Journal of Sport and Kinetic Movement Vol. I I, No. 302017 [629204]

Journal of Sport and Kinetic Movement Vol. I I, No. 30/2017

NERVOUS INTEGRATION OF VOLUNTARY MOVEMENT

Dănoiu Mircea1, Manuela Băcănoiu2, Zăvăleanu Mihaela1

1Faculty of Physical Education and Sport, University of Craiova, Romania
2County Emergency Hospital Craiova, Romania
Correspondence author address : [anonimizat]

Abstract
Designed as a true cyber scheme, execution of volitional movements is a synergistic combination of different sensory
and motor factors which is reflected in muscle contractions, adequate control over the intensity, hierarchy, chronology
and spatial location of body or different parts of the body.
All body biomechanical activities results from a double command which simultaneously produces the contraction of
two muscle groups with antagonistic action. Those are the flexors and extensors. The first group contract and produce
the desired movement, the second group provides relaxation and modulates movement. The movement would lose
precision and safety, also can occur excessive contractions without this synchronization between the muscles agonists
and antagonists.
Voluntary movement involves a complex process of coordinated steps required not only for initiation, but also for the
cessation of muscle contraction, and the intimate nature of the processes in which volitional consciousness is capable of
expressing itself in terms of movement remains incomprehensible.
In the rehabilitation and sport, the accuracy of the voluntary movements is crucial. The learning and repetition for
learning of one motion require a complex image of the temporal and spatial succession and nervous integrationof the
elementary movements that must be executed in a special order to achieve the desired action. Those succesion are the
base of rehabilitation and sport and must be well understude in order to achive the ideal voluntary movement.
Key words: muscle contraction, nervous integration, voluntary movements

