Cerebellum Flashcards

Question

Lateral Zone Inputs

Answer 1

**Input to lateral hemisphere and paravermis.** _4 types:_ 1. **Corticopontine input** * pontocerebellar fibers 2. **Spinal and trigeminal input** * DSCT * VSCT * CuCT * TCT 3. **Reticular formation input** * RetCT 4. **Inferior olive input** * olivocerebellar tract

Answer 2

**_Cortico-Ponto-Cerebellar Tract_** * _Carries:_ * motor commands from **limb area of motor cortex** * for coordination of ongoing movements of extremities * info from **all cortices** including **premotor cortex** * for motor planning * Cortical input terminates in **ipsilateral pontine n.** * From pontine n., fibers _decussate_ as **transverse pontine fibers** * Enter **contralateral cerebellum** via **MCP**

Answer 3

**All tracts enter ipsilateral cerebellum via ICP.** Terminates in lateral hemisphere and paravermis. 1. **Dorsal spinocerebellar tract (DSCT)** * carries ipsi lower body proprioception * orginates in **Clarke's n.** 2. **Cuneocerebellar tract (CuCT)** * carries ipsi uuper body proprioception * orginates in **lateral (acc.) cuneate n.** 3. **Trigeminocerebellar tract (TCT)** * carries info from face * originates in **spinal trigeminal n.**

Answer 4

**_Ventral spinocerebellar tract (VSCT)_** * Carries **efferent copy of spinal cord LMN commands** → "spy tract" * Originates in **spinal cord** (border cells) * _Decussates twice:_ 1. **ventral white commissure** → forms VSCT 2. **SCP** → enter cerebellum * Carries ipsi info to ipsi cerebellum

Answer 5

1. **Reticulocerebellar tract (RetCT)** * carries **cutaneous information** * originate from **lateral reticular n.** of _medullary reticular formation_ * enter **ipsilateral cerebellum** via **ICP**

Answer 6

**_Olivocerebellar tract (OCT)_** * carries info used for **timing and motor learning** * originate from **inferior olivary n.** in _medulla_ * fibers **decussate** and enter **contralateral cerebellum** via **ICP** * terminates as **climbing fibers** in **lateral hemisphere** and **paravermis**

Answer 7

1. **Dorsal spinocerebellar tract** * from Clarke's n. * ipsilateral lower limb proprioception 2. **Cuneocerebellar tract** * from lateral (acc.) cuneate n. * ipsilateral upper limb proprioception 3. **Reticulocerebellar tract** * from reticular formation * complex sensory inputs including visual and auditory 4. **Vestibulocerebellar tract** * from vestibular n. and ganglion * gravity and momentum info * balance info 5. **Trigeminocerebellar tract** * from spinal trigeminal and chief sensory n. * ipsilateral proprioception from face 6. **Olivocerebellar tract** * from contralateral inferior olive * via climbing fibers * integrated sensory info

Answer 8

**Only caries afferents from corticopontocerebellar tract.** **No efferents.**

Answer 9

**Only carries afferents from VSCT.** "Spy tract" compares what MN is "told" to do and what it is doing. Many efferents.

Answer 10

* Receives **collaterals** from **afferents** to cerebellum * Receives **processed info** from **cerebellar cortex** via Purkinje cell axons * **Glutamatergic** (excitatory) projections to **brainstem** and **thalamus** * Many projections form part of polysynaptic loops feeding back to cerebellum

Answer 11

Receives input from Purkinje neurons in **vermis** of all cerebellar lobes. **Bilateral projections** via **ICP** to: **medial reticular formation** (inhibitory) **vestibular nuclei** esp. lateral vestibular (Deiter's) n.

Answer 12

Receive afferents from cortex of cerebellar hemispheres. Represents limbs.

