cerebellum

what input does the cerebellar nuclei receive?

cerebellar nuclei receive inhibitory input from the purkinje cells, each from a particular functionally distinct region of the cerebellum

actions of the reticular formation

extensor and flexor muscles are activated alternately in locomotion extensor and flexor muscles are activated together to stabilize a joint circuits with the cerebellum enable the reticular formation to learn postural patterns for complex movements

dysdiadochokinesis

inability to perform rapid alternating movements

what is the function of the cerebellum

this sensory structure influences the motor systems by evaluating disparities between intention and action and by adjusting the operation of motor centers in the brainstem and cortex while a movement is in progress plays an important role in motor adaptation and learning

what sensory information does the dorsal spinocerebellar tract bring via the ICP to the cerebrum?

sensory info about limb position and muscle tension synapse with neurons in the grey matter (nucleus dorsalis-Clarke's column c8- L2/3) that head up the dorsal spinocerebellar tract

where in the grey matter do neurons carrying sensory information synapse in the grey matter? how do they travel in order to get up to the cerebellum?

sensory information synapses with a secondary neuron at the dorsal horn. the second neuron crosses to the other side via the anterior commissure and heads up to the ventral spinocerebellar tract. when it enters the cerebellum through the SCP it crosses the midline once more

cerebellar lesions in the midline

so this impacts the spinocerebellum and vestibulocerebellum and will cause a wide-based gait and a loss of balance, abnormal movements

the sensory input of the vestibular system to the vestibulocerebellum entets through which cerebellar peduncle? output?

the ICP (VIP) for both sensory input and output

does the dorsal spinocerebellar tract double cross or never cross?

uncrossed! they remain ipsilateral. it is is a 2 neuron chain path that synapse in the nucleus dorsalis (clarke's column)

how do the axons originating in the accessory cuneate nucleus enter the cerebellum?

via cuneocerebellar fibres through the ICP (considered in this class to still be part of the DSCT)

output of the spinocerebellum via the SCP

the cerebellum communicates with the contralateral thalamus in order to have effects on the cerebral cortex. this will indirectly effect UMN corticospinal tract output it also communicates with the contralateral red nucleus in order to impact neuronal axons that are part of the rubrospinal tract

where is the cerebellum located in terms of gross anatomy?

the cerebellum is located dorsal to the brainstem, caudal to the occipital lobe of the cerebrum

cerebellum only contributes to ___ percent of the brain mass but it contains more than _____ of the neurons in the brain

the cerebellum only contributes to 10% of brain mass, it contains more than half of the neurons in the brain

what pair of deep cerebellar nuclei is involved in the cerebrocerebellum?

the dentate nucleus. (Dentist cleaning)

where pair of deep cerebellar nuclei are important to the vestibulocerebellum?

the fastigial nucleus

what cerebellar cortex is important to the vestibulocerebellum?

the flocculonodular lobe (flocculus and nodulus)

what is the involved area of the cortex and deep cerebellar nuclei for the spinocerebellum?

the interposed nuclei and the midline vermis and paravermal regions (SIM)

what is the cerebellar cortex involved in the cerebrocerebellum?

the lateral parts of the cerebellar hemispheres

descending pathways: reticulospinal tracts (MEDULLARY)

the medullary reticular formation projects to LMNs innervating flexor muscles bilaterally of the trunk and proximal limbs via interneurons the axons descend in the ventral and lateral funiculi intermingled with those of the pontine reticular formation

descending pathways: reticulospinal tracts (PONTINE)

the pontine reticular formation projects bilaterally to LMNs innervating extensor muscles of trunk and proximal limbs, via interneurons the axons descend in the ventral and lateral funiculi, intermingled iwth those of the medullary reticular neurons

what is the spinocerebellum involved in?

the spinocerebellum functions to coordinate motor activities involved in locomotion

what part of the thalamus does the cerebellum send its axons out via the SCP to?

the ventral anterior and ventral lateral

talk about the output of the vestibulocerebellum and how this contributes to balance and eye movements

the vestibulocerebellum sends output via the ICP. it sends signals modifying motor activity back to the vestibular nucleus in the brainstem which, in turn signals motor neurons that drive postural and extraocular muscles. **remember the many projections of the vestibular nucleus? :P

the vestibulospinal tract descending pathway from the vestibular nucleus

the vestibulospinal tract descends in the ventral/lateral funiculus it innervates ipsilateral lower motor neurons of extensor muscles in the proximal limbs and back it acts to increase extensor (antigravity) tone

what about fibers that enter below L3? what happens to them until the reach the level of the nucleus dorsalis?

