Brainstem Flashcards
Describe the conduit, cranial nerve, and integrative functions of the brainstem.
conduit- acts like a “pipe” to transfer info from brain to spinal cord
cranial nerve- the brainstem takes care of the same sensory and motor functions for the head that the spinal cord does for the body
integrative functions- reticular formation controls the maintenance of consciousness
Describe the characteristic gross anatomical features of the medulla.
includes pyramids, olives, and part of the 4th ventricle
Describe the characteristic gross anatomical features of the pons.
includes the basal pons, middle cerebellar peduncles, and part of the 4th ventricle
Describe the characteristic gross anatomical features of the midbrain.
includes superior and inferior colliculi, the cerebral peduncles and the cerebral aqueduct
Describe the posterior fossa and tentorium:
What forms the floor of posterior fossa?
What forms the roof of posterior fossa?
What major brain subdivisions are found in the posterior fossa?
floor- occiput (some temporal bone)
roof-tentorium
major brain subdivisions- cerebellum, brainstem
What are the colliculi? Where do they sit? What are they termed?
The colliculi are 4 little “hills” which sit upon the dorsum of the midbrain and are also termed collectively the tectum.
Describe the functions of the Inferior and superior colliculi.
The IC are involved in hearing, the SC are concerned with vision.
“slo-aim”—Superior colliculi talk to the Lateral geniculate which is dealing with Optic functions, while the Auditory system uses the Inferior colliculi which communicate with the Medial geniculate
Describe the 3 cerebellar peduncles.
There exists 3 sets of cerebellar peduncles—The superior is efferent and is in the midbrain, the middle is afferent and attaches to the pons, the inferior is afferent and is associated with the medulla.
Describe the 2 cerebral peduncles
There are 2 cerebral peduncles—their home is the midbrain and they connect the cerebrum with the brainstem and thus spinal cord.—all of these peduncles consist of fibers—mostly myelinated—thus white matter staining black with a myelin stain.
Describe the olive.
The olive connects to the dentate nucleus of the cerebellum, and looks like it on cross section. Fibers leaving the olive and travelling to the cerebellum are termed “climbing fibers”.
Describe the pyramid.
The pyramid consists of pyramidal tract fibers of the CST. It decussates as the medulla becomes the spinal cord.
Describe the 4th ventricle.
The 4th ventricle sits above the medulla and below the cerebellum. It has 4 major openings—inferiorly the obex opens into the central canal and superiorly the aqueduct of sylvius opens into the 4th ventricle. Also—CSF flows out of the 4th ventricle via the Lateral placed foramen of Lushka, and out the posterior Midline foramen of Magendi.
Where does the cortex project?
The cortex projects to the pontine gray nuclei which then project contralaterally to the cerebellum—”mossy fibers”
Which is the main CN coming out of pons?
V
How is the facial colliculus formed?
The facial colliculus is formed by the 7th nerve coursing over the 6th nucleus
What is the pineal gland near?
3rd ventricle.
Which is only CN to come off dorsum of brainstem?
IV
What do mammilary bodies do?
Mammillary bodies play a role in memory—connect to hippocampus via fornix and degenerate in severe alcoholism
What is the location of the corticospinal and spinothalamic tracts? (CST and STT)
consistent locations throughout the brainstem
Where is the medial lemniscus?
forms in the caudal medulla
What does the rostral medulla contain?
inferior olivary nucleus and part of 4th ventricle
What is the caudal pons attached to?
attached to cerebellum by the middle cerebellar peduncle
Where does the superior cerebellar peduncle join the brainstem?
in the rostral pons
Where does the superior cerebellar peduncle decussate?
in the caudal midbrain
What does the rostral midbrain contain?
red nucleus and substantia nigra
Describe the STT (spinal trigeminal tract).
The spinal trigeminal tract descends from the pons (where 5 enters and exits) down into the cervical cord to synapse on the spinal trigeminal nucleus. It relays pain and temp from the head.
Fibers in the spinal tract of V descend from the face, thru the semilunar ganglion, into the pons, and then down to the spinal cord to synapse with the spinal n. of V
Describe the medial longitudinal fasciculus.
The MLF deals with coordinating the nuclei of 3,4, and 6 with each other and spinal reflexes. Here we can see the crossing climbing fibers consisting of olivo-cerebellar afferents
What is seen at the level of caudal medulla?
Pyramids
Internal arcuate fibers
Nucleus gracilis
Nucleus cuneatus
Spinal tract and nucleus of V
Medial lemniscus
What is seen at level of rostral medulla (open medulla)?
Inferior cerebellar peducle
Inferior olivary nucleus
Wide open 4th ventricle
MLF-medial longitudinal fas.
What is seen at the level of caudal pons?
Deep cerebellar nuclei, fat guys eat donuts, fastigal,globose, emboliform, dentate
Basal pons
Pontine gray nuclei
Ponto-cerebellar fibers (mossy fibers)
Huge middle cerebellar peduncle
What is seen at level of rostral pons? (cerebellum gone, and 4th ventricle is closing)
Note large basal pons
Medial lemniscus preparing to enter the thalamus “upside-down” (VPL)
STT entering VPL also
Beginning of PAG (peri aqueductal gray)—pain and autonomic functions
Also: observe the SCP (mostly efferent) preparing to cross(decussate) on its way to the red nucleus
Describe the level of caudal midbrain.
Crossing of the SCP
Formation of a true aqueduct
Appearance of the inferior colliculus (slo-aim)
IC deals with auditory functions via the medial geniculate
Cerebral peduncles (feet of the cerebrum) replace the basal pons. CST runs in center
(Level of CN IV)
Describe the functions of the reticular core of the brainstem?
participates in the control of movement through connections with both the spinal cord and cerebellum
modulates the transmission of information in pain pathways
contains autonomic reflex circuitry
involved in control of arousal and consciousness
What does Locus Ceruleus (blue point) contain?
noradrenalin
(extensive CNS projections, may adjust background level of sensitivity)
(rostral pons)
What do neurons of substantia nigra and ventral temental area contain?
dopamine
substantia nigra is a 2 part structure - part further from cerebral peduncle (compact part) is where dopaminergic neurons live
What does a lesion in SNc and lesion in VTA imply?
Lesion SNc (to putamen, caudate nucleus…compact part - of substantia nigra) parkinson’s
Lesion VTA (vental tegmental area goes to limbic structures, cerebral cortex) - some form of mental illness
What do neurons of the Raphe contain?
serotonin
serotonergic raphe nuclei in the caudal pons.
like those of the LC these neurons project all over the place and may adjust levels of attention or arousal
What do neurons of the rostral brainstem and basal forebrain contain?
Acetylcholine
What are the 2 key nuclei in the basal forebrain containing Ach?
What might destruction of these pathways lead to?
basal nucleus of Meynert (projects to widespread areas of cerebrum)
septal nuclei (project to hippocampus)
Destruction of these pathways may lead to alzheimer’s
Describe the MCA stroke/Wallenberg’s. What doe sit affect and produce?
This stroke thus affects balance, taste, pain, speech, and produces a Horner’s syndrome.—also very important—loss of pain and temp in lower body below lesion on contralateral side——————————loss of pain and temp on ipsi side (V) of head
Which CN comes out of the interpeduncular fossa?
CN III
interpeduncular fossa above pons
