40 Questions
What percentage of visual fibers terminate in the Lateral Geniculate Nucleus (LGN)?
90%
Which of the following is a characteristic of the optic nerve fibers?
1 million to 2.22 million fibers
What is the name of the structure where the optic tract carries fibers from the chiasm?
Lateral Geniculate Nucleus
Which segment of the optic nerve is characterized by an S-shaped movement around the sphenoid bone?
Intraorbital segment
What is the name of the condition that damages the optic nerve fibers?
Glaucoma
Which artery supplies the posterior radiations of the optic radiations?
Posterior cerebral artery
What is the pattern of fibers in the retina from the nasal side?
Radial fibers
Which part of the retina is responsible for the visual field defect in the event of damage to the afferent pathway?
Retina
What is the blood supply to the striate cortex?
Calcarine branch of the posterior cerebral artery
What is the primary function of astrocytes in the optic nerve?
To provide structural support and store glycogen
In the intracanalicular and intracranial segments of the optic nerve, what happens to the papillomacular bundle?
It migrates inward towards the core of the nerve
Which of the following vessels supplies blood to the optic nerve?
All of the above
What is the significance of the lamina cribrosa in the optic nerve?
It is the site of scleral perforations, allowing retinal fibers to pass through
What is the characteristic of retinal fibers as they pass through the scleral perforations of the lamina cribrosa?
They are unmyelinated but become myelinated later in the optic nerve
What is the correct sequence of events for retinal fibers in the optic nerve?
Unmyelination, then myelination, then transmission of visual signals
Which part of the visual pathway is responsible for receiving visual information from the nasal fibers of each eye?
Optic chiasm
What is the consequence of damage to the nasal fibers of the optic nerve?
Confrontation visual field defects
What is the term for the connective tissue that surrounds the central retinal vessels throughout its course in the optic nerve?
Perivascular connective tissue
What is the outermost layer of the meningeal sheaths surrounding the optic nerve?
Dura mater
Which part of the visual pathway is responsible for transmitting visual information to the primary visual cortex?
Optic radiations
What is the name of the space that contains cerebrospinal fluid and lies between the arachnoid and pia mater?
Subarachnoid space
What is the embryological origin of the optic nerve?
Neural ectoderm
What is the characteristic of the optic nerve fibers that are not myelinated?
They are unmyelinated only until birth
Which structure penetrates as far as the central retinal artery in the middle of the optic nerve?
Pial septae
What is the term for the arrangement of the myelinated nerve fascicles in the orbital portion of the optic nerve?
Fascicular pattern
What is the characteristic visual field defect associated with a lesion in the left parietal lobe?
Right homonymous inferior quadrantanopia
A lesion in the left optic tract can cause which of the following visual field defects?
Right homonymous hemianopia
What is the term for the visual field defect caused by pressure exerted on the optic chiasm by a pituitary tumor?
Bitemporal hemianopia
What is the term for the visual field defect caused by inflammation of the optic disk or optic nerve?
Central scotoma
What is the term for the visual field defect caused by a lesion in the left temporal lobe, affecting the optic radiation?
Right homonymous superior quadrantanopia
What is the primary function of the border tissue of Jacoby?
To separate the choroid from the optic nerve fibers
What is the significance of the spur of collagenous tissue in the optic nerve head?
It separates the anterior lamina cribrosa from the choroid
What is the characteristic of retinal fibers as they pass through the optic nerve head?
They are non-myelinated
What is the role of the intermediary tissue of Kuhnt in the optic nerve head?
It surrounds the optic nerve fibers and separates them from the retinal layers
What is the significance of the lamina cribrosa in the optic nerve head?
It is the site of scleral perforations through which retinal fibers pass
What is the characteristic of the marginal tissue of Elsching in the optic nerve head?
It is a ring of collagenous tissue
What is the significance of the astroglial membrane in the optic nerve head?
It forms a barrier between the optic nerve fibers and the retinal layers
What is the characteristic of the optic nerve fibers in the intracranial segment?
They are myelinated
What is the significance of the central meniscus of Kuhnt in the optic nerve head?
It separates the optic nerve fibers from the sclera
What is the characteristic of the retinal fibers in the optic nerve head?
They are non-myelinated
Study Notes
Visual Pathway
- The visual pathway consists of the series of cells and synapses that carry visual information from the environment to the brain for processing
- Includes: retina, optic nerve, optic chiasm, optic tract, Lateral Geniculate Nucleus (LGN), optic radiations, and primary visual cortex
Optic Nerve
- Carries visual information from the eye to the brain
- Divided into four segments: intraocular, intraorbital, intracanalicular, and intracranial
- The optic nerve head is the part of the optic nerve that leaves the eye and enters the optic chiasm
- Contain unmyelinated axons that become myelinated by oligodendrocytes in the optic nerve
Histology of the Optic Nerve Head
- The optic nerve head consists of the surface nerve fiber layer, the physiologic cup, and the lamina cribrosa region
- The three layers of meninges surrounding the nerve are clearly visible: dura, arachnoid, and pia mater
- Blood supply of the optic nerve includes branches from the central retinal artery, circle of Zinn-Haller, choroidal branches, and pial branches
Blood Supply to the Visual Pathway
- Optic radiations are supplied by the anterior choroidal artery and the middle cerebral artery
- Striate cortex is supplied by the calcarine branch of the posterior cerebral artery
- Visual cortex is supplied by the posterior cerebral artery
Fiber Orientation in the Retina
- Axons of the ganglion cells are arranged in three basic patterns: papillomacular bundle, superior and inferior temporal fibers, and radial fibers from the nasal retina
- In the optic disc, nasal fibers radiate directly to the nasal side, while the papillomacular bundle courses directly to the temporal side
Fiber Orientation in the Optic Chiasm
- Temporal fibers remain uncrossed
- Nasal fibers decussate (cross) to the opposite side of the brain
Embryological Development
- The optic nerve develops from the optic stalk by axons of the ganglion cells
- Myelination of the axons within the optic nerve begins shortly before birth and continues after birth
Test your knowledge of the visual pathway, from the optic tract to the visual cortex, and learn about the effects of glaucoma on optic nerve fibers. Explore the anatomy of the optic nerve and its role in visual processing.
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