Unit 2_Special Senses: Vision Flashcards
What system do the following control:
Focus images on back of retina (fovea; where rods and cones are located)
Adjust dark/light intensity
Color detection
Shape and movement detection
Localize visual stimuli
Functions of the Visual System
What structure in the eye includes the socket, contains eyeball, blood vessels, nerves, and fractures can cause visual disturbance?
Orbit
What muscles under control of vestibular system and brainstem keep eye fixated on target?
Extraocular muscles
What structure protects eyes, includes Orbicularis oculi (closes eyelid - CN VII), Levator palpebrae superioris (opens eyelid - CN III), smooth muscle Sympathetic Nervous System (SNS) also opens eye?
Eyelid
What disease is caused by an injury to Orbicularis oculi (closes eyelid-CN VII) or a lesion of the nerve or facial motor nucleus in pons?
Bell’s Palsy
What disease is caused by an injury to Levator palpebrae superioris (opens eyelid-CN III) or a
lesion CN III or oculomotor nucleus in midbrain?
Ptosis
What structure is needed for tears, innervated by CN VII and a lesion CN VII or lacrimal nucleus in pons (Bell’s Palsy) inability to tear (dry eye)?
Lacrimal Glands
What structure of the eyeball is the bump on eye that helps with light refraction and focusing image, acts as a protective mechanism (blink reflex in response to touch), includes sensory innervation by CN V and reflex-CNV and CNVII?
Lesion either CNV or CNVII or facial motor nucleus in pons will impair blink reflex to touch.
Cornea
What structure of the eyeball includes the pupil (hole), constricts and dilates in response to light,
controlled by Para- & Sympathetic nerves, Para-constricts CNIII from Edinger Westphal nucleus in the midbrain, sympathetic nervous system stimulation causes dilation?
Iris
What structure of the eyeball is an extension of anterior wall of orbit, includes smooth muscles attach to lens (contracts and changes shape of lens), includes ciliary muscles – innervated by E-W nucleus in midbrain CNIII, helps with focusing on close objects?
Ciliary Body
What structure of the eyeball sits in retina and includes 2 kinds: Rods and Cones?
Photoreceptor
What kind of photoreceptor is the following:
-highly sensitive to light for night vision
-no color vision
-does not help with visual acuity
Rods
What kind of photoreceptor is the following:
-for colors and visual acuity
-low sensitivity to light
Cones
What is the point of entry of the optic nerve on the retina, insensitive to light?
The blind spot
What visual field includes the following:
Nasal retina from left eye
Temporal retina from right eye
Left Visual Field
What visual field includes the following:
Nasal retina from right eye
Temporal retina from left eye
Right Visual Field
What pathway do the following steps describe:
- Photo Receptors (Retina)
2 Ganglion cells - Optic Nerve (Axons of ganglion cells)
4 Optic Chiasm (Nasal retina crosses here) - Optic Tract
- Lateral Geniculate Nucleus (synapse, cells of origin of optic radiation)
- Optic radiation (part of Internal Capsule)
- Primary Visual Cortex-occipital lobe, calcarine sulcus, Posterior Cerebral Artery (PCA)
Pathway from Retina to Cerebral Cortex for Vision
What do axons of ganglion cells form?
Optic Nerve (CN II)
What does the main visual pathway to occipital cortex involve?
Lateral Geniculate Nucleus (LGN) of the thalamus
What does the main auditory pathway to Temporal Lobe involve?
medial geniculate nucleus (MGN)
What are the following terminations related to?
- Visual Association Cortex (Posterior Cerebral Artery)
- Object agnosias (problems recognizing objects)
- Prosopagnosias (inability to recognize faces) - Limbic System (Emotional response to light; seasonal affective disorder)
- CN VII (blink response to light and also from touch)
- Superior Colliculus which gives rise to tectospinal pathway
- Hypothalamus (Circadian rhythms)
- Superior Colliculus, Pretectum & E-W Nucleus (Pupillary light reflex)
- Superior Colliculus (Visual discrimination and integration with somatosensory and auditory input to help orient eyes)
Optic pathway terminations
What is a rapid movement of the eye between fixation points?
According to Kandel et al., 2012 “The gaze system stabilizes the image of an object on the retina when the object moves in the world or the head moves and keeps the eyes still when the image remains stationary”
Saccades
What coordinate eye movements with input from the Frontal Eye Fields, Vestibular system and auditory system?
Brainstem structures and cranial nerve nuclei
What act to maintain conjugate eye movement?
Paramedian pontine reticular formation (PPRF) and the CN nuclei
What clinical implication results when a person cannot focus well on near objects but can see fine at a distance?
Hypermetropia (farsighted)
What clinical implication results when a person cannot focus well on far objects but can see near objects very well?
Myopia (nearsighted)
What clinical implication results when a person experiences a reduction in visual acuity due to aging in which individuals have trouble focusing on near objects?
Presbyopia
What clinical implication is an age-induced painless production of a fibrous protein that clouds the lens reducing vision in the eye?
Cataracts
What clinical implication is due to an increase in intra-ocular pressure which damages the retina-early sign is tunnel vision?
Glaucoma
What retina picks up light coming from the periphery?
Nasal retina
What type of tract is the optic radiation tract?
Association Tract / Fibers
What issue in the Visual Association Cortex (Posterior Cerebral Artery) may a patient have that causes problems recognizing objects?
Object agnosias
What issue in the Visual Association Cortex (Posterior Cerebral Artery) may a patient have that causes the inability to recognize faces?
Prosopagnosias
What will give patients emotional response to light; seasonal affective disorder?
Limbic System
What CN gives rise to blink response to light and also from touch?
CN VII
What gives rise to tectospinal pathway?
Superior Colliculus
What gives rise to Circadian rhythms?
Hypothalamus
What gives rise to Pupillary light reflex?
Superior Colliculus, Pretectum & E-W Nucleus
What gives rise to Visual discrimination and integration with somatosensory and auditory input to help orient eyes?
Superior Colliculus
What happens if we cannot maintain eye fixation with head movements?
Patient will have to correct vision
What is the nucleus inside the pons that is going to be involved with the reflex and integration of our different cranial nerves that control eye movement: Oculomotor nerve (CN III), Trochlear nerve (CN IV), Abducens nerve (CNVI).
Paramedian pontine reticular formation (PPRF)
If nuclei or cranial nerves are damaged in this area, we can begin to lose conjugate eye movement?
Pons
