cerebellum and basal ganglia
TRANSCRIPT
The Cerebellum & Basal GangliaCsilla Egri, KIN 306 Spring 2012
The cerebellum. Fighting the drunken stooper since 1862.
Outline
General function Anatomy of the cerebellum
Functional divisions Projections
Anatomy of the basal ganglia Projections
Basal ganglia disorders Parkinson’s disease
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General functions3
Cerebellum Major role in timing of motor
activities and in rapid, smooth progression of movements Monitors and makes corrective
adjustments to motor plan Basal ganglia
Helps plan and control complex patterns of movement Relative movement intensities,
directions, and sequenceNo direct projections to lower motor
neurons of skeletal muscleMovement influenced by regulation of
activity of upper motor neurons
Cerebellar cortex:functional divisions
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3 functional divisions Vestibulocerebellum
Flocculus + nodulus Spinocerebellum
Vermis and adjacent intermediate zone
Cerebrocerebellum Lateral zone
Sunderland Fig 19.1 (online access http://www.ncbi.nlm.nih.gov/books/NBK10799/ use search function to browse chapter contents)
Cerebellar cortex: functional divisions
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Vestibulocerebellum Inputs:
From vestibular nuclei in brainstem Function:
Regulate movements underlying posture and equilibrium
Coordination of eye and head movements Damage:
Impairs ability to stand upright, maintain posture and balance
Cerebellar nystagmus
Cerebellar cortex: functional divisions
6
Spinocerebellum Inputs:
Directly from spinal cord Function:
Lateral portion Movement of distal muscle (ex. gross
movements during walking) Central portion (vermis)
Movement of proximal muscles Damage:
Overshoot and intension tremor Impaired gait
Cerebellar cortex: functional divisions
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Cerebrocerebellum Inputs:
Many areas of cerebral cortex (relayed thru pons) Function:
Planning and timing of sequential movements Speech
Damage: Ataxia: incoordination of complex, purposeful movements of
hands, fingers, feet and speech apparatus Failure of smooth progression of movement
Lesions to any division of cerebellum result in impairments on ipsilateral side of the body
Cerebellum: projections8
4 deep cerebellar nucleireceive input from
cerebellarcortex and send projections to thalamus1. Fastigial
2. 2 Interposed
3. Dentate
Information travels viacerebellar peduncles1. Superior (efferent)
2. Middle (afferent)
3. Inferior (mixed)Sunderland Fig 19.1
Cerebellum: inputs
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Receive many inputs from periphery, spinal
cord and brain regions
Sunderland Fig 19.3
Cerebellum: outputs
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Sunderland Fig 19.6
Why would lesions to the cerebellar cortex affect movement on ipsilateral
side of the body?
The basal ganglia
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Sunderland Fig 18.1
Striatum
Receives inputs from and projects back to motor cortex via thalamus
Closed loop
The basal ganglia:inputs
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Striatum is main input center
integrates inputs from a variety of structures, including substantia nigra pars compacta
No input directly from spinal cord
Send inhibitory connections to two main output centers
Sunderland Fig 18.2
The basal ganglia:outputs
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Internal globus pallidus and substantia nigra pars reticulata are main output centers
SN-pars reticulata mainly projects to superior colliculus
Eye movement Internal globus pallidus
mainly projects to thalamus Relays output to motor
cortices Each send tonic inhibitory signals
Sunderland Fig 18.5
The basal ganglia: general circuitry
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Input: to striatumOuput: internal globus pallidus and
substantia nigra pars reticulata Inhibitory connections
GABA throughout most of basal ganglia
Excitatory connections: Glutamate from cortex,
subthalamic nucleus and thalamus
Dopamine from subsantia nigra pars compacta can be either inhibitory or excitatory
Sunderland Fig 18.1
The basal ganglia: generalcircuitry
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Outputs of striatum project via two different pathways
each pathway is modulated by dopamine from substantia nigra pars compacta
Direct Facilitates movement Excited by dopamine (D1
receptors) Indirect
Inhibits movement Inhibited by dopamine (D2
receptors) Kandel Figure 43-3
What effect does dopamine release have on movement?
The basal ganglia: generalcircuitry (supplementary slide)
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The basal ganglia enables the proper motor program to be activated via the direct pathway and inhibits competing motor programs via the indirect pathway.
Can be modulated by SnC
The basal ganglia: direct pathway
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Sunderland Fig 18.8
Dopamine release onto D1 = Increased excitation of motor cortices
Cortical projections to direct pathway result in dis-inhibition of thalamus
The basal ganglia: indirect pathway18
Sunderland Fig 18.8
Dopamine release onto D2 = Increased excitation of motor cortices
Cortical projections to indirect pathway result in dis-
inhibition of subthalamic nucleus and inhibition of
thalamus
Disorders of the basal ganglia19
Parkinson’s Disease Characterized by resting tremor,
slowed/absent movement (hypokinesia), rigidity of the extremities and neck, & reduced facial expressiveness
Caused by the loss of the dopaminergic neurons in the substantia nigra pars compacta
Typically treated with L-Dopa
WebCT readings: Circuits within the basal ganglia system
Parkinson’s Disease20
Increased output of indirect pathway, decreased output
of direct pathwaySunderland Fig 18.10
Objectives
After this lecture you should be able to: Discuss the general role of the cerebellum and basal ganglia in
voluntary movement Describe the organization of the cerebellum
List the major inputs/outputs to and from the cerebellum List the major functions of the three functional divisions of the
cerebellum Describe the organization of the basal ganglia
List the major inputs/outputs to and from the basal ganglia and their corresponding neurotransmitters
Trace the connections of both the direct and indirect pathway of the basal ganglia and their contributions to movement Relate how disorders of the basal ganglia such as
Parkinson’s disease affect these pathways
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1. The globus pallidus interna primarily projects to the ______________________ whereas the substantia nigra pars reticulata primarily projects to ______________________.
2. Inhibition of the subthalamic nucleus results in increased or decrease motor movement?
3. The __________________________ cerebellar peduncle is the main pathway for efferent fibers.
Test your knowledge