Term
Optic nerve - ganglion axon bundles
optic chiasm - cross bridge for optic nerve canal
optic tract - following optic chiasm where nerves split off and talk to both sides of the brain
Lateral geniculate nucleus - blue dot where most optical nerves go from optic tract
Hypothalamus - where the regulation of circadian rhythms (Diurnal), just below chiasm at the top |
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Definition
Pretectum - reflex control of the pupil and lens (Pupil)
Superior Colliculus - Controls the movement of the head and eyes (Eye movements)
Optic radiation - nerve fibers immanating from the LGN that connect to the striate cortex that enables us to percieve vision and see things.
Striate Cortex - Controls the visual perception |
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Term
Visual stimuli arounds us affects the |
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Definition
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Term
The Direct Neuron Chain follows this sequence: |
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Definition
photoreceptors – bipolar cells – ganglion cells. |
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Term
This chapter 12 talks about the path from the ganglion cells to the _____________. |
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Definition
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Term
Information supplied by retina:
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Definition
1) stimulates more conventional reflexes such as the
pupil of the eye.
2) regulates homeostatic behaviors that are tied to the
day/night cycle.
3) directs eyes to targets of interest.
4) leads to conscious perception of the visual scene. |
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Term
Principle pathway for visual perception is from the |
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Definition
retina to dorsal lateral geniculate nucleus (in the thalamus) and then on to primary visual cortex
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Term
Ganglion cell axons exit the retina through the circular
region in its nasal part called the _________ |
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Definition
optic disk (or optic papilla) – bundle together to form the optic nerve. |
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Term
Visual system - complex neural circuitry - optic nerve over ______ nerve fibers. |
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Definition
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Term
The region has no _________, is insensitive to _______,
and produces the _______. |
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Definition
photoreceptors, light, blind spot |
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Term
Optic disk or optic papilla is easily recognized as a ________
region using an ophthalmoscope. |
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Definition
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Term
Also recognized as the site from which the ophthalmic _____ and ______ enter (or leave) the eye. |
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Definition
artery (enter), veins (leave) |
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Term
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Definition
Macular lutea - Area of focus/vision
Fovea - Area of sharpest focus, dot in middle of macular lutea
Optic disk (papilla) - Where all nerve axons exit, blind spot
Branch of opthalmis vein - Where bloods leaves eye, goes through optic disk
Branch of othalmic artery - Where blood enters the eye, goes through optic disk |
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Term
1. Axons in the optic nerve run a straight course to the _______.
2. ______ cross while ______ continue to the thalamus
and midbrain targets on the same side.
3. Once past the chiasm – ganglion cell axons on each side form the optic _______.
4. Thus the optic tract, unlike the optic nerve contains fibers from _______ eyes.
5. ________ allows information from _______ eyes to be processed by the _______ . |
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Definition
1. optic chiasm
2. 60%, 40%
3. tract
4. both
5. Partial crossing, both, brain
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Term
4 main pathways that the optic tract projects to:
• Lateral _______ nucleus
• ___________
• __________ colliculus
• ____________
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Definition
geniculate
Pretectum
Superior
Hypothalamus |
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Term
1. Major target (in the diencephalon and midbrain) is the
dorsal lateral geniculate nucleus (LGN) of the thalamus.
2. Neurons in LGN send their axons to the cerebral cortex via the internal capsule.
3. Terminate in primary visual or striate cortex.
Eye LGN Cortex
Retinogeniculostriate pathway |
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Definition
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Term
Diurnal Variations
Retinal ganglion cells also go to the suprachiasmatic nucleus of the hypothalamus
The retinohypothalamic pathway is the route by which
variations in light influence visceral functions that are entrained to the day/night cycle.
Ganglion cells that innervate the hypothalamus are important sensing light variation – not for acuity, color, motion.
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Definition
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Term
Pupil Reflexes
Major target of the ganglion cell axons is a collection of
neurons that lie in a region known as the
pretectum
Pretectum is the coordinating center for the
pupillary light reflex. (This is the reduction in the diameter of the pupil when light falls on the retina).
Clinicians use this reflex to examine the integrity of the
visual sensory apparatus, motor outflow to pupilary muscles, and central pathways mediating the reflex.
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Definition
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Term
Figure 12.2 Circuitry responsible for the pupillary light reflex
Afferents from both eyes activate Edinger-Westphal nuclei.
Efferent projections go to the ciliary ganglion.
Thus, afferents from one eye can cause pupillary responses in both eyes.
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Definition
| check image page 13 Chp 12 Part 1 |
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Term
Shining light on the eye leads to an increase in activity of the pretectal neurons, which stimulate Edinger-Westphal neurons, and cause the pupillary constrictor muscles to
contract. Slide 14 image with text
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Definition
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Term
Eye-Head Movements
Retinal ganglion cells also go to the superior colliculus
that coordinates eye-head movements which we will focus on in detail in the latter part of the course.
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Definition
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Term
| Review image slide 16 Chp 12 Part 1 |
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Definition
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Term
Points in B fall on the nasal retina of the left eye and
temporal retina of right eye.
Points in C fall on the nasal retina of the right eye and
temporal retina of left eye.
Temporal retina do not cross over at optic chiasm.
Nasal ganglion neurons cross at the optic chiasm.
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Definition
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Term
The Retinotopic Representation of the Visual Field
Left half of the visual scene represented in right
side of brain.
Right half of the visual scene represented in left
side of brain.
Does not matter which eye, but depends on which side of the visual scene.
How might this redundancy help?
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Definition
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Term
Visual Cortex Representation
Map in the lateral geniculate nucleus is maintained in the
visual cortex.
Fovea is most posterior part in visual cortex.
Peripheral regions of the retina anterior.
Upper visual field is below the calcarine sulcus
Lower visual field above calcarine sulcus
Macula is very large, occupying most of the caudal pole of the occipital lobe.
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Definition
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Term
Figure 12.5 Visuotopic organization of the striate cortex in the right occipital lobe
What does the representation of the macula in striate cortex remind you of?
ion channel/gates... check out slide 20
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Definition
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Term
LGN to Visual Cortex
Optic radiation axons carrying information from superior portion of the visual field sweep around the lateral horn of the ventricle in the temporal lobe.
Axons carrying information about the inferior portion of the visual field travel in the parietal lobe.
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Definition
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Term
| Check out brain image slide 22 |
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Definition
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Term
Figure 12.6 Visual field deficits resulting from damage along the primary visual pathway
(A) Loss in right eye.
(B) Bitemporal hemianopsia.
(C) Left homonymous hemianopsia.
(D) Left superior quadrantanopsia.
(E) Left homonymous hemianopsia with macular sparing.
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Definition
| Match with image on slide 23 |
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Term
Visual Field Deficits
• Relatively large visual field deficits are called anopsias.
• Smaller visual field deficits are called scotomas.
• Damage to the retina or optic nerve before the optic chiasm indicates damage to the eye of origin.
• Damage to the regions central to the optic chiasm will result in deficits in the visual field.
• Damage to the optic chiasm itself results in damage to non-overlapping parts of the visual field.
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Definition
Play Animation of Chapter 12
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