Introduction to the Brainstem Flashcards
Functionally, the brainstem is divided into three parts. What are they?
Conduit
Cranial nerves
Integrative (life-sustaining functions mediated by the reticular formation)
“The brainstem is kind of like a spinal cord that never closed up.” Explain.
The alar plate (sensory) is lateral/posterior to the basal plate (motor), but they have not fused. It’s like a C.
Cerebral peduncle is the modern name for ____________.
crus cerebri
The olives are _________ and ________ to the pyramids.
lateral; posterior
The colliculi are on the dorsal surface of the _______.
midbrain
The predominant features of the dorsal pons are the _________.
cerebellar peduncles
The DCML synapses on _________.
[dorsal column medial lemniscus (DCML)] on the nucleus gracilis and nucleus cuneatus
The inferior colliculus looks more ___________.
ovoid
The superior colliculus looks like _____________.
“a butt” (they’re more rounded)
The substantia nigra lies between ___________.
the cerebral peduncles and the body of the midbrain
The upper medulla looks like ____________.
a butterfly
Where is the best cross section to see the cerebellar peduncles?
The upper medulla
The olivary nucleus is visible in which cross sections?
Upper medulla and upper middle medulla (it is the “squiggly line” –the monster’s mouth)
The superior colliculus carries ________ reflexes.
visual
The inferior colliculus carries __________ reflexes.
auditory
If you’re looking at the ventral surface of the medulla, at what landmark is the decussation?
The base of the pyramids
In the cerebral peduncles, the corticospinal tract is _________.
in the middle (there are other tracts dorsal and ventral)
What is the SCP?
The superior cerebellar peduncles (visible in the upper pons–the ears of the cat)
If you’re viewing a cross section of the upper medulla, where will the corticospinal tracts be?
Ventral to the olivary nuclei
The ICPs will be seen dorsal to what?
Olivary nuclei (upper medulla section)
In the caudal medulla, the nucleus gracilis and nucleus cuneatus are ________ to their respective fasciculi.
deep/ventral
Where is the medial lemniscus in the medulla?
Medial/deep to the olivary nuclei and posterior/deep to the corticospinal tracts
In the medial lemniscus in the medulla, the upper body is _________ to the lower body.
posterior
In the medial lemniscus in the pons, the upper body is ___________ to the lower body.
medial
Where do the medial lemniscus go in the midbrain?
Laterally (but still posterior to the substantia nigra)
In relation to the medullary olive, where is the spinothalamic tract?
Posterior, on the lateral edge of the brainstem
The “sleeping cat” is which cross section?
Upper pons
Describe Dr. Stabio’s basic guide to identifying the location of brainstem lesions.
Nuclei serve as indicators of latitude and axon tracts serve as indicators of longitude.
Where are the cranial nerve nuclei located?
Cerebrum: 1, 2
Midbrain: 3, 4
Pons: 5, 6, 7, 8
Medulla: 9, 10, 11, 12
Most long tract lesion signs will be ____________, while most cranial nerve nuclei signs will be __________.
contralateral; ipsilateral
What is the upper-motor neuron equivalent of the cranial nerves (i.e., what is the cranial-nerve version of the corticospinal tract)?
The corticobulbar tract
What is the “chemical formula” mnemonic for ocular muscles?
(LR6SO4)3
Lateral rectus: 6 (abducens)
Superior oblique: 4 (trochlear)
All the rest: 3 (oculomotor)
The skinny part of the trigeminal nerve (which exits from the pons) carries ____________.
motor (mastication)
What is the sensory component of CN VII?
Taste (the motor is EXPRESSION)
The only cranial nerve that exits from the back of the brainstem is ___________.
CN IV (TRochlear is TRicky –it is also the only decussating nerve)
There are _________ nuclei in the brainstem for CN V.
four
- mesencephalic [in the upper pons]
- main motor (mastication) [in the mid pons, medial to the main sensory nucleus]
- main sensory (mechanoreceptors of the face)
- spinal nucleus (pain)
The oculomotor nucleus can be seen in the ________. Where will it be?
upper midbrain; it is directly anterior to the cerebral aqueduct
What does the MLF do?
It coordinates eye movements with head movements to stabilize vision while moving. The MLF connects to CN 3, 4, 6, and 8. It involves the cerebellum and vestibulocochlear system.
What is weird about the relationship between the axons of CN VII and the nucleus of CN VI?
The axons of CN VII go posteriorly and wrap around the nucleus of CN VI and the spinal tract of CN V.
The nucleus of CN VII is split into ________.
upper and motor divisions.