Answer 13

**Three-layer cortex** with several interneuron types and Purkinje cells which projects out. 1. **Granule layer (deepest)** * **Granule cells** → glutamateric → excitatory * axons ascend to molecular layer * bifurcate to form **parallel fibers** * only excitatory interneuron * **Golgi cells** → GABAergic → inhibitory 2. **Purkinje Layer** * **Purkinje cells** → GABAergic → inhibitory * extensive dendritic arborization to molecular layer * synapses with parallel fibers, basket cells, and stellate cells * up to 100k connections * major integrator of cerebellum * project to **deep cerebellar n.** * some cells from **flocculonodular lobe and anterior vermis** project **directly to vestibular n.** 3. **Molecular Layer (superficial)** * **Stellate cells** → GABAergic → inhibitory * **Basket cells** → GABAergic → inhibitory * parallel fibers & Purkinje cell dendritic arbors **White matter** contains axons of Purkinje cells and afferent fibers going to cortex. 1. **Climbing fibers** * contra. inferior olive → directly and repeatedly on _Purkinje cell dendrites_ 2. **Mossy fibers** * terminates on _granule cells dendrites_ * indirect contact w/ Purkinje cells **Climbing & mossy fibers → Glutamatergic → excitatory.**

Answer 14

**Medial zone** → correcting regulatory output → smooth coordination of **trunk muscles** → **balance and equilibrium**. **Lateral zone** → correcting regulatory output → smooth coordination of **distal muscles** + **motor planning**. Cerebellum → **brainstem motor n.** + **thalamus** → **corticospinal, reticulospinal, vetibulospinal, rubrospinal** tracts.

Answer 15

**_Vermal-Fastigial System_** 1. **Purkinje cells** in **vermis** and **flocculonodular lobe** * ⊖ → **fastigial n.** and **lateral vestibular neurons** * ∆ firing to correct for errors in trunk movement, balance, position * ⊖ → **medial vestibular neurons** and **oculomotor n.** (not shown) * **∆ MVST** for coordination of head and eye movements 2. To **fastigial n.** * Via **ICP** → ⊕ **medullary reticular formation** * facilitate extensor inhibition by **MRST** * Decussate in SCP → ⊕ contralateral **VL thalamus** * ****⊕ → **motor cortex** (trunk area) * ⊕ → **VSCT** controlling trunk muscles during movement 3. To **lateral vestibular neurons** via **ICP** * **∆ LVST** output to extensor antigravitic muscles

Answer 16

**Bilateral** control of **axial and proximal movement** via **lower brainstem nuclei**. For **postural adjustments** including trunk fixation & head position to maintain **gait, balance, and posture**. **Efferents via ICP.** 1. **Cerebelloreticular tract** * fastigial n. → medullary reticular formation → MRST 2. **Cerebellovestibulo tract** * fastigial n. → vestibular n. → LVST 3. **Inhibitory Purkinje fibers** (flocculonodular/vermis) → lateral vestibular n. **Lesion produces hypertonicity.** Disinhibition of trunk extensors.

Answer 17

**_Hemisphere-Lateral System_** 1. **Purkinje cells** in **paravermis** and **lateral hemisphere** * **⊖ → interposed n. & dentate n.** * ∆ firing to provide regulatory signal * correct for errors in ongoing limb movement * participate in motor planning 2. **Interposed & Dentate nuclei** * ⤮ in SCP → contra. **VL thalamus** → **motor cortex** (limb area) → ∆ **LCST** → distal muscles * ⤮ in SCP → contra. **red nucleus magnocellular neurons** → **RST** → upper limb flexors * ⤮ in SCP → contra. **red nucleus parvocelluar neurons** → **inferior olive** → ⤮ in **ICP** → **climbing fibers** → cerebellum * ∆ cerebellar circuits for timing and motor learning **Lesion results in hypotonia.**

Answer 18

Functions in **coordinated movements** and **motor planning**. * Dentate & Interpositus n. project via **SCP** * **⤮ in lower midbrain** * maintains somatotopy * Exerts control over **all supra-spinal motor pathways**. * **Dentatothalamo tract** (aka cerebellothalamo tract) * **Dentatorubro tract** (aka cerebellorubro tract) * interpositus n. → magnocellular red n. * **Dentatorubroolivary tract** (aka cerebellorubroolivary tract) * dentate n. → parvocellular red n. → inferior olive

Answer 19

1. **Hypertonia** 2. **Ataxia** 3. **Hypotonia** 4. **Cerebellar nystagmus** 5. **Intentional tremors** * tremors when trying to move * error in movement end-point → attempt to correct → error in opposite direction 6. **Dysmetria (past-pointing)** * mid-course correction made en route esp. w/ eyes closed 7. **Dysarthria** * inability to coordinate speech muscles 8. **Dysdiadochokinesia** * uncoordinated rapid antagonist exercise 9. **Dysrhythmia**

