Neuroanatomy Lab 3: Structures And Concepts.

Front 1

What is the source of the Internal Arcuate Fibers?

Back 1

The Internal Arcuate Fibres arise from the Nuclei Cuneatus and Gracilis.

Front 2

What do the Internal Arcuate Fibers form?

Back 2

They cross at the Sensory Decussation and form the contralateral ascending Medial Lemniscus.

Front 3

What pathway is the Medial Lemniscus a part of?

Back 3

It is part of the somatosensory pathway, which carries proprioceptive, fine touch and vibration sensation up the Dorsal Column (DC).

Hint 3

The DC consists of either the Fasciculus Cuneatus or Gracilis, depending on whether the upper or lower limbs are the source.

Front 4

What is the function of the Lateral (Accessory) Cuneate Nucleus?

Back 4

It is the source of the Cuneo-Cerebellar Fibers, which convey proprioceptive information to the Cerebellum from the arm.

It is analogous to the Nucleus Dorsalis (of the spinal cord) for the legs.

Front 5

Where do the Corticospinal Tracts arise?

Back 5

They originate from the Frontal and Parietal lobes.

Front 6

What do the Corticospinal Tracts form in the Medulla?

Back 6

The Pyramids.

Front 7

How many of the axons of the Corticospinal Tracts cross at the Decussation of the Pyramids?

Back 7

Approximately 85% of the axons cross at the Decussation and descend the spinal cord through the Lateral Corticospinal Tracts.

Hint 7

The remainder descend ipsilaterally through the Anterior Corticospinal Tracts.

Front 8

What is the extent of the Hypoglossal Nerve Nucleus?

Back 8

It extends the length of the Medulla.

Front 9

Where does the Hypoglossal Nucleus appear in cross section?

Back 9

It appears close to the midline, as is common for motor nuclei.

Front 10

How many Vestibular Nuclei are there?

What part of the brainstem are they in?

Back 10

Four: 1. Superior, 2. Inferior, 3. Lateral, and 4. Medial.

The Medial and Inferior nuclei are in the Rostral Medulla, and the Superior and Lateral nuclei are in the Caudal Pons.

Front 11

What is the posterior surface feature marking the location of the Hypoglossal Nucleus?

Back 11

In the Open Medulla, the Hypoglossal Trigone visibly shows the position.

In the Closed Medulla, the Gracile and Cuneate Nuclei obscure the position of the Hypoglossal Nucleus

Front 12

What two nuclei sit on either side to the Dorsal Vagal Nucleus?

Back 12

Medially the Hypoglossal Nucleus.
Laterally the Solitary Nucleus (and tract).

Front 13

What does the Dorsal Vagal Nucleus innervate?

Back 13

It provides parasympathetic preganglionic fibers that innervate the viscera of the thorax and the abdomen.

(and apparently receives visceral afferents, but we don't go into that)

Front 14

What is the vertical extent of the Vagal Dorsal Motor Nucleus?

Back 14

The extent of the Medulla, similar to the Hypoglossal Nucleus.

Front 15

How can you locate the Nucleus Ambiguus in cross section?

Back 15

It's difficult to visualize, but two landmarks are that it's medial to the Spinal Tract of CN V, and dorsal to the Dorsal Accessory Olivary Nucleus, in the middle of the Medulla.

Front 16

What sort of neurons are found in the Nucleus Ambiguus?

Back 16

It is the source for lower motor neurons of CN IX, X, and XI.

It provides:
CN IX: Somatic efferent to Stylopharyngeus muscle.
CN X: Somatic efferent innervation to the muscles of the soft palate, the pharynx, the larynx and the upper third of the esophagus. It controls speaking and swallowing.
CN XI: Fibers of CN XI from the Nucleus Ambiguus join X to innervate the larynx (often actually just considered part of X)

Hint 16

It also provides parasympathetic preganglionic innervation to the heart.

Front 17

What is the vertical extent of the Nucleus Ambiguus?

Back 17

It extends rostrally to just below the Pontomedullary Junction, and caudally to the level of the Foramen Magnum.

Front 18

What does the Solitary Nucleus and Tract contain?

Back 18

Sensory fibers derived from
CNs VII, IX, and X.

Taste fibers synapse on the rostral portion of the solitary nucleus. General Visceral Afferent input terminate on the Caudal portion of the nucleus.

Front 19

What is the vertical extent of the Solitary Tract and Nucleus?

Back 19

It extends rostrally to just above the level of CN X, and caudally to around the level of the Decussation of the Pyramids

Front 20

What type of input does the Spinal Trigeminal Tract (and Nucleus) receive?

Back 20

It receives General Afferent fibers from, primarily, CN V, as well as CN IX and X.

Front 21

What is the vertical extent of the Spinal Trigeminal Nucleus and Tract?

Back 21

It extends rostrally to the mid-pons, and caudally down into the cervical spine.

Front 22

What is the role of the Vestibular Nuclei?

Back 22

They mediate information about balance and equilibrium, and coordinates head and eye movement in part by projecting axons via the Medial Longitudinal Fasciculus (MLF).

Front 23

What is the source of axons for the Medial Longitudinal Fasciculous?

Back 23

The Vestibular Nuclei.

Front 24

What type of signal is carried by the Medial Longitudinal Fasciculus?

Back 24

It carries mainly vestibular information that coordinates activities like the vestibulo-ocular reflex and gaze-holding.

Front 25

What is the function of the Tectospinal Tract?

