Autonomic Nervous System and Eye

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Questions and Answers

What type of receptor is present in the radial dilator pupillae muscle?

M3 receptor

α1 receptor (correct)

β2 receptor

β1 receptor

Which of the following muscles receives parasympathetic supply and has M3 receptor?

Radial dilator pupillae muscle

Circular sphincter pupillae muscle (correct)

Ciliary muscle (correct)

All of the above

What is the effect of α1 receptor stimulation in the radial dilator pupillae muscle?

Mydriasis (correct)

Miosis

Accommodation

Increased intraocular pressure

Which of the following is NOT a layer of the eye?

Retinal pigment epithelium Signup and view all the answers

What is the function of the ciliary muscle?

Accommodation Signup and view all the answers

Which of the following receptors is present in the ciliary epithelium?

β2 receptor Signup and view all the answers

Which type of receptor is involved in the contraction of radial dilator pupillae muscles?

α1 Signup and view all the answers

What is the effect of parasympathomimetic drugs on pupil size?

Decrease pupil size Signup and view all the answers

Which of the following is responsible for the light reflex?

Sphincter circular pupillae muscle Signup and view all the answers

What is the effect of sympatholytic drugs on pupil size?

Decrease pupil size Signup and view all the answers

What is the nerve responsible for the afferent pathway of the corneal reflex?

Trigeminal nerve Signup and view all the answers

What is the effect of parasympatholytic drugs on the light reflex?

Loss of light reflex Signup and view all the answers

Which of the following can cause loss of corneal reflex?

All of the above Signup and view all the answers

What is the most common symptom of Myasthenia Gravis?

Skeletal muscle weakness Signup and view all the answers

What is the effect of sympathomimetic drugs on pupil size?

Increase pupil size Signup and view all the answers

What is the target of the autoimmune attack in Myasthenia Gravis?

Nicotinic acetylcholine postsynaptic receptors Signup and view all the answers

What is the effect of epinephrine on the eye?

Mydriasis Signup and view all the answers

Which of the following is an indication for glaucoma surgery?

Progressive glaucoma Signup and view all the answers

What is the effect of choline esters like carbachol?

Lacrimation and salivation Signup and view all the answers

What should be avoided in an asthmatic patient?

Epinephrine Signup and view all the answers

What is the effect of pilocarpine on the eye?

Miosis Signup and view all the answers

What is the demographic most commonly affected by Myasthenia Gravis?

All of the above Signup and view all the answers

Study Notes

Autonomic Nervous System and Eye

The eye receives both sympathetic and parasympathetic innervation, which affects many characteristics of the eye.
The eye consists of three layers: outer fibrous coat (cornea and sclera), middle pigmented layer (uveal tract: iris, ciliary body, and choroid), and inner nervous layer (retina).

Eye Structure

Iris muscles consist of:
- Radial (dilator pupillae) muscles
- Circular (constrictor pupillae) muscles
Ciliary body consists of:
- Muscle (accommodation)
- Epithelium (aqueous humor, intraocular pressure)

Autonomic Receptors in Eye

Cholinergic (M3) receptors are present in:
- Circular sphincter pupillae muscle
- Ciliary muscle
- Lacrimal gland
Adrenergic receptors:
- Alpha 1 (α1) receptors are present in radial dilator pupillae muscle
- Beta 2 (β2) receptors are present in ciliary epithelium

Effect of Autonomic Drugs on Eye

Pupil size is controlled by smooth muscles of iris:
- Radial dilator pupillae muscles (sympathetic, α1) increase size (mydriasis)
- Sphincter circular pupillae muscles (parasympathetic, M3) decrease size (miosis)
Pharmacology of pupil size:
- Parasympathomimetic (muscarinic agonist): Active miosis
- Parasympatholytic (muscarinic antagonist): Passive mydriasis
- Sympathomimetic (αlpha agonist): Active mydriasis
- Sympatholytic (αlpha antagonist): Passive miosis

Light Reflex

Physiology:
- When shining light is directed to one eye, it causes miosis of both eyes
- Sphincter circular pupillae muscle (parasympathetic, M3) is responsible for light reflex
Pharmacology:
- Parasympathomimetic (muscarinic agonist): Intact light reflex
- Parasympatholytic (muscarinic antagonist): Loss of light reflex
- Sympathomimetic (αlpha agonist): Intact light reflex
- Sympatholytic (αlpha antagonist): Intact light reflex

Corneal (Blinking) Reflex

Physiology:
- Stimulation of cornea (foreign body) causes blinking or closure of both eyelids
- Afferent (ophthalmic division of trigeminal nerve) → CNS → efferent (facial nerve) → eyelid muscle
Pharmacology:
- Parasympathomimetic (muscarinic agonist): Intact corneal reflex
- Parasympatholytic (muscarinic antagonist): Intact corneal reflex
- Sympathomimetic (αlpha agonist): Intact corneal reflex
- Sympatholytic (αlpha antagonist): Intact corneal reflex

Glaucoma

Primary open-angle glaucoma:
- Unusual features: physical obstruction of the angle of the anterior chamber of the eye
- Indications for glaucoma surgery: progressive glaucoma
Avoid timolol in asthmatic patients

Myasthenia Gravis

Definition: an acquired, autoimmune disorder caused by an antibody-mediated blockade of neuromuscular transmission resulting in skeletal muscle weakness and rapid muscle fatigue
Prevalence: affects both men and women, and occurs across all racial and ethnic groups, with a higher impact on young adult women (under 40) and older men (over 60)