Gamma loop mechanism To initiate all somatic motor actions the influence of motor system upon gamma motor neuron is significant. The motor pathways depolarized dominantly gamma motor neurons which in turn initiate the contraction of intrafusal fibres of muscle spindle organ. These results in activation of group Ia afferent fibres. These fibres monosynaptically connect with […]

Demonstration of the motor control of the brain Motor control system of the brain is studied by removal of a particular portion and observing the alterations in the somatic motor activity. Decorticate preparation Decorticate preparation is demonstrated in cat or dog. In such preparations cerebral cortex with underlined white matter will be removed. Such animal

Pyramidal system and Major motor control Pyramidal and extra pyramidal system Descending (Motor) tracts of spinal cord consist of pyramidal and extra pyramidal system. Pyramidal system Pyramidal system controls the voluntary and fine motor movements in association with pyramidal motor cortex. This tract is well developed in primates and carnivores, but absent in birds and reptiles.

Descending tract of Spinal cord Cortico spinal tract Cortico spinal tract originates from the pyramidal (Betz) cells of the motor cortex‚ (60% from primary motor cortex and 40% from somasthetic motor cortex).  Enter the internal capsule, pass through the cerebral peduncles, form the pyramids at he base of the medulla and then enter the spinal

Ascending tract of Spinal cord Dorsal spinocerebellar tract Dorsal spinocerebellar tract Occupies a portion of the lateral funiculus between the lumbar vertebrae and medulla. This fiber tract originates from the ipsilateral dorsal nucleus and ends within the ipsilateral cerebellar cortex. The fibers terminate in two regions of the cerebellar cortex. Conduction velocity of these fibers

Lateral funiculus of spinal cord Lateral funiculus of spinal cord are not as clearly seen as that of the dorsal funiculus. Ascending fiber tracts of lateral and ventral funiculi. Lateral funiculus of spinal cord contains the following spinal tracts- Dorsal spino cerebellar tract Ventral spino cerebellar tract Rostral spino cerebellar tract Spino cervical tract Spinothalamic tract (Ventral

Motor Nuclei of spinal cord Motor Nuclei of spinal cord are placed in the medial, lateral and intermediolateral columns of the spinal grey matter and controls somatic and visceral motor activities. They include- Medial motor nuclei Extend throughout the length in the medial motor column of the spinal grey matter and controls the motor functions of

Sensory Nuclei of spinal cord Spinal cord has 9 laminae nuclei of spinal cord. Nucleus Dorsomarginalis Corresponds to lamina I. Extends the length of the spinal cord. Covers the dorsal and lateral surfaces of the dorsal horn of the spinal cord. Cells are spindle shaped. Neurons receive afferent fibers from the dorsal root fibers and

Gray matter and white matter Gray matter Two types of cells– Motor neurons and Internuncial neurons. 1. Motor neurons Motor neurons project their axons into the PNS  They are of 3 types Somatic or Alpha motor neurons – supplying skeletal muscles Autonomic neurons – supplying visceral organs Intrafusal or Gamma motor neurons – supplying special receptors called muscle

Physiology of Spinal cord Spinal cord is a caudal extension of the medulla oblongata present throughout the length of the vertebral canal. Each spinal segment provides a pair of spinal nerves that are formed by the fusion of dorsal root (sensory) fibres and the ventral root (motor) fibres. Structure of spinal cord Spinal cord is