ANA 305 Histology of the Midbrain & Pons

Question 1

Describe the midbrain

Answer 1

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

Question 2

crus cerebri carries which nerve fibers?

Answer 2

1. Corticospinal
   2.Corticonuclear
2. Pontine spinal tracts

Question 3

What is the role of the central cerebral aqueduct of the midbrain?

Answer 3

It connects the 3rd ventricle superiorly to the 4th ventricle inferiorly

Question 4

The midbrain is separated relative to

Answer 4

The cerebral aqueduct

Question 5

Anterior and posterior to the cerebral aqueduct is

Answer 5

Posterior: tectum (floor)
Anterior: tegmentum (roof)

Question 6

Describe the posterior surface of the midbrain

Answer 6

It consists of the corpora quadrigemina which is comprised of the bilateral superior colliculi and bilateral inferior colliculi

Question 7

Function of the superior colliculi

Answer 7

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

Question 8

Function of the inferior conuculli

Answer 8

Involved in auditory processing and connect to their corresponding medial geniculate nuclei via inferior branchium

Question 9

Just inferior to the inferior coniculli at the posterior midline is located

Answer 9

Trochlear nerve CNIV

Question 10

Why is CN IV so unique?

Trochlear nerve

Answer 10

It is the only cranial nerve to emerge from the posterior surface of the midbrain

Question 11

Which other CN arises from the midbrain?

Answer 11

CN III Occulomotor nerve

Question 12

Describe the location of CN III

Occulomotor nerve

Answer 12

Arises from the midbrain on the oculomotor sulcus in the medial surface of the crus cerebri, within the interpenduncular cistern

Question 13

What are some of the nuclei within the midbrain?

Answer 13

The red nucleus (plays role in motor coordination)
the substantia nigra (produces dopamine)
Dorsal raphe nucleus (produce seratonin)

Question 14

What surrounds the cerebral aqueduct

Answer 14

The periaqueductal grey

Question 15

The largest of the raphe nuclei are in____________

Answer 15

The anterior midline of the periaqueductal grey and the location of the ventral tegmental area is near the midline medial to the red nucleus

Question 16

Function of substantia nigra

Answer 16

Contains dopaminergic neurons that help to regulate movement associated with basal ganglia

Question 17

The ventral tegmental area contains_______

Answer 17

Dopaminergic neurons and projects widely throughout the brain

Question 18

The periaqueductal grey is thought to play a role in__________

Answer 18

Pain suppression

Question 19

Function of the red nucleus

Answer 19

Is involved in movements and contains many connections with the cerebellum

Question 20

Medial longitudinal fasciculus lies anterior to the periaqueductal gray and plays a role in_____________

Answer 20

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)

Question 21

Midbrain is also known as the_________

Answer 21

Mesencephalon

Question 22

What is the pons?

Answer 22

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

Question 23

What are features of the pons?

Answer 23

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

Question 24

What are the longitudinal fibers of the pons?

Answer 24

Corticospinal tracts that continue as the medullary ramus and corticopontine tracts that terminate on the interspersed pontine nuclei

Question 25

What is the locus coeruleus?

Location & Function

Answer 25

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

Question 26

Role of the pons

Answer 26

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

Question 27

It houses the cranial nerve nuclei for the

Answer 27

1. trigeminal nerve (CN V)
2. abducens nerve (CN VI)
3. facial nerve (CN VII)
4. vestibulocochlear nerve (CN VIII).

Question 28

What are the raphe nuclei

Answer 28

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

Question 29

What lies in the basilar groove of the pons?

Answer 29

basilar artery

Question 30

The posterior pons is connected to the cerebellum by the…

Answer 30

middle cerebellar peduncles

Question 31

What forms the superior portion of the floor of the 4th ventricle

Answer 31

the posterior portion of the pons

Question 32

Important nuclei of the pons include

Answer 32

1. cranial nerve nuclei
2. locus coeruleus
3. pontine nuclei

Question 33

Clinical significance of the locus coeruleus

Answer 33

it suffers compromise in Alzheimer

Question 34

What are the pontine nuclei?

Answer 34

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