Brainstem

Question 1

Obex

Answer 1

apex of fourth ventricle where it narrows it the central canal opens to spinal cord (Medulla)
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Question 2

Pyramidal decussation

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Answer 2

interrupts anterior median fissure, at junction of brainstem and spinal cord. Contains corticospinal tract, motor fibers form cerebral cortex on their way to the spinal cord. Note pyramid bounded by anterolateral sulcus. (anterior surface)
�Caudal Medulla

Question 3

CN XII

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Answer 3

Hypoglossal nerve (cranial nerve XII) rootlet exit via anterolateral or preolivary sulcus
�Rostral MEDULLA

Question 4

Olive

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Answer 4

Bulge created by inferior olivary nucleus (MEDULLA)

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Question 5

CN IX and CNX

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Answer 5

Rootlets of glossopharyngeal (IX) and vagus (X) nerves emerge from the post olivary sulcus, lateral to the olive.
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Question 6

cuneate tubercle

Answer 6

Fasciculus cuneatus extends to cuneate tubercle, marking site of the nucleus cuneatus. Fibers leave these nuclei and travel in an arch across the midline to form the medial lemniscus.
�(MEDULLA)

Question 7

gracile tubercle

Answer 7

Fasciculus gracilus extends to the gracile tubercle which is at the site of nucleus gracilus. Fibers leave these nuclei and travel in an arch across the midline to form the medial lemniscus.
(Medulla)

Question 8

Sulcus limitans

Answer 8

Sulcus limitans: Embryonic dividing line between sensory (now lateral) and motor (now medial) nuclei.
extends down spinal cord
sensory component swins out laterally during development

MEDULLA

Question 9

Hypoglossal trigone

Answer 9

triangular swelling in floor of 4th ventricle made by underlying hypoglossal nerve nucleus.
MEDULLA

Question 10

Vagal trigone

Answer 10

triangular swelling in floor of 4th ventricle made by underlying dorsal motor nucleus of the vagus nerve. Vagus nerve is longest nerve
MEDULLA

Question 11

Facial colliculus

Answer 11

Facial colliculus: Actually in pons, but since we are in the floor of the fourth ventricle now we can see it. This little hill is not due to the facial nerve motor nucleus, instead this is the site where the facial nerve loops over the abducens nerve nucleus as it goes on its way out of the brainstem.

Question 12

Basal pons

Answer 12

Large bulge on anterior surface of brainstem. Site of many neurons that receive axons from cerebral cortex, the pontine neurons then send an axon across the midline of the pons (so-called crossing fibers) that collect laterally forming the middle cerebellar peduncle. )This is part of the cerebropontocerebellar pathway; more to come).

Question 13

Middle cerebellar peduncle (MCP)

Answer 13

Major cerebellar input pathway. CAUDAL pons is attached to the cerebellum by the middle cerebellar peduncle

Question 14

Trigeminal nerve (V):

Answer 14

Enters at midpontine level thru middle cerebellar peduncle.

lateral to pons but at midline

Question 15

Abducens nerve (VI)

Answer 15

Exits brainstem at the pontomedullary junction near midline, near edge of pyramid as it emerges from the pons. Motor and sensory component.. Motor is rostral

Question 16

Facial nerve (VII)

Answer 16

Exists lateral the abducens at the pontomedullary junction. Has two parts: motor root that is larger and more medial than the sensory root. Sometime the sensory root is known as the intermediate nerve. Cerebellar pontine angle

Question 17

Vestibulocochlear nerve (VIII)

Answer 17

Exists lateral the facial nerve at the pontomedullary junction. Has two parts: a medially situated vestibular division and a more laterally situated cochlear division. Cerebellar pontine angle

Question 18

Superior cerebellar peduncle (brachium conjunctivum)

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Answer 18

Forms much of the roof of the fourth ventricle. It emerges from the cerebellum (it is mostly a cerebellar out flow pathway) and moves towards the midline entering the brainstem near the junction of the pons and midbrain. (roof)
Can see the superior cerebellar peduncle (SCP) leaving the cerebellum at ROSTRAL pons. Then enters the CAUDAL midbrain and decussates. After Some superior cerebellar peduncle fibers end in the red nucleus in the ROSTAL midbrain , but most proceed to the thalamus.

Question 19

Lateral lemniscus

Answer 19

Band of fibers that covers the superior cerebellar peduncle in the rostral pons that is part of the ascending auditory pathway which terminates in the inferior colliculus, a midbrain structure.

Question 20

Cerebral aqueduct

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Answer 20

Narrow channel in midbrain the connects the 3rd and 4th ventricles. Remnant of the lumen of the embryonic mesencephalon. Lesions in the aqueduct are not an uncommon cause of CSF obstruction narrow, which can be series as the aqueduct is also the only way CSF fluid can reach the fourth ventricle. Can be seen in midbrain cross sections with periaqueductal gray matter (PAG) around it, which is very important in descending pain control. Opens up into ventricle at ROSTRAL pons making the ventricular opening smaller at this level.

Question 21

Superior colliculus

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Answer 21

Gray matter mass in roof (tectum) of rostral midbrain. Has roles in directing visual attention and controlling eye movements. Found on poster midbrain

Question 22

Inferior colliculus

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Answer 22

Gray matter mass in roof (tectum) of caudal and posterior midbrain. It is a major component of the auditory system. It received input from the lateral lemniscus; output goes thru the inferior brachium to the medial geniculate nucleus of the thalamus.

