Brainstem Flashcards
What are the functions of brainstem?
reflexive and unconscious behaviour (for survival)
modulation of various arousal and conscious states
What are the components of brainstem?
mid brain, pons, medulla, oblongata
Where is the brainstem located? How far does it extend?
in the posterior cranial fossa
extends from Mammillary bodies to the pyramidal decussation
What are the surface structures of midbrain, both anteriorly and posteriorly
anterior: cerebral peduncles (contains pyramidal tracts from cortex)
posterior: superior and inferior pairs of colliculi (for eye movement control and hearing)
Where is the connection between cerebellum to brainstem?
Pons, via cerebellar peduncles
where is the facial colliculi? what are they formed by?
along the floor of the 4th ventricle, between pons and cerebellum
formed by abducens nucleus and fibres of CNVII
What’s located on the dorsal aspect of medulla?
dorsal columns and nuclei-gracile and cuneate tubercle
what’s located on the ventral aspect of medulla?
two bulges of inferior olivary nuclei (superior) and pyramidal decussation (posterior)
Where is the tectum?
the roof of the midbrain
where is the tegmentum
ventral to the ventricular system, running all the way from brainstem to the spinal cord
What does the tegmentum cover?
cranial nerves, reticular formation
What is the midbrain important for?
it contains important descending motor tracts (corticospinal)
it has a range of nuclei modulating the descending motor fibres
What are the pathology associated with midbrain damage both 1) ventrally 2) dorsally
1) tectum and tegmentum are located ventrally, damage can cause major problem with movement
2) cranial nuclei are located dorsally, so damage will cause cranial nerve deficit
Do cranial nerves exit the brainstem in order?
Yes, CNIII most rostrally, CNXII most caudally
which cranial nerves are mix nerves
trigeminal, facial, glossopharyngeal, vagus
which CNs exit the medulla?
glossopharyngeal, vagus, accessory, hypoglossal
which CNs exit the pons?
trigem, abducent, facial, vestibulocochlear
which CNs exit above the pons?
olfactory, optic, oculomotor, trochlear
Embryologically, where are 1) motor nuclei 2) sensory nuclei developed?
1) basal plate
2) Alar plate
Which embryological plate shifts laterally? Why does it shift?
alar plate
because the ventricles are in the way
How are nuclei of the CN placed in the brainstem?
in columns
What is the significance of alar plate shift?
CN sensory nuclei are positioned laterally, whereas motor nuclei are towards the midline
What are the three types of brainstem motor nuclei?
general somatic motor
branchial motor
general visceral
What happens when the inferior cerebral peduncle is damaged?
peduncle contains projection to cerebellum, so any damage can lead to ataxia (clumsiness)
What are the three types of brainstem sensory nuclei?
general sensory
visceral sensory
special sensory
Which CN nuclei are located in the midbrain?
oculomotor and trochlea
they are both pure motor nerves, so are located medially
Where can you find reticular formation?
within the tegmentum, which extends rostrally with thalamus, through the brainstem, and continuous with gray of spinal cord
What is the function of reticular formation rostrally
in the midbrain and upper pons, they maintain alert conscious state
What is the function of reticular formation caudally
working with CN and spinal cord to carry out survival reflex like breathing and control of heart rate
How does the reticular formation modulate the forebrain?
the rostral RF provides long ascending tracts that release different neurotransmitters to modulate the forebrain
What is the function of ventrolateral medullary reticular formation (VMRF)
regulate vagus functions such as GI response (swallowing, vomiting), respiratory activities, CV response
What are the three long fibre tracts?
dorsal column medial leminiscus system
anterolateral system
corticospinal tract
Where do the three long fibre tracts decussate?
dorsal column - dorsal medulla
anterolateral system - spinal cord
corticospinal tract - pyramidal decussation at ventral oblongata