Introduction
The muscle is the active effector part of the
system that realizes a movement. This is how the
body reacts to the constant changes in the
environment, all range of external attitudes is feel
in the functionality of central nervous system that
can ultimately reduced to a single fundamental
phenomenon that is the movement.
For point -to-point movements, the model provides
predictions on (1) movement trajectory, (2)
equilibrium trajectory, (3) muscle control inputs,
and (4) antagonist muscle stiffness, as well as
other variables. [1]
The striated muscle is the actualy effector device
of this system that has two fundamental
properties: excitability and contractility, also
guarantee that the electro -chemical influx that is
perceived at his level is transformed into
mechanical energy through a complex processes.
The various movements of the body are carried by
the muscles closely related to the nervous system
that is based on integrates internal/external
information. After the integration of those
informations the brain is emitting commands for
the muscles that are end effectors and finally do
the required and learned movement. For many
years thereafter the role of the motor cortex was
relegated to that of a simple map of muscles and
muscle activity patterns by which the rest of the cerebral cortex controlled spinal motor neurons.
[2]
Franz & McCommick [3] highlighted there is a
tendency in the brain to economise cognitive
resources, while at the same time optimising
behaviour. Further, the brain is continually
monitoring sensory and cognitive information to
glean essential associations used to efficiently
guide behavior. [4]
The motor system can learn new behavioral
strategies or new reactions to familiar stimuli to
improve behavioral outcom es, and it can learn
new skills to cope with predictable variations and
perturbations of the environment.Thus the neural
control of voluntary movement involves far more
than simply generating a particular pattern of
muscle activity. [2] Many aspects of the neural
response may be quite ‘non-muscle like’ even if
muscle commands are the final output . [5]
In 1997, Ning Lan talk about the multi- joint arm
movements performed by humans, the
coordination strategy for a set of redundant
muscles and the consequent invariant features of
movements that are not well understood. [6] Also
the Ning article speek about the fact that extensive
experimental studies have been carried out to
identify biological control strategies of
movements.
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There are several types of muscle fibres that differ
with regard to their functional, biochemical and
morphological properties. [7] Nevertheless,
muscle fibres belonging to a particular motor unit
are all identical and are specialized to carry out
the tasks demanded from them by the
motoneurones that activate them. [7]
The heterogeneity of the muscle fibers is the base
of the flexibility which allows the same muscle to
be used for various tasks from continuous low-
intensity activity (e.g., posture), to repeated
submaximal contractions (for example,
locomotion), and to fast and strong maximal
contractions (jumping, kicking). [8] In addition,
the structural and functional properties of the
fibers, which are generally referred to as fiber
phenotype, can change in response to hormonal
and neural influences, nerve -activity being a
major determinant of the fiber type profile. [8]
Needham (1971) [9] provides a comprehensive
account of the history of muscle contraction and
metabolism and quotes Berzelius (1807) for the
discovery that the muscles of an exhausted stag
contained lactic acid.
Skeletal muscle accounts for approximately 50%
of total body weight, and is known to be the
largest tissue in the human body, mainly
responsible for force generation, movement and
breathing. [10, 11 ]
After Best and Garret skeletal muscle comprises
the largest tissue mass in the body, accounting for
40–45% of body mass [12, 13]. It is responsible of
locomotion and also for the changes in body size
and shape of the internal organs, so:
a) the muscle transform the chemical energy into
mechanical and thermal energy. In order to fully
appreciate the physiology of skeletal muscle, you
must know how muscle transforms the food we
eat into the muscular action that produces force
and motion. This flow of energy is called skeletal
muscle energetics and it focuses on the creation
and use of adenosine triphosphate (ATP). [14]
b) the mechanical effect is realized by muscular
contraction that manifest also in pressure on
cavitary organs, also by the resistance to changing
of the posture of a body or different body parts
(specialy the postural muscles) or for carry out
active movements (walking, running, jumping
etc.)
c) actomiozionic complex consists the structural
basis that couple the excitation with contraction in
muscle fiber d) ATP (adenozintrifosforic acid) is
the direct power source necessary for the
contraction named by Engelhard "universal
energy currency of living matter". ATP is a complex nanomachine that serves as the primary
energy currency of the cell [15]. A nanomachine
is a complex precision microscopic- sized machine
that fits the standard definition of a machine. ATP
is the “most widely distributed high-energy
compound within the human body” [16]. AllenD.
G et all from 2008, have cite many studies that
have reported that cytoplasmic [ATP] does not
drop below ∼60% of the resting level during
either imposed stimulation or voluntary exercise.
[17]
e) the muscle contraction is triggered by a
physiological stimulus (nerve impulse), stimulus
that represent the information.
The human body is a complex machine that poses
many sub-systems interacting each other and a
main control to make efficient this interaction: the
nervous system. [18]
The various muscle functions are controlled by
signaling pathways that allow the muscle fiber
respond to changes in the metabolic and
functional demands of the body. Indeed, examples
in the world of sports, therapy, surgery, and
trauma support the idea that skeletal muscle is one
of the most adaptable tissues in the body. [19]
Some forms exercise training, such as strength
training and resistance training, can produce an
increase in skeletal muscle mass, known as