Answer 20

**Lesion of ICP, vermis, flocculonodular n., or fastigial n.** Impairs ability to use **vestibular and proprioceptive info** to coordinate movement. Unilateral lesion may result in bilateral deficits. * **Truncal ataxia** * **Wide-based unstable gait** * **Vertigo, nystagmus** * Deficit in eye movements * altered smooth persuit * impaired suppresion of VOR * Dysarthria * _Lesion of ICP_ ⟾ **hypertonia** * **Unilateral lesion of fatigial n.** ⟾ hypertonia, nystagmus, and ipsilateral stumbling

Answer 21

_Unilateral lesion_ of **SCP, lateral hemisphere, interposed or dentate n.** ⟾ _ipsilateral deficits._ Characterized by errors in direction, force, speed, and amplitude of movements. 1. **Hypotonia** * ****Due to loss of tonic cerebellar facilitation of motor cortices 2. **Delays in initiating movements** 3. **Decomposition of multiple-joint movements** * ****breaks down smooth movement into several jerky components 4. **Intentional tremors** * oscillations caused by "intentional" or goal-directed movement 5. **Dysmetria** * past-pointing which occurs due to overshoot/undershoot of target 6. **Dysdiadochokinesia** * inability to perform rapid alternating movements

Answer 22

Person is skating on ice: * **Balance** and movements **continuously checked** and **adjusted smoothly** by _medial and lateral zones_ * Uses _spinal, vestibular, and visual cues_ * Regluation of _axial/proximal muscles_ * To jump, _premotor and supplementary motor_ send **motor plan** to _lateral zone_ * Lateral zone also receives info from _all cortices_ about the **state of skater** * _Lateral zone_ * **processes** info * **compares** with internal stored components of **learned skilled movement** * provides _premotor and motor cortices_ with **motor plan** adjusted for **timing sequence** and **activation of each muscle** * interposed/dentate n. → VL thalamus → premotor/motor cortex * As person jumps, _medial and lateral zones_ compare: * **intended motor commands** (from cortex) * **real-time feedback** from muscles (DSCT, CuCt...) * what spinal cord **motor neurons are being told to do** (VSCT) * Checks if movement is occuring as intended * **Corrections** made via **tune up of motor centers** controlling: * axial/proximal muscles * fastigial/vestibular → MRST / LVST * fastigial → VL thalamus → trunk area of motor cortex * distal muscles * interposed/dentate → VL → limb area of motor cortex * interposed/dentate → red nucleus * Ensures motor sequence is done correctly and smoothly * As skater _repeats sequence_, **climbing fibers** generate **teaching signal** → modifies cerebellar circuits → **motor learning** → stores new learned skilled motor sequences

Answer 23

May also be critical for **thought, behavior, and emotion**. Disruption of cerebellar influences on higher functions may lead to **dysmetria of thought** and **impairment of mental agility**. * classical conditioning * navigational skills * cognitive flexibility * modulation of emotion, sham rage, predatory attack, and agression * linguistic and sensory processing * verbal working memory, shifting attention, mental imagery

Answer 24

* Mossy fibers ⟾ focal set of granule cells ⟾ beam of parallel fibers ⟾ activation of **longitudinal strip of Purkinje cells** and **associated basket/stellate cells** * Basket/stellate cells produces **lateral wave of inhibition** to surrounding Purkinje cells * **Deselects competing set of Purkinje cells** which may affect needed set of muscles for action * **Each parallel fiber** may represent a **diffferent program of percisely timed motor sequences** Actual function of parallel fibers still unclear.

Answer 25

Climbing fiber entering cerebellar cortex branches sagitally to excite 1-10 Purkinje cells. CF sagittal lines and beams of parallel fibers form a matrix. **CF activation** ⟾ robust complex spike in Purkinje cell ⟾ **LTD of parallel fibers**. _Purposed hypotheses:_ 1. CF **reset purkinje cell to baseline** 2. CF conditions Purkinje/parallel fiber synapse through LTD ⟾ role in **motor adapation and learning** 3. CF carry an error signal with repeated movements about the **inappropriate mossy fiber/Purkinje cell synapses to silence** 4. CF with internal timing function d/t capacity for synchronous and rhythmic firing ⟾ role in **motor coordination**

Cerebellum Flashcards

(50 cards)