Exam One - Pons/Mesencephalon Flashcards
What are the 2 regions of the pons?
- tegmentum
- basilar pons
where is the basilar pons
- ventral portion
What does the basilar pons contain?
-descending tracts: corticospinal, corticobulbar, and corticopontine (motor tracts)
-transversely oriented pontocerebellar tracts
-pontine nuceli
What does the tegmentum contain?
- cranial nerve nuclei
- ascending sensory pathways
- reticular formation
- periaqueductal grey matter
What is the one CN that crosses?
4
rhomboid fossa
floor of the 4th ventricle, named after shape
facial colliculus
swelling on the floor of the 4th ventricle, cause by CN 7 looping over CN 6 nucleus
vestibular area
overlies the vestibular nuclei
- balance and coordination of eye and head movements
sulcus limitans
groove in the floor of the 4th ventricle, separates motor and sensory nuclei
gracile tubercle
swelling on the dorsal surface of the medulla formed by the gracile nucleus
CN 6
- abducens nerve
- supplies somatic motor fibers to the lateral rectus muscle, which abducts the eye (turns it laterally)
CN 7
-facial nerve
0 carries nerve fibers that control facial movement and expression
-also carries fibers involved in taste to the ant 2/3 of the tongue and produces tears
- has small branches involved in moderating sensitivity to noise volume (stapedius muscle)
What supplies blood to the pons?
medial to lateral
branches of BA:
-paramedian
-short circumferential
- long cercumferential
cranial nerve associated with the pons proper
5
cranial nerves associated with the pontomedullary junction
6,7,8
if CN5 is damaged
-trigeminal
-ipsilateral alteration of pain, temperature, light touch on the face
if CN 6 is damaged
- abducens
- ipsilateral weakness of abduction (lateral movement of eye)
if CN 7 is damaged
- facial
-ipsilateral facial weakness
if CN 8 is damaged
- auditory
- ipsilateral deafness
The midbrain is the ______ segment of the brainstem
smallest
the midbrain is continuous with the pons ________
caudally
the midbrain is continuous with the diencephalon ________
rostrally
tectum
- “roof” of midbrain
- contains superior and inferior colliculi
crus cerebri
huge white masses, form the ventral surface (base) of the midbrain
tracts of midbrain
corticopontine
corticobulbar
corticospinal
substantia nigra
movement control center, sends dopaminergic fibers to the striatum
damaged in parkinson’s disease
tegmentum
core of the brainstem
superior colliculus
visual relay center
inferior colliculus
auditory relay center
______ changes orientation as it moves from the medulla to the VPL of the thalamus
medial lemniscus
What artery supplies the midbrain?
basilar
What specific branches off the basilar artery supply the midbrain?
- superior cerebellar a (SCA)
- posterior cerebral a (PCA) : also a branch of PCA called quadrigeminal artery (QA)
- posterior communicating a
what are the 2 cranial nerves found in the midbrain?
3 and 4
if CN3 is damaged
- oculomotor
- impaired adduction, supraduction and infraduction of the ipsilateral eye
- eye is turned out and slightly down
if CN 4 is damaged
- trochlear
- contralateral
- the eye is unable to look down when trying to look towards the nose
Where do CN 1&2 originate?
cerebrum
What are the 3 basic organizational principles for brainstem neurological syndromes?
1 - normally subdivided into medial (motor) or lateral (sensory) syndromes based on blood supply patterns and structures found within these patterns.
2 - unilateral involvement of long ascending/long descending tracts result in contralateral sensory and motor deficits
3 - cranial nuclei and nerve involvement result in ipsilateral motor and sensory deficits (except CN4)
