Unlike when we swing our hands while walking, why are we not able to walk fast with our arms folded?
Thiruvaiyaru, Tamil Nadu
It is an interesting phenomena that every of our muscles are controlled by nervous system for its function, described as ‘movement order’ from the brain. These are carried away from the brain from a place called ‘Motor Organization Cortex.’
This flow of impulses are modulated or regulated by various subordinate systems, just like a powerful water fall is regulated by various blockades of mountain on its way. These are extrapyramidal system, cerebellar system, and various other inhibitory or break pathways.
They ultimately end in spinal cord neurons, gets relayed there and as a final common pathway end in muscle receptors. The contracting muscle position is relayed to the brain as a ‘feed back’ through an organ called tendon organ of Golgi, which informs the brain about the stage and state of contraction.
During normal process of walking, this phenomenon is constantly happening. But in situations where when there is artificial stretching or contraction happens in the body, as we fold the hands tightly or grip the fingers, or hand tightly these impulses are generated from the tightening muscles to the brain that some part of the body is undergoing over stretch or contraction.
This information from the muscles in the hands warns the brain that the muscles are overcontracting. Thereafter the ‘power of movement’ from the brain, will try to reduce in order to protect the over contracting muscles. This effect is volleyed over to lower limbs also, and therefore the speed of walking is reduced.
This is a reflex phenomena of nervous system, rather a protective mechanism.
This phenomenon is called reinforcement of muscle contraction.
DR. V. NAGARAJAN
PROFESSOR EMERITUS IN NEUROSCIENCES
TAMIL NADU DR MGR MEDICAL UNIVE
Courtesy The Hindu