NOTE: Free essay sample provided on this page should be used for references or sample purposes only. The sample essay is available to anyone, so any direct quoting without mentioning the source will be considered plagiarism by schools, colleges and universities that use plagiarism detection software. To get a completely brand-new, plagiarism-free essay, please use our essay writing service.
One click instant price quote
Stress is the nonspecific response of the body to any demand made on it. Each demand made on the body is specific. Each drug or hormone has specific actions, yet they all have one thing in common; they increase the demand for readjustment. This demand is nonspecific; it requires adaptation to a problem.
In other words, in addition to their specific actions, all agents to which we are exposed also produce a nonspecific increase in the need to perform adaptive functions to re-establish normality. This is independent of the specific activity that caused the rise in requirements. The nonspecific demand for activity is the basis of stress. It is irrelevant whether the situation faced is pleasant or unpleasant; all that counts is the intensity of the demand for adaptation. Stress is not only nervous tension. In man, with his highly developed nervous system, emotional stimuli are in fact the most common stressors.
Stress reactions do, however, occur in lower animals that have no nervous system, and even in plants. Stress can be associated with pleasant or unpleasant experiences. The physiological stress level is lowest during indifference but never goes down to zero. Pleasant as well as unpleasant emotional arousal increases physiological stress.
In 1936, Hans Selye M. D. conducted experiments in order to answer the question: how could different stimuli produce the same result? In the experiment, rats were injected with various impure and toxic gland preparations that, no matter which tissue they were made of or their hormone content; the injections produced a set of simultaneously occurring organ changes. These were characterized by enlargement and hyperactivity of the adrenal cortex, shrinkage of the thymus gland and the lymph nodes, and the appearance of gastrointestinal ulcers. The adrenals are endocrine glands positioned above the kidneys.
They consist of two parts, the outer layer (cortex), and the inner core (medulla). The cortex produces hormones called corticoids, and the medulla secretes adrenalin and related hormones, all of which play important roles in the response to stress. The thymus and lymph nodes (also called glands) form a single system called the lymphatic system, which is mainly involved in immune defense reactions. Lymph nodes are positioned at various points of the body and are connected.
They gather bacterial samples, which are introduced to the body through disease, and create immunized white blood cells that are sent into the circulatory system. After more of these experiments, Selye observed that the same organ changes caused by the glandular extracts were also produced by cold, heat, infection, trauma, hemorrhage, nervous irritation, and many other stimuli. The reaction of the adrenal enlargement and thymus shrinkage became known as the general adaptation syndrome (G. A. S. ), or the biological stress syndrome.
It involves three stages: the alarm reaction, the stage of resistance, and the stage of exhaustion. During the alarm reaction stage the body shows changes typical of the first exposure to a stressor, and its resistance is diminished. At the stage of resistance, resistance develops because of continuous exposure to the stressor and it rises above normal as adaptation occurs. More continuous exposure to the same stressor results in the exhaustion stage. In this stage the adaptation energy is consumed, the signs of alarm reaction reappear, but are now irreversible, and the individual dies.
The three phases of the general adaptation syndrome gave the first indication that the body s adaptive energy is finite. Exposure to cold, muscular effort, hemorrhage, and other stressors can only be withstood for limited amounts of time. It is generally recognized that the emergency discharge of adrenalin represents only one aspect of the phase of the primary alarm reaction to stressors. Equally important in the maintenance of homeostasis (the body s stability) is the hypothalamus-pituitary-arena-cortical axis, which participates in the development of many diseases. This axis is a connected system consisting of the hypothalamus (a brain region at the base of the skull) that is connected to the pituitary gland, which regulates adrenocortical activity. The stressor excites the hypothalamus to produce a substance that stimulates the pituitary to discharge the hormone ACTH (adrenocorticotropic hormone) into the blood.
ACTH in turn causes the external, cortical portion of the adrenal to secrete corticoids. These stimulate thymus shrinkage, simultaneously with many other changes, such as shriveling of the lymph nodes, inhibition of inflammatory reactions, and production of sugar. Another typical feature of the stress reaction is the development of peptic ulcers in the stomach and intestine. Their production is reduced through an increased level of corticoids in the blood. The fact that the same stressors can cause different damage in different individuals has been traced to conditioning factors that can selectively enhance or inhibit stress effect.
