Anatomy of the Cerebellum Flashcards
What is the cerebellum?
motor part of the brain
What are the functions of the cerebellum?
- Maintain equilibrium
- Posture control
- Coordinate muscle contraction in both stereotype and non-stereotype (voluntary movements)
What is the location of the cerebellum?
- Located on the lower part of the posterior cranial fossa.
- Separated from the occipital lobe by tentorium cerebelli
- Lies behind the posterior aspect of the pons and medulla
- Forms the roof of the 4th ventricle
Describe the structure of the cerebellum?
- Two cerebellar hemispheres (left and right)
- The central part called vermis unites the hemispheres
- The surfaces bears curved fissures between narrow folds called folia
Describe the 2 important fissures of the cerebellum?
- Primary fissure (on superior surface) – divides it into:
- Anterior lobe
- Posterior lobe - Posterolateral fissure (on inferior surface) – separate floccularnodular lobe from the body of the cerebellum (corpus cerebelli)
What is the vermis of the cerebellum?
an unpaired medial structure that separates the cerebellar hemispheres
Describe the structure of the vermis?
- Superior vermis – slight ridge extends anteriorly to include the lingula of medullary vellum
- Inferior vermis – clearly demarcated by valleculla cerebelli
- Antero-posteriorly divided into:
> Nodule - extends a stalk to the flocculus forming flocculonodular lobe
> Uvula
> Pyramid
What is the tonsil of the cerebellum?
partially separated lobule that over hangs the inferior vermis
Describe the lobes of the cerebellum?
- Anterior lobe – marked behind by the primary fissure
- Posterior lobe – remainder of hemispheres + uvula + pyramid
- Flocculonodular lobe – nodue + flocculum
Name the 10 lobules of the cerebellum?
Lingula, Central, Culmen, Declive, Folium, Tuber, Pyramis, UvulaTonsil, Flocculonodular
What is the archcerebellum?
- First to develop with the vestibular nuclei
- Well developed in fish
- In humans, represented by:
1. Flocculonodular lobe + lingula
2. Vestibular system - Involved in mechanisms of balance (equilibration)
What is the paleocerebellum?
- second to develop
- Well developed in terrestrial vertebrates –reptiles
- In humans, represented by:
1. Anterior lobe
2. Anterior and posterior vermis - Connect to spinal cord through motor neurons for muscle tones
What is the neocerebellum (posterior lobe)?
- Last to develop
- Well developed in humans
- Controls non-stereotyped, skilled learned activities
What are the cerebellar peduncles?
- Connects the cerebellum to the brainstem (medulla, pons and midbrain)
- convey inputs and outputs from parts of the body to cerebellar cortex
Name the cerebellar peduncles?
- Superior peduncle (brachium conjuctivum)
- Middle peduncle (brachium pontis)
- Inferior peduncle (restiform body)
Describe the superior peduncle?
- Connects the cerebellum to the junction of the pons and the midbrain
- Contains both afferent and efferent fibers
> to red nucleus and thalamus - efferent fibers leave the cerebellum to the thalamus and spinal cord
- they normally relay to red nucleus at the level of the superior colliculus
Describe the middle cerebellar peduncle?
- Connects the cerebellum to the pons
- Contains afferent fibers from pontine nuclei of contralateral side
- Involves fibers from contralateral pons to cerebellum
Describe the inferior cerebellar peduncle?
- connects the cerebellum to the medulla oblongata
- carries both afferent and efferent fibers
- carries fibers from spinal cord (spinocerebellar fibers), medulla oblongata (cuneocerebellar -from nucleus cuneatus), reticular formation (reticuocerebellar fibers) to cerebellum.
- Carries climbing fibers from the inferior olivary nucleus to cerebellum
Describe the components of the cerebellum?
- Cortex or Surface layer (gray matter)
- contained in transverse folds or folia
- Detailed structure is uniform throughout - Medullary center (white matter)
- contains four pairs of deep intracerebellar nuclei:
- Nuclei lie in the roof of 4th ventricle – hence called roof nuclei
What are the deep cerebellar nuclei?
- Buried in medullary center of each hemisphere.
- These nuclei are ( from medial to lateral):
1. Fastigial nucleus
2. globose nucleus
3. emboliform nucleus
4. the dentate nucleus
Describe the fastigial nucleus of the deep cerebellar nuclei?
- Lie close to midline on the anterior surface of the superior vermis
- Well developed in fish
- Controls the functions of the arch cerebellum
Describe the globose nucleus of the deep cerebellar nuclei?
- Lies on lateral side of the fastigial but medial to emboliform nucleus
- control the functions of the paleocerebellum
Describe the emboliform nucleus of the deep cerebellar nuclei?
- Lies on the medial side of the dentate
- control the functions of the paleocerebellum
Describe the dentate nucleus of the deep cerebellar nuclei?
- occupies the center of the cerebellar hemispheres
- Has a hilum that faces medially
- Well developed in humans
- Controls the functions of the neocerebellum
Describe the cerebellar cortex?
Is a uniform three – layered structure:
1. molecular layer
2. purkinje layer
3. granular layer
Describe the molecular layer of the cerebral cortex?
Consists of axons and dendrites of various cerebellar neurons.
Made up of sublayers:
> stellate cell layer ( scattering stellates outermost + modified stellate cells called basket cells) (outermost)
Describe the Purkinje fibers layer of the cerebellar cortex?
- Made up of purkinje cells their dendrites ramify the molecular layer
- climbing fibers synapse with dendrites of purkinje fibers in the molecular layer
Describe Purkinje cells?
Describe the contents of the granular layer of the cerebellar cortex?
- granular cells
their short denrites synapse with mossy-fibers forming glomeri
their axons synapse in the molecular layer
axons divide in T-shape to form parallel fibers - golgi cells are scattered among granular cells form glomerulus
- Golgi cells: receive input from mossy and parallel fibers, and inhibit the mossy fiber to granule cellls synapses, thus modulating the signal on the parallel fibers.
- basket cells: receive input from and inhibit the Purkinje cells, providing a kind of gain control. Long range, offbeam inhibition.
- Stellate cells: apparently the same function as basket cells. Short range inhibition
- Lugaro cells receive input from 5 -15 Purkinje cells and project to basket, stellate, and Golgi cells.
- Unipolar brush cells. Excitatory interneurons using glutamate as the neurotransmitter
Describe the 3 types of nerve fibers in the white matter of the cerebellum?
Describe the white matter of the cerebellum?
- Fibers from peduncles enter the white matter.
- Thin lamina of white matter join the two sides
- Thin lamina divide white matter into:
1. superior medullary velum
2. inferior medullary velum
The white matter of the cerebellum is made up of?
- afferent fibers from outside the cerebellum
- projection fibers from the cerebellar cortex to cerebellar nuclei
- Association fibers that connect different parts of the cerebellar cortex
- commissural fibers that connect the two cerebellar hemispheres
- fibers from cerebellar nuclei +cortex to centers outside the cerebellum
Describe the intrinsic pathway of the cerebellum?
Describe the cerebellar afferent pathway?
