CN 2: Optic Nerve (Scheme, Pathway, Lesions) | Neuroanatomy

Content:
Introduction: 0:00
Optic Nerve Scheme: 01:02
Eye Anatomy: 03:18
Retina: 04:47
Visual Field: 07:48
Course of the Visual Pathway: 09:47
Visual Pathway Collaterals: 16:33
Olfactory Pathway 09:27
Clinical Relevance: 18:36
Recap: 21:21
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Visual Pathway Scheme / Overview:
- Visual Stimuli - 1st 2nd and 3rd order neurons in retina - Optic Nerve - Half fibers cross the optic chiasma - Optic Tract - Lateral Geniculate Body - Primary Visual Cortex
Eye Anatomy:
- Cornea
- Anterior Chamber
- Pupil
- Iris
- Lens
- Posterior Chamber
- Ciliary Muscles
- Sclera
- Choroid
- Retina
- Optic Disc
- Vitreous Humor
- Hyaloid Canal
Retina:
- 1st order neurons: Rods and Cones
- 2nd order neurons: Bipolar cells
- 3rd order neurons: Ganglion cells
Olfactory Neuron:
- Dendrites detect smell through a g-protein couples membrane receptor.
- Signals pass through the cell body and axon
- Axons form nerve bundles (fila olfactoria)
Visual Fields:
- Fovea: Highest acuity of vision
- Retina is split into temporal half and the retinal half
- Medial fibers go to contralateral side
- Lateral fibers go to ipsilateral side
Course of the Visual Pathway:
- 1st neuron: Rods and Cones
- 2nd neurons: Bipolar cells
- 3rd neurons: Ganglion cells
- Optic Nerve (nervus opticus)
- Optic Chiasma (chiasma opticum)
- Optic Tract (tractus opticus)
- 4th order neuron lateral geniculate bodies
- Optic Radiations (radiato optica) and Meyer's Loop
- Primary Visual Cortex (area 17)
Visual Pathway Collaterals:
- Accomodation reflecx
- Direct and consensual light reflex
- Saccadic eye movement
- Tectospinal tract (for reflectory movements according to unexpected visual irritation)
- Medial Longitudinal fasciculus
Clinical Relevance:
- Lesion in optic nerve: complete blindness of affected side
- Lesion in optic chiasma: Visual field Bitemporal hemianopia
- Lesion in optic tract and geniculate body: Homonymous hemianopia
- Lesion in Optic Radiation: Quadrantanopia
- Lesion in the visual cortex causes cortical blindness: Homonymous hemianopias with or without macular involvement
Sources:
- Singh, I. (2017). Human neuroanatomy (10th ed.). Helwany M, Bordoni B. Neuroanatomy, Cranial Nerve 1 (Olfactory) [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-
- Kozlowski, T. (2017). Memorix Anatomy: The Complete Study Guide. 2nd ed. Thieme Medical Publishers.

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[@geno5169]

I lost my optic nerve at age of 47! I’m limited with prefer! Can’t read menus or see things on self’s! I wish there was a cure

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[@FY-rc7hh]

Hi My mom lost her peripheral eye sight in her left eye in just one night. She wakes up in the morning and can see almost nothing to the left, can see some things in front, and a bit better to the right. Her right eye's pherifiral and streight vision are ok. But in your video, if I understand you right, you say that damage to the optic nerve affects BOTH EYES. What did then happen to her left eye? Can it be brain damage on the right side of her brain? Maybe she did have a stroke? But she did not have other symptoms related to strokes. She only had very high blood pressure before the eye sight loss. Please answer my question. Thanks