Back 25

It is involved in coordinating head and eye movements, similar to the MLF.

Front 26

What is the source of axons for the Tectospinal Tract?

Back 26

It arrises from the contralateral Superior Colliculus.

Front 27

What is the extent of the Tectospinal Tract?

Back 27

It descends from the contralateral Superior Colliculus all the way through the brainstem and to the cervical spinal cord.

Front 28

What signals do the Vestibular Nuclei receive?

Back 28

They receive input from the vestibular apparatus
(the semicircular canals and ampulllae, and the saccule and utricle).

Front 29

How many nuclei are included in each Inferior Olive?

Back 29

Three:
1. Principal,
2. Dorsal Accessory, and
3. Medial Accessory Olivary Nuclei.

Front 30

What sources give input to the Inferior Olives?

Back 30

They receive inputs from:
1. Spinal,
2. Brainstem,
3. Cerebellar, and
4. Cerebral cortical sources.

Front 31

What fibres do the Olivary Nuclei give off? Where do they go?

Back 31

They give rise to Olivocerebellar Fibres, which cross the midline and enter the Cerebellum via the Inferior Cerebellar Peduncle.

Front 32

What is the Reticular Formation?

Back 32

An area of intermingled grey and white matter occupying the central region of the brainstem throughout its extent.

It is actually groups of nuclei and their afferent and efferent connections.

Front 33

What does the Reticular Formation do?

Back 33

It influences many things:
1) Level of consciousness (shown),
2) Coordination of somatic motor activity,
3) Control of respiration,
4) Modulation of pain transmission,
and other functions.

Front 34

Where does the Lateral Lemniscus derive its fibres?

Back 34

A variety of sources:
1) Dorsal and Ventral Cochlear Nuclei,
2) Nucleus of the Trapezoid Body, and
3) the Superior Olivary Nucleus.

Front 35

What is the Lateral Lemniscus a portion of?
What information does it carry?

Back 35

It is a portion of the auditory pathway.
It conveys information related to hearing.

Front 36

Where do the ascending fibres of the Lateral Lemniscus terminate?

Back 36

They terminate in the Inferior Colliculus.

Front 37

What nucleus is indicated by the red arrow?
What occurs at the blue arrow?

Back 37

The Facial Motor Nucleus.
The Genu of the Facial Nerve, where the fibres of the Facial Nerve course around the Abducens Nucleus.

Front 38

What does the Facial Nucleus innervate?

Back 38

It provides motor innervation to the muscles of facial expression.

Front 39

What surface feature do the does the Genu of the Facial Nerve form?

Back 39

It forms the Facial Colliculus seen in the floor of the Fourth Ventricle.

Front 40

Where does the Facial Nerve exit the Brainstem?

Back 40

After encircling the Abducens Nucleus, they continue ventro-laterally toward their exit at the lateral margin of the ponto-medullary junction.

Front 41

What nucleus is indicated by the red arrow?

Back 41

The Abducens Nucleus.

Front 42

What does the Abducens Nucleus innervate?

Back 42

It provides motor innervation to the Lateral Rectus muscle of the eye.

Front 43

Where do the fibres of CN VI exit the Brainstem?

Back 43

They exit medially on the ponto-medullary junction.

Front 44

What nucleus is indicated by the green arrow?

Back 44

The Locus Ceruleus.

Front 45

What system is the Locus Ceruleus a part of?

Where do its axons project?

Back 45

It's a component of the Reticular Formation.

It's neurons project to all levels of the nervous system with highly branched axons.

Front 46

How many nuclear groups are associated with the Trigeminal Nerve?

Back 46

Four (3 sensory; 1 motor):
1) The Spinal Tract and Nucleus,
2) Principal Sensory Nucleus,
3) Mesencephalic Tract and Nucleus, and
4) the Trigeminal Motor Nucleus.

Front 47

What does the Motor Nucleus of the Trigeminal Nerve innervate?

Back 47

It provides innervation to the muscles of mastication, through the Mandibular division of the Trigeminal Nerve.

Front 48

What is the role of the Principal Sensory Trigeminal Nucleus?

Where is it located?

Back 48

It mediates sensations of touch and pressure from various regions of the head.

It's located laterally at the mid-pontine level.

Front 49

What does the Mesencephalic Tract of CN V contain?

Back 49

It consists of of axons of the pseudounipolar neurons which make up the Mesencephalic Nucleus.

Front 50

What type of sensation does the Mesencephalic Nucleus of CN V mediate?

Back 50

It mediates Proprioceptive information, particularly from the Temporomandibular Joint and the teeth.

Front 51

Where do the Corticopontine Fibres originate?

Back 51

They originate from Frontal, Parietal, and to some extent Occipital regions of the Cerebral Cortex.

Front 52

Where do the Corticopontine terminate?
Where does the pathway continue after that?

Back 52

They terminate by synapsing on the Pontine Nuclei.
The Pontine Nuclei project axons that cross the Pons as Transverse Fibres and enter the Cerebellum through the Middle Cerebellar Peduncle.

Front 53

Which of the Cerebellar Peduncles carries mostly efferent fibres from the Cerebellum?

Back 53

The Superior Cerebellar Peduncle (it has very few afferent).

The Inferior also has some too, but not as much.

Front 54

What happens to the fibres of the Superior Cerebellar Peduncle at the level of the rostral Pons and the caudal Mesencephalon?

Back 54

They undergo a decussation.