[Functional characteristics and distribution of neuromuscular spindles].

This study investigates the distribution and functionality of neuromuscular spindles (NMS) in various muscles of horses and pigs, revealing the presence of NMS in certain muscles and their absence in others. It also suggests that muscles at the extremities might play a role in modifying activity in muscles closer to the body, and non-locomotive striated muscles do not contain NMS.

Distribution of Neuromuscular Spindles

• The study found a high concentration of Neuromuscular Spindles (NMS) in the mm. lumbricales and mm. capsulares muscles of horse’s shoulders and hip joints. These are small muscles located in the hands and feet, and around joints respectively.
• NMS were also found in the mm. interossei muscles of pigs. These are small muscles located between the larger muscles of limbs.
• However, these NMS weren’t found in the mm. interossei of horses, indicating a differing distribution of NMS between species.

Absence of Neuromuscular Spindles

• The study noted absence of NMS in certain muscles: The m. orbicularis (muscle around the eye), m.hyo-epiglotticus and m. palatinus (muscles in the mouth and throat region) in horses lacked NMS.
• NMS were also absent in the vestigial muscles, like the m. extensor digitorum brevis (a muscle in the foot) and the m. of Thiernesse (an unidentified muscle). The absence in vestigial muscles, which are typically underdeveloped or unused, aligns with the suggested function of NMS in movement and locomotion.

Functional Characteristics of Neuromuscular Spindles

• The research proposes that the presence of NMS in distal muscles (at the body’s extremities) suggests these muscles might play a role in modifying signals or activity in proximal muscles (those closer to the body’s midline).
• The paper proposes that NMS are absent in striated muscles that are not involved in locomotion. Striated muscles are characterized by their appearance under a microscope and are typically involved in skeletal movement. Thus, their absence in non-locomotive striated muscles suggests these spindles play a key role in facilitating movement.