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

EXTRACORTICAL REFLEXES

• It is mediated through spinal cord, medulla and pons. It is of two types - the tonic neck reflexes and tonic labyrinthine reflexes.

Tonic neck reflex

• Neck receptors include muscle stretch receptors and receptor organs that sense the position of joints between cortical vertebrae related to head position.
• Extension of the head to dorsal position causes flexion of the hind limbs, but extension of the forelimbs occurs when the head is moved downwards.

• Turning of head to right side causes the extension of both the right limbs and the flexion of both the left limbs to support the body against gravity; this helps to prevent falling.
• If the turning is on the left side, it results in the extension of the left limbs and the flexion of the right limbs.