Question 23

Cerebral peduncles:

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Answer 23

Large bundle of white matter at the base of the midbrain located anteriorly. It contains tightly packed fibers from the cerebral cortex on their way to the brainstem and spinal cord.
Base that connects cerebrum and brainstem

Question 24

Oculomotor nerve (III)

Answer 24

Lower motor neurons for extraocular muscles and contains preganglionic parasympathetic neurons that control pupillary sphincter and ciliary muscles. Nucleus is located in rostral midbrain and emerges from space between the cerebral peduncles (aka the interpeduncular fossa)

Question 25

``` Trochlear nerve (IV) � ```

Answer 25

Found in caudal and dorsal midbrain. The nerve leaves the dorsal aspect of the brainstem (the only one that does this) just below the inferior colliculus Innervates the superior oblique muscle.

Question 26

Inferior brachium (a.k.a. brachium of inferior colliculus):

Answer 26

Part of ascending auditory pathway. Contains fibers from the inferior colliculus that project to the medial geniculate nucleus of the thalamus.

Question 27

Tegmentum

Answer 27

Tissue anterior to ventricle

Question 28

Tectum

Answer 28

(“roof”): Tissue posterior to ventricle

Question 29

What is a peduncle?

Answer 29

A bundle of white matter that connects different parts of the brain. Cerebellar ones connect cerebellum to brain stem and cerebral ones connect cerebral cortex to brainstem

Question 30

Corticospinal tract

Answer 30

Descending tract and most anterior.. The nerve axons travel from the cortex through the cerebral peduncle and into the brainstem and anterior medulla. Discrete in midbrain then breaks up in pons into noticeable bundles then discrete again in medulla in large anterior pyramids. Bound by the anterolateral sulcus, forming the pyramids of the medulla. Majority of Axons cross over at the pyramidal decussation before continuing in the spinal cord. The nerve axons traveling down the tract are referred to as upper motor neurons and will synapse either directly with lower motor neurons or interneurons first.

Question 31

Spinothalmic tract

Answer 31

Spinothalmic is ascending. Joins up with medial lemniscus at level of the pons. Anterolateral

Question 32

Medial lemniscus

Answer 32

These fibers crossing the midline are known as internal arcuate fibers or the sensory decussation. Fibers from gracile nucleus and cuneate nuclease come in. Pathway: Internal arcuate fibers form medial lemniscus in the CAUDAL medulla. In the medulla the medial lemniscus is arranged so that fibers carrying cervical information are most posteriorly situated. As it travels through the pons, information from the feet is lateral and cervical areas are near the midline. Horizontally oriented in the pons as well. Note that as the ML moves laterally and it approaches the spinothalmic tract in the rostral pons, which is a good thing as these tracts will proceed together to the thalamus.

Question 33

Lateral or external cuneate nucleus

Answer 33

Embedded in fasciculus cuneatus this serves as the arm’s equivalent of Clarke’s nucleus (proprioception) and the axons of the neurons here join up with the posterior cerebellar tract in the inferior cerebellar peduncle at a more rostral level.

Question 34

Inferior olivary nucleus (IO):

Answer 34

This nucleus make the bump we call the olive on the external surface of the medulla. Fibers leave the hilum of the inferior olivary nucleus and cross the midline to reach the inferior cerebellar peduncle; these are the internal arcuate fibers. Internal arcuate fibers form medial lemniscus in the ROSTRAL medulla

Question 35

pontine nucleus

Answer 35

The pontine nuclei are a part of the pons involved in motor activity. They are anteriorly located and in the basal pons. They are numerous and scattered about crossing fibers and are is the gray matter found amongst the coritcospinal tract.. The crossing fibers collect at the lateral pons and form the middle cerebellar peduncle at the CAUDAL end of the pons

Question 36

Substantia nigra (SN):

Answer 36

Nucleus that contains neurons that use dopamine as a neurotransmitter and heavily innverate the putamen and caudate of the cerebrum. Neuronal loss results in Parkinson’s disease. First found in the ROSTRAL midbrain immediately posterior to the cerebral peduncles.

Question 37

red nucleus

Answer 37

The red nucleus is a structure in the rostral midbrain involved in motor coordination. Found anterior to periaqueductal gray matter. Some superior cerebellar peduncle fibers end in the red nucleus , but most proceed to the thalamus.

Question 38

What artery supplies medial medulla?

Answer 38

paramedian branches of vertebral artery and anterior spinal artery

Question 39

What artery supplies lateral medulla?

Answer 39

PICA!!!! 1. ) Arises from the vertebral artery at the level of the medulla 2. ) supplies lateral medulla and inferior cerebellum (olive)

Question 40

What artery supplies lateral pons?

Answer 40

AICA and SCA 1.) AICA: level of caudal pons lateral caudal pons and small region of cerebellum 2.) SCA: Level of rostral pons supplies superior cerebellum and rostrolateraldorsal pons

Question 41

What artery supplies midbrain?

Answer 41

POSTERIOR CEREBRAL ARTERY!

Question 42

What artery supplies medial pons?

Answer 42

paramedian branches of the basilar artery