muscle hypertrophy [20]. These interactions
suggest that the dynamic regulation of skeletal
muscle mass is not simply a balance between
synthesis and protein degradation, but a finely
regulated process. [19]
The motor system was born, not made, and many
of the characteristics of the human motor system
reflect its history. [21] The ability to store motor
memories enables the motor system to select a
wide variety of movements in a highly flexible
manner. People can select actions from a large
repertoire of skills that have been previously
learned, depending on context. [21]
Force and movement depend on muscle proteins,
principally myosin and actin, both of which form
strands within the muscle fibers. Molecules of
myosin store kinetic energy as a result of
metabolizing adenosine triphosphate (ATP), and
muscle activation converts this chemical energy
into mechanical force and work. Muscles generate
force through a cascade of electrical and
biochemical events, beginning with the release of
acetylcholine by motor neuron synapses at the
neuromuscular junction. [21]
Nerves from the motor neurons are also called
efferent fibers which carry signals to the end
organs. Sensory or afferent neurons carry sensory
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signals from these organs to the CNS for
processing.
Striat skeletal muscle that is involved in voluntary
motion, should be framed in general metabolism
of the body, which influences and by which it is
influenced. The contractile activity is mainly
dependent in terms of source energy, muscle is the
main producer of lactic acid that is consider the
"metabolic waste" which in human represent an
important energy substrate for cardiac muscle.
The skeletal muscle is the main producer of CO2
in the body also as the main source of heat from
the body.
Lactic acid that appear after the anaerobic
glycolysis should not be seen as a negative factor
but also as a possible source of energy, although
in certain situations may occur that increased
acidity potential destabilizing affects muscle
function and metabolism. Lactic acid is produced
continuously, even at rest, so when training
athletes, in cool-down period of training are
indicate carbohydrate supplements that restores
glycogen accumulation.
Considered as an organ, the striated muscle is
made of elementary fibers in their turn joined in
fascicles by connective tissue. The muscle fibers,
which represent 85% of the striated muscle is
wrapped in a thin sheath of connective tissue
called endomysium, which bond tight between
them. The muscle fibers are arranged in parallel
and grouped in bundles by 20-50 fascicles with a
diameter of 0.5-1 mm, surrounded in turn by a
rich connective tissue, called internal perimysium.
The entire striate muscle is wrapped in a tissue
sheath (epimysium). The epimysium composed of
a thick layer of collagen fibers is fibrous elastic
tissue and allows muscle to contract and move
while maintaining its structural integrity; it also
separates muscle from other tissues and organs.
From the surface of epimisium protrude depth in
the muscle septa of connective fibers which
separate in different clusters each constituting as a
whole internal perimisium. From this emerge
thinner fibers of connective tissue, so single
muscle fibers partly constituting the endomysium.
The fibro -conjunctiv tissue is represented by
collagen fiber, elastic, by fibroblasts, histocite, fat
cells and the tendons, all those structures binds to
muscles to the bones that they put it in motion.
Striated muscle contraction is closely related to
Central Nervosus System, striated muscle is an
organ that works only under control peripheral
nerve. Therefore, the muscles are innervated by
rich motor, sensory and autonomic nerve fibers.
The best metabolism of striated muscle depending on the integrity of its innervation, (neurotrophic
effect ).
Two aspects of motor control have been
traditionally considered separately from each
other. The first relates to the nature of
physiological variables that are used by the brain
to control muscles. The second relates to the
problem of motor redundancy [22]: How does the
brain select particular solutions from infinite sets
afforded by the redundant design of the
neuromotor system at all levels of its analysis?
[23]
In most skilled sensory -motor tasks, the body acts
as a multivariable continuous control system
synchronizing movements with the behavioural of
the environment [24].
An important movement control strategy used by
the central nervous system (CNS) is the activation
of multiple muscles acting in concert with each
other to achieve a specific movement [22, 25].
Studies indicated that cortical activity related to
sensory response and perception is modified by
movement executing mechanisms. [26]
Coordination of the movement by the motor
cortex provides both the start, support of motion
and the finish of voluntary movements, just
following the established patterns. First the
movement is the design in cortical area. Next the
sensorimotor information from the cortex
(regarding the spatial environment need for the
movement, time and its sequences, the necessary
effort required to execute them). The next of step
is the transmission down of the efector outgoing
messages thru the central and peripheric motor
path to the muscular system.
The osteo -articular mobilization occure by the
transmission of mio-artro -kinetic proprioceptive
information mainly to the cerebellum. The
cerebellum intervenes to motor control with a
share alongside the Reticular Form to modulate
alpha and gamma motoneuron activity.
Such coordination has a specific purpose and it is
ensured by a reflex mechanism, partly borned
with and partly perfected in the period of
development of the child by various motor skills
gained as character automatism or "dynamic
stereotype" . [27]
Motor fibers representing axons of spinal
motoneurons or motor cranial nuclei are
myelinated fibers. Axons link to skeletal muscle
fiber is made thru a synapse modified has
presynaptic segment, a synaptic cleft and a post-
synaptic segment. The gap between the button
terminal and the muscle fiber membrane is called
the synaptic space and the folds of the post
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Journal of Sport and Kinetic Movement Vol. I I, No. 30/2017

