cerebellum
TRANSCRIPT
Cerebellum Lecture Class by
Pratap Sagar Tiwari, MD, Lecturer, NGMC
Nervous System Development : Anatomical subdivisions
Source : http://en.wikipedia.org/wiki/File:EmbryonicBrain.svgReference: Gray’s Anatomy
Nervous System Development : Anatomical subdivisions
Primary division of neural tube
Sec. subdivision Final segments
Prosencephalon 1. Telencephalon2. Diencephalon
1. The cortex, Caudate, Putamen, Globus pallidus 2. Thalamus, hypothalamus, subthalamus, subthalamic nuclei
Mesencephalon Mesencephalon Mesencephalon (Midbrain), Substantia nigra pars compacta (SNc), Substantia nigra pars reticulata (SNr)
Rombencephalon 1. Metencephalon2. Myelencephalon
1. Pons and cerebellum2. Medulla
The cerebellum is divided into anatomically distinct lobes.The main body of cerebellum has three functional regions: the central vermis and the lateral and intermediate zones in each hemisphere. It is divided by the primary fissure into anterior and posterior lobes. The posterolateral fissure separates the flocculonodular lobe.
The Cerebellum Has Three Functionally Distinct Regions
Cerebellum & its connections
Connections with brainstem:• Superior cerebellar peduncle connects to
midbrain• Middle cerebellar peduncle connects to pons• Inferior cerebellar peduncle connects to
medulla
Afferent connections with spinal cord and brain
Afferent connections with spinal cord and brainCortico-cerebellar projectionVentral spinocerebellar tractDorsal spinocerebellar tract
Efferent connections
Efferent connectionsThalamusRed nucleusReticular formationVestibular nucleus
Sections of the Cerebellum
Vestibulocerebellum or archicerebellum• Comprises the flocculonodular lobe• Extensive connections with the vestibular systemSpinocerebellum or paleocerebellum• Comprises the vermis (medial) & paravermal (intermediate) region• Extensive connections with the spinal cord & brainstemCerebrocerebellum or neocerebellum• Comprises lateral portions of cerebellar hemispheres (excluding
paravermal regions)• Extensive connections with cerebral cortex through relay stations
in cerebellar nuclei and dorsal thalamus
CEREBELLAR PEDUNCLES
Superior cerebellar peduncle (brachium conjunctivum)
• Connects to midbrainAfferents: only ventral spinocerebellar tractEfferents:• Most of the efferents from the cerebellum• All of the efferents from three (out of four)
pairs of nuclei: dentate, emboliform, and globose
Middle cerebellar peduncle (brachium pontis)
• Connects to ponsAfferents: from cerebral cortex (“corticoponto-cerebellar system”).Corticopontine projections (originating in the cerebral cortex) synapse in ipsilateral basal pons. From there, most pontocerebellar projections decussate, pass through middle cerebellar peduncle and enter cerebellum.• A small number remain ipsilateral.Efferents: none.
Inferior cerebellar peduncle (“corpus restiform” or “restiform body”)
• Connects to medulla• Two components:• Restiform body
– Afferents:• Ascending spinal proprioceptive fibers from three of the spinocerebellar tracts
(dorsal, rostral, and cuneocerebellar)• Ascending fibers from contralateral inferior olivary nuclei to cerebellar cortex
(olivocerebellar projections)• Reciprocal connections with motor reticular formation and spinocerebellum
(paleocerebellum): reticulocerebellar and cerebelloreticular projections
• Juxtarestiform body– Mostly contains reciprocal connections to and from vestibulocerebellum
(archicerebellum) and vermal portion of spinocerebellum (paleocerebellum): vestibulocerebellar and cerebellovestibular fibers
Cerebellar Cortex
Deep Cerebellar Nuclei:Dentate
InterposedFastigial
PNS Fig. 42-1
General View
Gross features of the cerebellum, including the nuclei, cerebellar peduncles, lobes, folia, and fissures. (Adapted from Nieuwenhuys et al. 1988)A. Dorsal view. Part of the right hemisphere has been cut out to show the underlying cerebellar peduncles.B. Ventral view of the cerebellum detached from the brain stem.C. Midsagittal section through the brain stem and cerebellum, showing the branching structures of the cerebellum.
upper motor neuron
UMN
upper motor neuron
UMN
BASALGANGLIA
BASALGANGLIA
Pyramidal Tract and Associated CircuitsPyramidal Tract and Associated Circuits
lower motor neuron
UMN
lower motor neuron
UMN
pyramidal tract
CerebellumCerebellum
Motor Hierarchy
Exerts influenceat all levels
Intent
Actual
1° Som sensory
IVth vent VermisIntermediate hem.
Spinocerebellum: Vermis Intermediate hem.Spinocerebellum
(Vermis + Intermed. Hem)
Control of limbs and trunk
Lateral hem.
Cerebrocerebellum: Lateral hem.
Cerebrocerebellum(Lateral hemisphere)
Planning of movement+
Floculo-nodular lobe
Vestibulo-cerebellum(Floculo-nodular lobe)
Control of eye & head movementsBalance
Cerebellar divisions
NTA Fig. 13-1
Inputs and Outputs of Cerebellum
The Cerebellum Has Three Functionally Distinct Regions
Cerebellar CortexInputs
Output
Interneurons
Climbing fibers•from Inferior olive
Mossy fibers
Purkinje neurons
Stellate neurons
Granule neurons
Basket neurons
Golgi neuronsMolecular
PurkinjeGranular
NTA Fig. 13-11
The Cerebellum Has Three Functionally Distinct Regions
The three functional regions of the cerebellum have different inputs and outputs.
Cerebellar Ataxia
Ataxic gait and position: Left cerebellar tumor
a. Sways to the right in standing position
b. Steady on the right leg
c. Unsteady on the left leg
d. ataxic gait
a b c
d
Cerebellar dysfunction
Dysfunction: damage produces the following:• Ataxia- a disturbance that alters the direction andextent of voluntary movements; abnormal gait anduncoordinated movements• Dysmetria- altered range of motion (misjudge distance)• Intention Tremor-oscillating motion, especially of head,during movement• Vestibular signs-nystagmus, held tilt
Cerebellar dysfunction
1. Small lesions produce no signs or only transient symptoms; small deficits are compensated for by other parts of the brain2. Lesions of the cerebellar hemispheres result inloss of muscular coordination and jerky puppet-like movements of the limbs on the ipsilateral side (same side as lesion)3. Lesions of the vermis result in truncal tremorand gait ataxia (splayed stance and swaying ofthe body while walking)[
References