Neuroanatomy 5: Visual and Auditory Pathways Flashcards
Which CN is involved in hearing?
CN VIII - Cochlear nerve
What route is taken by the cochlear nerve to reach the thalamus?
ECOLI Cochlear nerve (EIGHTH CN) --> Cochlear nucleus (C) --> Superior olivary nucleus (O)--> (LATERAL LEMNISCUS) Inferior collicus (I) --> Medial geniculate body (in thalamus)
A unilateral hearing problem is typically an issue with the cochlea. True/ False?
False
Typically, a brainstem issue
Superior to cochlear nuclei, some fibres are crossed and some are not = bilateral input
What are the auditory ossicles of the middle ear?
Malleus, incus and stapes
What is contained within the organ of corti in the cochlea?
Inner and outer hair cells
What is the role of the spiral ganglion within the cochlea?
Bipolar neurones that are stimulated by hair cells and carry action potentials from organ of corti to cochlear nuclei in pons
Where is the primary auditory cortex in the brain - in terms of lobes and fissures?
Temporal lobe
Close to lateral fissure
What area of the auditory cortex do low frequency fibres end, versus high frequency fibres?
Anterolateral
Posteromedial
What is the function of the superior olivary nucleus and lateral lemniscus in hearing?
Sound localization and relays info for stapedial and tensor tympani reflexes
What is aphasia? Which side of the brain is dominant for language?
Inability to use language
Left predominantly
What would we expect to happen if there was damage to Broca’s area? Where is Broca’s area?
MOTOR/ EXPRESSIVE APHASIA
Difficulty in producing language - typically few words/ most important (‘broken’)
Frontal lobe
What would we expect to happen if there was damage to Wernicke’s area? Where is Wernicke’s area?
SENSORY/ RECEPTIVE APHASIA
Difficulty comprehending language - words out of order/ meaningless words
Temporal lobe
Which CN is involved in balance?
CNVIII - vestibular nerve
Which part of the inner ear is involved in balance?
3 semicircular canals
What are the main connections of vestibular nuclei?
Thalamus
Nuclei of CN III, IV, VI (Eye control)
Cerebellum (flocculonodular lobe)
Spinal cord
There is no ‘vestibular cortex’, where does the projection of vestibular information typically converge?
Parietal cortex/ posterior to postcentral gyrus that represents hand and mouth)
Anterior to primary auditory cortex
Posterior insular cortex
What part of the thalamus is involved in processing visual information?
Lateral geniculate nucleus
Each optic tract, LGN, optic radiation and visual cortex deals with visual information from the contralateral/unilateral field.
Contralateral
What is the role of the superior cocculi in vision?
Recieve inputs and outputs to nuclei of CN III, IV, VI and motor nucleus of VII and spinal cord
Mostly involved in ‘automatic vision’
Where is the primary visual cortex located in the brain - in terms of lobes and fissures?
Occipital lobe
Above and below the calcarine sulcus
Which visual field is projected to gyrus superior to the calcarine sulcus?
Lower visual field
Upper projects to inferior
Which pole of the cortex does the macula project to?
Posterior pole (occupies large proportion)
What is Meyer’s loop?
Fibres of geniculocalcarine tract that form part of the internal capsule
Visual information from upper half of field first loop anteriorly around temporal part of lateral ventricle
What type of eye movement is the visual cortex involved in?
Movements in response to visual stimuli (tracking moving objects) - SMOOTH
What type of eye movement is the frontal eye fields involved in?
Movements of command (no moving visual stimuli) - JUMPY
In the consensual light reflex, what is the mechanism behind the constriction of the contralateral pupil?
Pretectal fibres project bilaterally to EW nucleus
In the accommodation reflex, what receives inputs from the visual cortex?
Oculomotor nerve
EW nucleus
What is the route for sympathetic nerve supply to the eye?
T1 sympathetic trunk ganglion ---> Superior cervical sympathetic ganglion ---> Internal carotid plexus ---> Ciliary ganglion ---> Short ciliary nerve
Why is the macula spared in occipital lobe lesions affecting vision?
There is dual blood supply from posterior and anterior cerebral arteries
Where are the medial and lateral olives located?
Two small ovals on the medulla
