Nervous system anatomy/functions

Nervous system anatomy correlates with function... 

Nervous system anatomy correlates with brain function. At the same time, neural circuits associated with some functions extend to several brain regions. 

We understand many aspects of the anatomy, physiology, and biochemistry of the human nervous system. The central points are the subjects of this chapter. As we come to understand them, much of great interest will be revealed to us. We will get important insights into how the nervous system functions and, in disease, malfunctions. We will also begin to understand why many molecules are effective in treatment of mental health disorders or induce abnormal states of consciousness in people. 

As we move forward, it will prove helpful to get some basic aspects of the human nervous system in place. An enormous amount of work has gone into making associations between brain anatomy and function. Starting with the three main parts of the brain, we know that the cerebrum is the seat of consciousness. It is divided into two hemispheres, which are linked by the corpus callosum. In a very general sense, the left hemisphere is associated with intellectual and the right hemisphere with emotional responses. Within the cerebrum, one can associate a number of brain areas (the prefrontal, frontal, temporal, parietal, and occipital lobes, for example) with functions including vision and hearing. One can make crude maps in which function is mapped onto brain structure. 

First, you will learn about the human nervous system and how it works when it is healthy. This will include an introduction to the structure (anatomy) of the nervous system and the function (physiology) of the nervous system. Next, we ll describe the things that can go wrong. We ll look at how the system breaks down and malfunctions. Then we ll show you how these breakdowns can result in psychiatric illness. Finally, we ll introduce you to the medications used to treat psychiatric illness. You will learn where these medications work and our best guess of how they work. The presumed mechanism of action of many medications is just that, presumed. In contrast to antibiotics, in which we know quite a lot about the ways that they kill bacteria or stop them from reproducing and how these mechanisms ultimately effect a cure for an infectious disease, less is known about how psychotropic medicines work. Oh, we pretty well understand what psychotropic medicines do when they reach the nerve cell. For example, most of the antidepressants used today block the reuptake of serotonin at the nerve cell, but we re still not sure why blocking serotonin reuptake gradually improves mood in someone with depression. This will lead to a tour, if you will, of what happens to a medication from the time the pill is swallowed, until it exerts its therapeutic effect. 

On the left (A) is a profile of the human brain, and on the right, a magnified view (B) of a slice through the brain as indicated by the dotted line. The anatomy of the brain consists of two hemispheres, each covered with multiple layers of important cells known as the cerebral cortex. White matter, which consists of wiring —projections from one cell to another—lies beneath the cerebral cortex, along with some groups of cells that perform various functions. The ventricles are cavities through which runs a substance called cerebrospinal fluid, which helps protect and cushion the delicate structures of the nervous system. 

Tire anatomy of the brain is quite complex, and only a few terms will be defined here. Tire cerebrum, which is made up of two hemispheres, accounts for the largest part of the brain. Tire deeply folded outermost layer, the cerebral cortex, consists of gray matter, a mass of cell bodies, and fine unmyelinated nerve fibers. Beneath this lies a layer of white matter made up of myelin-covered axons connecting the cerebral cortex with other parts of the brain. Tire two cerebral hemispheres are connected by the corpus callosum, a band of 2 x 108 nerve fibers. Remarkably, these fibers can be completely severed with a relatively minimal disruption of the nervous system. In the past the corpus callosum was sometimes cut to control almost incessant epileptic seizures that could not be prevented by drugs. The "split-brain" patients suffered relatively little disability as long as both eyes functioned normally. Studies of these patients provided some insights into the differing functions of the two hemispheres of the cerebrum.395... 

This section reviews basic principles of brain anatomy and function to provide a framework within which to discuss the effect of plants on the CNS. The human nervous system is exceptionally complex, it is the body s major communication system, and is divided into central and peripheral regions. The central nervous system consists of the brain and spinal cord, and the peripheral nervous system consists of all other nerves. Although thought processes and reason are most commonly associated with the CNS, almost every aspect of physiological function is affected by CNS activity. After all, Brain death is widely accepted as the definition of the end of human life 10). The follow description of CNS anatomy and physiology can be foimd in most text books on the and reviews on the subject 11, 17). 

This classic in the field of pharmacology provides detailed information on anatomy and functions of the autonomic nervous system. Although primarily concerned with drugs and how they act upon the body, there are also excellent sections on the toxicity of gases and vapors and heavy metals. Goodman and Gilman thoroughly evaluate many of the more widely used compounds utilized by the pharmaceutical industry. 

The autonomic nervous system (ANS) is the major involuntary, unconscious, automatic portion of the nervous system and contrasts in several ways with the somatic (voluntary) nervous system. The anatomy, neurotransmitter chemistry, receptor characteristics, and functional integration of the ANS are discussed below. 

The structure and function of the human brain have preoccupied physicians and philosophers alike since the dawn of history. Prominent Greek physicians such as Alcmaeon of Groton, Hippocrates, and Galen correcdy considered the nervous system to be the source of sensations, emotions, and cognitive faculties. In the sixteenth and seventeenth centuries, the anatomy of the brain was described in detail by Flemish physician Andreas Vesalius and English physician Thomas Willis. The term neurology was first used by Willis to describe the study of the brain. 

Once its anatomy became better defined, studies into vagal function were initiated. In 1814, Brodie published some of the first known experiments on vagal physiology and gastric function. In the report of his findings to the Royal Sodety of London, he noted that his work was inspired by Edward Home s report of some facts which render it probable that the various animal secretions are dependent on the influence of the nervous system. Home, in fact, studied secretion in the electric eel ... 

The analysis of hundreds of lesion experiments conducted mainly on octopuses (review in 28) and of several dozens of serial histological sections of the brains of the animals allowed Young and coworkers to describe the functional anatomy of the nervous system by identifying a circuitry leading to their visual and tactile processing a circuit where learning and memory is achieved by a series of intersecting matrices [2, 22]. 

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