HNN Topic 5 - Cerebellum and Brainstem

Question 1

Describe the position of the cerebellum

Answer 1

‘Little brain’, at same level as but posterior to pons, under occipital + temporal lobes of the cerebral cortex

Question 2

Describe the function of the pons

Answer 2

• Pontine nucleus - connect cerebrum to cerebellum, coordinate voluntary movement
• CN nuclei -
  
  • Trigeminal (V)
  • Abducens (VI)
  • Facial (VII)
  • Vestibulocochlear (VIII)

Question 3

Describe the function of the gracile fasciculus

Answer 3

Posterior structure formed by the gracile nucleus, relays sensory information from the lower body to the thalamus via the medial lemniscus pathway

Question 4

List the components of the midbrain

Answer 4

1. Tectum (or corpora quadrigemina)
2. Tegmentum
3. Ventricular mesocoelia (cerebral aqueduct)
4. Cerebral peduncles
5. Nuclei + fasciculi

Question 5

What forms the medullary pyramids?

Answer 5

• Elevation of the corticospinal tract
• In lower part of medulla 85% of fibres cross over at the decussation of the pyramids (covers the anterior median fissure)

Question 6

List the main nuclei of the cerebellum

Answer 6

1. Fastigal nucleus
2. Interposed nuclei - emboliform and globose nuclei
3. Dentate nucleus
4. Vestibular nucleus

Question 7

Describe the components and function of the vestibulocerebellum

Answer 7

• Flocculonodular lobe + connections
• Involved with vestibular organs e.g. in vestibuloocular reflex

Question 8

Describe the function of the cuneate fasciculus

Answer 8

Posterior structure formed by the cuneate nucleus, relays sensory information from the upper body to the thalamus via the medial lemniscus

Question 9

List the general functions of the cerebellum

Answer 9

1. Maintenance of balance and posture
2. Coordinating voluntary movements
3. Motor learning
4. Cognitive functions

Question 10

Describe the gross anatomical structure of the cerebellum

Answer 10

• Two hemispheres divided by the vermis - narrow midline area
• Cerebellar deep nuclei (grey matter) encased by a highly convoluted sheet of tissue - cerebellar cortex
• Characterised by intricate pattern of folds and fissures

Question 11

What are the components of the internal anatomy of the pons?

Answer 11

1. Ventral pons
2. Tegmentum
3. Tracts

Question 12

What would be the effect of damage to the tegmentum of the pons?

Answer 12

Anosgnia for hemiplagia - unawareness of paralysis

Question 13

What is the function of the olivary nucleus?

Answer 13

Relays sensory information to the cerebellum via the inferior cerebellar peduncles

Question 14

Describe the location and function of the cerebral peduncles

Answer 14

• On either side of the midbrain anteriorly
• Connect the thalamic nuclei to the rest of the midbrain
• Assist in motor refinement, motor skill learning and converting proprioceptive information to balance and posture maintenace

Question 15

Describe the structure and function of the tectum of the midbrain

Answer 15

• Superior and inferior colliculi
• Posterior portion
• Superior colliculus = visual processing and eye movement (e.g. tracking)
• Inferior colliculus = auditory processing

Question 16

List the tracts which pass through the pons

Answer 16

• Corticospinal
• Corticobulbar
• Medial lemniscus
• Spinothalamic

Question 17

Describe the components (input and output) and function of the spinocerebellum

Answer 17

• Vermis and intermediate zones
• Input from the spinocerebellar tract
• Output to rubrospinal, vestibulospinal + reticulospinal tracts
• Integration of sensory input (proprioception), error correction, adaptive motor coordination

Question 18

List the functional centres of the medulla and explain their functions

Answer 18

1. Cardiac centre - regulates HR and contractility
2. Respiratory centre - regulatrs respiratory movements
3. Vasomotor centre - regulates BV diameter
4. Reflex centres - vomiting, sneezing, coughing, swallowing

Question 19

Describe the ventral pons

Answer 19

Contains the pontine nucleus (coordinates movement) - fibres cross at midline and form the cerebellar peduncles

Question 20

How is the cerebellum involved with cognitive functions?

Answer 20

E.g. language - role not understood

Question 21

What are the medullary olives?

