In a physically healthy human, muscles are 70–85% of body weight. Muscles are the body’s largest organ. Muscles work via calcium ions, the same as astrocytes.
Muscles are sense organs in a sense. We can feel our muscles, especially when they are out of sorts. This feedback is essential to gaining motor skills. Yet muscles themselves provide no conscious sensation, as Swiss physiologist Albrecht von Haller observed in 1757.
Peripheral nerve tissue is surrounded and supported by muscle tissue. For example, the sciatic nerve is the longest and widest single nerve fiber in the human body, supplying sensing for the leg and foot, both skin and muscle. It begins in the lower back, well in the grip of the deep rotators of the hip.
The trigeminal nerve, the largest of the cranial nerves, gives sensation and muscle control in the face and scalp. The brachial plexus provides innervation for the hands and arms. Both are enveloped by the neck muscles. And so on, muscular nerve bundle by bundle.
This juxtaposing of muscle and nerve forms a functional interdependency. The muscles are given feeling while the nerves are fed. Peripheral nerves rely upon surrounding tissues for nourishment and waste removal, like astrocytes manage brain neurons.
Disused, flaccid muscles don’t provide enough pumping action for intercellular fluids which are essential to proper feeding and bathing of nerve cells. The circulation of fluids within the long axon tubes is critical to the health of nerves’ membranes and propagation of action potentials. Inadequate pumping action of surrounding muscles reduces this hydraulic flow.
Chronically tense muscles are worse. Not only is fluid circulation for nerve cells curtailed, but the capillaries that supply nutrition and carry off waste are squeezed by constricted muscles. At the same time, these contracted muscles demand more nutrients and produce more waste. Toxins build and oxygen supply lessens, irritating nerves, which contributes to further tension in a dynamic feedback loop.
Chronically high pressure on nerve trunks from tight muscles impairs nerve electrical conductivity. 5 pounds of pressure on a nerve for 5 minutes can reduces transmission efficiency as much as 40%.
A capillary is delicate, with walls only a single cell thick. Once chronically constricted muscles squeeze a capillary so hard to crush it the capillary becomes a corpuscular corpse: replaced by scar tissue, with local circulation permanently impaired.
The results of such pressures, depending upon the muscles and nerves affected, can be numbness, tingling, spasms, pains, and headaches. Since nerve functioning to internal organs can be similarly afflicted. Dysfunctions propagate.
Such organ dysfunctions can have symptoms but are next to impossible to diagnosis because no local disease is apparent: at least for a while. Complications following in the wake of chronic muscular contraction can become grave. Areas in the body with interrupted flow stagnate like a brackish swamp, creating septic situations ripe for discomfort, decay, and disease.
This is a sorry sort of muscle memory. Regular exercise is preventative, and regular massage can be curative to some degree.
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Motor skills are the output of muscle memory, of which glia are the keepers. Astrocytes store the patterns that make for motor skills, while the nerves serve as communication conduits.
Strength training is exemplary. Strength increases well before muscle hypertrophy (muscle mass growth) and decreases in strength from detraining precede muscle atrophy.
Strength training begins with astrocyte growth coupled to synaptogenesis (synaptic growth) and enhanced motor neuron responsiveness. In other words, strength is first gained, or lost, by enhanced muscle memory and communication – mind before matter.
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Fine motor skills are of transitive movements, often done using tools as simple as a toothbrush. Muscle memory of fine motor skills is subject to disruption via task interference.
For example, in learning a 2nd finger pattern 6 hours after learning the 1st, the 1st is retained. But if the 2 patterns are learned back to back, the initial one is much more easily forgotten.
Dance classes capitalize on this muscle memory limitation by teaching several patterns in a single lesson, thus maximizing the learning curve and necessitating more dance lessons. Understanding how fine muscle memory works assists a dance instructor’s fine motor skills in lightening pupils’ pocketbooks.
Puzzle cubes involve a combination of algorithmic and muscle memory. Memorization corresponding to cube moves is incredibly difficult, but an advanced cuber learns efficiently with muscle memory riding shotgun on algorithmic repetition.
The finest of fine motor skills, especially the fingering required to master musical instruments such the piano, or the coordination between mouth and fingers in wind instruments such as the clarinet, weave learning patterns across multiple mind-brain regions which become interconnected.
There are functional differences between the mind-brains of professional musicians and their fans. These adaptations reflect early exposure to musical training and many years of practice.
A pianist hearing a learned musical piece can trigger involuntary synonymous fingering. There is a coupling between music perception and motor activity in trained musicians. Hence the ability of tight bands to jam with interlocking synchronicity through anticipation and minimal signaling of variation: there is mental room to focus attention on the artistic aspect of performance without needing to consciously control fine motor actions.
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The cerebellum is the physiological home base for motor learning. It is a primitive brain portion, similar across all vertebrates, including fish, birds, reptiles, and mammals, but there is considerable variation in size, shape, and development sophistication among these various creatures. Cephalopods with well-developed brains, such as octopi, have an analogous brain structure.