Central Nervous System

Every action, emotion, response, and human characteristic involves the central nervous system (CNS). The CNS is comprised of the brain and spinal cord and is involved with physiological actions throughout the entire human body. The CNS is one of the two major divisions of the nervous system. The associated system that coordinates with the CNS is the peripheral nervous system (PNS), which is outside the brain and spinal cord in the extremities and trunk. The CNS is involved with hunger, taste, and overall food intake regulation. The CNS is also involved with overall metabolism. The past decade has witnessed an explosion of information regarding the role of the CNS in the development of obesity and the influence of peripheral hormonal signals that regulate nervous system function.

The PNS connects the CNS to sensory organs (such as the eye and ear), other organs of the body, muscles, blood vessels, and glands. The peripheral nerves include the 12 cranial nerves, the spinal nerves and roots, and what are called the autonomic nerves. These are concerned specifically with the regulation of the heart muscle, the muscles in blood vessel walls, and glands.

These glands such as the pituitary, parotid, and thyroid release hormones throughout the blood, and when they dysfunction they can be linked to many issues and newly understood pathological mechanisms involving obesity. For example, an overproduction of human growth hormone (hGH) from the pituitary gland in the brain can lead to uncontrollable weight gain and obesity. The capacity to adjust food intake in response to changing energy requirements and environment is essential for survival. Any change in these biochemical processes can lead to obesity and long-term health concerns.

One of the new questions much research is aiming to answer and better understand is why not all people become obese when in an obesogenic environment. Obesogenic is a newer medical term meaning factors tending to make individuals obese. Much of this new research is looking at genetic dispositions and failures in hormonal levels that lead to obesity. Metabolism is the sum of all chemical processes, assimilation, incorporation, detoxification and excretion of food in the body. Inborn and acquired abnormalities with metabolism can lead to obesity and, in some instances, excessive weight loss.

The CNS controls and oversees homeostasis. Homeostasis is the inherent tendency in the human body toward maintenance of physiological stability. The physiological importance of this homeostatic control system is highlighted by the severe obesity that results from dysfunction of any of the several key components. Basically, when the CNS or another component fails, homeostasis is no longer maintained and one such outcome can be excessive weight gain and eventual morbid obesity. New research is looking at the detailed reasons and causes behind such pathologies and putting things into context of the global obesity epidemic. Last, some new research relating to the CNS and obesity aims at identifying potential avenues for therapeutic intervention and reversal of this obesity epidemic.

For example, some such studies include animals and look at the genetic propensity to develop diet-induced obesity (DIO) by observing a reduced responsiveness to signals such as leptin and insulin. Obesity and type 2 diabetes are on the rise in the United States and are major health concerns. The two hormones thought to play a critical role in both energy homeostasis and glucose metabolism are the adiposity hormones insulin and leptin. Both of these hormones circulate in proportion to body fat stores and interact with their respective receptors expressed in key brain areas such as the hypothalamic arcuate nucleus (ARC) that regulate food intake and glucose metabolism.

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