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Cerebellum
| Question | Answer |
|---|---|
| What is the function of the cerebellum? | Affects ipsilateral motor function, balance and posture, fine tuning of skilled motor functions, initiation/termination/coordination/timing of movements, planning of motor movements, motor learning |
| With respect to motor function, how does the cerebellum's role differ from that of the cortex? | Oversees movement or coordinates it. Makes sure everything is fine and body wants to do it |
| How does the cerebellum exert motor influence? | Rubrospinal, vestibulospinal, reticulospinal tract, connects to cerebrla cortex |
| What kind of movements are influenced via rubrospinal? | Skeletal muscle control, tone, posture |
| What kind of movements are influenced via vestibulospinal? | Balance in response to head movements |
| What kind of movements are influenced by reitculospinal? | Influences reflexes and voluntary muscle contraction at the spinal level |
| What can be influenced because of its connection to the cerebral cortex? | Corticospinal tracts |
| What is the origin of the cortico-ponto-cerebellar pathway? | Starts from motor cortex |
| What are the crossovers and synapses of the cortico-ponto-cerebellar pathway? | Fibers from motor cortex synapse in ipsilateral pons then cross over |
| Where is the cerebellar entry for the cortico-ponto-cerebellar pathway? | Middle cerebellar peduncle |
| What is the function of the cortico-ponto-cerebellar pathway? | Tells cerebellum what intended action is |
| What is the origin of the cortico-olivary-cerebellar pathway? | Cortex, red nucleus, and spino-olivary tracts send fibers to synapse in inferior olive |
| What are the crossovers and synapses of the cortico-olivary-cerebellar pathway? | Fibers from inferior olive cross over in brainstem and enter cerebellum via inferior peduncle |
| What is the cerebellar entry of the cortico-olivary-cerebellar pathway? | Inferior cerebellar peduncle |
| What is the function of the cortico-olivary-cerebellar pathway? | Carries cutaneous and proprioceptive information to cerebellum |
| What is the origin of the corticoreticulo cerebellar? | Spinal cord, cortex, brainstem and vestibular system send input to reticular formation |
| What is an example of origin of the corticoreticulo cerebellar? | Somatosensory receptors in periphery send fibers to synapse in dorsal horn and ascend in lateral column via spinoreticular tract to reticular formation |
| What are the crossovers and synapses of the corticoreticulo cerebellar? | Fibers synapse in reticular formation and do not cross |
| What is the origin of the posterior spino-cerebellar? | Proprioceptive receptors in periphery send fibers below level of C8 to synapse in Clarke's column in spinal cord then ascend in lateral column |
| What are the crossovers and synapses of the posterior spino-cerebellar? | No other synapses: fibers travel to cerebellum |
| What is the cerebellar entry of the posterior spino-cerebellar? | Inferior cerebellar peduncle |
| What is the cerebellar entry of the corticoreticulo cerebellar? | Inferior cerebellar peduncle |
| What is the function of the corticoreticulo cerebellar? | Carries information that influences consciousness to cerebellum |
| What is the function of the posterior spino-cerebellar? | Carries proprioceptive information fro lower limb and trunk to cerebellum |
| What is the origin of the cuneo-cerebellar? | Proprioceptive receptors in periphery send fibers from level of C8 and above to ascend in posterior column and synapse in external cuneate nucleus |
| What are the crossovers and synapses of the cuneo-cerebellar? | No other synapses: fibers travel to cerebellum |
| What is the cerebellar entry of the cuneo-cerebellar? | Inferior cerebellar peduncle |
| What is the function of the cuneo-cerebellar? | Carries proprioceptive information from upper limb to cerebellum |
| Where is the cerebellar entry of most of the pathways and what is the exception and where? | Inferior cerebellar peduncle. Exception: cortico-ponto-cerebellar pathway via middle cerebellar peduncle |
| What pathway carries cutaneous and proprioceptive info to cerebellum? | Cortico-olivary cerebellar pathway |
| What pathway tells cerebellum what intended action is? | Cortico-ponto-cerebellar pathway |
