Brainstem/Cerebellum Flashcards
- Locate the hypoglossal nucleus and the hypoglossal nerve exiting the brainstem
- Point out the reticular formation
What is the reticular formation?
Diffuse nerve network throughout the entire brainstem that connects all the surrounding structures
What are the cranial nerves in the medulla?
CN IX, X, XI, and XII (9-12)
Name the labeled structures
What CN(s) come out the dorsal surface of the brainstem?
Only CN IV (trochlear)
What functional fibers are in CN XI?
-what does CN XI innervate?
GSE
- for this course consider CN XI (accessory) to contain GSE (as if it’s innervating muscles from somite, not branchial arch, derivatives)
- CN XI innervates trapezius and SCn
Point out the pyramidal decussation and medullary pyramids
Point out the place where the dorsal medial pathway fibers decussate and travel
Where does the hypoglossal nerve exit the brain?
Exits most medially out of the medulla. Exits out on the preolivary sulcus between the olive and the pyramids
How does the hypoglossal nerve leave the skull?
Out the hypoglossal foramen to provide motor innervation (GSE) to the tongue
Locate the spinal accessory nucleus in the image
Which number if the hypoglossal nuclei?
11
- most medial (b/c motor) in the medulla oblongata
- contains GSE fibers
Which number is the accessory nucleus?
20
-very medial (second most medial) in the superior spinal cord, GSE fibers
Point out the
(a) Nucleus that provides the SVE fibers to the vagus nerve
(b) Exit of CN X
(a) Nucleus ambiguus provides the parasympathetics to the vagus nerve
(b) CN X exits out the inferior olivary sulcus (right below the inferior olive)
Locate the nucleus that provides parasympathetics to the vagus nerve
= Dorsal motor nucleus of the vagus
Differentiate the location of the 4 pathways/nuclei that provide fibers to the vagus nerve
- yellow = nucleus ambiguus, provides the SVE fibers to muscles derived from the VI and VIth branchial arch
- darker blue = dorsal vagal motor nucleus, provides the GVE (parasympathetic) fibers for motor to the gut
- teal (most lateral) = spinal trigeminal nucleus (GSA fibers)
- purple/green = solitary nucleus (GVA and SVA)
Label the blue arrows and red line
- red line = sulca limitans, separates the motor and sensory components of the brainstem
- see CN IX exiting
- inferior salivatory nucleus provides the parasympathetics (GVE) to CN IX
- spinal trigeminal nucleus provides the somatic sensory (GSA) to both CN X and IX
- nucleus solitarious provides the visceral sensory (GVA) to both CN X and IX
- nucleus ambiguus provides the somatic sensory (GSA) to both CN X and IX
What is the main structure of the posterior fossa?
Cerebellum, takes up mostly all the psace in the posterior fossa => if anything takes up space it can cause herniation
What structure forms the roof of the 4th ventricle
Cerebellum
-then the lateral walls of the 4th ventricles are the peduncles running and out of the cerebellum
Which cerebral peduncle(s) are the main outflow tract of the cerebellum?
Superior cerebellar peduncles = main outflow tract for efferent fibers leaving the cerebellum
Which cerebral peduncle(s) are the main inflow tract of the cerebellum?
Middle and inferior cerebellar peduncles act as the inflow tracts for the afferent fibers going into the cerebellum
What is the clinical significance of the cerebellar tonsils?
Tonsils = lowest (most inferior/caudal) part of the cerebellum
=> any mass-consuming lesion in the posterior fossa (ex: hemorrhage, tumor, increased pressure) can cause herniation of the cerebellar tonsils thru the foramen magnum
Define a brainstem nucleus
Nucleus = gray matter- collection of neurons in a specific anatomical space
Which part of the cerebllum controls distal limb coordination?
Intermediate hemisphere
Which part of the cerebellum controls gait and balance?
Vermis and floculonodular lobe in the middle
Which part of the cerebllum controls the VOR reflex?
Vermis and floculonodular lobe in the middle
Name the main nuclei of the cerebellum
Dentate, fastigial, globose, and emboliform
-then interposed nuclei = emboliform + globose
What are purkinje cells?
GABAergic neurons in the cerebellum
Define dysmetria
Type of ataxia associated w/ lack of coordination of movement typified by under or overshoot of the intended position
Define hypometria
= undershooting
ex: trying to do finger to nose but undershoot the distance
Define hypermetria
= pass-pointing
- overshooting
ex: when doing finger to nose and pt overshoots - type of dysmetria which is a type of ataxia
Define dyssynergia
= aspect of ataxia characterizted by uncoordinated and aburpt movement
-decomposition of mov’t
Define dysdiadochokinesia
Feature of cerebral ataxia
= inability to perform rapid, alternating movements
ex: disorganized mov’t when asked to move palms up and down
Define titubation
Postural sway in the AP direction
Define a positive Babinski sign
When you stroke the sole of the foot and the big toe goes up
-sign of possible pathology if the big toe goes up when the sole of the foot is stroked
Define asthenia
Weakness only during movement (not seen at rest)
-can be a result of cerebellar dysfunction
Define rebound as a symptom of cerebellar dysfunction
-upward displacement of outstretched arm when tapped
Describe the cerebellum’s role in cognition?
Learning new motor tasks and some perception
What is multiple system atrophy? Name one way in which it can present
Multiple system atrophy type C (MSA-C) is a neurodegenerative disease which can present as sporadic ataxia
What is Friedreich’s ataxia
Autosomal recessive inherited form of ataxia
-due to trinucleotide repeat
What is SCAs?
A group of autosomally dominant inherited ataxias
SCA = spinocerebellar ataxias
What are the three most common forms of SCA?
SCA 2,3, and 6 are the most common, make up about 50% of the diagnoses
-over 30 described clinical SCA syndromes
What is the cause of SCAs?
Spinocerebellar ataxias = genetic, auto dom
-trinucleotide repeat expansion
Which side is rostral vs. caudal?
Distinguish the 4 parts (thalamus, midbrain, pons, medulla)
Point out all the cranial nerves in the image
Name each of the colored columns
Motor columns shown on the left:
- Most medial = red = somatic motor column (GSE)
- middle = GVE = parasympathetic column
- most lateral of the motor columns (still medial to all the sensory) = SVE = branchial motor column
Sensory columns shown on the right:
- most medial (still lateral to all motor) = SVA and GVA = Visceral sensory column
- Middle/lateral: GSA = general somatic sensory column
- Middle/lateral = SSA = special somatic sensory column
Name the location of the nucleus of CN VIII
Vestibular and cochlear nuclei- mainly in the medulla, little bit extending upwards into the pons
-situated laterally b/c they’re purely sensory (SSA)
What are the 3 sets of arrows pointing to?
- pink arrows = Vestibular nuclei
- blue arrows = cochlear nuclei
- other blue arrows = CN VIII
What is the function of the medial geniculate body of the thalamus?
Relay station btwn the inferior colliculus (of the midbrain tectum) and the auditory cortex (in the transverse temporal gyrus)
-fxn in hearing
What forms a unique wine glass appearance on cross section?
Lateral lemniscus
-where the auditory fibers run up to get to the inferior calliculus in the auditory pathway
Name the arrowed structures
Name the circled structure
Spinal trigeminal tract and nucleus
-
Name the arrowed structures
Which nucleus mediates the jaw jerk reflex?
Mesencephalic nucleus which contains the GVA fibers of CN V (trigeminal) for proprioception
