Basal ganglia (PDF)

					       Basal Ganglia

Control of movements and posture
Lecture contents
 Introduction and anatomy
 Functional anatomy
 Functions of basal ganglia
 Common pathology
 Conclusion
Introduction
 Cerebrum – gray and white matter
 Gray matter = cerebral cortex and basal ganglia
 Basal ganglia – consists of THREE nuclei, deep within
 each cerebral hemisphere
 Situated lateral to the thalamus, globus pallidus,
 putamen and superiorly caudate nucleus
Functional anatomy
 BG receive input from cerebral cortex and provide
 output back to motor parts of cerebral cortex
 BG exerts an inhibitory effect on the thalamus and brain
 stem to modulate voluntary motor activity
 Nuclei of BG have extensive connections with one
 another
 Also speculated to have interconnections with the limbic
 system
Functions 1
    Complex role in control of voluntary movement and
    muscular tone/body posture:
i. regulating muscle tone throughout the body (balance
    between excitatory and inhibitory inputs to neurons
    innervating skeletal muscle)
ii. Selecting and maintaining purposeful motor activity
    while suppressing useless or unwanted patterns of
    movement
iii. Monitor and coordinate slow, sustained contractions,
    especially pertaining to posture and support.
    BG does not directly influence efferent motor neurons
    It modifies ongoing activity in the motor pathways
Functions 2
 Regulates initiation and termination of movements
 Also control subconscious contractions of skeletal
 muscles eg. arm swings while walking,
 laughing/smiling in response to a joke
 Functions of the BG can be more clearly seen during
 disease states eg. Parkinson’s disease (see infra)
 Other unclear functions:
 Speculated to help initiate and terminate some
 cognitive processes (attention, memory, planning)
 May act together with the limbic system to regulate
 emotional behaviors
Basal ganglia pathology
 Mainly affects motor functions or movements
 Eg. Parkinson’s disease (hypokinesia), Huntington’s
 disease (hiperkinesia - chorea. athetosis, ballism)
 Parkinson’s disease – neuronal degeneration of BG
 Neurotransmitter imbalance (dopamine < -- > Ach)
 Causing: resting tremors, increase in muscle tone
 rigidity, ‘poker’ face (masklike appearance)
 impaired motor performance – bradykinesia (slow),
 hypokinesia (decreasing range of movement) – written
 words become smaller, poorly formed illegible,
 shuffling gait, speech impairments ie. fine movements
 affected
Conclusion
 Basal ganglia are paired gray matter structures deep in
 both cerebral hemispheres
 Have complex connections with the cerebral cortex,
 hypothalamus and motor pathways
 Modulates/ modify motor impulses in motor pathways
 to improve /correct muscular tone and movements
 Disruption of this function occurs in Parkinson’s
 disease causing abnormal muscular tone and
 movements
Terima Kasih
Basal ganglia anatomy
Basal ganglia (coronal section)