20.2 NS: Overview of the brainstem Flashcards
What is the brainstem made up of?
What are its rostral to caudal boundaries?
Midbrain
Pons
Medulla
Mamillary bodies to pyramidal decussation
What do we see on the dorsal aspect of the brainstem?
Midbrain: colliculi
Pons: linked w/ cerebellum, 4th ventricle limits (on floor there are facial colliculi formed by abducens nucleus and NVII fibres)
Medulla: caudal-dorsal columns, nuclei gracile and cuneate tubercle
What do we see on the ventral aspect of the brainstem?
Midbrain: Cerebral peduncles
Pons: Attached to cerebellum dorsolaterally by cerebellar meduncles (sup/mid/inf)
Medulla:
Rostral: inferior olivary nuclei
Pyramids descend to pyramidal decussation
What are the tectum and tegmentum and basis for?
Tectum: roof of 4th ventricle (colliculi)
Tegmentum: covering (continuous with spinal cord), cranial nerves and reticular formation
Basis: important for descending motor control
Where do spinal nerves end? (or where is there no dermatome)
C2 (no C1 dermatome)
What order do the cranial nerves exit the brainstem? Dorsal or ventral surface?
In order, rostral to caudal
Exit ventral (except IV)
What does the rostral and caudal parts of the reticular formation do?
Rostral: midbrain/upper pons, maintain alertness (ascending reticular activating system)
Caudal: pons/medulla, motor reflex/autonomic functions
What are ascending pathways (long fibre tracts) for?
Touch, pain
What ascending pathway is responsible for touch? Where does it cross?
Dorsal column-medial lemniscus system
- Fine touch-tactile, vibration
- Crosses in medulla (medial lemniscus)
What ascending pathway is responsible for pain? Where does it cross?
Anterolateral system, crosses in spinal cord (three pathways terminate in: thalamus, midbrain, reticular formation)
What is the descending pathway for? Where does it cross?
Descending pathway: corticospinal tract
Controls motor function, crosses at pyramidal decussation
Where do the cranial nerve nuclei and reticular formation sit within the brainstem?
Dorsally
Where do the corticospinal tracts sit in the brainstem?
Ventrally (basis)
What important structures are in the ventral:
Midbrain
Pons
Medulla
Midbrain: cerebral peduncles, substantia nigra, red nuclei
Pons: CB nuclei, middle cerebellar peduncle
Medulla: inferior olivary nuclei
What regulates the visceral functions of Vagus nerves?
Ventrolateral medullary reticular formation
