Pons Flashcards
parts of the pons
tegmentum
basis pontis
tegmentum
- what is it?
- location
portion of gray matter containing cranial nerve nuclei and ascending and descending tracts
lies between fourth ventricle and more ventrally located basis pontis or ventral pons
basis pontis
- contains
- marked by…
ventral portion containing pontine nuclei and crossing pontine fibers running transversely
marked by large fascicles of fibers containing corticospinal, corticobulbar and corticopontine axons
crossing pontine fibers in the basis pontis that run transversely become the…
middle cerebellar peduncle
corticospinal, corticobulbar, and corticopontine axons in the basis pontis are running with what direction
caudal
cerebellar peduncles
- how many?
- what are their names
- can all be seen at the _____ level
inferior
middle
superior
can be seen at the pontine level
cerebellar peduncles
-function
inferior and middle
-allow cerebellar afferents to enter the cerebellum
superior
-allow cerebellar efferents to exit the cerebellum
CNs associated with the pons
5-8
CN VIII
-which division are we concerned with in relation to the pons
cochlear division
CN VIII cochlear division
-function
relay of auditory information from the cochlea
auditory information is distributed in what fashion?
bilaterally through brain stem and cortical auditory areas
unilateral lesions of CNS auditory structures results in…
does not result in unilateral deafness
in relation to CN VIII
-what must be damaged to result in ipsilateral deafness
both cochlear nuclei
how is the cochlear division of CN VIII organized
tonotopically
-like topographic, but with sounds instead of body parts
CN VIII cochlear division
- where does the information go?
- what information is sent?
cerebral cortex for perception of spoken word and sound
-primary auditory cortex
primary auditory cortex location
superior surface of superior temporal gyrus
- within lateral sulcus
- Brodmann’s areas 21 and 42
- Transverse Temporal Gyri of Heschl
function of cross-communication between sides of CN VIII cochlear division nuclei before arriving at cortex
supports the ability to localize sound to one side
cochlear nerve
-consists of…
consists of axons or central process of neurons bringing afferent information from the inner ear
cochlear nerve
- enters brainstem at…
- where does it go after this?
enters brainstem at cerebellopontine angle
birfurcates to synapse in both dorsal and ventral cochlear nuclei
cochlear nerve nuclei location
superficial
located in rostral (open) medulla
-adjacent to base of inferior cerebellar peduncle and alongside the lateral aperture of the 4th ventricle
CN VIII cochlear division
-synapses that occur after the cochlear nuclei
dorsal and ventral cochlear nuclei superior olivary nucleus lateral lemniscus (bilateral pathway for sound localization) nucleus of inferior colliculus brachium of inferior colliculus medial geniculate nucleus primary auditory cortex
protective auditory reflexes
inferior colliculus > superior colliculus > tectospinal tract = reflex turning fo head to sound
protective auditory reflexes
- function
- how does it accomplish this?
important for protection against loud noise
superior olivary nucleus projects to CN VII - stapedius muscle
-dampening of noise at the stapes
superior olivary nucleus also projects to CN V - tensor tympani muscle
-dampening of noise at the malleus
acoustic neuroma
- what
- where
- malignant or benign?
- where does it begin?
tumor growing in the cerebellopontine angle
usually benign and beginning on the VIIIth nerve
acoustic neuroma
-S/S
vestibular component
-irritative lesion; changes in perception of head position - spinning sensation, vertigo
tinnitus (ringing of the ears) - irritative lesion
CN V
-function
general sensation of the face and head area
motor output to the muscles of mastication
CN V
-sensory parts carry same modalities as what other systems
dorsal column system
spinothalamic tracts
CN V carries general somatosensation for…
anterior 2/3 of the face
CN V divisions
V1 -ophthalmic division; above the eye V2 -maxillary division; below the eye, above the mouth V3 -mandibular division; jaw
CN V LMNs that innervate the muscles of mastication have their cell body in the…
motor nucleus of V
CN V motor component also innervates…
tensor tympani
nerve to mylohyoid
-mylohyoid
-anterior digastric
CN VII
-LMNs innervate…
ipsilateral
- muscles of facial expression
- platysma
- stapedius
CN VII LMNs
-axons location
travel around the abducens nucleus to form the facial colliculus (bump on the floor of the 4th ventricle)
CN VII
-where does it exit the pons?
exits at anterolateral part of tegmentum of lower pons
CN VII
-which part of the face (upper or lower) receives bilateral UMN control?
upper
CN VII
-the LMNs that innervate the lower part of the face receive UMN input from the _____ hemisphere
contralateral
CN VII preganglionic parasympathetic neurons
-location
reticular formation in the caudal pons
CN VII preganglionic parasympathetic neurons
- functions
- -specific part responsible for each function
tear production
-postganglionic cell bodies in pterygopalatine ganglion (lacrimal gland)
salivation
-postganglionic cell bodies in submandibular ganglia (submandibular and sublingual glands)
CN VII
-what sensory function does it perform?
taste
CN VII LMN lesion results in what disorder
Bell’s Palsy
UMN or Central Facial Palsy
-where does the deficit occur?
contralateral lower face
-upper face has bilateral UMN innervation
Sx of facial nerve lesions
LMN deficit of ipsilateral face
dry cornea; ulcerated cornea
loss of taste over ipsilateral anterior 2/3 of tongue
inability to produce saliva
hyperacusis - stapedius can’t dampen sound
corneal blink reflex is a combination of functions by which CNs
trigeminal
facial
blink reflex
- what is it
- what are the components of the reflex?
touch the cornea and both eyes close direct reflex -closure of the touched eye indirect or consensual response -closure of the untouched eye
circuits of blink reflex
-what are the components
receptor afferent limb interneurons direct reflex efferent limb indirect reflex efferent limb
blink reflex receptor
free nerve ending in cornea (peripheral process of sensory neuron in the ophthalmic division of CN V)
how do you elicit a response from the blink reflex receptor?
with cotton wisp
blink reflex afferent limb
-where does the central process end?
central process ends in main sensory nucleus of V
blink reflex interneurons
- location
- project to…
in main sensory nucleus of V
project directly to ipsilateral facial motor nucleus and to RF interneurons
direct blink reflex efferent limb
ipsilateral facial motor nucleus to orbicularis oculi
indirect blink reflex efferent limb
RF interneurons project to contralateral facial motor nucleus to activate contralateral orbicularis oculi
