Question

3- Please explain the action of adrenergic alpha 1 receptor, and adrenergic beta 2 receptor.

Answer 1

3.)  adrenergic alpha 1 receptor,

alpha1-receptors primarily mediate smooth muscle contraction, but have important functions elsewhere as well. Both epinephrine and norepinephrine activates the alpha -1 receptors.When the alpha receptor is stimulated by epinephrine or norepinephrine, the arteries constrict.(vasoconstriction)This increases the blood pressure and the blood flow returning to the heart. The blood vessels in skeletal muscle do not have alpha receptors, Activation of these receptors by sympathetic nervous system transmission or drugs will result in vasoconstriction and an increase in peripheral resistance and systemic arterial blood pressure.

beta 2 receptor is the dominant regulatory receptor in vascular and non vascular smooth muscle, these receptors are activated by epinephrine,  Activation of the beta2 receptor leads to vascular and nonvascular smooth muscle relaxation.The beta 2 receptors are located in the bronchioles of the lungs and the arteries of the skeletal muscles. When these receptors are stimulated, they increase the diameter of the bronchioles(vasodilation) to let more air in and out during breathing and they dilate the vessels of the skeletal muscles so they can receive the increased blood flow, this is the reason drugs that activate the beta2 receptor can be used to treat as asthma by relaxing airway smooth muscle and premature labor by relaxing uterine smooth muscle.