Which of the following clearly states the role of basal ganglia in motor function:
Correct Answer: Planning
Description: A i.e. Planning Basal ganglia is concerned with planning and organizing voluntary movementsQ whereas, spinocerebellum (spinocerebellar tract) smoothen & coordinates movementsQ Control of Posture & Movements Pa Function Coical Association Areas Commands for Voluntary movements originateQ Basal ganglia & neocerebellum (lateral poion of cerebellum) & coex Are pa of a feedback circuit to premotor & motor coex that is concerned with planning & organizing voluntary movemente2 Supplementary motor area Involved primarily in programming motor sequences. Lesions l/t awkwardness in performing complex activities & difficulty with bimanual co - ordination Premotor Coex Concerned with setting posture at the sta of a planned movement and with getting individual ready to perform Somatosensory area (Posterior parietal coex) Lesion causes inability to execute learned sequences of movements as eating with knife & fork. Neurons in area 5 is concerned with aiming hand toward an object & manipulating it, where as area 7 is concerned with hand- eye co-ordination. Spinocerebellum (medial & intermediate poion of cerebellum) Movements is smoothened & co- ordinatedQ Coico spinal & Coico-bulbar system Primary pathway for the initiation of skilled voluntary movementsQ. Rubrospinal, Reticulo-spinal, Tecto- spinal & Vestibulo spinal tracts Are main brainstem pathways concerned with posture & co- ordination Control of Posture & Movement Coical Motor Areas Motor response are produced by stimulation 01 - Motor Coex (M1) - Supplementary motor area - Premotor coex - Somatic sensory area I (in post central gyrus) - Somatic sensory area II (in wall of syln fissure) These observations fit with the fact that 30% of fibers making contricospinal & coicobubar tracts come from the motor coex but 30% come from premotor coex and 40% from parietal lobe, especially the somatic sensory area. The various body pas are represented in precentral gyrus with the feet at the top & face at the bottom. The facial area is represented bilaterally but the rest of representation is generally unilateral. The size of representation is propoionate to the skill with which the pa is used in fine, voluntary movements. The axial musculature & proximal poion of limbs are represented along the anterior edge of the precentral gyms and distal pa of limbs along the posterior edge Motor coex show same kind of plasticity as the sensory coex (i.e. the motor maps are not immutable & they change with experience) Coicospinal & Coicobulbar System The nerve fibers that pass from motor coex to cranial nerve nuclei form coicobulbar tract The nerve fibers that cross the midline in medullary pyramids and form lateral coicospinal tract make up -- 80% of fibers in coicospinal tract. The remaining 20% make up the anterior or ventral coicospinal tract which does not cross up the midline until it reaches the level of the muscles it control. In the brain stem & spinal cord medial or ventral pathways & neurons are concerned with the control of muscles of the trunk & proximal poion of limb, whereas lateral pathways are concerned with the control of muscles in the distal poions of the limb The axial muscles are concerned with postural adjustments & gross movements where as the distal limb muscles are those that mediate fine, skilled movements So ventral coicospinal tract & medial descending paths (tectospinal, reticulospinal & vestibulospinal tracts) are concerned with adjustments of proximal muscles and posture, whereas the lateral coicospinal tract & rubrospittal tract .,reconcerned with distal muscles & skilled voluntary movements Postural Reflexes Optical rightning reflex, placing reactions % hopping reactions are integrated in cerebral coex - Labyrinthine / Neck / Body on head/Body on body - rightining reflexes are integrated in midbrain - Tonic neck reflex, tonic labyrinthine reflexes & streth reflex are integrated in medulla. - Negative suppoing reaction, positive suppoing (magnet) reaction and stretch reflexes are integrated in spinal cord Antigravity reflexes in medulla and locomotor reflex in midbrain & thalamus
Category:
Physiology
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