SSA And Cerebellum Flashcards
What are the special visceral afferent (SVA) neurons??
Smell and taste
CN I
CN VII, IX, X
What are the special visceral efferent neurons?
Supply motor innervation to muscles of pharyngeal arch
CN V, VII, IX, X, and XII
What are the special somatic afferent (SSA) neurons??
Vision. Hearing and balance
CN II
CNVIII
The _________ retinae receives light from the peripheral visual fields. Do these axons cross at the optic chiasm?
Nasal ; yes
The __________ retinae receives light from the binocular vision field. Do these axons cross over at the optic chiasm?
Temporal; no
How do visual fields differ in predator and prey animals
Prey- eyes more laterally placed, have wide peripheral vision
Predator- eyes more rostral; overlapping visual field increase depth perception
What is the site where optic nerves cross?
Optic chiasm
Optic tracts synapse onto the __________________ of the thalamus
Lateral geniculate body
Neurons within the optic tract can project to where?
Thalamus -> (primary visual pathway) conscious
Midbrain-> unconscious
What is the primary visual pathway?
Nasal and temporal retina
Optic nerve
Optic chiasm -> nasal retinae cross over; temporal retinae remain ipsilateral
Optic tract
Lateral geniculate nucleus (thalamus)
Optic radiation (component of internal capsule)
Occipital cortex
Once in the visual cortex, where can visual information be directed?
Contralateral visual cortex via corpus callosum
Bilateral motor fortifies (frontoparietal)
Cerebellum via pons
Tectum/rostral colliculus
Tegmentum
Nuclei of crainial nerves III, IV, VI via rostral colliculus
What is the pathway of the menace response?
Primary motor pathway to occipital lobe -> motor cortex via internal capsule -> pons and cerebellum -> facial nuclei -> facial nerve-> orbcularis oculi m.
A small percentage of optic tracts for unconscious reflex travel and synapse at what two nuceli?
Pretectal nuceli (at junction of midbrain and thalamus)
Rostral colliculi (tectal nuceli)
In pupillary light reflex and visual accommodation, what nuceli does the optic tract synapse to?
Pretectal nuceli
In somatic motor responses of the eye what nuclei does the optic tract synapse to?
Rostral colliculi (tectal nuclei)
What is the pathway for pupillary contraction?
Optic nerve -> optic chiasm -> optic tract -> pretectal nuclei (ipsilateral and contralateral) ->PSNS oculomotor nucleus -> oculomotor nerve -> ciliary ganglion -> constrictor muscle
What is the pathway of pupillary dilation ?
Optic nerve -> optic chiasm -> optic tract -> rostral colliculus nuclei -> descend in lateral horn (sympathetic =throacolumbar) -> cervical sympathetic chain -> crainal cervical ganglion -> dilator muscle
Tectobulbar axons and tectospinal axons both arise from the rostral colliculus. What cranial nerves do each of these axon tracts influence ?
Tectobulbar –> eye movement
CN III, IV, and VI
Tectospinal –> head movement
CN XI
Circadian rhythms us the ___________ pathway. Stimulated by dark/night the pineal gland releases _____________
Retinohypothalmic; melatonin
Pineal gland is sympathetic innervated -> must descend to thoracic level and ascend back to the superficial cervical ganglion before stimulating the pineal gland
What stimulates the cochlear afferent neuron?
Movement of stapes at vestibular window > displace perilymph -> defect cochlear hairs (mechanoreceptor ) -> cochlear neurons
Where are the cell bodies of the cochlear neuron (SSA) located>
Spinal ganglia
What is the conscious auditory pathway?
Cochlear nerve -> spiral ganglia -> cochlear nuceli (medulla) -> caudal colliculus -> medial geniculate nucleus (thalamus) -> internal capsule -> auditory cortex
The hearing reflex pathway goes through what nuclei to what tract?
Caudal colliculus -> tectospinal tract –> motor neurons
A reflex elicited by a sudden onset of tactile, vestibular, or acoustic stimuli that exceeds a certain intensity threshold
Startle reflex
In a startle reflex, descending pathways of the tectospinal tract causes?
Flexion of almost all skeletal muscle
What type of hearing loss results because of damage to structures of external or middle ear preventing conduction of sound waves to the internal ear?
Conductive hearing loss
What type of hearing loss results due to damage of structures of the inner ear preventing stimulation of electrical impulses or due to damaged central nuclei/pathways
Sensorineural
Organ that senses balance and acceleration and aids in maintaining stable orientation relative to gravity
Vestibular organ
What motor pathways does the vestibular organ influences
Position of eyes, neck, trunk, and limbs relative to movement of head
What are the vestibular organs?
