HNN Topic 5 - Cerebellum and Brainstem Flashcards
Describe the position of the cerebellum
‘Little brain’, at same level as but posterior to pons, under occipital + temporal lobes of the cerebral cortex
Describe the function of the pons
- Pontine nucleus - connect cerebrum to cerebellum, coordinate voluntary movement
- CN nuclei -
- Trigeminal (V)
- Abducens (VI)
- Facial (VII)
- Vestibulocochlear (VIII)
Describe the function of the gracile fasciculus
Posterior structure formed by the gracile nucleus, relays sensory information from the lower body to the thalamus via the medial lemniscus pathway
List the components of the midbrain
- Tectum (or corpora quadrigemina)
- Tegmentum
- Ventricular mesocoelia (cerebral aqueduct)
- Cerebral peduncles
- Nuclei + fasciculi
What forms the medullary pyramids?
- 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)
List the main nuclei of the cerebellum
- Fastigal nucleus
- Interposed nuclei - emboliform and globose nuclei
- Dentate nucleus
- Vestibular nucleus
Describe the components and function of the vestibulocerebellum
- Flocculonodular lobe + connections
- Involved with vestibular organs e.g. in vestibuloocular reflex
Describe the function of the cuneate fasciculus
Posterior structure formed by the cuneate nucleus, relays sensory information from the upper body to the thalamus via the medial lemniscus
List the general functions of the cerebellum
- Maintenance of balance and posture
- Coordinating voluntary movements
- Motor learning
- Cognitive functions
Describe the gross anatomical structure of the cerebellum
- 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
What are the components of the internal anatomy of the pons?
- Ventral pons
- Tegmentum
- Tracts
What would be the effect of damage to the tegmentum of the pons?
Anosgnia for hemiplagia - unawareness of paralysis
What is the function of the olivary nucleus?
Relays sensory information to the cerebellum via the inferior cerebellar peduncles
Describe the location and function of the cerebral peduncles
- 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
Describe the structure and function of the tectum of the midbrain
- Superior and inferior colliculi
- Posterior portion
- Superior colliculus = visual processing and eye movement (e.g. tracking)
- Inferior colliculus = auditory processing
List the tracts which pass through the pons
- Corticospinal
- Corticobulbar
- Medial lemniscus
- Spinothalamic
Describe the components (input and output) and function of the spinocerebellum
- 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
List the functional centres of the medulla and explain their functions
- Cardiac centre - regulates HR and contractility
- Respiratory centre - regulatrs respiratory movements
- Vasomotor centre - regulates BV diameter
- Reflex centres - vomiting, sneezing, coughing, swallowing
Describe the ventral pons
Contains the pontine nucleus (coordinates movement) - fibres cross at midline and form the cerebellar peduncles
How is the cerebellum involved with cognitive functions?
E.g. language - role not understood
What are the medullary olives?
- Large masses of grey matter lateral to the pyramids
- Contain the inferior olivary nucleus
What is the function of the reticular formation of the pons?
Involved in regulating sleep-wake cycle and filtering incoming stimuli
Describe the structure and function of the tegmentum of the midbrain
- 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
Describe the other functions of the medulla
- Houses the special sense nuclei - gustatory nucleus (taste), cochlear nucleus (hearing) and vestibular nucleus (balance)
- Cranial nerve nuclei - glossopharyngeal, vagus, accessory, hypoglossal
List the surface features of the medulla oblongata
- Pyramids
- Olives
- Gracile fasciculus
- Cuneate fasciculus
Describe the relation of the pons to the cerebellum
- Pons connected to cerebellum on posterior surface by the middle cerebellar peduncles
- The structures are separated by the 4th ventricle
List the areas of the midbrain and their functions
- 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)
Describe the location and components of the brainstem
- Most inferior part of brain, continuous with brain to form spinal cord
- Components:
- Midbrain
- Pons
- Medulla oblongata
Describe the tegmentum of the pons
Forms part of the reticular formation - responsible for arousal and attentiveness
Describe the zones of the cerebellum
- Either side of the vermis = intermediate zone
- Laterally - lateral hemispheres
- No clear gross morphological border between
List the parts of the reticular formation
- Raphe nucleus
- Magnocellular red nucleus
- Parvocellular reticular nucleus
Describe the appearance of the pons
Appears as a broad anterior bulge rostral to the medulla
Describe the components (input and output) and function of the cerebrocerebellum
- 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
How does the cerebellum contribute to the coordination of voluntary movement?
Coordinates timing and force of muscle groups to produce fluid movements, receives sensory input to adjust movements for error correction
How is the cerebellum divided anatomically?
- Anterior, posterior and flocculonodular lobes
- Anterior and posterior lobes divided by primary fissure
- Posterior and flocculonodular lobes divided by the posterolateral fissure
Describe the important anatomical structures of the pons
- Basilar groove - midline, where basilar artery is located
- Pontomedullary junction - angle between lower border of pons + superior border of medulla
List the functional divisions of the cerebellum
- Vestibulocerebellum
- Spinocerebellum
- Cerebrocerebellum
Which cranial nerves originate from the pons?
- Trigeminal (V)
- Abducens (VI)
- Facial (VII)
- Vestibulocochlear
List the ways in which the cerebellum can be divided
- Anatomically
- By zones
- Functionally
How does the cerebellum contribute to maintenance balance and posture?
Input from vestibular, visual and proprioceptors, modulates commands to motor neurons to adjust posture in order to maintain balance
Describe the attachments of the midbrain
Attached to diencephalon above and pons below
Describe the location of the pons
Above medulla, below midbrain, anterior to cerebellum
Which structural feature is seen on the anterior surface of the medulla?
Anterior median fissure
Describe the position of the medulla oblongata
- Most inferior part of the brainstem, continuous with the pons above and spinal cord below
- Exits skull through foramen magnum