Answer 21

• Large masses of grey matter lateral to the pyramids
• Contain the inferior olivary nucleus

Question 22

What is the function of the reticular formation of the pons?

Answer 22

Involved in regulating sleep-wake cycle and filtering incoming stimuli

Question 23

Describe the structure and function of the tegmentum of the midbrain

Answer 23

• Many unconscious/reflexive pathways, motor centre that relays inhibitory signals to the thalamus/basal ganglia to prevent unwanted movement
• Extends from substantia nigra to the cerebral aqueduct
• Contains nuclei of oculomotor and trochlear cranial nerves

Question 24

Describe the other functions of the medulla

Answer 24

• Houses the special sense nuclei - gustatory nucleus (taste), cochlear nucleus (hearing) and vestibular nucleus (balance)
• Cranial nerve nuclei - glossopharyngeal, vagus, accessory, hypoglossal

Question 25

List the surface features of the medulla oblongata

Answer 25

1. Pyramids 2. Olives 3. Gracile fasciculus 4. Cuneate fasciculus

Question 26

Describe the relation of the pons to the cerebellum

Answer 26

* Pons connected to cerebellum on posterior surface by the middle cerebellar peduncles * The structures are separated by the 4th ventricle

Question 27

List the areas of the midbrain and their functions

Answer 27

* Superior colliculus - visual response * Inferior colliculus - auditory response * Tegmentum - fine motor function * Substantia nigra - coordination of movement * Red nucleus - subconscious movement * CN nuclei * Oculomotor (III) * Trochlear (IV)

Question 28

Describe the location and components of the brainstem

Answer 28

* Most inferior part of brain, continuous with brain to form spinal cord * Components: * Midbrain * Pons * Medulla oblongata

Question 29

Describe the tegmentum of the pons

Answer 29

Forms part of the reticular formation - responsible for arousal and attentiveness

Question 30

Describe the zones of the cerebellum

Answer 30

* Either side of the vermis = intermediate zone * Laterally - lateral hemispheres * No clear gross morphological border between

Question 31

List the parts of the reticular formation

Answer 31

* Raphe nucleus * Magnocellular red nucleus * Parvocellular reticular nucleus

Question 32

Describe the appearance of the pons

Answer 32

Appears as a broad anterior bulge rostral to the medulla

Question 33

Describe the components (input and output) and function of the cerebrocerebellum

Answer 33

* Lateral hemispheres and dentate nuclei * Connections with cerebral cortex * Planning and timing of movements, motor learning * Input - cerebral cortex, pontine nuclei * Output - thalamus, red nuclei

Question 34

How does the cerebellum contribute to the coordination of voluntary movement?

Answer 34

Coordinates timing and force of muscle groups to produce fluid movements, receives sensory input to adjust movements for error correction

Question 35

How is the cerebellum divided anatomically?

Answer 35

* Anterior, posterior and flocculonodular lobes * Anterior and posterior lobes divided by primary fissure * Posterior and flocculonodular lobes divided by the posterolateral fissure

Question 36

Describe the important anatomical structures of the pons

Answer 36

1. Basilar groove - midline, where basilar artery is located 2. Pontomedullary junction - angle between lower border of pons + superior border of medulla

Question 37

List the functional divisions of the cerebellum

Answer 37

1. Vestibulocerebellum 2. Spinocerebellum 3. Cerebrocerebellum

Question 38

Which cranial nerves originate from the pons?

Answer 38

1. Trigeminal (V) 2. Abducens (VI) 3. Facial (VII) 4. Vestibulocochlear

Question 39

List the ways in which the cerebellum can be divided

Answer 39

1. Anatomically 2. By zones 3. Functionally

Question 40

How does the cerebellum contribute to maintenance balance and posture?

Answer 40

Input from vestibular, visual and proprioceptors, modulates commands to motor neurons to adjust posture in order to maintain balance

Question 41

Describe the attachments of the midbrain

Answer 41

Attached to diencephalon above and pons below

Question 42

Describe the location of the pons

Answer 42

Above medulla, below midbrain, anterior to cerebellum

Question 43

Which structural feature is seen on the anterior surface of the medulla?

Answer 43

Anterior median fissure

Question 44

Describe the position of the medulla oblongata

Answer 44

* Most inferior part of the brainstem, continuous with the pons above and spinal cord below * Exits skull through foramen magnum