Fibers that terminate at the caudal colliculus are for which reflex?
The Startle Reflex
Fivers that terminate at the auditory cortex are for?
The Primary Auditory Pathway
Where do descending pathways of the Startle Reflex go to?
Go to LMNs of skeletal muscles of the limbs
The Auditory is for _______ perception of sound.
Conscious perception
Trace the Auditory Pathway starting at the cochlear nuclei.
From cochlear nuclei (ipsilaterally and contralaterally)
- -> Caudal colliculi (via Olivary Nuclei)
- -> Medial Geniculate Nuclei (MGN)
- ->Auditory Cortex for conscious perception of sound
When sound cannot get from ear to vestibular window due to disease, damage, or obstruction (like an ear infection) is associated with what type of deafness?
Conduction Deafness
When sound gets to the vestibular window but cannot be transmitted to the auditory cortex
Sensorineural Deafness
Deafness associated with damage to the cochlea, cochlear nerves, central auditory pathway, or auditory cortex
Sensorineural Deafness
What is Prebycusis?
Deafness of old age- a type of Sensorineural Deafness
Ototoxic drugs can cause what kind of deafness?
Sensorineural Deafness
Which type of deafness is reversible?
Conduction Deafness
What kind of reflexes are associated with the Vestibular System?
Motor reflexes
What is the major goal of the vestibular system?
To maintain a stable orientation in relation to gravity and motion
What does the vestibular system sense?
Balance and Acceleration
“The guy in the VEST is a BA (badass)”
The Vestibular System is also called what?
Special Proprioception
The vestibular system compares the positions of the eyes, limbs, neck and trunk to the position and movement of the _______.
Head
Axons of neurons from the utricle, saccule, and semicircular canals form which nerve?
The vestibular nerve
What drives the reflexes of the vestibular system to re-orient or balance the body?
The ASYMMETRY of the inputs going from Cranial Nerve 8 to the vestibular nuclei in the hindbrain
What 3 locations does info from vestibular nuclei go to?
- Motor nuclei of CN 3,4, and 6
- Through the cerebellum
- Thalamus and then Cortex
To control EYE MOVEMENT in response to vestibular movement, signals from the vestibular nuclei are sent where?
To the motor nuclei of CN 3, 4, and 6
The ________ receives info from the vestibular nuclei in order to control posture and balance.
Cerebellum
The cerebellum carries out 2 reflexes. Name them.
Vestibulospinal Reflex (Trunk stability) Vestibulocollic Reflex (Head and Neck stability)
Describe the vestibular pathway for control of EYE MOVEMENTS
CN8 –> Vestibular Nuclei–> Via Ascending MLF–> CN-3,4,6
This is bilateral, ipsilateral and contralateral
MLF= Medial longitudinal fasciculus in the brainstem
Describe the vestibular pathway for control of POSTURE and BALANCE
CN8–> Vestibular Nuclei–> Cerebellum–> MVT or LVT
MVT: medial vestibulospinal tract- Bilateral
LVT: lateral vestibulospinal tract- Ipsilateral
Describe the vestibular pathway for conscious perception of movements
CN8–> Vestibular Nuclei–> Thalamus–> Via thalamocortical (bilateral) pathway–> Cortex
What is tested in the Tracking Test?
The vestibulo-ocular reflex
What is nystagmus?
The slow movement of eyes as they are catching up to movement of the head
What types of nystagmus are indicative of vestibular disease?
Resting nystagmus and
Positional nystagmus
What is Estropia?
Crossed eyes- physiological nystagmus
Siamese and Himalayan cats
A unilateral lesion causes resting nystagmus. The fast phase of the vestibulo-ocular reflex goes towards the _____ side.
intact side
The fast phase of the vestibulo-ocular reflex goes away from the _______ side.
lesioned
What kind of nystagmus is seen in an animal with a peripheral vestibular lesion?
Horizontal or Rotatory Nystagmus ONLY
Does NOT change when head moves, not positional
What kind of nystagmus is seen in an animal with a central vestibular lesion?
Horizontal, Rotatory or Vertical Nystagmus
MAY CHANGE when animal is in recumbancy, may be positional
What does the Vestibulocollic Reflex do?
Produces neck movements and forelimb extension to counteract head tilt
What is a unilateral lesion?
When one side fires and one side does not, or is impaired
What happens to the vestibulocollic reflex when there is a unilateral lesion?
Controlled by cerebellum
Head tilts towards LESIONED side
What is the Vestibulospinal reflex responsible for?
Controlled by cerebellum
To prevent falling when head moves by producing limb extension
If there is a unilateral lesion, what happens to the vestibulospinal reflex?
The animal will lean or circle toward the side of the lesion
What problem is associated with the Emetic Center?
Motion sickness