The cytoskeleton provides support in a cell. It is a network of protein fibers supporting cell shape and anchoring organelles within the cell. The three main structural components of the cytoskeleton are microtubules (formed by tubulins) , microfilaments (formed be actins) and intermediate filaments.
epinephrine binds to beta 2 receptors to relax airway smooth muscle and relaxes larger arteries to supply more blood to metabolizing tissues What is theophylline? an inhibitor of phosphodiesterase so it will potentiate the effect of epinephrine and inhibit cAMP breakdown to relax smooth muscle
Beta-blockers are drugs that bind to beta-adrenoceptors and thereby block the binding of norepinephrine and epinephrine to these receptors. This inhibits normal sympathetic effects that act through these receptors. Therefore, beta-blockers are sympatholytic drugs. Some beta-blockers, when they bind to the beta-adrenoceptor, partially activate the receptor while preventing norepinephrine from binding to the receptor. These partial agonists therefore provide some background of sympathetic activity while preventing normal and enhanced sympathetic activity.