Motor Pool

Ronald Sommers, Daniel Paz de Araujo, Jazmine Estrada

The following proposal outlines the changes we wish to make for the page on the motor pool. Our research into the topic is still a work in progress, and accordingly, the following outline may be subject to small changes.

Our group labor will be divided by subsection (to be determined according to personal interest), but we will work closely to assure coherence and to avoid repetitious material.

Introduction

A motor pool is a group of specialized motor spinal neurons that collectively innervate the same skeletal muscle. The number of neurons in a motor pool has physiological consequences: the number of neurons assigned to an individual muscle correlates with the level of precision the brain may exercise over the individual muscle's movements. The development of specific motor pools is therefore highly regulated.

Anatomy

Motor pools are not homogenous structures. Each motor pool varies not only in its size, but also in its neuronal composition. Different motor pools consistent of different classes and subtypes of motor neurons. We will discuss these motor pool "customizations". As an introduction to this discussion, we may decide to briefly discuss the basic anatomy of a motor unit for context.

Function

As we previously alluded to, motor pool composition has physiological significance regarding the precision with which the brain may control an individual muscle. We will discuss the physiology of muscle precision as it relates to the structure of a motor pool.

Development

The development of individual motor pools is complex, and it involves Hox gene regulatory networks. In development, individual spinal motor neurons receive individual pool identities that allow them to form selective connections with their assigned muscle. We will elaborate on this mechanism of specialization.

Evolution

We will briefly discuss a few novel examples of motor pool evolution -- specifically in the case of humans and the evolution of the motor pools controlling hand and finger muscles. These examples will highlight the significance of motor pool size and composition, and will contextualize the discussion given in the "Function" section.

Clinical Significance

We will explore the effects of aging on the physiology of the motor pool. We will research further the connection between specific neurodegenerative diseases and the function of motor pools. Considering our discussion on the development of motor pools, we will also further research developmental diseases that affect motor pool specialization.

References

Dasen, Jeremy S et al. "A Hox regulatory network establishes motor neuron pool identity and target-muscle connectivity." Cell 123.3 (2005): 477-491.
Cappellini, Germana et al. "Migration of motor pool activity in the spinal cord reflects body mechanics in human locomotion." Journal of neurophysiology 104.6 (2010): 3064-3073.
Fuglevand, Andrew J, David A Winter, and Atfab E Patla. "Models of recruitment and rate coding organization in motor-unit pools." Journal of neurophysiology 70.6 (1993): 2470-2488.
Wakeling, James M et al. "A Muscle’s Force Depends on the Recruitment Patterns of Its Fibers." Annals of Biomedical Engineering (2012): 1-13.
Enoka, Roger M. "Morphological features and activation patterns of motor units." Journal of clinical neurophysiology: official publication of the American Electroencephalographic Society 12.6 (1995): 538.
Enoka, Roger M, and Andrew J Fuglevand. "Motor unit physiology: some unresolved issues." Muscle & nerve 24.1 (2001): 4-17.
Tracy, Brian L, Paul D Mehoudar, and Justus D Ortega. "The amplitude of force variability is correlated in the knee extensor and elbow flexor muscles." Experimental brain research 176.3 (2007): 448-464.
Baker-Herman, Tracy L., and Kristi A. Strey. "Similarities and Differences in Mechanisms of Phrenic and Hypoglossal Motor Facilitation." Respiratory Physiology & Neurobiology 179.1 (2011): 48-56. Print.
Jessell, Thomas M, Gülşen Sürmeli, and John S Kelly. "Motor Neurons and the Sense of Place." Neuron 72.3 (2011): 419-24. Print.
Kanning, Kevin C., Artem Kaplan, and Christopher E. Henderson. "Motor Neuron Diversity in Development and Disease." Annual Review of Neuroscience 33 (2010): 409-40. Print.