Cerebellum & Brainstem (13) Flashcards
What do cerebellar slow feedback pathways allow for?
Long term improvement of motor tasks
What role does the cerebellum serve?
Coordinator and predictor of movement and mediated skilled movement - integrates sensory input with the executive functions (plans) coming from the cortex
What do cerebellar fast-forward mechanisms allow for?
Regulating second to second movements to keep actual movements close to the intended movements
What two part of the cerebellum help control axial (neck, trunk muscle) musculature?
The vermis and paravermian portions (both centrally located in the cerebellum)
What parts of the cerebellum help control the limbs?
Lateral hemispheres
What is the flocculonodular lobe of the cerebellum involved in regulating?
Balance
What are the four deep cerebellar nuclei?
From lateral to medial : 1. Dentate nucleus 2. Emboliform nucleus 3. Globose nucleus 4. Fastigial nucleus (Globose + Emboliform = interpositus nuclei)
Which area of cerebellum projects to the dentate nuclei?
Lateral hemispheres
What part of cerebellum projects to the interpositus nuclei?
Paravermal zones
What nuclei does the vermis project to?
Fastigial nuclei
The anterior spinocerebellar tract, and acoustic and optic sensory afferents are transmitted to the cerebellum via what?
Superior cerebellar peduncle
What is the major outflow pathway of the cerebellum?
Superior cerebellar peduncle - dentatorubothalamic tract and dentatothalamic tract
The outflow tracts of the cerebellum direct movement on which side relative to the cerebellar hemisphere of origin? How?
Coordinates movement in a limb ipsilateral to the cerebellar hemisphere of origin - from the lateral portions of the anterior and posterior cerebellar cornices to thalamus and then to the contralateral motor cortex, which coordinates movement in the opposite side, which is ipsilateral to original cerebellar hemisphere producing the signal
Which structure do the vestibulocerebellar tract and posterior spinocerebellar tract go through to reach the cerebellum?
Inferior cerebellar peduncle
Where do the fibers leaving through the inferior cerebellar peduncles (cerebellovestibular/ cerebelloolivary tracts) start in the cerebellum and where do they go? Function?
From vermis and flocculonodular nodes through EGF nuclei to vestibular nuclei, olivary nuclei, brainstem reticular formation.
- important for maintaining balance
What are the three layers of cerebellar gray matter (cortex)?
- Molecular layer (outer)
- Middle layer
- Granule layer (innermost)
What two kinds of cells are found in the outer molecular layer in cerebellar gray matter?
Basket and stellate cells
What kind of cell makes up the middle layer of cerebellar gray matter?
Purkinje cells
What two cell types are found in the Granule layer of the cerebellar gray matter?
Golgi and Granule cells
What cells are the only output cells of the cerebellar cortex?
Purkinje cells (synapse on one of the deep nuclei that in turn send efferents out of the cerebellum)
What fibers offer the only direct input to the cerebellar output (Purkinje cells) from outside the cerebellum?
Climbing fibers - have their origins in the olivary nuclei
What fibers bring in input to the cerebellar Purkinje cells from all other brain areas? Where do they first synapse?
Mossy fibers - synapse in cerebellar glomeruli with Golgi and Granule cell dendrites, which then pass the info along to Purkinje cells
*granule and Golgi cells have an excitatory effect on Purkinje cells
Which two cell types in the cerebellar cortex have an inhibitory effect on the Purkinje cells there (and hence inhibit output from cerebellum?
Stellate and basket cells
What are the terms vestibulocerebellum, spinocerebellum, and cerebrocerebellum referring to?
These are the functional anatomical divisions of the cerebellum
What is the function of the vestibulocerebellum?
Coordinate eye, head, and neck movements and also maintains balance
What two parts of cerebellum make up the vestibulocerebellum?
Flocculonodular lobe and inferior part of paravermis
What is the function of the spinocerebellum?
