists, they cause smooth muscle relaxation. 2 adrenergic agonists’ effects on smooth muscle cause dilation of bronchial passages, vasodilation in muscle and liver, relaxation of uterine muscle, and release of insulin.

Detailed explanation-2: --Adrenergic-receptor agonists work to arrest uterine contractions by binding 2-adrenergic receptors on the myometrial cell (Figure 19.1). This interaction leads to increased levels of cyclic AMP which activates protein kinase.

Detailed explanation-3: -Human airway smooth muscle contains only beta 2-receptors which, when stimulated, stimulate a rise in intracellular cAMP and activation of PKA (protein kinase A), which in turn phosphorylates several cellular proteins, resulting in relaxation.

Detailed explanation-4: -Both adrenergic receptor subclasses have been shown to mediate the contractile response of the uterus upon catecholamine stimulation: alpha-adrenergic receptors cause uterine contraction while beta-adrenergic receptors induce relaxation.