Chapter 5: The Brain Stem (continued) Flashcards
Describe the course the accessory nucleus takes.
accessory nucleus is found in the cervical spinal cord.
- axons of the spinal accessory nerve arise from the accessory nucleus, pass through the foramen magnum to enter the cranial cavity, and join the fibers of the vagus to exit the cranial cavity through the jugular foramen
What does the curve of the facial nucleus form?
the internal genu of the facial nerve
What is the purpose of the superior olivary nucleus?
recieves auditory impulses from both ears by way of the cochlear nuclei
Where is the main sensory nucleus of pons located?
just lateral to the motor nucleus of pons where trigeminal motor neurons are transmitted
What is the purpose of the main sensory nuceus of the ponns?
receives tactile and pressure sensation from the face, scalp, oral cavity, nasal cavity and dura
What is the spinal trigeminal nucleus?
a caudal continuation of the main sensory nucleus
Where does the spinal trigeminal nucleus extend?
from the mid pons through the medulla to the cervical cord
What is the purpose of the spinal trigeminal nucleus?
central processes from cells in the trigeminal ganglion conveying pain and temperature sensation from the face descend in the spinal tract of V and synapse on cells in the spinal nucleus
What part of the thalamus relays touch, pain, temperature (CN V) and taste (CN VII, IX) sensations to cortex?
VPM
Where is the mesencephalic nucleus located?
at the point of entry of the fifth nerve and extends into the midbrain
Purpose of the mesencephalic nucleus?
recieves proprioceptive input from joints, muscles of mastication, extraocular muscles, teeth, and the periodontium
Label figure III.5.5 include note at bottom
What is another name for corticobulbar innervation of cranial nerve nuclei?
Corticonuclear innervation of CN nuclei
What is the purpose of corticobulbar fibers?
serve as the source of upper motoneruon innervation of the LMN in CN nuclei
Corticobulbar innervation of facial motoneruons to muscles of the upper face is contralateral or bilateral?
bilateral
UMN of corticobulbar fibers that innervate the upper face are responsible for what action of the face?
wrinkling of the forehead and shutting the eye
Corticobulbar tract innervation to the lower part of the face is bilateral or contralateral?
contralateral
Cortiocbulbar innervation to the lower part of the face innervates which structure?
muscles of the mouth
Bells palsy cause and presentation?
facial nerve lesion
complete ipsilateral paralysis of muscles of facial expression, including an inability to winkle the forehead or shut the eyes and a drooping of the corner of the mouth
Presentation of a lesion of corticobulbar nerves to the tongue muscles?
lesion of the left will cause deviation of tongue to the right
Label the structures of the ear.
What does the spiral ganglion contain?
contains cell bodies whose peripheral axons innervate auditory hair cells of the organ of Corti
Why do middle ear diseases result in conductive hearing loss?
because of a reduction in amplification provided by the ossicles
What are some middle ear disease?
otitis media, otosclerosis
What lesions may result in hyperacusis?
leisons of the facial nerve in the brain stem or temporal bone (Bell palsy)
Hyperacusis.
an increased sensitivity to loud sounds
What does presbycusis result from what occurring?
loss of hair cells at the base of the cochlea
If air conducton > bone conduction an indication of sensorineural hearing loss or conductive?
sensorineural hearing loss
If bone conduction is greater that air conduction this is a type of sensorineural or conductive hearing loss?
conductive hearing loss
Describe the path of the auditory system from cells of the cochlear nuclei to the cerebral cortex.
Axons go from ventral cochlear nuclei and bilaterally innervate the superior olivary nuclei
reach lateral lemniscus which carries auditory input from the cochlear nuclei and the superior olivary nuclei to the inferior colliculus in midbrain
Inferior colliculus carries auditory information to MGB (medial geniculate body) of the thalamus,
auditory radiation projects to the primary auditory cortex located on posterior portion of the transverse temporal tyrus (Heschl’s gyrus; Brodmann areas 41 and 42)
If a patient presents with a significant hearing loss in one ear, the lesion is most likely where?
in middle ear, inner ear, eighth nerve, or cochlear nuclei
What is conductive hearing loss caused by?
passage of sound waves through external or middle ear is interrupted. Causes: obstruction, otosclerosis, otitis media
Sensorineural hearing loss cause?
damage to cochlea, CN VIII or central auditory connnection
Weber test
place tuning fork on vertex of skull
if unilateral conductive loss > vibration is louder in affected ear;
if unilateral sensorineural loss > vibration is louder in normal ear
Rinne test
place tuning fork on mastoid process (bone connduction) until vibration is not heard, then place fork in front of ear (air conduction).
If unilateral conductive loss > no air condution after bone conduction is gone;
if unilateral sensorineural loss> air conduction present after bone conduction gone