OAP2 Lecture 8&9 Nerve Supply to the Eye PDF

Nerve supply to the Eye Professor LIN School of Optometry 1 Review on previous lecture: release glutamate release glycine /GABA feedback i...

Nerve supply to the Eye Professor LIN School of Optometry 1 Review on previous lecture: release glutamate release glycine /GABA feedback inhibition RGC receptive field 2 Review on previous lecture: ON-center OFF-center OFF-surround ON-surround + + RGC receptive field 3 Review on previous lecture: 2 types of ganglion cells: response given by shining centre response goven by shining periphery ON-center OFF-center OFF-surround ON-surround minimal fire more line = light response? A.P.? duration on centre RGC receptive field 4 Review on previous lecture: determine by bipolar cells express 2 types of receptors excitatory or inhibitory Read: Linear receptove field RGC receptive field 5 Review on previous lecture: receptor field of this ganglion cell "area in which stimulation leads to response of a particular sensory neuron" RGC receptive field 6 Review on previous lecture: fovea: tiny dendritic tree tiny receptive field midget = small responsible for big area different pattern RGC receptive field 7 Objectives: v Understand sensory and motor pathways; v Describe the operation of cranial nerves (CN) that affect the eye: v Optic nerve (CN II); v Oculomotor nerve (CN III); v Trochlear nerve (CN IV); v Trigeminal nerve (CN V); v Abducens nerve (CN VI); v Facial nerve (CN VII). 8 Division of the nerve system: 1. Central nervous system (CNS): cerebrum, cerebellum, brainstem and spinal cord 2. Peripheral nervous system (PNS): spinal nerves and sensory ganglia, cranial nerves 3. Autonomic nervous system (ANS): sympathetic and parasympathetic divisions. Division of the nerve system: Division of the nerve system: Sensory and motor systems: 12 Sensory and motor systems: 13 Sensory and motor systems: 14 Sensory and motor systems: Afferent pathway Sensory cortex Motor cortex Efferent pathway 15 Sensory and motor systems: 16 Sensory and motor systems: 17 Cranial Nerves: these 6: ocular system 18 Cranial Nerves: The eyes are served by the following cranial nerves (CN) and their branches: v Optic nerve (CN II); v Trigeminal nerve (CN V: V1 and V2); v Ocular Motor Nerves: Ø Oculomotor nerve (CN III); Ø Trochlear nerve (CN IV); Ø Abducens nerve (CN VI). v Facial nerve (CN VII). 19 Cranial Nerves: optic nerve 20 Sensory and motor systems: lateral geniculate nucleus of thalamus 21 Cranial Nerves: optic nerve Ø Arises from the retina of the eye; Ø Functions solely by transferring visual information from the retina to the vision centers of the brain via electrical impulses. Ø The optic nerve transmits the special sensory information for sight. 22 Ocular Motor Nerves: III, IV and VI 23 Ocular Motor Nerves: III, IV and VI Ocular Motor Nerves: CNIII 25 Ocular Motor Nerves: CNIII 26 Ocular Motor Nerves: CNIII 27 Ocular Motor Nerves: CNIII 28 Ocular Motor Nerves: CNIV 29 Ocular Motor Nerves: CNIV 30 Ocular Motor Nerves: CNIV 31 Ocular Motor Nerves: CNIV v Trochlear nerve innervates the superior oblique muscle; v Primarily a motor nerve that directs the eyeball; v Signs: Diplopia (double vision), weakness in depression of adducted eye. 32 Ocular Motor Nerves: CNVI 33 Ocular Motor Nerves: CNVI 34 Ocular Motor Nerves: CNVI v Primarily a motor nerve innervating only one extraocular muscle, the lateral rectus muscle (abducts the eye; thus the name abducens); v Signs: inability to abduct the affected eye. 35 Ocular Motor Nerves: summary 36 Ocular Motor Nerves: summary 37 Cranial Nerves: CNIII 38 Cranial Nerves: CNIII Parasympathetic System tragerminal nerve connect to eye sympathetic system Ø Sphincter pupillae: the pupillary light reflex; 39 Ø Ciliary muscle: the accommodation reflex.  Cranial Nerves: CNIII Ciliospinal center; Intermediolateral cell column of T1; 40 Preganglionic fibers; Postganglionic fibers. Cranial Nerves: CNIII 41 Cranial Nerves: CNIII 42 Cranial Nerves: CNIII 43 Cranial Nerves: CNIII 44 Cranial Nerves: CNIII Retina ® optic nerve ® optic chiasma ® optic tract ® superior brachium ® pretectal nucleus ® ipsilateral visceral (E- W) nucleus (CN III) ® contralateral visceral (E-W) nucleus (C3) (consensual LR) ® Pupil constrict [direct (ipsi-) and consensual (contra-) PLR] 45 Cranial Nerves: CNIII Pupillary reflexes: v Changes in pupil diameter due to changes in retinal luminance, accommodation, emotion and pain; v A greater intensity of light causes the pupil to constrict (miosis), whereas a lower intensity of light causes the pupil to dilate (mydriasis) Miosis: Ø Direct light reflex – miosis in one eye which has the retinal luminance increase; Ø Consensual light reflex – simultaneous miosis in one eye since the retinal luminance increases in other eye; Ø Latency of miosis ~ 0.2 – 0.5 sec (inversely proportional to brightness); Ø Afferent and efferent pathways. 