Week 3 Lecture 6: Brainstem and Intro to Cerebellum Flashcards
What is a conduit?
a natural or artificial channel through which something is conveyed e.g fluid
What does the reticular formation control?
- consciousness
- cardiovascular and respiratory functions
- perception of pain
- arousal
- sleep wake cycle
What is the reticular formation?
diffused area of neurones that spans the whole area of brainstem
Which structure in the brain gives rise to cranial nerves 3-12?
brainstem
What are the 3 structures that the brainstem is composed of?
midbrain, pons and medulla oblongata
What structure sits above the midbrain?
diencephalon
What structure is found caudal to the medulla?
spinal cord - at the level of the foramen magnum
What is found dorsal and ventral to the brainstem?
dorsal - clivus of the occipital bone
ventral - cerebellum
Which components of the brainstem run through the ventricular system?
- IVth ventricle - between the pons and medulla anteriorly and the cerebellum posteriorly
- cerebral aqueduct (Caq) - at the level of the midbrain
What is the embryological origin of the structures that make up the brainstem?
mesencephalon (midbrain)
rhombencephalon - metencephalon and myelencephalon (pons and medulla oblongata respectively)
What is the internal structure of the brainstem composed of?
- tectum (most dorsal/ posterior to ventricular system)
- tegmentum (anterior to ventricular system)
- basal area (most ventral)
In locked in syndrome, how is the patient able to breath?
the stroke is at the level of the pons
the tegmentum is unaffected which explains why patients can breath and CVS is intact
What is the junction between the pons and the medulla called?
pontomedullary junction
What structure defines the midline of the medulla and seperates the two pyramids?
anterior median fissure
What are pyramids (in medulla)?
bumps on either side of the anterior median fissure
underneath is white matter fibres coming from the cortex that are sent down the CNS
Where is there crossing over of fibres contained in the medullary pyramids?
decussation of pyramids - this is where fibres from the left and right hemispheres meet so they can instruct the other side of the body
What structure separates the pyramids from the olives?
antero-lateral sulcus
Which cranial nerve fibres do we find at the antero-lateral sulcus?
hypoglossal nerve
Which cranial nerves emerge at the postero-lateral sulcus?
IX (glossopharyngeal), X (vagus), XI (spinal)
What is the rhomboid area/ fossa?
floor of the 4th ventricle
What two tubercles can we see on the dorsal aspect of the medulla?
- gracile fasciculus - either side of midline - bump that contains white matter fibres travelling from SC to brainstem
- cuneate fasciculus (lateral to gracile fasciculus)
What is the name of the point that marks the end of the 4th ventricle?
obex
How do we divide the medullas?
- rostral or ‘open’ medulla
- caudal or ‘closed’ medulla
What are the cuneate and gracile tubercles?
bumps in the gracile fasciculus and cuneate fasciculus because of the nucleis containing cell bodies underlying them
What is the defining feature of the open medulla
is open dorsally to the 4th nucleus at the obex
Which structures do we find in the closed (caudal) medulla?
- gracile tubercle
- cuneate tubercle
- pyramid
What is the name of the junction between the midbrain and pons?
pontomesencephalic junction
Where does the basilar artery sit?
in the basilar groove
What is the name of the junction between the cerebellum and the pons?
cerebellopontine angle
Which cranial nerves emerge from the cerebellopontine angle?
CN VII and CN VIII - facial and vestibulochochlear
What attaches the cerebellum to the midbrain?
superior cerebellar peduncle
What attaches the cerebellum to the pons?
middle cerebellar peduncle
What attaches the medulla to the cerebellum?
inferior cerebellar peduncle
In what direction do the fibres run in the pons?
transverse
Which structure forms the roof of the 4th ventricle?
superior cerebellar peduncle
What are cerebral peduncles?
a collection of descending motor fibres coming from the cortex
What lies in between the left and right cerebral peduncles?
interpeduncular fossa
Which cranial nerves emerge from the midbrain?
CN III (from the interpeduncular fossa) and CN IV
What are the names of the 2 paired bumps found on the dorsal aspect of the midbrain and what is the significance of each?
superior colliculus - important for the visual system
inferior colliculus - important for the auditory system
What is the brachium of the superior colliculus and inferior colliculus?
colliculi have a projection that extends to connect with the thalamus
Explain the key features of the anterior view of the midbrain
main feature - cerebral peduncle
seperated by interpeduncular fossa
oculomotor nerve emerges
what are the key features of the dorsal view of the midbrain?
- superior and inferior colliculi
- trochlear nerve emerges
- has cerebral aquaduct running through it
Where is the reticular formation?
in the tegmentum of the brainstem
Which arteries are involved in the blood supply to the brainstem?
- PCA (midbrain/ occipital lobe)
- basilar artery (pons)
- SCA
- AICA
- PICA
- vertebral artery (medulla)
State where each of cranial nerve 3-12 emerge from?
3- oculomotor arises between left and right peduncle
5 - trigeminal emerges from middle of pons
6 - abducens in pontomedullary junction
7/8 - facial and vestibulocochlear at level of cerebellar pontine angle
9,10,11 - glossopharyngeal, vagus and accessory emerge lateral to olives
12 - hypoglossal emerges between pyramid and olives
What is the cerebellum responsible for?
co ordination of movement, maintenance of balance and posture
What is the anatomical location of the cerebellum?
found under the occipital lobes of the cerebral hemispheres and dorsal to brainstem
What divides the anterior and posterior lobes of the cerebellum?
primary fissure
What seperates the two hemispheres of the cerebellum?
vermis
What is tonsillar herniation?
- there are two tonsils seen in the ventral view of the cerebellum, just posterior to the medulla
- if there is increased intracranial pressure the tonsils might herniate into the medulla
