An allometric analysis of the number of muscle spindles in mammalian skeletal muscles

Abstract

An allometric analysis of the number of muscle spindles in relation to muscle mass in mammalian (mouse, rat, guinea-pig, cat, human) skeletal muscles is presented. It is shown that the trend to increasing number as muscle mass increases follows an isometric (length) relationship between species, whereas within a species, at least for the only essentially complete sample (human), the number of spindles scales, on average, with the square root rather than the cube root of muscle mass. An attempt is made to reconcile these apparently discrepant relationships. Use of the widely accepted spindle density (number of spindles g − 1 of muscle) as a measure of relative abundance of spindles in different muscles is shown to be grossly misleading. It is replaced with the residuals of the linear regression of ln spindle number against ln muscle mass. Significant differences in relative spindle abundance as measured by residuals were found between regional groups of muscles: the greatest abundance is in axial muscles, including those concerned with head position, whereas the least is in muscles of the shoulder girdle. No differences were found between large and small muscles operating in parallel, or between antigravity and non-antigravity muscles.For proximal vs. distal muscles, spindles were significantly less abundant in the hand than the arm, but there was no difference between the foot and the leg.

Allometry (scaling) of blood components in mammals: connection with economy of energy?

“…This is in agreement with earlier observations that tissues that undergo the most rapid and extensive changes in energy utilization have the highest levels of P-CR and CK (Walker 1979). Scaling of P-CR and CK in mammalian muscles has only been done to a very limited extent (Newsholme et al 1978), but the number of muscle spindles in mammalian skeletal muscles scales with muscle mass (b = 0.35, 95% CI = 0.31-0.39, p < 0.0001) (Banks 2006).…”

Effects of prolonged patellar tendon vibration on force steadiness in quadriceps femoris during force-matching task

“…Banks (2006) determined the number of muscle spindles in individual skeletal muscles in humans, and noted that the relative spindle abundance was similar across the four individual QF muscles. The VM is the nearest of the four QF muscles to the patellar tendon, and some ultrasonographic studies have shown that the muscle thickness and fascicle angle of the VM at the distal site are greater than those of the other QF muscles at each site (Blazevich et al 2006;O'Brien et al 2010;Ando et al 2015).…”

Simulation system of spinal cord motor nuclei and associated nerves and muscles, in a Web-based architecture

“…These nuclei are associated with the following muscles: soleus (SOL), medial gastrocnemius (MG), lateral gastrocnemius (LG) and tibialis anterior (TA). The total number of neurons simulated for these nuclei is shown in Table 1, based on estimates from human and cat literature (Feinstein et al 1955;Cooper 1966;Ariano et al 1973;Johnson et al 1973;Buchthal and Schmalbruch 1980;Dum and Kennedy 1980;McComas 1991;Jankowska 1992;Carr et al 1998;Banks 2006). Interneuron numbers are underestimated, in order to improve system performance.…”