Each nerve root level of the spinal cord (segment) is represented by a dorsal (sensory) and a ventral root (motor) with connection through a CNS segment of the spinal cord. Additionally, each segment innervates two segmental components: Extensor and flexor muscle groups that together act as either agonist and antagonist motor groups.

• Each nerve root level of the spinal cord (segment) is represented by a dorsal (sensory) and a ventral root (motor) with connection through a CNS segment of the spinal cord. Additionally, each segment innervates two segmental components: Extensor and flexor muscle groups that together act as either agonist and antagonist motor groups.

• Monosynaptic reflex connections are formed of:

• Dorsal root ganglial neurons with receptor endings at their peripheral terminations as muscle based stretch receptor organs. From these DRG neurons, central projections enter the dorsal horn of spinal cord. These DRG axons target Alpha Motoneurons (ventral horn motor neurons), directly through a single synapse.
• Alpha Motoneurons produce muscle contraction, monosynaptically by direct input of the stretch DRG neuronal receptor.