Coordinate trunk and proximal limb movements
What is the function of the cerebrocerebellum? (3 functions)
- Coordinate fine motor planning of limbs
- Anticipate sensory consequences of movement
- Cognitive memory of motor functions
What side of the body does a cerebral hemisphere control? (Ipsilateral vs. Contralateral)
Ipsilateral side - right cerebellar hemisphere controls right body, arm, and leg
What kind of gait might be seen in cases of cerebellar dysfunction?
“Sailor’s gait” - unstable gait and stance with a tendency to fall
What is dysmetria of movement? (Is a sign of cerebellar dysfunction)
Goal oriented behavior that over or undershoots the target
What three eye issues may be seen with cerebellar dysfunction?
Nystagmus, saccadic and smooth pursuit dysmetria
How might speech be affected by cerebellar dysfunction?
Difficulty maintaining speech rhythm, intonation, and correct articulation
Functions in control of reflex movements that orient the eyes, head, and neck in response to visual, auditory, and somatic stimuli
Superior colliculus
Functions in the processing of autonomic and limbic activities as well as modulation of nociception
Periaqueductal gray matter
Passageway connecting third and 4th ventricles
Cerebral aqueduct
Parasympathetic innervation to the eye to constrict the iris and to the ciliary muscle to alter lens shape for accommodation
Nucleus of Edinger-Westphal
Thalamic relay nuclei for auditory information
Medial geniculate
Thalamic relay nuclei for visual information
Lateral geniculate
Fiber bundles of the corticospinal tract connecting cerebral cortex to brainstem
Cerebral peduncle
Relay nucleus b/n cerebellum to the thalamus
Red nucleus
Fiber pathway b/n the vestibular nuclei and the CN nuclei III, IV, VI to coordinate head/eye movements
Medial longitudinal fasciculus (MLF)
Collection of neurons in the pons that receive input from the neocortex and send crossing fibers through the middle cerebellar peduncle
Pontine nuclei
Noradrenergic brainstem nucleus involved in mood and sleep/wake cycle
Loculus coeruleus
One of several serotoninergic type nuclei involved in mood and sleep/wake cycle
Raphe nucleus pontis
Origin of the climbing fibers to the cerebellar Purkinje cells
Inferior olivary nucleus
Network of neurons and axons in the brain stem tegme rum involved in arousal, respiration, and HR control
Reticular formation (major integrator in the brain)
If a pt. is experiencing ipsilateral 3rd nerve paresis and contralateral hemiparesis, what region and part of brainstem has a lesion?
Base of Midbrain
Ipsilateral 3rd nerve paresis, contralateral tremor, contralateral ataxia - where in brainstem is lesion?
Tegmentum of midbrain
Ipsilateral 3rd nerve paresis, contralateral hemiparesis, contralateral tremor, contralateral ataxia = where in brainstem is the lesion?
Base and Tegmentum of brain
What is a common thread in brainstem syndromes, in terms of clinical symptom distribution?
Most involve a pattern of contralateral body weakness or sensory loss coupled with ipsilateral cranial nerve weakness (or sensory loss) - terms realities to the lesion
Contralateral hemiparesis and ipsilateral LMN facial paresis = lesion in what part of brainstem?
Medial pons (base and Tegmentum)
- sometimes also have ipsilateral gaze paresis; lesion is in same place though
Contralateral arm/leg weakness, contraleral decrease in position/vibration, ipsilateral tongue weakness = lesion where in the brainstem?
Medial medulla
Ipsilateral ataxia, vertigo, nausea ; inpsilateral decrease in face pain perception; ipsilateral Horner’s; dysphagia = where in brainstem is lesion?
Lateral medulla
Where in brainstem is often damaged in posterior circulation strokes?
Lateral medulla (Wallenberg’s syndrome)
What three parts of the cerebellum make up the spinocerebellum?
Anterior lobe, vermis, superior part of para vermis
