Lectures 81 - 83 Flashcards
A ___________ is a localizable region of the nervous system that is dysfunctional ordamaged
lesion
A lesion can be________________________
unilateral or bilateral
what is the first step in a general neuro exam?
Onset: What was the initial abnormality (problem) observed by the owner?
what is the 2nd step in a general neuro exam?
Duration: what was the abnormality initially observed?
What is the 3rd step in a general neuro exam?
Progression: how has the character of the problem or the patient’s condition changed since the problem was initially identified
What is the final step in a general neuro exam?
Disease course: Acute, chronic, progressive or nonprogressive, continuous etc.
what is EAD
Exam at a distance: patient observed for abnormalities
what will you look at for EAD
Mental status/ behavior, posture/gait, muscle tone, size and symmetry, eyes, function(eating, drinking, defecation, resp, ambulation)
What could effect a gait?
° Toxins affected Ach
° CNS
° Lesion
° UMN/LMN damage
what would you say to describe mental status?
WNL, obtunded, stuporous, comatose, seizuring, inappropriate/abnormal other
What do you need to make sure you look at during an EAD
Ocular exam
What do you need to look for during an EAD ocular exam
• Strabismus
• Nystagmus
• Enophthalmos
• Exophthalmos
• Ptosis
• Blepharospasm
• Lagophthalmus
• Elevated
• Mydriasis
• Miosis
• Anisocoria
what is strabismus
non-alignment of the eye
what is nystagmus
involuntary eye deviations
what is Enophthalmos?
posterior displacementof globe
what is exopthalmos
anterior displacementof globe
what is ptosis
drooping of upper eyelid
what is blepharospasm
twitching eyelid
what is lagophtalmus?
eyelids can’t close
what is mydriasis?
Pupil dilated
what is miosis
pupil constricted
what is anisocoria?
unequal pupil size
what nerve is affected in B, D and C?
B: paralysis of the oculomotor nerve
D: paralysis of the trochlear neurons CN 111, Oculomotor nerve, trochlear nerve, abducent nerve
C: Paralysis of abducens neurons
what are you looking at to check posture?
head tilt, tremors, hunched back, stance
Pupillary Light Reflex ________________ pupil size (constriction) -reduces the amount of light that enters the eye. Retina,Optic Nerve, Chiasm & Tracts and Midbrain
Decreases
Pupillary light response: Optic tract contains a mixture of ___________________ fibers
‘PLR’ and ‘vision’
‘PLR’ fibers (20%) go to _____________________ and move to rostralcolliculus (bypass the LGN
midbrain pretectal nucleus
‘PLR’ fibers (20%) go to midbrain pretectal nucleus and move to ?
rostral colliculus (bypass the LGN
80% of vision fibers go where?
To LGN in the thalamus
Where is the AP generated during rapid adaptation to changing light conditions?
retina
The light during PLR travel through CN2 continue both?
optic tracts
Rapid adaptation to changing light conditions: AP generated in retina travel through CN2 continue both optic tracts go to thalamus to ________________________
LGN and enter pretectal area in midbrain
Rapid adaptation to changing light conditions: Where do synapses occur for PLR?
protectal area in midbrain (LGN)
Rapid adaptation to changing light conditions: Synapses of PLR occur in LGN and pretectal neurons cross to caudal commissure and synapse onto?
° GVE
° PSNS
° LMNs
Rapid adaptation to changing light conditions: Synapses of PLR occur in LGN and pretectal neurons cross to caudal commissure and synapse onto GVE PSNS LMNs in ?
contralateral oculomotor nucleus ofmidbrain
Synapses of PLR occur in LGN and pretectal neurons cross to caudal commissure and synapse onto GVE PSNS LMNs in contralateral oculomotor nucleus of midbrain. What happens next?
