Motor Function In The Spinal
The branched dorsal and ventral nerve root filaments coalesce into dorsal and ventral nerve roots, respectively. These nerve roots join to
form the spinal nerves (bundles of mixed motor and sensory axons) after exiting the vertebral foramen. A motor pool consists of all individual spinal cord motor neurons interweaving itself into a single muscle. They are grouped together in the ventral horn of the gray matter. Motor pools are arranged into motor columns that may span across multiple spinal segments.
Reflexes
A spinal reflex is a circuit contained entirely within the spinal cord, resulting in muscle movement without supraspinal input. This means the the message that was received from the nerve never reached the brain. Instead the signal was then intercepted by the spinal cord and an action was sent back to the muscles connected to that nerve. These reflexes involve signaling from sensory neurons directly onto motor neurons. This occurs very quickly - before you are even aware of the stimulus and can process it with a conscious mind. For this reason spinal reflexes are important for survival (e.g., pulling your hand away from a hot stove without thinking about it). The myotatic (stretch) reflex is an important spinal reflex that has a huge role in the automatic maintenance of posture. It is also involved in the knee-jerk reflex. The major function of the myotatic reflex is adaptive muscle movement for stabilization of the body. A plausible example can be a waiter holding an empty tray, then someone places an object on the tray – the waiter must adjust his arm muscles to accommodate the extra load without dropping the tray.
The flexor reflex is initiated by pain receptors (nociceptors) and allows withdrawal of the body away from a noxious stimulus. We have all experienced this reflex after accidentally touching a hot stove or a sharp object. We withdraw our hand before we can consciously experience the pain we have endured . This fast reflex removes the extremity from the noxious stimulus more quickly than if the pain signal had to travel up to the brain in order to trigger a decision to withdraw the limb.
The reflexes are only two ways the spinal cord can induce movement of our limbs. The spinal cord has numerous pathways that our lab currently look at to try and map out. We also look at the transplantation on neural progenitor cells into injured spinal cords to observe if our grafts are viable in different injury environments. However, this is just the tip of the ice berg of the Dulin Lab research. As always, we encourage you tot Follow The Science!
References:
Knierim, J. (n.d.). Neuroscience online: An electronic textbook for the Neurosciences: Department of
Neurobiology and Anatomy - the University of Texas Medical School at Houston. Neuroscience
Online: An Electronic Textbook for the Neurosciences | Department of Neurobiology and Anatomy
- The University of Texas Medical School at Houston. Retrieved, from
https://nba.uth.tmc.edu/neuroscience/