46 Cranial Nerves: CNIII Mydriasis: Ø Reduced retinal luminance cause pupil dilation Ø Afferent pathway – retina ® optic nerve ® optic chiasma ® optic tract ® superior brachium ® pretectal nucleus ® Interstitial nucleus ® superior cervical ganglion Ø Efferent pathway – superior cervical ganglion ® sympathetic pathway (via internal carotid plexus) ® orbital sympathetic system ® iris dilator Ø Pain will cause the mydriasis and eyelid retracted 47 Cranial Nerves: CNIII summary 48 Cranial Nerves: CNIII summary v The oculomotor nerve consists of two components with distinct functions: Ø Somatic motor (general somatic efferent); Ø Visceral motor (general visceral efferent). v The somatic motor component supplies all the extraocular muscles except superior oblique (trochlear) and lateral rectus (abducens), and also supplies the elevator of the upper eyelid; v The visceral motor component innervates the ciliary ganglion which controls the sphincter of pupil and the ciliary muscle which controls lens accomodation. v Signs: dilated pupil with ptosis (drooping of upper eyelid), eye is turned down and out. 49 Cranial Nerves: Trigeminal (V1) V1 V2 V3 50 Cranial Nerves: Trigeminal (V1) 51 Cranial Nerves: Trigeminal (V1) 52 Cranial Nerves: Trigeminal (V1) 53 Cranial Nerves: Trigeminal (V1) 54 Cranial Nerves: Trigeminal (V1) § Sympathetic fibers in the short ciliary nerves pass through the ciliary ganglion without forming synapses. 55 Cranial Nerves: Trigeminal (V1) v It carries sensory information from the face/scalp and sympathetic fibers for pupil dilation in the long ciliary branch of the nasociliary nerve; v Supplies branches to the cornea, ciliary body, and iris; to the lacrimal gland and conjunctiva; to the part of the mucous membrane of the nasal cavity; and to the skin of the eyelids, eyebrow, forehead and nose; v Before entering the orbit through superior orbital fissure, it divides into three branches: Ø Lacrimal, Ø Frontal; Ø Nasociliary. 56 Nerve supply to conjunctiva: Trigeminal nasociliary ophthalmic nerve nerve division long ciliary lacrimal frontal & nerves branch lacrimal maxillary branches sensory innervation division to bulbar sensory innervation conjunctiva from lateral side to the inferior palpebral superior palpebral infraorbital conjunctiva and that of conjunctiva and nerve the inferior fornix superior fornix conjunctiva sensory innervation from medial side to the inferior palpebral conjunctiva and that of the inferior fornix Cranial Nerves: Facial (VII) 58 Cranial Nerves: Facial (VII) 59 Cranial Nerves: Facial (VII) 60 Cranial Nerves: Facial (VII) Orbicularis oculi: v The orbicularis oculi is a muscle in the face that closes the eyelids. v The muscle acts to close the eye, and is the only muscle capable of doing so. v Loss of function for any reason results in an inability to close the eye, necessitating eye drops at the minimum to removal of the eye in extreme cases. 61 Cranial Nerves: Facial (VII) 62 Cranial Nerves: Facial (VII) Corrugator supercilii: v The corrugator supercilii is a small, narrow, pyramidal muscle close to the eye; v It is located at the medial end of the eyebrow, beneath the frontalis and just above orbicularis oculi muscle; v The corrugator draws the eyebrow downward and medially, producing the vertical wrinkles of the forehead; v It is the "frowning" muscle, and may be regarded as the principal muscle in the expression of suffering; v It also contracts to prevent high sun glare, pulling the eyebrows toward the bridge of the nose, making a roof over the area above the middle corner of the eye and typical forehead furrows. 63 Cranial Nerves: Facial (VII) 64 Cranial Nerves: Facial (VII) v Bell’s palsy: paralysis of facial muscles on affected side and loss of taste sensation; v Caused by herpes simplex I virus; v Lower eyelid droops; v Corner of mouth sags; v Tears drip continuously and eye cannot be completely closed (dry eye may occur); v Condition may disappear spontaneously without treatment. 65 Nerve supply to the cornea: Nerve supply to the cornea: Trigeminal Ophthalmic Nasociliary nerve nerve (V) division (V1) long ciliary Ciliary short nerves (70-80) ganglion ciliary nerves Oculomotor sensory Inferior innervation to nerve (III) division cornea  Any questions? 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