Autonomic control of pupillary size and accommodation - sphincter, radial, ciliary muscle
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Autonomic control of pupillary size
Autonomic control of pupillary size and accommodation - sphincter, radial, ciliary muscle
Three muscles involved:
Sphincter muscle (circular)==* in the middle ==* has M3 receptor for middle. =====* when contracts, it causes miosis (decrease pupil size)
Radial muscle ==* on the outside ==* has Alpha 1 receptor ==* outside for alpha ==* when contracts, it causes mydriasis (increase in pupil size.
Ciliary muscle has M3 receptor, when it contracts, it causes accommodation for near vision.
Muscarinic agonist: When you give a patient a muscarinic agonist you activate the sphincter muscle to cause it to contract, which leads to miosis. You also activate the M3 receptor on the ciliary muscle causing to contract ==* accommodation for near vision. (Miosis, accommodation)
Muscarinic antagonist: When you give a patient muscarinic antagonist, you block M3 receptor on both the sphincter muscle and the ciliary muscle. Blocking M3 on sphincter muscle causing it to unable to contract, the radial muscle will predominates and contracts more causing mydriasis (dilation of the pupil). Blocking the M3 on the ciliary muscle causing it to unable to contract, therefore, the patient is unable to accommodate for near vision which is also called cycloplegia. (Mydriasis, cycloplegia)
Alpha 1 agonist: If you give the patient an alpha 1 agonist, it will activate alpha 1 receptors on the radial muscle and causing it to contract. This leads to mydriasis (dilation of the pupil). Since the ciliary muscle doesn't have any alpha 1 receptor, it has no effect on accommodation. (Mydriasis, no cycloplegia)
To differentiate between mydriasis cause by alpha 1 agonist or muscarinic blocker (antimuscarinic), look to see if accommodation is affected. Since ciliary muscle has M3 receptor involved in accommodation, only antimuscarinic would block that pathway and cause cycloplegia. Whereas alpha 1 agonist does not.
I tried my best to explain these concepts to the best of my knowledge and made it as simple as possible. I hope that you might find them helpful while you are reviewing your materials for your steps! Good luck to you all!
======================
DISCLAIMER: THE AUTHOR DISCLAIMS ANY LIABILITY, LOSS, INJURY, OR DAMAGE INCURRED AS A CONSEQUENCE DIRECTLY OR INDIRECTLY OF THE USE AND APPLICATION OF ANY OF THE CONTENT AND MATERIAL CONTAINED IN THIS VIDEO. ALTHOUGH THE INFORMATION IN THIS VIDEO HAS BEEN CAREFULLY REVIEWED FOR CORRECTNESS, THE AUTHOR CANNOT ACCEPT ANY RESPONSIBILITY FOR ANY
ERRORS OR OMISSIONS THAT MAY BE MADE. THE AUTHOR MAKES NO WARRANTY. EXPRESS OR IMPLIED. AS TO THE COMPLETENESS, CURRENCY OR ACCURACY OF THE CONTENTS OF THIS VIDEO. THE INFORMATION CONTAINED IN THIS VIDEO SHOULD NOT BE CONSTRUED AS SPECIFIC INSTRUCTIONS FOR INDIVIDUAL PATIENTS, MANUFACTURER'S PRODUCT INFORMATION AND PACKAGE INSERTS SHOULD BE
REVIEWED FOR CURRENT INFORMATION. INCLUDING CONTRAINDICATIONS. DOSAGES. AND PRECAUTIONS.
©USMLEAID123. This is video is made and uploaded exclusively for USMLEAID123, any reuploading is prohibited and will be reported to Youtube as copyright infringement.
Three muscles involved:
Sphincter muscle (circular)==* in the middle ==* has M3 receptor for middle. =====* when contracts, it causes miosis (decrease pupil size)
Radial muscle ==* on the outside ==* has Alpha 1 receptor ==* outside for alpha ==* when contracts, it causes mydriasis (increase in pupil size.
Ciliary muscle has M3 receptor, when it contracts, it causes accommodation for near vision.
Muscarinic agonist: When you give a patient a muscarinic agonist you activate the sphincter muscle to cause it to contract, which leads to miosis. You also activate the M3 receptor on the ciliary muscle causing to contract ==* accommodation for near vision. (Miosis, accommodation)
Muscarinic antagonist: When you give a patient muscarinic antagonist, you block M3 receptor on both the sphincter muscle and the ciliary muscle. Blocking M3 on sphincter muscle causing it to unable to contract, the radial muscle will predominates and contracts more causing mydriasis (dilation of the pupil). Blocking the M3 on the ciliary muscle causing it to unable to contract, therefore, the patient is unable to accommodate for near vision which is also called cycloplegia. (Mydriasis, cycloplegia)
Alpha 1 agonist: If you give the patient an alpha 1 agonist, it will activate alpha 1 receptors on the radial muscle and causing it to contract. This leads to mydriasis (dilation of the pupil). Since the ciliary muscle doesn't have any alpha 1 receptor, it has no effect on accommodation. (Mydriasis, no cycloplegia)
To differentiate between mydriasis cause by alpha 1 agonist or muscarinic blocker (antimuscarinic), look to see if accommodation is affected. Since ciliary muscle has M3 receptor involved in accommodation, only antimuscarinic would block that pathway and cause cycloplegia. Whereas alpha 1 agonist does not.
I tried my best to explain these concepts to the best of my knowledge and made it as simple as possible. I hope that you might find them helpful while you are reviewing your materials for your steps! Good luck to you all!
======================
DISCLAIMER: THE AUTHOR DISCLAIMS ANY LIABILITY, LOSS, INJURY, OR DAMAGE INCURRED AS A CONSEQUENCE DIRECTLY OR INDIRECTLY OF THE USE AND APPLICATION OF ANY OF THE CONTENT AND MATERIAL CONTAINED IN THIS VIDEO. ALTHOUGH THE INFORMATION IN THIS VIDEO HAS BEEN CAREFULLY REVIEWED FOR CORRECTNESS, THE AUTHOR CANNOT ACCEPT ANY RESPONSIBILITY FOR ANY
ERRORS OR OMISSIONS THAT MAY BE MADE. THE AUTHOR MAKES NO WARRANTY. EXPRESS OR IMPLIED. AS TO THE COMPLETENESS, CURRENCY OR ACCURACY OF THE CONTENTS OF THIS VIDEO. THE INFORMATION CONTAINED IN THIS VIDEO SHOULD NOT BE CONSTRUED AS SPECIFIC INSTRUCTIONS FOR INDIVIDUAL PATIENTS, MANUFACTURER'S PRODUCT INFORMATION AND PACKAGE INSERTS SHOULD BE
REVIEWED FOR CURRENT INFORMATION. INCLUDING CONTRAINDICATIONS. DOSAGES. AND PRECAUTIONS.
©USMLEAID123. This is video is made and uploaded exclusively for USMLEAID123, any reuploading is prohibited and will be reported to Youtube as copyright infringement.
7 سال پیش
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