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from Guyton and Hall Textbook of Medical Physiology (4th South Asia Edition) write a proper 5 mark short answer on Functions of Basal Ganglia

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Functions of the Basal Ganglia

(Guyton and Hall, Textbook of Medical Physiology, South Asia Edition)
Introduction The basal ganglia, like the cerebellum, form an accessory motor system that ordinarily works not on its own but in close association with the cerebral cortex and the corticospinal motor system. They receive most of their input from the cerebral cortex and send almost all their output back to the cortex, mainly via the thalamus. Anatomically they include the caudate nucleus and putamen (together forming the striatum), the globus pallidus, the substantia nigra, and the subthalamic nucleus (Guyton and Hall, p. 713-714).
Major Functions
  1. Execution of subconscious, learned patterns of movement (Putamen circuit) - The basal ganglia work with the corticospinal system to execute learned, largely automatic motor patterns, such as those needed for writing the letters of the alphabet, throwing a ball, typing, or other skilled hand and postural movements, without requiring conscious attention to each individual muscle contraction.
  2. Planning and sequencing of complex movements (Caudate circuit) - They help the mind plan multiple parallel and sequential patterns of movement needed to carry out a purposeful task, integrating a series of individual motor acts into a smooth, coordinated overall action (e.g., the stepwise motor response needed to respond to a sudden, unexpected situation).
  3. Scaling/control of movement dimensions - The basal ganglia modify and control the scale or amplitude of motor patterns, for example adjusting the same handwriting pattern to be written very small or very large while preserving its form.
  4. Cognitive control of motor sequences - At a higher level, a combined cerebral cortex-basal ganglia circuit, beginning in the thinking areas of the cerebrum, provides overall sequential steps of action in response to new situations, linking cognition with motor output.
  5. Regulation via neurotransmitter pathways - Dopaminergic fibers from the substantia nigra to the caudate nucleus, along with other neurotransmitter systems (GABA, acetylcholine, glutamate) within the basal ganglia circuitry, regulate the excitability and balance of these motor circuits; disruption of this dopamine pathway underlies Parkinson disease (rigidity, tremor, bradykinesia), while other basal ganglia lesions produce chorea, athetosis, or hemiballismus.
Clinical correlation: Because the basal ganglia function so intimately with the corticospinal system, damage to them does not abolish movement but disrupts its planning, smoothness, and background muscle tone, producing the characteristic movement disorders described above.
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