Visual and Auditory Systems Flashcards
What type of cells make up the pigment epithelium of the retina?
Single layer cuboidal cells
These cells contain pigment granules and play a role in the exchange of substances with photoreceptor neurons.
What do rods in the retina contain and what are they sensitive to?
Contain rhodopsin; sensitive to low light
Rods are more abundant in nocturnal animals.
What do cones in the retina contain and what is their function?
Contain iodopsin; responsible for day vision and color vision
Cones are essential for visual acuity in bright light.
What is the external limiting membrane in the retina?
Junctional complexes between photoreceptor neurons and supporting radial astrocytes
What does the external nuclear layer of the retina contain?
Nuclei of the bodies of photoreceptor cells
Cone nuclei are adjacent to the external limiting membrane, and rods constitute most of this layer.
Which layer of the retina contains axons and telodendria of photoreceptors?
External plexiform layer
What is the role of the internal nuclear layer in the retina?
Contains nuclei of bipolar neurons; connects photoreceptors to ganglionic neurons in the visual pathway
What are the components of the internal plexiform layer?
Axons and telodendria of bipolar neurons; axons and dendritic zones of ganglionic neurons
What do ganglion cells in the ganglion layer of the retina do?
Project via optic nerve to the brain
They are large multipolar neurons and have unmyelinated axons.
What characterizes the area centralis in the retina?
High resolving power; devoid of large blood vessels; increased cone to rod ratio
What is the optic disc?
Origin of optic nerve; degree of myelination varies
What happens at the optic chiasm?
Most axons from an optic nerve cross to enter the opposite optic tract
What is the pathway for conscious perception in the visual pathway?
Optic tract neurons terminate in the lateral geniculate nucleus; LGN axons project to the cerebral visual cortex
Where do optic tract neurons terminate in the PLR pathway?
Mesencephalic pretectal nucleus
What is the primary receptor in the auditory system?
Spiral organ (organ of Corti)
How do sound waves travel from the external ear to the cochlea?
Transmitted from air medium of external ear canal to tympanum and ossicles to perilymph in scala vestibuli
What does the cranial nerve VIII cochlear division consist of?
Axons from dendritic zone of hair cells course into the modiolus where cell bodies of spiral ganglion are located
What is the role of the cochlear nuclei?
Influence LMN in brainstem nuclei directly or indirectly through caudal colliculus
What is BAER testing used for?
To assess auditory pathway function
Different waves correspond to various structures in the auditory pathway.
What is conduction deafness?
Obstruction to passage of sound waves and mechanical energy created in ossicles; receptor is still functional
What is presbycusis?
Age-related deafness
Can involve both conduction and sensorineural components.