The ________ division of the facial nucleus receives bilateral innervation.
upper
What structure divides the two nuclei of CN VIII?
The ICP (the cochlear nucleus is on the lateral side of the ICP and the vestibular nucleus is on the medial side)
What information does the inferior cerebellar peduncle carry?
Spinal cord information to the cerebellum
Vestibular-cerebellar connection
Inferior olivary nucles-cerebellum connection
The middle cerebellar peduncle is the route by which _________________.
cerebral information passes to the cerebellum via pontine nuclei
The superior cerebellar peduncle is the route by which __________________.
the cerebellum gets information back to the cerebral cortex by way of the thalamus
also come cerebral-cerebellar communication
The 4th ventricle is “embraced” by which peduncles?
SCP and MCP
True or false: the alar/basal division pertains to tracts.
False! Only nuclei
MLF stands for _________________.
medial longitudinal fasciculus
The trigeminal nerve enters the brainstem through the ____________.
mid pons
What two trigeminal nuclei are ipsilateral to the entry point of the nerve?
The motor and principal sensory nucleus (analogous to the nucleus cuneatus/gracilis)
Axons from the principal sensory nucleus of the trigeminal nerve turn _________.
caudally before crossing at the base of the medulla
The Edinger-Westphal nucleus is part of what CN nuclei?
III
What are the three longitudinal sections of the brainstem?
Basis (anterior)
Tegmentum (middle)
Tectum (posterior)
The cerebral aqueduct can be seen in cross sections of what structure?
The midbrain
At what cross-sectional level does the medial lemniscus flip from an anterior-posterior axis to a medial-lateral axis?
Between the upper medulla and the lower pons
In the upper pons, the spinothalamic tracts are just ____________ to the medial lemnisci.
lateral
In the midbrain the spinothalamic tracts are just ___________ to the medial lemnisci.
posterior
What nuclei are in the upper midbrain periaqueductal gray matter?
CN III (with Edinger-Westphal like a scoop of ice cream on the cone)
Upon physical exam, how will damages to the right CN II and CN III present?
CN II: when you shine a light on the right eye neither pupil constricts (though shining a light on the left eye causes both pupils to constrict)
CN III: when you shine a light on the right eye the left pupil constricts but the right does not
The nuclei to what cranial nerve is just posterior to the medial longitudinal fasciculus in the lower midbrain?
CN IV
The MLF connects to what cranial nerve nuclei?
Think about it: it needs to coordinate eye movements with head movements; thus, it connects to all of the nuclei involved in eye movements (3, 4, and 6) with the vestibulocochlear nucleus (8).
What is in the cat’s ears?
The mesencephalic nucleus of the trigeminal nerve
The sensory nucleus of the trigeminal nerve is ___________ to the motor nucleus in the _______ pons.
lateral; mid
The “eyes” of the monster in the upper-mid medulla are the _____________.
nuclei ambiguus
What cross section would you be looking at if you saw the nuclei of 10 and 12 (with 12 being lateral and posterior to 10)?
Upper mid medulla
What information does the solitary nucleus process?
Taste (7, 9, 10)
The spinal tract for CN V is ___________ to the spinal nucleus for CN V.
lateral
The sensory neurons that mediate the stretch reflex synapse where?
In the mesencephalic nucleus
The corneal blink reflex is mediated by __________ sensory neurons.
pain (so those that synapse on the spinal nucleus)
The sensory axons from the face (for pressure/vibration) synapse on _____________.
the main sensory nucleus of the trigeminal ganglion (analogous to the nucleus gracilis)
What structure is just posterior to the spinothalamic tract in the midbrain?
The lateral lemniscus (carrying auditory information)
In the midbrain, posterior to the medial lemniscus and medial to the lateral lemniscus is what?
The SCP
Axons that arise from cells in the pons terminate in the ______________.
cerebellum (for movement coordination)
Anterior to the MLF in the lower midbrain is the _______.
SCP
Axons from the ______________ synapse on the red nucleus.
contralateral cerebellum
The lower pons looks kind of like _______________. What are its ears?
the aliens from Independence Day (at least to my eyes); the MCP
The deep cerebellar nuclei are opposite the ____________.
lower pons (across the 4th ventricle)
The 5th nerve exits ___________.
mid pons
Anterior and lateral to the fasciculus cuneatus is the ___________.
spinal trigeminal nucleus
The axons from the dentate nucleus pass through the ___________.
SCP to the thalamus
Where are the dentate nuclei?
On the opposite sides of the vermis