Conditioning can be internal (for example, genetic inclination, age, or sex) or external (treatment with certain hormones, drugs, or dietary factors). Under the influence conditioning factors, a normally well-tolerated degree of stress can become pathogenic and cause disease of adaptation, selectively affecting the prone body area Every agent possesses both stressor and specific effects. Stressors are nonspecific by definition, being common to various stimuli, while specific effects are variable and distinctive of each individual agent. However, the response does not depend solely on these two actions of the stimulus; the reactivity of the target also plays a role and this can be changed by many internal or external conditioning factors. Since all stressors have some specific effects they cannot always stimulate exactly the same response, and even the same stimulus will act differently in different individuals, depending on the internal and external conditioning factors which determine how each will react. Stress plays some role in the development of every disease.
That is why the effect of stress can be curative or damaging, depending on whether the biochemical reactions typical of stress combat or intensify the trouble. Homeostasis depends mainly on two types of reactions: syntonic and catatonic. In order to resist different toxic stressors, the body can regulate its reactions through chemical messengers and nervous stimuli that either soothe or stimulate to fight. The syntonic stimuli act as tissue tranquilizers, creating a state of inactive tolerance which allows a kind of symbiosis, or peaceful coexistence with aggressors. The catatonic agents cause chemical changes mainly through the production of destructive enzymes, which actively attack the disease producer, or pathogen, usually by increasing its decline in the body. In the course of evolution, living beings have learned to defend themselves against all kinds of assaults through two basic mechanisms, which help us put up with aggressors (syntonic) or destroy them (catatonic).
One of the most effective syntonic hormones are the corticoids. When the aggressor is dangerous, the defensive reaction must be increased above the normal level. This can be done by catatonic substances, which carry the chemical order for the tissue to attack the pathogen even more actively than normally. While a great deal is know about the bodys ability to produce syntonic hormones, which induce a desired state of symbiosis with various pathogens, considerably less is known about the ability of the human organism to produce catatonic substances. The most active catatonic compounds are synthetics. Homeostasis largely depends on the appropriate production of syntonic and catatonic agents by the body, in response to potential pathogens.
These natural remedies can be improved by synthesizing them and adjusting their balance in the body to meet its requirements. The natural mechanism is usually enough to maintain a normal state of resistance, however, when faced with unusually heavy demands, ordinary homeostasis is not enough. The level of resistance must be raised in this case. For this process, the term hetero stasis is introduced as the establishment of a new balanced state by treatment with agents which stimulate the physiological adaptive mechanisms through the development of normally inactive defensive tissue reactions.
In homeostatic defense, the potential pathogen automatically sets usually adequate catatonic or syntonic mechanisms into motion. Heterostasis depends on treatment with artificial remedies that have no curative action, but teach the body to produce unusually high amounts of its own natural catatonic or syntonic agents. The most important difference between homeostasis and hetero stasis is that the first maintains a normal steady state by physiological means, and the second resets the level of resistance of heightened capacity for defense by artificial intervention from outside the body. Homeostasis responses depend essentially on the automatic adjustments of the manufacture of stress hormones by the body, through feedback mechanisms which adjust supply to demand. Heterostasis merely helps the body to reset these feedback mechanisms to a higher level. As a result, the bodys own normally inactive capacities for producing defensive compounds are raised to levels far above those required for resistance to commonly encountered demands.
The defensive hormones share the property of increasing resistance to great many potentially pathogenic agents. All these agents contribute to the body s reaction to stress. The direct response to a stressor results in either adaptation or resistance to the stimulus, which can be damaging or beneficial. In any case, the organism learns to adjust to stress and is able to continue due to the adaptation mechanisms it possesses.
Free research essays on topics related to: catatonic, resistance, adaptation, lymph nodes, nervous system
Research essay sample on Lymph Nodes Nervous System
