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

MUSCLE-SPINDLE ORGAN

Muscle-spindle organ -Complex receptor organs

• Made up of specialized striated muscle called intra fusal muscle fibres, present within a connective tissue capsule and are attached to the skeletal musclel.

Extra-fusal-fibres

• These are the muscle fibres which produces physical shortening of the muscle.
• Alpha motor neurons innervates them.

Speciality of intra fusal muscle fibres

• Have contractile proteins at their polar ends only and not in the centre.i.e. polar ends can contract without the contraction of centre portion.
• Centre portion is known as equatorial region from where sensory nerve arises and carries information to CNS from muscle spindle via peripheral nerves.
• The contractile ends of intra fusal fibres are innervated by gamma motor neurons (ventral horn of spinal cord).