VPB 121: Veterinary Physiology - II (2+1)

MAJOR MOTOR CONTROL

• Many fibres connect adjoining and distant segments of the spinal cord with each other and do not project outside the spinal cord , called the Propriospinal fiber systems.
• They make up a major mass of the white matter of the spinal cord.
• They originate from the spinal gray matter except the motor nuclei.
• They are important in the interrelation of neural activities within the spinal cord.
• Reflex ats and complex reflexes involve several such relays.

• During walking or running, they are responsible for coordination of motor activity required to maintain equilibrium and allow the proper sequence of limb movement for propelling the animal forward.
• In spinal animals after a period of weeks , if assisted in maintaining balance , exhibit stepping movements similar to those observed in normal locomotion.
• The central motor control system includes the motor cortex, basal ganglia and the cerebellum. The motor cortex transmits its signals through caudate nucleus, putamen, globus pallidus, subthalamic nucleus, substantia nigra and reticular nuclei of the brain stem into the spinal cord.
• The motor cortex controls pyramidal and extra pyramidal systems. The motor cortex-pyramidal system is associated with voluntary performance of fine skilled movements. Gross involuntary movements are generated by the motor cortex-extra pyramidal system.
• The primary motor cortex controls the contraction of individual muscles and evokes discrete movements. The secondary cortex regulates complex movements of head, neck, trunk and limbs. The premotor cortex controls fine movements of hands, fingers, mouth and tongue, co-ordinated movements of eyes and head.
• Both the basal ganglia and the cerebellum are concerned with co-ordinated movements with pyramidal and extra-pyramidal systems. Co-ordination of slow or ramp movements is associated with basal ganglia. The cerebellum co-ordinates the fast or ballistic movements.