ciliary muscle innervation, B2?

[AxiomaticTruth]

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All of my sources say that the ciliary muscle controlling lens shape is only innervated by parasympathetic M3 receptors which contracts it... except for First Aid which says that B2 receptors control relaxation of the ciliary muscles. What gives?

 

[walakin25]

ciliary muscle is innervated by parasympathetic m3 receptors. this makes sense since cycloplegia (or paralysis of ciliary muscles = loss of accomodation) is caused by a drug like atropine, a muscarinic antagonist. B2 innervation is only to the ciliary body which produces aqueous humor hence the role of Timolol in glaucoma.

 

[AxiomaticTruth]

ciliary muscle is innervated by parasympathetic m3 receptors. this makes sense since cycloplegia (or paralysis of ciliary muscles = loss of accomodation) is caused by a drug like atropine, a muscarinic antagonist. B2 innervation is only to the ciliary body which produces aqueous humor hence the role of Timolol in glaucoma.

Right, which is why I'm confused why FA has B2 innervation to the ciliary muscle. This is in both 2016 and 2015.

 

[walakin25]

where in 2015 does it say this?

 

[AxiomaticTruth]

p. 248 (pharmacology) under B2 (ciliary muscle relaxation)

 

[walakin25]

hopefully @Transposony can help, TIA.

 

[Transposony]

Ciliary muscle does indeed have beta receptors (beta 2 > beta 1) and can causes relaxation (mydriasis - dilation).
However, their effect on ciliary muscles is insignificant since they are not innervated (just like M3 on vascular).
In contrast, M3 receptors ( and alpha 1 ) are innervated and thus have major effect on ciliary muscles.