Maculae (utricli and sacculi) Cristae ampulares (semicircular canals)
Where are the cell bodes of the vestibular organs (SSA) located?
Vestibular ganglia
What are the three vestibular pathways?
Ascending medial longitudinal fasciculus (brainstem) -> control eye movement
Vesibulospinal tract -> cerebellum to adjust posture and balance
Thalamocortical pathway -> thalamus -> cortex for conscious perception of balance
What is the overall effect of stimulation of the vestibular organ?
Goes to vestibular nuclei -> spinal cord ->
Ipsilateral : inhibit flexors and stimulate extensor
Contralateral: inhibit extensor
Prevents falling
A lesion the the left vestibular organ/pathway will make the animal feel like there is movement to the _________________ side. To compensate, the animal will move their poster and balance to the ________ side.
Right (away from lesion) ;left (toward lesion)
LEFT lesion: feel right, go left
The _____________reflex produces neck and forelimb movement that counteracts the tilt of the head
Vesibulocollic
A lesion to the RIGHT vestibulocollic pathway causes the animal to feel movement toward the ___________ side. The animal will counteract this by tiling the head to the __________
Left; Right
RIGHT lesion: feel left, go right
Describe the vestibule-ocular reflex
Eye maintains a fixed position while the head moves
Head movement toward any side will stimulate vestibular organ on that side -> both eyes move in opposite direction to maintain position (compensatory) -> eyes rapidly move in same direction as head rotation for new focus point
What is physiological nystagmus?
Normal movement of the eyes in response to head movement
First in opposite direction (slow phase) followed by fast phase movement toward direction of head turn
Rapid movement of the eyes when the head is not moving or when the body changes position
Resting/positional nystagmus
NOT normal -> vestibular problems
Slow phase followed by fast phase
In a peripheral vestibular disorder, the fast phase nystagmus is (toward/away) the side of the lesion and the slow phase it (toward/away) the side of lesion ?
In a peripheral vestibular disorder, the fast phase nystagmus is AWAY from the side of the lesion and the slow phase it TOWARD the side of lesion
What nystagmus can be present with disorders of the central vestibular system?
Horizontal, vertical, or rotary
Peripheral vestibular disorders– only horizontal or rotary
A peripheral disorder of the vestibular system can be a lesion in the ?
Vestibular receptors
A central vestibular disorder can result from lesions in the ?
Vestibular ganglion
CN VIII
Vestibular nuclei
Excessive stimulation of the vestibular system to the ______ center causes nausea
Emetic center
Eg motion sickness
The cerebellum is made up of a __________, located between right and left hemispheres
Vermis
What is located on the ventral cerebellum and is the major pathway of communication with he vestibular nuclei?
Flocculonodular lobe
What is the main function of the cerebellum>?
Determine rate, range and force of movements
Does NOT initiate movement –> frontal lobes job
Afferents project to the cerebellum cortex and cerebellar nuclei via what tracts?
Cerebellar peduncles
What 4 afferent pathways can project to the cerebellum
General proprioception (spinocerebellar)
Special proprioception (vesibulocerebellar)
Special somatic (tectocerebellar)
UMN (extrapyramidal)
Efferent from the cerebellum can project through the cerebellar peduncles to what three nuclei?
Vestibular nuceli (spinal cord- vesibulospinal tract)
Reticular formation (cerebral cortex)
Extrapyramidal nuceli (motor cortex)
The _____________ cerebellar peduncles communicates from the spinal cord to the cerebellum containing mostly primarily afferent neurons
Caudal
The ___________ cerebellar peduncle is a tract from the pons to the cerebellum containing entirely afferent fibers
Middle
The ________ cerebellar peduncle is a tract from the cerebellum to the mesencephalon (midbrain) containing mainly efferent fibers
Rostral
On the brainstem, the cerebellar peduncles are found in what order from medial to lateral?
Rostral, caudal, middle
___________ species have early cerebellum development and can get up soon after birth
Precocial
______________ species have a longer development of the cerebellum and develop their motor skills, coordinator, and senses later
Altricial
Cerebellar disease causes?
Inadequate/inappropriate motor response
Incoordination
What are the three types of ataxia?
Cerebellar
Proprioceptive
Vestibular
Cerebellar ataxia has what signs
Dysmetria -inability to judge distance or force
Hypermetria -overmeasurement of gait
Burst effect of movement because it is delayed and exaggerated response
Wide-based stance, intention tremors, truncal sway, delay onset of menace response
Cerebellar ataxia can be due to lesions where?
Cerebellar cortex
Cerebellar peduncles
Cerebellar nuclei
