Vestibular System Flashcards
(31 cards)
ReviewWhy is visual acuity greater at the fovea?
The fovea is the focal point where the lens focuses the images. Visual acuity is greater here because there are higher amounts of cones, a 1:1 ratio (each photorecetor is associated with a single bipolar cell), and light does not have to pass through the layers of cells before reaching the photoreceptors within the fovea.
Less diffraction of light equals…?
Greater visual acuity
How does each eye contribute to depth perception and “making the picture whole”?
Eyes have two inputs, which cross and create depth perception. Each eye contributes a different part of the visual field.
Where is the first level of visual processing in the brain and influences how we feel?
The LGN (thalamus)
What is cortical blindness?
Lesions to the primary visual cortex
What is visual agnosia?
Damage to more anterior cortex such as the posterior occipital and/or temporal lobes
What are cortical receptive fields?
Receptive fields that respond best when the stimulus is of a certain shape with a given orientation and/or moved in a given direction.
What is orientation selectivity?
This is expressed by cells within the visual cortex, when such cells increase impulse or signal activity for specific oriented degree of shape-presented within the visual field.
What is direction selectivity?
When a neuron fires action potentials in response to moving bar of light
What is parallel processing?
Perception combines individual identified properties of visual objects, achieved by simultaneous, parallel processing of several visual pathways.
What is a good example of parallel processing?
The sound produced by an orchestra of visual areas rather than the end product of an assembly line
What is an afterimage?
An afterimage is a type of optical illusion in which an image continues to appear briefly even after exposure to the actual image has ended
What are positive afterimages?
Images that retain the colors of the original stimulus
What are negative afterimages?
Images that have their colors in reverse
What are conditions that favor the production of afterimages?
Brief exposures to intense or very bright stimuli in dark conditions, prolonged exposures to colored stimuli in well-lighted conditions
What does the vestibular system control?
Balance, equilibrium, posture, head, body, eye movement
What do the semicircular canals control?
Head rotation by the use of hair cells, like auditory system, to detect changes
What is going on within the semicircular canals as the head rotates?
There is a push-pull activation as the fluid within the canals moves around.
Why does disorientation happen in the clouds?
Vestibular and visual systems disagree.
What do the otolith organs do?
Detect changes in head angle and linear acceleration (and gravity)
If otoliths are displaced, what might happen?
They activate hair cells within the semicircular canals and can make it to where the patient feels extreme vertigo and their quality of life significantly decreases.
Where are utricles placed? Where are saccules placed?
They are linear to measure acceleration in the horizontal plane.
On the vertical plane
What does the vestibulo-ocular reflex do?
Senses rotations of head, commands compensatory movement of eyes in opposite direction and stabilizes image on retina during head movement
What is Meniere’s Disease?
There is a lot of swelling in the inner ear which causes episodes of vertigo, ringing in the ears (tinnitus), feeling of fullness or pressure, fluctuating hearing loss
