The brain regulates the choice of a person to be physically active. Stimuli from the environment and from the tissues excite receptors and nerves which in turn excite the muscles. The central nervous system has three general areas that are associated with the complexity of the movement and the familiarity of the various stimuli. The areas include the spinal cord which handles simple reflex actions, the lower brain which organizes more complex responses while the cerebral cortex controls the most complicated responses and stores general motor programs. The spinal cord consists of two-way tracks of nerve fibers which carries both sensory fibers as well as motor fibers between the periphery and the brain. Continual flow of afferent information from the sensory receptors to the higher levels of control is permitted by the spinal cord. The spinal cord also contains the efferent motor fibers which carry command information from the cerebrum to the periphery organs or muscles. The sensory nerves have one of its branches which end in the gray matter of the spinal cord while the other branch is carried to the higher levels.
The lower brain processes certain afferent sensory information in order to modify a movement for greater efficiency. Basically, the lower brain is made up of the brain stem, the cerebellum and the basal ganglia. Several pathways of motor control are either directly or indirectly under the control of the lower brain. The brain stem connects to the spinal cord and all the sensory and motor information must pass through it. The brain stem has a specialized collection of neurons known as reticular formation. The neurons helps to coordinate skeletal muscle function, maintain muscle tone, to control cardiovascular and respiratory functions and to determine the state of consciousness of a person. It is highly involved in ballistic movements such as running, jumping and agility training. The cerebellum assists the primary motor cortex and the basal ganglia to adjust the actual movement patterns being produced to conform to the desired motor patterns established by the higher brain. It always monitors and modifies movement therefore making it highly involved in integrating all specific elements of technique into any exercise. The basal ganglia help the higher brain with control of complex motor activities and almost all sensory and motor nerve fibers connecting the cerebral cortex with the spinal cord pass between the basal ganglia. Therefore, one of the primary functions of the basal ganglia is to initiate and control repetitive and continuous movement patterns such as walking and running.
The cerebral cortex is the higher brain and contains two hemisphere connected by the corpus callosum which allows the two to communicate with each other Wilmore states, that the cerebral cortex is the conscious brain and allows people to think, to be aware of the stimuli and to voluntary control their movements. The cerebral cortex controls the most complex motor patterns and is in charge for the initiation of all voluntary movements. The two function areas concerned with the movement are the motor cortex and the somatic sensory cortex (Wilmore, et. al, 2008). The cerebral cortex processes afferent input from the somatic sensory cortex and coordinates the various activities of the motor cortex with all the area of the lower brain and the spinal cord simultaneously. The motor cortex is divided further into three basic areas which include the primary motor cortex, the premotor area and the supplementary area. The primary motor cortex helps to control fine voluntary movements and to organize reflex actions while the premotor area helps to coordinate motor commands and muscle activity. The supplementary area helps with the adjustments in postures and the maintenance of balance while exercising (Wilmore, et. al, 2008).
Diencephalon is the region of the brain that is composed of the thalamus and the hypothalamus. The thalamus is a sensory integration center that is important and regulates what sensory input reaches the conscious brain thus very important for motor control. The hypothalamus is below the thalamus and is responsible for maintaining homeostasis by regulating all processes that affects the body internal environment such as regulating the blood pressure, body temperature, thirst, emotions among others. The spinal cord, the lower brain and the upper brain together with the rest of the central nervous system and proprioceptors continually attempts to learn, store, recall, and modify movement to help our bodies move and interact within our changing environment more efficiently. The whole control system is constantly being programmed and reprogrammed on a daily basis to adapt to changes within the active and passive systems as well as changes in the environment. The reduced dopamine or loss of dopamine receptors in the brain appears to be related to the decline in physical activity associated with age. Genes that might help explain motivated running or spontaneous physical activity have yet to be identified. The brain also has a pain control system called an analgesia system. The enkephalins and β-endorphin are important opiate substances that act on the opiate receptors in the analgesia system to help reduce pain. Wilmore states that research has demonstrated that exercise of long duration increases the natural levels of these opiate substances (Wilmore, et. al, 2008).
The three systems are affected by changes in a person such as when they grow or shrink gains strengths or lose and improve or damage the working parts. Ultimately, the control system integrates improvements or compensate for the deficits. This process continues throughout a person’s life and requires constant coordination of the neuromuscular system which reinforces the need for consistent and efficient exercise (Aaberg, 2006). People receive sensory information about their present environment and feedback to the central nervous system continually. There are three primary sources for sensory information which are from visual input, vestibular input and through Proprioception. Proprioception is the input from peripheral sensory receptors and joint mechanoreceptors. The skin and the cutaneous tissues have sensory receptors that sense changes in pressure and movement of soft tissue. The mechanoreceptors located in the muscles, joints and connective tissues give continual information and feedback on joint position, stability, movement, muscle length, tension and pressure from external and the internal forces. In order to trigger the necessary reflex actions and generate the appropriate motor commands to move, stabilize and control the body, sensory information from all the three sources is processed at different levels of the central nervous system (Aaberg, 2006). Reflex actions are extremely sensitive to specific stimuli and can be trained for higher efficiency. The studies show that the sensory and the motor areas of the adult brain can adapt according to how they are used in five days (Aaberg, 2006).
In conclusion, there is growing evidence that lack of physical activity may lead to brain dysfunctions including those that affects the motivational domain (Zelick, 2007). According to Zelick, recent studies have linked brain circuits that regulate feeding, mood, pain, reward, liking and wanting to those regulating physical activity such as exercise, suggesting positive motivation modulating properties of exercise (Zelick, 2007). Emotional and motivational disturbances are related to several common brain disorders such as autism (Zelick, 2007).
Wilmore, J., David L. Costill, D., & W. Larry Kenney, W. (2008). Physiology of sport and exercise. Canada: Human Kinetics.
Aaberg, E. (2006). Muscle mechanics. New York: Human Kinetics.
Zelick, P. (2007). Issues in the Psychology of Motivation. New York: Nova Publishers.