Visual System Flashcards
Structure: Focuses light on the fovea within the macula
Lens
Structure: Changes the shape of the lens
Ciliary muscle
Structure: Dilates/constricts pupil
Iris
Structure: Location where the arteries and veins enter/exit the eye
Optic disc
Structure: Important for peripheral, low light vision, provides gray scale
Rods
Structure: Located in the peripheral retina
Rods
Structure: Important for central vision and visual acuity, bright ligh vision, provides color
Cones
Structure: Most located in the fovea
Cones
Describe the how rods and cones effect your functionality
Cones: in daylight provide much greater spatial sensitivity in the central retina, however can’t perceive color in our periphery/in low light due to low cone density in the peripheral retina
Rods: In low light we are much more sensitive in our peripheral vision, however in daylight we have poor visual acuity in our periphery
Describe phototransduction
Photopigments in photoreceptors absrob light resulting in change in photoreceptors membrane potential. Information is transmitted to ganglion cells which transmit AP through the optic n. to the brain
Light energy is transformed into neural energy before reaching the ganglion cells
Visual area: Nasal receptors in the eye receive information from
Peripheral visual fields
Visual area: Temporal receptors in the eye receive information from
Central visual fields
Structure: Receptors that cross in the optic chiasm
Nasal receptors in the eye
Structure: Receptors that remain on the same side
Temporal receptors in the eye
Describe where the left hemifield information ends up
In the right cortex
Structure: Connections from CN nuclei to the primary visual cortex
Optic radiations
Describe where information from the superior and inferior optic radiation are coming from
Superior optic radiations carry information from the inferior visual field
Inferior optic radiations carry infromation from the superior visual field
Describe the difference between the pupillary and consensual reflex
They are both elicited by the same stimulus: light in one eye
Pupillary reflex constricts the pupil in the eye that is directly stimulated
Consensual reflex constricts the pupil in the opposite eye
Pathway: Afferent limb of the pupillary/consensual reflex
Retinogeniculocalcarine pathway
Describe what can be differentiated between the pupillary reflex and accomodation reflex
Pupillary occurs in the brainstem and is unconscious
Accomodation occurs in the cortex and is conscious
Allows you to differentiate between the location of the problem
Cortical area: Controls voluntary eye movement and requires planning
Frontal eye fields
Cortical area: Provides information about the movement of visual objects
Occipital and temporal eye fields
Cortical area: Provides spatial information for eye movements
Posterior parietal cortex
2 Objectives of the Visual System
- Keeping the position of hte eyes stable during head movements so that the environment does not appear to bounce (maintain stable gaze)
- Directing gaze at visual targets
Describe how maintaining a stable gaze is achieved
By the VOR: using information from head motion to keep eyes still
By the optokinetic reflex: using visual information to keep eyes still
Describe how directing your gaze at visual targets is achieved
- Saccades (fast movements to switch gaze)
- Smooth pursuit (slow movements following a moving object)
- Di/Convergence (movement toward/away from midline)
Describe the function of the MLF
The medial longitudinal fasciculus connects several nuclei/axons (oculomotor, trochlear, abducens, vestibular, accessory) in order to coordinate head and eye movement
