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The Biological basis of behavior

Behavior can be “explained” by discovering its causes – those events that are responsible for its occurrence. If we can describe events that caused the behavior to occur, we have “explained” it. Human behavior is at the root of most of the world’s problems, poverty, crime, overpopulation, drug addiction, bigotry, pollution and war. Health related problems – such as cardiovascular disease, some forms of cancer, and a large number of psychosomatic illnesses - are caused, or at least aggravated by an individual’s behavior.

Although we often find ourselves doing things that we had not planned to do (or had planned not to do) by and large we feel that we are in control of our behavior. That is, we have the impression that our behavior is controlled by our consciousness. We consider alternatives; make plans, and then act. We get our muscles moving, we engage in behavior.

To the degree that our behaviors are similar we tend to assume that our mental states, too resemble one another. Psychologists are more interested in the behavioral functions of the brains, but the regulatory functions are important too.

The brain has two roles, controlling the movement of the muscles and regulating physiological functions of the body. The first role looks outwards toward the environment and the second looks inward. The outward-looking role includes several functions; perceiving events in the environment, learning about them, making plans and acting. The inward-look role requires the brain to control physiological processes in the body – to measure and regulate characteristics such as body temperature, blood pressure and level of nutrients.

Thus the brain has two major functions: control of behavior and regulation of the body’s physiological functions. 

The central nervous system consists of the spinal cord and the three major division of the brain: the brain stem, the cerebellum and the cerebral hemispheres. The cerebral hemispheres are wrinkled by the fissures and gyri and are covered by the cerebral cortex. The brain communicates with the rest of the body through the peripheral nervous system, which includes the spinal nerves and cranial nerves. 

We become aware of events in our environment by means of the five major senses: vision, auditions, olfaction, gestation (taste) and somatosenses (body sense: touch, pain, and temperature.) Three areas of the cerebral cortex receive information from the sensory organs - the primary visual cortex, the primary auditory cortex and the primary somatosensory cortex. 

The regions of primary and motor cortex occupy only a small part of the cerebral cortex. The rest accomplishes what is done between sensations and action: perception, learning, planning and action. These processes take place in the association areas of the cerebral cortex. 

Although the two cerebral hemispheres cooperate with each other, they do not perform identical functions. Some functions are lateralized – located primarily on one side of the brain. In general the left hemisphere participates in the analysis of information. This ability makes the left hemisphere particularly good at recognizing events whose elements occur one after the other and control serial behaviors. In contrast the right hemisphere is specialized for synthesis; it is particularly good at putting isolated elements together to perceive things as a whole. 

The primary business of the occipital lobe is seeing, the temporal lobe is learning and the primary sensory function of the parietal lobe is perception of body. The principle function of the frontal lobe is motor activity. Its functions seems to be related to planning, changing strategies, being aware of oneself, attention to emotionally related stimuli and performing a variety of spontaneous behavior. It also contains the region involved in speech. 

The brain stem is divided into three structures - the medulla, the pons, and the midbrain. These structures contain circuits of neurons that control functions and behaviors vital to the survival of the organism in general and of the species in particular.

Circuits in the medulla control heart rate, blood pressure and rate of perspiration. Circuits in the pons control some stages of sleep. Circuits of neurons in the midbrain control movements used in fighting and sexual behavior and decrease sensitivity to pain while engaged in these activities.

The cerebellum plays an important role in the control of movement. The thalamus performs two basic functions. The first and most primitive – is similar to that of the cerebral cortex. The second role – that of a relay station for the cortex – is more important. The thalamus receives sensory information from the sensory organs, performs some simple analysis, and pass the result on to the primary sensory cortex. Thus all sensory information is sent to the thalamus before it reaches the cerebral cortex.

The hypothalamus received the sensory information, including information from receptors inside the organs of the body; thus it is informed about changes in the organism’s physiological status. It controls the pituitary gland which is called the “master gland’ because it controls the activity of the rest of the endocrine glands. Thus by controlling the pituitary gland, the hypothalamus exerts control over the entire endocrine system. The homeostatic function of the hypothalamus can involve either internal physiological changes or behaviors. The hypothalamus is a very important structure.

The limbic system consists of several regions of the limbic cortex and plays an important role in learning and in the expression of emotion. 

Neurons or nerve cells are the elements of the nervous system that brings sensory information to the brain, stores memories, reach decisions and control the activities of the muscles.

by Meeka O'Brien - Dip.Clin.Hyp

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