Cerebellum Flashcards
What is the cerebellum concerned with?
All somatic motor activity, regulation of muscle tone and mechanisms that maintain equilibrium
The cerebellum processes what?
Unconscious proprioceptive and tactile info to affect gradual alterations of muscle tension necessary for proper maintenance of equilibrium and posture
The cerebellum assures what?
The smooth and orderly sequence of muscular contraction characteristic of voluntary skilled movements
What are the 4 pairs of deep cerebellar nuclei that are embedded within the corpus medullares?
Fastigial nucleus, globose nucleus, emboliform nucleus and dentate nucleus
What is the role of the fastigial nucleus?
Vestibular connections and function
Medial globose and fastigial nuclei project what?
Cerebellovestibular efferents to the vestibular system and RF
Efferents from the lateral globose course with fibers from what?
The emboliform and dentate nuclei
Projects through the superior cerebellar peduncle
The emboliform nucleus sends efferent through what?
The superior cerebellar peduncle along with fibers from the dentate nucleus
Describe the dentate nucleus
Projects dentato-rubral and dentato-rubro-thalamic fibers to the red nucleus, ventral lateral nucleus of the thalamus, brainstem and RF
Mostly responsible for the planning and execution of fine movement
what are the fibers that run through the inferior cerebellar peduncle?
Dorsal spinocerebellar tract (DSCT) Direct arcuate fibers Trigemiocerebellar tract Arcuocerebellar fibers Retiuclocerebellar fibers Olivocerebellar fibers DDT always ruins olives
Describe the spinocerebellar tract (DSCT)
Conveys unconscious precise proprioceptive info from the lower 1/2 of the body and LE to the cerebellum
Originates in the nucleus dorsalis
Courses through ipsilateral inferior cerebellar peduncle
Terminates in the anterior vermis of cerebellum
Describe the arcuate fibers of the inferior cerebellar peduncle
Unconscious precise proprioceptive info from the upper 1/2 of the body and UEs
Originate in the accessory cuneate nucleus and terminate in the vermis
What kind of info does the trigeminocerebellar tract convey?
General proprioceptive and exteroceptive info from the head
Olivocerebellar fibers of the inferior cerebellar peduncle are a critical link between what?
The EPS and cerebellum
What fibers form the middle cerebellar peduncle?
Pontocerebellar fibers which form an important feedback loop b/w the motor cortex and cerebellum
Which tracts/fibers ar associated with the superior cerebellar peduncle?
Ventral spinocerebellar tract, trigeminocerebellar tract and tectocerebellar fibers
The ventral spinocerebellar tract (VSCT) of the superior cerebellar peduncle conveys what?
Unconscious general proprioceptive info from the lumbosacral levels to the cerebellum
Describe the trigeminocerebellar tract of the superior cerebellar peduncle
Arises from the main sensory nucleus of CN V
Conveys unconscious precise tactile and proprioceptive info from the head to the cerebellum
Describe the purkinje cell layer of the cerebellar cortex
Forms the middle layer of the cortex and comprises a single sheet of inhibitory Purkinje cell bodies
All info entering the cerebellar cortex converges on these cells
Their axons are the only efferents from the cerebellar cortex
Most terminate in the deep cerebellar nuclei
What are the two major afferent fibers in the cerebellar cortex?
Climbing and mossy fibers
Describe climbing fibers
The most direct afferent to the cerebellar cortex
Terminals of the olivocerebellar fibers that originate in the inferior olivary nucleus
Have a powerful excitatory effect upon the purkinje cells
Describe mossy fibers
Golgi cell axons inhibit the postsynaptic membrane of the granule cell dendrites near the cerebellar glomerulus and thereby modify the info entering the granule cell circuit
Unilateral lesions of the cerebellum result in what?
Ipsilateral deficits
S/S: ataxia, dysmetria, dysdiadochokinesia, tremor, decomposition of movement, slurred or scanning speech, rebound phenomenon, hypotonia, asthenia and nystagmus
What is ataxia?
Broad based staggering gait
Can be midline, appendicular, cerebellar or sensory
What is dysmetria?
Missing the mark during tests such as touching the fiber up to the nose with the eyes closed
What is dysdiadochokinesia?
Inability to perform rapidly alternating movements such as pronation and supination
Describe tremor
Usually characteristic of lesions involving the superior cerebellar peduncle or dentate nucleus
Present during voluntary movement and absent during rest
What is decomposition of movement?
Breakdown of the fluid, multijoint patterns of movement
Movements tend to be performed one joint at a time and take on a robotic appearance
What is rebound phenomenon?
Inability of opposing muscles to stop an action
What is asthenia?
Pt may demonstrate weakness of the limb or axial musculature
Nystagmus is caused by lesions of the what?
Vestibulocerebellum