| What pathway carries info that influences consciousness to cerebellum? | Corticoreticulo cerebellar pathway |
| What pathway carries proprioceptive information? | Posterior spino-cerebellar, cortico-olivary cerebellar, and cuneo-cerebellar |
| Which two pathways carry similar information and have similar origins? | Posterior spino-cerebellar, cuneo cerebellar |
| How does the posterior spino-cerebellar and cuneo-cerebellar pathways differ? | Origin which influences function |
| How does the origin between the posterior spino-cerebellar and cuneo-cerebellar pathways differ? | PSC - below level of C8 in Clark's column in spinal cord and then ascend in lateral column. CC - from level of C8 and above to ascend in posterior column and synapse in external cuneate nucleus |
| What is Clarke's column? | Neurons in central grey matter of spinal cord between levels of L3 and C8 |
| Where do neurons below L3 ascend in? | Posterior column before synapsing in Clarke's column |
| Why is all proprioceptive information to cerebellum unconscious? | Because does not reach cortex |
| What is the function of the anterior spinocerebellar tract? | Carries info from lower extremity to cerebellum |
| What is the function of the rostral spinocerebellar tract? | Mirrors anterior spinocerebellar tract for upper extremity |
| What is the sensory feedback mechanism for motor control and posture? | Proprioception and kinesthesia |
| Why was proprioception developed by the nervous system? | Keep track of and control different parts of the body |
| What lobes make up the cerebellum? | Anterior, posterior, and floculonodular lobes |
| What is a vermis? | Worm that separates the two hemispheres |
| What is foli? | Gyri-like convolutions on the surface of the cerebellum |
| What is the deep nuclei of the cerebellum? | Dentate, Interposed, and Fastigial |
| What makes up the interposed nuclei? | Emboliform and globose nuclei |
| What structure in the cerebellum supervises voluntary movements? | Dentate and Interposed |
| What structure in the cerebellum influences balance? | Fastigial |
| What is the superior peduncle connected to? | Midbrain |
| What is the middle peduncle connected to? | Pons |
| What is the inferior peduncle connected to? | Medulla |
| List the layers of the cerebellar from inner most to outermost | Granular → Purkinje layer → Molecular |
| What makes up the granular layer? | Granule cells, golgi cells |
| What is the function of the granule cells? | Excitation of Purkinje cells |
| What is the function of the Golgi cells? | Feedback inhibition to granule cells |
| What makes up the Purkinge layer? | Pukinje cells |
| What is the function of the Purkinje cells? | Inhibition of deep cerebellar nuclei |
| What makes up the molecular layer? | Basket cells and stellate cells |
| What is the function of the basket and stellate cells? | Inhibition of deep cerebellar nuclei |
| What two fibers terminate on the cells of the cerebellar cortex? | Climbing and Mossy |
| What is the origin of climbing fibers? | Inferior olivary nuclei |
| What is the function of the climbing fibers? | Directly excite Purkinje cells |
| How many times does one climbing fiber connect with one Purkinje cell? | Many times |
| What is the origin of the mossy fibers? | Everywhere else except inferior olivary nuclei - spinocerebellar, cortico-ponto-cerebellar fibers, etc. |
| What is the function of the mossy fibers? | Directly excite granule cells |
| How many times does a granule cell connect with one pukinje | One time but contracts many Purkinje cells |
| How are the granule cells connected with Purkinje cells? | Parallel fibers |
| What is the excitation of the two fibers (climbing, mossy) like? | Strong - climbing, weak from mossy |
| What does the vestibulocerebellum correspond to? | Floculonodular nobe |
| What is the function of the vestibulocerebellum? | Balance, coordination of eye movements |
| What are the major inputs of the vestibulocerebellum? | Vestibular fibers from vestibulocochlar nerve and vestibular nuclei |
| What are the major outputs of the vestibulocerebellum? | Vestibulospinal tract, reticulospinal tract, medial longitudinal fasciculus |
| What structure allows the major output of vestibulocerebellum? | Fastigial nucleus |
| What is the function of the vestibulospinal tract? | Motor balance |
| What is the function of the reticulospinal tract? | Motor influences |