these fibres run in the nucleus gracilis until they reach the level of nucleus dorsalis where they will synapse

are cerebellar lesions ipsilateral or contralateral

they are ipsilateral! think about the double cross

talk about the output of the cerebrocerebellum

they project back to the motor areas of the cortex via the SCP and the VA/AL areas of thalamus

what about the fibres that enter above c8? what happens to them?

they run rostrally in the fasciculus cuneatus to the accessory cuneaute nucleus (lateral to n. cuneatus in medulla) where they synapse

describe the 4 subnuclei of the vestibular nucleus

1) 2 lateral nuclei (Dieter's nucleus) 2) superior 3) medial

pop question from Cranial nerves 2 flashcard set. where are the places the the vestibular nucleus projects to ? (5)

1) ascending MLF 2) descending MLP 3) vestibulospinal tract 4) thalamus to cortex for conscious appreciation of balance 5) reciprocal connections to the cerebellum

what are the 2 sensory input tracts that enter the cerebellum involved in the spinocerebellum? through what peduncle do they enter the cerebellum through?

1) dorsal spinocerebellar tract- enters via ICP (DIP DIP DIP) 2) ventral spinocerebellar tract- enters via SCP (VESPA)

what are the 4 bilaterally paired grey matter nuclei in the cerebellum?

1) fastigial nucleus closed to the midline 2) the interposed nuclei (globuse and emboliform) 3) the dentate nucleus (the only nucleus that is visible grossly

describe the circuitry of the cerebellum in terms of input and output

1) input comes in from the brainstem, spinal cord, and all areas of the cerebral cortex and enters via one of the cerebellar peduncles 2) this input first goes to the granule neurons in the cerebellar cortex 3) then to the purkinje cells 4) then to the deep cerebellar nuclei 5) and then they exit through a cerebellar peduncle once again and send this output to the thalamus and brain stem

what are the three layers of the cerebellum?

1) molecular layer 2) purkinje cell layer-the output cells of the cerebellum 3) granular layer

what are the three sensory sources important for postural movements/balance?

1) somatosensory signals, especially from proprioreceptors (muscle spindles, tendon organs) 2) vestibular signals encoding gravity and movement of the head 3) visual input (slower than the other 2 sources)

explain why we see ipsilateral deficits when it comes to cerebellum damage?

because sensory fibres coming into the cerebellum dont cross the midline. they cross once coming out of the cerebellum and cross again in the form of motor tracts. these 2 crosses negate each other and thus there is not cross and lesions will show ipsilateral deficits in motor coordination

the vestibular nuclei can be found in the _____ and _____

caudal pons and rostral (open) medulla. know where these are in the cross sections!!

dysmetria

issues judging distances or range of movement

another descending pathway from the vestibular nucleus is the descending medial longitudinal fasciculus. where does it descent within the spinal cord? innervation of LMNs?

it descends in the ventral funiculus and innervates bilaterally LMN of neck muscles. it acts to coordinate head and trunk muscles to maintain balance and visual fixation

what is the cerebrocerebellum involved in?

it evolved with the skilled, asymmetric movements of the upper limb and is best evolved in primates it is involved in PLANNING OF skilled, complex movements primarily of the hands

is the ventral spinocerebellar pathway uncrossed or double crossed?

it is double crossed

what is postural equilibrium?

it is the state in which all forces acting on the body are balanced so that the body rests in an intended position (static equilibrium) or is able to progress through an intended movement without losing balance (dynamic equilibrium)

what type of input does the spinocerebellum receive?

it receives sensory signals from the spinal cord encoding limb position and muscle tension via the dorsal and ventral spinocerebellar tracts

what is the output of the spinocerebellum?

it sends signals to the motor areas of the cerebrum and to the red and vestibular nuclei in the brainstem which, in turn, signal the motor neurons involved in locomotion

what would damage to the cerebellum cause?

it would disrupt the spatial accuracy and temporal coordination of movement lesions would result in ipsilateral deficits

cerebellar lesions in the lateral hemispheres

lack of coordination of voluntary movement: dysmetria, dysdiadochokinensis, intention tremor, dysarthric speech

what is posture?

posture is the relative position of the various parts of the body with respect to one another and to the environment

what are the sensory inputs to the cerebrocerebellum and through which cerebellar peduncle are they received from?

receives signals from the cerebral cortex via pontine nuclei and the MCP. 2 neuron chain synapsing at the poutine cerebellar nuclei