Cerebellum | Anatomy2Medicine
Cerebellum,Anatomy

Cerebellum

The Cerebellum

    • The cerebellum is dorsal to the pons and medulla
    • involved in the planning and fine tuning of skeletal muscle contractions.
    • It can be divided into three major lobes by transverse fissures: (MCQ)
      • The anterior fissure separates the anterior and posterior lobes.

 

  • The posterolateral fissure separates the small flocculonodular lobe from

 

the posterior lobe.

      • The flocculonodular lobe, or vestibulocerebellum, controls balance and eye movement. (MCQ)
      • Input is to the vestibular nuclei.
    • A functional separation consists of a midline zone (vermis), which separates the two lateral cerebellar hemispheres.

 

  • The vermis and intermediate zones, or spinocerebellum, control rate,

 

force, and direction of movement with principal input to the spinal cord.

 

  • The hemisphere, or pontocerebellum, is involved in the planning and initiation of movements; principal input is to the cerebral cortex. (MCQ)

 

    • The cerebellar cortex has three layers:
      • The molecular layer (MCQ)
        • outer layer
        • contains basket and stellate cells, as well as parallel fibers, which are the axons of the granule cells.
        • Dendrites of the Purkinje cell extend into this layer.
      • The Purkinje layer (MCQ)
        • middle and most important layer because all in- puts to the cerebellum are directed toward influencing the firing of the Purkinje cells
        • only Purkinje cell axons leave the cerebellar cortex.
        • Output is always inhibitory.
      • The granular layer (MCQ)
        • innermost layer
        • comprises Golgi type II cells, granule cells, and glomeruli.
        • Each glomerulus has a granule cell, which is the only excitatory neuron in the cerebellar cortex.
    • The cerebellar cortex has two major afferents:
      • originate from the inferior olivary nuclear complex on the contralateral side of the medulla. (MCQ)
      • Climbing fibers provide excitatory input to Purkinje cells by synapsing on them. (MCQ)
      • Climbing fibers (MCQ)

 

  • They play a role in cerebellar motor learning(MCQ)

 

      • Mossy fibers (MCQ)
      • represent axons from all other sources of cerebellar input. (MCQ)
      • They provide an indirect, diffuse excitatory input to Purkinje cells as well as inhibitory neurons (ie, stellate, basket, and Golgi type II cells). (MCQ)
      • All mossy fibers exert an excitatory effect on granule cells, which give rise to parallel fibers that stimulate Purkinje cells. (MCQ)
    • The cerebellar cortex has four major efferents
      • has efferents first to the thalamus and then to the cortex
      • influences lower motoneurons via the corticospinal tract. (MCQ)
      • Purkinje cells (MCQ)
        • are the only output
        • are always inhibitory via the neurotransmitter Gamma-aminobutyric acid (GABA). (MCQ)
      • The spinocerebellum
        • has efferents to the red nucleus and reticular formation
        • influences lower motoneurons, via the reticulospinal and rubrospinal tracts(MCQ)
        • adjust posture and effect movement. (MCQ)
      • The pontocerebellum

 

  • These efferents produce precise, sequential voluntary movements. (MCQ)

 

    • The vestibulocerebellum
      • has efferents to the vestibular nucleus
      • elicits positional changes of the eyes and trunk in response to head movements. (MCQ)