| What is the path of the medial longitudinal fasciulus? | Runs from vestibular nuclei to interconnect oculomotor, trochlear, and abducens nuclei in brainstem |
| What is a common problem with lesion in the vestibulocerebellum? | Nystagmus |
| What corresponds to the majority of vermis? | Spinocerebellum |
| What is the function of the spinocerebellum? | Adjusts movements as they are occurring, corrective feedback to fine-tune motor skills |
| What are the major inputs of the spinocerebellum? | Spinocerebellar, cuneo-cerebellar, corticopontocerebellar fibers |
| What is the function of spinocerebellar and cuneocerebellar tracts? | Proprioception from periphery |
| What is the function of the corticopontocerebellar fibers? | Primary motor: copy from cortex |
| What are the major outputs of the spinocerebellum? | Rubrospinal, corticopinal |
| What structure allows the major outputs of the spinocerebellum? | Interposed nuclei |
| What is a commo problem with lesions to the spinocerebellum? | Gait because of loss of motor coordination |
| What corresponds to majority of the cerebral hemispheres? | Cerebrocerebellum |
| What is the cerebrocerebellum also called? | Neocerebellum or pontocerebellum |
| What is the function of the Cerebrocerebellum? | Planning movements, rapid alternating movements, fine dexterity, initiation/termination/coordination/timing of movements, motor learning |
| What are the major inputs of the Cerebrocerebellum? | Corticopontocerebellar and olivocerebellar |
| What structure allows major outputs for the Cerebrocerebellum? | Dentate nucleus |
| What are the major outputs for the Cerebrocerebellum? | Corticospinal, rubrospinal |
| What are the common problems with lesions in the Cerebrocerebellum? | Dysmetria, dysdiadochokinesia, asynergia |
| What is ataxia? | Inability to coordinate muscle activity during voluntary movement |
| What usually causes ataxia? | Disorders of the cerebellum or posterior column of spinal cord |
| What structures may be affected with ataxia? | Limbs, head, trunk |
| What is dysarythria? | Ataxia of laryngeal muscles - jerky articulations, separation of syllables, changing sound intensities |
| What is cerebellar nystagmus? | Ataxia of ocular muscles - tremor of eyeballs that usually occurs when patient attempts to fix eyes on an object off to side |
| What is truncal ataxia? | Inability to maintain an upright position - affects gait - unstable, wide gait with irregular steps and lateral veering |
| What is dysmetria? | "wrong distance" - can't judge distances - movements overshoot then overcompensates - patient can't touch finger to nose - leads to intention tremor |
| What is Dysdiadochokinesia? | Without ability to make rapidly alternating movements - can't predict where a body part will be at a given time leading to the next movement in a sequence starting too early or too late |
| How would you test for dysdiadochokinesia? | Asking patient to rapidly turn palm up and down - results in jumbled movements |
| What is hypotonia? | Low muscle tone |
| What is asynergia? | Lack of coordination amoung various muscle groups during performance of complex movements, resulting in loss of skill and speed |
| What happens in a severe case of asynergia? | Decomposition of movement, wherein complex motor acts are perfrmed in a series of isolated movements - caused by cerebellar disorders |
| Where do most afferent tracts enter the cerebellum? | Inferior and middle cerebellar peduncles |
| What kind of tracts connect the superior cerebellar peduncles? | Mostly efferent tracts of the cerebellum |
| How many more afferent tracts are there than efferent? | Afferent > efferent - 40:1 |
| Inferior cerebellar peduncles receive what kind of tracts and from what structure? | Afferent from medulla, efferent to the vestibular nuclei |
| Middle cerebellar peduncles receive what kind of tracts and from what structure? | Afferent from pontine nuclei |
| Superior cerebellar peduncles receive what kind of tracts and from what structure? | Efferent from cerebellar nucleo, afferent from spinocerebellar |
| Which peduncles receive input and output, based on the types of tracts are involved. | Input - primarily inferior and middle cerebellar peduncles. Output - primarily superior cerebellar peduncle |
