Be ta 2 receptors on smooth muscle cells work through a G s m ec ha nis m tha t ac tiva tes ad en ylyl cyclas e. T his pr odu ces 3',5'cyc lic AM P. T he c AM P ac tivates PK A tha t

A) Releases Ca₂+ from the S R th roug h IP
B) Releases Ca₂+ from the SR through RyR receptors and Increases force by activat ing MLCK
C) Depolarizes the membrane, leading to Ca₂+ entry by the voltage-gated Ca chan ne l, and Increases force by activat ing MLCK
D) Phosphorylates protein phosphatase and relaxes the smooth muscle by dephosphorylating the m yos in lig ht c ha in
E) Phosphorylates phospholamban, reducing [Ca₂+] and relaxing the smooth muscle by reduc ing M LCK activity