ANA 305 Histology of the Midbrain & Pons Flashcards
Describe the midbrain
It serves as a conduit between the diencephalon and pons as well as connecting to the cerebellum at posteriorly via the superior cerebellar peduncles
It is the most superior part of the brainstem
Anteriorly it consist of the crus cerebri each with interperduncle fossa between them
crus cerebri carries which nerve fibers?
- Corticospinal
2.Corticonuclear - Pontine spinal tracts
What is the role of the central cerebral aqueduct of the midbrain?
It connects the 3rd ventricle superiorly to the 4th ventricle inferiorly
The midbrain is separated relative to
The cerebral aqueduct
Anterior and posterior to the cerebral aqueduct is
Posterior: tectum (floor)
Anterior: tegmentum (roof)
Describe the posterior surface of the midbrain
It consists of the corpora quadrigemina which is comprised of the bilateral superior colliculi and bilateral inferior colliculi
Function of the superior colliculi
Involved in visual reflexes such as saccadic eye movements
Each superior coniculli sends fibers to the corresponding lateral geniculate body and optic tract through the superior brachium
Function of the inferior conuculli
Involved in auditory processing and connect to their corresponding medial geniculate nuclei via inferior branchium
Just inferior to the inferior coniculli at the posterior midline is located
Trochlear nerve CNIV
Why is CN IV so unique?
Trochlear nerve
It is the only cranial nerve to emerge from the posterior surface of the midbrain
Which other CN arises from the midbrain?
CN III Occulomotor nerve
Describe the location of CN III
Occulomotor nerve
Arises from the midbrain on the oculomotor sulcus in the medial surface of the crus cerebri, within the interpenduncular cistern
What are some of the nuclei within the midbrain?
The red nucleus (plays role in motor coordination)
the substantia nigra (produces dopamine)
Dorsal raphe nucleus (produce seratonin)
What surrounds the cerebral aqueduct
The periaqueductal grey
The largest of the raphe nuclei are in____________
The anterior midline of the periaqueductal grey and the location of the ventral tegmental area is near the midline medial to the red nucleus
Function of substantia nigra
Contains dopaminergic neurons that help to regulate movement associated with basal ganglia
The ventral tegmental area contains_______
Dopaminergic neurons and projects widely throughout the brain
The periaqueductal grey is thought to play a role in__________
Pain suppression
Function of the red nucleus
Is involved in movements and contains many connections with the cerebellum
Medial longitudinal fasciculus lies anterior to the periaqueductal gray and plays a role in_____________
Coordinating eyes movements
particularly integrating movements between the eyes and head
and integrated the cranial nerves involved in eye movement CN III (oculomotor), IV (trochlear), and VI (abducens)
Midbrain is also known as the_________
Mesencephalon
What is the pons?
The pons is the largest part of the brainstem
A part of the brainstem that connects the medulla oblongata inferiorly to the midbrain superiorly
It is anterior to the cerebellum
What are features of the pons?
It is dominated by a large base (basal pons or basis pontis) and by its large white matter connection in the cerebellum
It is connected to the cerebellum via the superior and inferior cerebellar peduncles
What are the longitudinal fibers of the pons?
Corticospinal tracts that continue as the medullary ramus and corticopontine tracts that terminate on the interspersed pontine nuclei
What is the locus coeruleus?
Location & Function
Location: near the 4th ventricle on each side of the pons is the locus coeruleus “blue spot’’
Located in the posterior lateral pons at the lateral border of the periaqueductal grey
Function: a small nucleus that contains a high density of pigment noradrenergic neurons that project diffusely through the CNS
It produces norepinephrine and has projections that spread widely throughout the CNS and is involved in reticular activating system
Role of the pons
It serves as a bridge between the cerebellum and cerebral hemispheres.
Pons, in a literal sense, means “the bridge”. It is so named because it acts as a conduit for the passage of fibres from one side of the cerebellum to the other by its transverse fibres constituting the middle cerebellar peduncle
It houses the cranial nerve nuclei for the
- trigeminal nerve (CN V)
- abducens nerve (CN VI)
- facial nerve (CN VII)
- vestibulocochlear nerve (CN VIII).
What are the raphe nuclei
They are near the midline throughout the brainstem but concentrated mostly in the dorsal pons
They contain large serotonergic neurons that project extensively throughout the brain
What lies in the basilar groove of the pons?
basilar artery
The posterior pons is connected to the cerebellum by the…
middle cerebellar peduncles
What forms the superior portion of the floor of the 4th ventricle
the posterior portion of the pons
Important nuclei of the pons include
- cranial nerve nuclei
- locus coeruleus
- pontine nuclei
Clinical significance of the locus coeruleus
it suffers compromise in Alzheimer
What are the pontine nuclei?
a collection of pontine motor nuclei in the anterior pons that have many connections with the cerebellum via the middle cerebellar peduncle and assist with coordinating movement and help to modulate breathing
