Practical 6 Flashcards
Vision and audition (26 cards)
What is the function of the optic nerve?
Carries visual information from the retina to the brain; composed of retinal ganglion cell axons.
What is the optic chiasm and why is it important?
The X-shaped structure where nasal retinal axons decussate; ensures each hemisphere processes the contralateral visual field.
What is the optic tract?
Carries visual signals from the optic chiasm to the lateral geniculate nucleus (LGN).
What is the lateral geniculate nucleus (LGN)?
A thalamic relay for vision; receives input from the optic tract and projects to V1.
What is the superior brachium?
A fibre bundle carrying auditory signals from the superior colliculus to the LGN.
What are optic radiations?
White matter tracts that carry visual information from the LGN to the primary visual cortex (V1).
Where is the primary visual cortex (V1) located?
On both banks of the calcarine sulcus in the occipital lobe.
What is the Stria of Gennari?
A band of myelinated fibers in V1; defines the striate cortex.
What are the two types of photoreceptors and their functions?
- Rods: peripheral vision, low light sensitivity.
- Cones: central vision, high acuity, color detection.
What are three special features of the fovea?
High cone density, absence of rods and blood vessels, displaced ganglion cells for direct light access.
What is the function of the retinal pigment epithelium?
Absorbs unabsorbed light to prevent scattering and improve visual clarity.
What is the function of the dorsal and ventral visual streams?
- Dorsal (‘where’): motion and spatial processing.
- Ventral (‘what’): object recognition and color.
What is partial decussation at the optic chiasm?
Only nasal retinal axons cross; temporal axons remain ipsilateral.
Why is partial decussation important?
Ensures that visual information from the same visual field is processed in the same hemisphere.
What visual deficit results from a lesion at the midline of the optic chiasm?
Bitemporal hemianopia (loss of peripheral vision in both eyes).
What happens with a lesion in the right optic tract?
Left homonymous hemianopia (loss of left visual field in both eyes).
What is the effect of a lesion in the left superior colliculus?
Impaired reflexive eye movements and visual attention on the right.
What happens with damage to the left calcarine sulcus?
Right visual field loss (right homonymous hemianopia).
Where does the auditory pathway begin?
In the cochlea, where sound activates inner hair cells.
What is the function of the vestibulocochlear nerve (CN VIII)?
Carries auditory and vestibular information from the inner ear to the brainstem.
What are the cochlear nuclei and where are they located?
Dorsal and ventral nuclei in the brainstem that receive input from the cochlear nerve.
What is the inferior colliculus and its role in audition?
A midbrain structure that acts as a major relay in the ascending auditory pathway.
What is the medial geniculate nucleus (MGN)?
A thalamic relay for auditory information; receives input from the inferior colliculus and projects to A1.
What is the inferior brachium?
A fibre bundle carrying auditory signals from the inferior colliculus to the MGN.