synaptic junctional area increases the area of each
terminal synaptic knobs depression lies on the
surface of a muscle fiber (called "synaptic gutter")
At the bottom of synaptic gutter the muscle fiber
shows numerous folding forming subneural clefts
which serves to increase the surface area on which
the neurotransmitter acts.
Each terminal nerve ending supplies single muscle
fiber , so each nerve fiber or a single axon. In the
post-synaptic membrane, there are numerous
receptors for acetylcholine
When the action potential reached the axon at the
button level it cause an opening of Ca2+ channel
ionic and the entry of Ca2+ in the termination
presynaptic (in a millisecond, thru a single opened
channel pass hundreds of Ca2+ due to the electrical
gradient -attracted by the negative charges on the
inside of the membrane, and also because the
extracellular concentration gradients are larger,
approx. 1- 2mM).
The alteration of the genetic control of protein
synthesis by membrane transport system (chanel
diseases) caused by inher ited mutations of ions
channel provides a unique insight into the
mechanisms of many neurological diseases.
However, they also provide new informations
about the fundamental biology and function of ion
channels and about the neurons and muscles.
For example, mutations in the genes: CHRNA2,
CHNRA4, CHRNB2 changes subunits α2, α4 and
β2 of nicotinic receptors in the postsynaptic
membrane and are involved in epileptic
syndromes idiopathic and mutations in the genes:
CHRNA1, CHRNB1 changes subunits α1 and α 2
of nicotinic receptors is associated with congenital
myasthenic syndromes. [28].
Striated muscle has a very active metabolism
which corresponds with a rich blood supply is also
a typical operating level.
Training and effort improves oxidative capacity
by increasing aerobic capacity, also increases the
proportion of fast-twitch fatigue -resistant fibers
when the intensity is begger then 80% Vo2max.
Nowadays motor synergies are studied using a
mathematical approach that identifies patterns of
muscle recruitment, incorporating the onset,
duration and magnitude of muscle activity. [29]
After stroke it can be difficult to identify patterns
of muscle activity due to the loss of strength and
control combined with disordered command
signals from the brain. In addition, movement
patterns that can be clearly distinguished in
healthy people become smaller and less distinct
after stroke. For example when walking the foot
may not be lifted off the ground and swung forward (reflecting two separate muscle
synergie s) but may be shuffled forward without
leaving the ground after stroke in a single muscle
synergy. [30]
Integration is the process when the stimuli that are
received by sensory structures from different parts
of the human body are communicated to the
central nervous system where that information,
based on the already know experience, is
processed and analised. Stimuli are compared
with, or integrated with, other stimuli, memories
of previous stimuli, or the state of a person at a
particular time. This will leads to the specific
response. [31]
In humans, even from birth it occure an
improvement in execution of some mouvements,
that happen in time because training determine a
change in the motor commands.
The specific coding of movement parameters in
the neurons that compose internal models have a
significant, measurable influence on behavior.
That influence can be observed in how our brain
learns to predict forces in control of reaching
movements. Training to make reaching
movements in a force field results is a specific,
highly reproducible pattern of force generalization
to other movements. [32]
Improvement in performance occurs because
training results in a change in the motor
commands. One possibility is that movements
improve because subjects co-contract antagonist
muscle groups. [32]
Conclusion
Voluntary movement involves a complex process
of different steps that need to be coordinate not
only for initiating, maintaining and finish of
muscle contraction. The intimate nature of the
processes in which volitional consciousness is
capable of expressing itself in terms of movement
remains incomprehensible.
To run a simple voluntary act there is a well-
defined sequence: the initiation and development
of voluntary movement transmitted to effectors;
there is a complex picture of the temporal and
spatial sequence of basic movements to be
performed to achieve the purpose, that is an" ideal
draft of the action".
Authors' contributions. What each author contributed
equally to the study and writing of the article.
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