![]() When the superior oblique muscle contracts alone, it causes the eye to torque inward and inferiorly. This muscle's action is unique due to its attachment. The muscle that receives its motor innervation from the trochlear nerve is the superior oblique muscle. The trochlear nerve also contributes to the motor function of the eyes, but it only innervates one muscle that attaches to the eyes. Lastly, the contraction of the ciliary muscle allows for the accommodation of the eyes. The action of the iris sphincter muscle is to constrict the pupils (miosis). The iris sphincter muscle is part of the autonomic nervous system, but specifically the parasympathetic nervous system. The levator palpebrae superioris muscle is responsible for elevating the eyelid during eye-opening. ![]() The inferior oblique muscle's role is unique because it causes torques the eye downward and laterally when it contracts. The inferior rectus muscle rotates the eye inferiorly when it contracts. The medial rectus muscle functions to adduct the eye. The action of the superior rectus muscle is to rotate the eye superiorly. The oculomotor nerve provides motor innervation to the superior rectus muscle, medial rectus muscle, inferior rectus muscle, inferior oblique muscle, levator palpebrae superioris muscle, ciliary muscle, and the sphincter muscle. The oculomotor nerve is responsible for innervating the major of the extraocular muscles of the eyes. Then the oculomotor nerve will constrict the pupils if the light is bright, and it will allow pupil dilation when light is dim. The optic nerve conducts the afferent impulse to the brain. The optic nerve also works in sync with the oculomotor nerve to change pupil size. The optic nerve then transmits this image into the cerebral cortex. The optic nerve senses the incoming light and image displayed on the retina. ![]() The function of the optic nerve is purely sensory in the eyes. Interestingly, the optic nerve arises from the optic disc in the eye then enters the brain as opposed to the other cranial nerve that originates in the brain and then exits peripherally. As for the trigeminal nerve, abducens nerve, and facial nerve, they originate from the pons. The oculomotor nerve and the trochlear nerve originate in the midbrain. The six cranial nerves are the optic nerve (CN II), oculomotor nerve (CN III), trochlear nerve (CN IV), trigeminal nerve (CN V), abducens nerve (CN VI), and facial nerve (CN VII). Six cranial nerves innervate motor, sensory, and autonomic structures in the eyes. These nerves work in sync to manifest movements, reflexes, and vision. The sensory and motor innervation of the eyes originate from six paired cranial nerves. Then, the light gets converted into an image in the brain. The eyes are responsible for detecting light that enters the eyes. The eyes are a set of sensory organs that play a crucial role in the visual system.
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