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

NUCLEI OF SPINAL CORD - MOTOR NUCLEI

These nuclei 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 skeletal muscles.
• Lateral motor nuclei
  • This group of nuclei is placed in lateral motor column of the spinal grey matter and they extend the entire length of the spinal cord. They control the motor functions of the muscles in forearm, hind limb, shoulder, hip and lateral portions of the trunk.
• Intermediolateral nuclei
  • They are located in the inter-mediolateral column of the spinal grey matter from first thoracic to third lumbar spinal segments that form the pre ganglionic sympathetic fibres which control the motor activities in the visceral organs.

• Large motor neurons ( alpha motor neurons) supply extrafusal muscles and small motor neurons ( gamma motor neurons ) supply either extrafusal or intrafusal muscle spindles
• Motor nuclei are placed somatotropically – laterally located cells supply distal extremity muscles and medially placed ones supply muscles of upper limb and trunk
• The cells of the motor neurons are excited monosynaptically by group Ia afferent fibers from muscle spindle receptors
• Multisynaptic activation or inhibition occurs by means of internuncial neurons of gray matter.