Constrict pupillary muscles in iris
Smaller number neurons project to ipsilateral oculomotor nucleus - - the light results in ___________________
consensual response
PLR: Direct light to eye evaluate direct and __________________________
consensual response
PLR: because midbrain decussation at commissure,______________________ receives greater PNS stimulation
CN 2 on ipsilateral side
PLR: Lesions restricted to visual pathways in cerebrum can cause ____________ but PLR intact
blindness
If there is a lesion and the OS menace response is present but OD menace response is absent where is the lesion?
Right optic nerve
If there is a lesion and the OS menace is present and the OD menace is present but the OD pupil is completely dilated where is the lesion?
Right cranial nerve
PLR is a polysynaptic reflex meaning it has more than
2 neurons
where are photoreceptors located
Retinal ganglion cell
what is the PLR process?
Retinal ganglion cell- optic nerve-optic chiasm-optic tract- LGN (midbrain)- pretectal nucleus- edinger-westphal nucleus- ciliary ganglion- short ciliary nerve and finally sphincter pupillae
Pretectal nucleus controls PSNS which controls
pupillary constriction via ciliary ganglion
Why can a blind animal still have a positive PLR?
Light gets to pretectal nucleus and controls ciliary ganglion
Initiates compensating eye movement to keep vision fixed when head turns
Vestibulo-ocular Reflex
equilibrium
the sense of motion, body orientation, and balance
hearing and auditory system: Both transduced n inner eye
Vestibulocochlear nerve
PLR: what should you expect to see
direct response (eye with light constricts) and intact neural pathway (consensual response: other eye constricts)
Where is the receptor for balance and posture?
in fluid-filled lumen comprising labyrinth in petrous portion of temporal bone
Large vestibule with three ________________________-(anterior, posterior,lateral); right angle orientation
semi-circular canals
Dilations are called?
Ampullae
Inner ear: connective tissue tubes within bony labyrinth
Membranous labyrinth
Bony labyrinths contain _____________
Perilymph (ECF/CSF)
Semicircular canals contain _________________
endolymph (similar to ICF, high in K+)
What cranial nerve is associated with PLR PSNS to cause the constriction
CN III Oculomotor
Rotation of the head around any plane causes endolymph to __________________
‘flow”(displacement)
SNS controls __________
dilation
At one end of each CC duct lies the ampulla - ____________________
contains crista, lined with columnar neuroepithelial cells
On surface of crista is cupula (contains ‘hair cells and _____________”)
KINOCILIUM
Auditory: Filaments extend into the cupula where _____________________
endolymph flows
Deflection of filaments - - leads to activation of ____________________
ionotropic receptors
Can you get a positive PLR in the left eye if there is a right optic nerve lesion?
YES (cross over/chiasm not blocked)
what controls balance and posture?
Vestibular
what are the vestibular receptors?
Three semicircular ducts, vestibule
Vestibular system is
Tonically active
Auditory canal is connected to
vestibular apparatus
Vestibular reflex is a
voluntary response
Voluntary reflex can also do
predictive inputs (bracing for a turn/standing)
Vestibular: Graded potentials are generated or inhibited on _____________sides of the head
opposite
How many semicircular canals are there?
3 on each side (bilateral)
Each canal of the semi-circular canal has a “specific” job. This is called?
Angular acceleration
What does angular acceleration feel/adjust of the 2 semi-circular canal? vestibular apparatus maintains equilibrium and balance during?
• Forward movement
• Head rotation
• Tilting of the head or trunk
Each semi-circular canal has its own
endolymph (aqueous solution)
The vestibular system is a
synergistic pair
Vestibular: When movement in one direction stimulates _______________ on one side of head, it inhibits excitation on the other side
excitation
Vestibular: Produces a jerk __________(involuntary movement of the eyes) = normal nystagmus
nystagmus
Vestibular: Slow phase (in one direction) and fast phase (in opposite direction).• Direction of nystagmus is direction of
fast phase
• Crista ampullaris
• Sense angular acceleration
Are what?
Three semicircular ducts
What are the two macula in the vestibule?
Macula saccule and macula utricle
Macula saccule and macula utricle: sense what?
static equilibrium/balance and linear acceleration
what is the 1st order neuron of vestibular apparatus?