| What side of the body receives input and output for cerebellum? | Ipsilateral for both input and output because cerebellum receives input from and controls output to ipsilateral side of body |
| What side of the body receives input and output for red nucleus? | Ipsilateral for both input and output - even for outputs to contralateral red nucleus |
| Why is input the red nucleus ipsilateral? | Because tract crosses midline at level of nucleus and cerebral cortex output to red nucleus affects ipsilateral side of body by a double-crossed pathway |
| Where is the fastigial nucleus? | Most medially located of the cerebellar nuclei |
| What are the inputs to fastigial nucleus? | Receives input from vermis and cerebellar afferent that carry vestibular, proximal somatosensory, auditory, and visual info |
| What does the fastigial nucleus project into? | Vestibular nuclei and reticular formation |
| Where are the interposed nuclei? | Situated lateral to the fastigial nucleus |
| What makes up interposed nuclei? | Emboliform nucleus and globose nucleus |
| What are the inputs for interposed nuclei? | Input from immediate zone and from cerebellar afferent that carry spinal. proximal somatosensory, auditory, and visual info |
| What does the interposed nuclei project into? | Contralateral red nucleus (origin of the rubrospinal tract) |
| What is the dentate nucleus? | Largest cerebellara nuclei |
| Where are the dentate nuclei? | Lateral to the interposed nuclei |
| What are the inputs for the dentate nucleus? | Lateral hemisphere and from cerebellar afferents that carry info from the cerebral cortex (via pontine nuclei) |
| Where does the dentate nucleus project into? | Contralateral red nucleus and ventrolateral thalamus nucleus |
| What are vestibular nuclei? | Functionally equivalent to cerebellar nuclei because of their connectivity patterns are identical to cerebellar nuclei |
| Where are vestibular nuclei? | Located outside the cerebellum, in the medulla |
| What are the inputs of the vestibular nuclei? | Flocculonodular lobe and from vestibular labyrinth |
| Where does the vestibular nuclei project into? | Motor nuclei and originate the vestibulospinal tracts |
| What are Purkinje cells? | Middle layer between granule (inner most) and molecular layer (outer most) |
| Describe the structure of Purkinje cells | Apical dendrites form a large fan of finely branched processes that are oriented parallel |
| What is the sole source of output from the cerebellar cortex? | Purkinje cells |
| What are granule cells? | Densely packed neurons that account for majority of neurons in cerebellum |
| What is the function of granule cells | Receive input from mossy fibers and project to Purkinje cells |
| What are mossy fibers? | Fibers that originate in the pontine nuclei, spinal cord, brainstem, reticular formation, and vestibular and project into cerebellar nuclei and grnaule cells in the cerebellar cortex |
| Why are they called mossy fibers? | Because of their tufted appearance of their synaptic contacts with granule cells |
| How many granule cells do mossy fibers innervate? | Each mossy fiber innervates hundreds of granule cells which send axons up towards cortical surface |
| What happens after a granule cell is excited by mossy fibers? | Each axons bifurcates in the molecular layer, sending a collateral in opposite direction → called parallel fibers |
| What are parallel fibers? | Fibers that run parallel to the folds of the cerebellar cortex where they make excitatory synapses with Purkinje cells |
| How are parallel fibers and Purkinje cells oriented? | Perpendicular to each other - like telephone lines running between telephone poles |
| How many purkinje cells come in contact with parallel fibers? | Hundred of purkinje cells |
| What are climbing fibers? | Fibers that originate in exclusively inferior olive and make excitatory projections onto cerebellar nuclei onto the Purkinje cells of the cerebellar cortex |
| Why are they called climbing fibers? | Because their axons climb and wrap around dendrites of the Purkinje cell like a climbing vein |
| How many purkinje cells come in contact with a climbing fiber? | Each climbing fiber contacts only 10 Purkinje cells |
| What is the implication of the small amount of Purkinje cells that climbing fibers contact? | Restricted but extremely powerful excitatory input onto Purkinje cells |
Created by:
nnguyen44
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