Vestibulocochlear nerve(VIII) and vestibular ganglion
• Special proprioception (SSA)
Vestibulocochlear nerve(VIII) and vestibular ganglion
• Special proprioception (SSA)
After the 1sr order neuron what happens next?
Travel to medulla or directly to cerebellum
2nd order neuron of vestibular apparatus:
vestibular nuclei in medulla
What macula senses vertical (static equilibrium)
Macula saccule
what macula senses horizontal (linear acceleration)
Macula utricle
Vestibulospinal tract
Ipsilateral ventral funiculus
Vestibulospinal tract does what to muscles?
Activates extensors and inhibits flexors (LMN)
where is crista ampullaris found?
in the semicircular ducts
Crista ampullaris is bathes in?
endolymph (high in K+)
Crista ampullaris has
Stereocilia tip towards kinocilium to induce AP
Crista ampullaris Lag behind endolymph during movement. Once the stereocilia tip is towards kinocilium it knows that?
standing upright
Macula Saccule and Macula Utricle have what?
Hair cells imbedded in gelatinous layer with otoliths
Macula Saccule and Macula Utricle: What weighs down otolith membrane and stimulate hair cells?
Otoliths
Macula receptors: Positioned on the surface of saclike structure covered in membrano-gelatinous ‘goo” called
statoconiorum
Macula: Contains columnar epithelial cells
(neuroepithelium with stereocilia)
On top of macula Contains columnar epithelial cells: On top lies?
calcareous crystalline bodies (otoliths AKA statoconia)
Macula: Displacement of the statoconia leads to
filament displacement
Vestibular disease:
deficit in synergistic pairing
Vestibular disease
• Loss of coordination: Abnormal posture/ataxia
• Difficulty standing/leaning/rolling/falling
• Circling (toward affected side)
• Head tilt
• Nystagmus
What is the main hair cell of the vestibular apparatus?
kinocilium connect to nerve cells
When stereocilia bends the kinocilium bends towards it this causes a?
depolarization
when stereocilia bends in an opposite direction (AWAY) of kinocilium this causes a?
Hyperpolarization
When the endolymph moves in semi-circular duct due to movement of horizontal plane this causes?
inertia of endolymph will cause the kinocilium to move in same direction
If i spin to the right the endolymph fluid of the semicircular ducts flows in the same way (pushing cilia in the same direction) in the LEFT side of the head the endolymph goes in the
OPPOSITE direction causing kinocilium and stereocilia to go in opposite direction
One side depolarizes the other side?
hyperpolarizes
When the vestibular apparatus does not have opposite AP this causes?
Vestibular deficits
Tonically active (always an AP on each side)
Vestibular apparatus
vestibular apparatus can sense ________________ because they are tonically active
Increase and decrease (AP frequency)
A circling animal has a head tilt towards the lesion because semi-circular canal is not in a
synergic pair (this is a vestibular deficit)
What will happen to extensors and flexors when there is a right vestibular lesion?
° Reduced extensor (increased flexor) tone on right side
° Increased extensor tone on left side
Medial longitudinal fasciculus found where?
medulla
Medial longitudinal fasciculus receives input from
vestibular apparatus and can control UMN
Medial longitudinal fasciculus does what?
Coordinate eye movement with movement of head
Medial longitudinal fasciculus• Goes to CNs III, IV, VI which innervate?
Extraocular muscles
Medial longitudinal fasciculus Coordinate eye movement with movement of head
Vestibular-ocular reflex
Vestibular apparatus sends information to Medial longitudinal fasciculus to control
involuntary movement in UMN
Macula Saccule and Macula Utricle have otoliths. Gravity affects these otoliths which
stimulate hair cell
Semi-circular canals
angular acceleration
which macula senses vertical
Macula saccule
Which macula senses horizontal?
Macula utricle
Static equilibrium
Macula saccule: vertical
Linear acceleration
Macula utricle: horizontal
Each semi-circular canal has its own
endolyphm
