Journal of Medicine Study & Research Category: Medical Type: Review Article
Physiology of Stress and its Management
- Dushyant Kumar Sharma1*
- 1 Department Of Zoology, Government Model Science College, Gwalior, Madhya Pradesh, India
*Corresponding Author:Dushyant Kumar Sharma
Department Of Zoology, Government Model Science College, Gwalior, Madhya Pradesh, India
Received Date: Feb 23, 2018 Accepted Date: Apr 26, 2018 Published Date: May 10, 2018
ACTH; Corticoids; HPA axis; Stress; Stressor; Stress hormones
Any factor or event that causes stress is called a stressor. Stressors can be of many types: physical or physiological changes in the body, changes in the environment, life events or behaviours. Even an unreal (imaginary) situation can act as a stressor and could be the reason of stress. In fact in most of the cases it is just an imagination which is the cause of a stress. Hence, it is very important how we perceive an event or a situation.
TYPES OF STRESS
Good and bad stress
Acute stress, episodic stress, and chronic stress
MECHANISM OF STRESS
The first step in stress response is the perception of the threat (stressor). Whenever there is some stressor - real or imagined, it acts at the level of brain. In the brain, it is the hypothalamus which perceives the stressor. When the hypothalamus encounters a threat it performs some specific functions: 1. activates autonomic nervous system (ANS) 2. Stimulates Hypothalamic Pituitary Adrenal (HPA) axis by releasing Corticotrophin Releasing Hormone (CRH) and 3. Secrets arginine vasopressin (Antidiuretic Hormone ADH). Autonomic nervous system consists of sympathetic (arousal) and parasympathetic (relaxed) nervous system. The ANS regulates visceral activities like circulation, digestion, respiration, temperature regulation and some vital organs.
The sympathetic system accounts for the flight-or-flight response. In response to a stressor catecholamines: epinephrine (adrenaline) and norepinephrine (nor adrenaline) are released at various neural synapses. The release of these catecholamines causes several changes like increase in the heart rate and force of myocardial contraction vasodilatation of arteries throughout working muscles and vasoconstriction of arteries to nonworking muscles; dilation of pupil and bronchi and reduction of digestive activities in the body. All these changes are required to prepare the body for fight-or-flight response. The effects of these hormones - epinephrine and nor epinephrine last for few seconds. The functions of parasympathetic nervous system are opposite to that of sympathetic nervous system and help in energy conservation and relaxation.
CRH acts at the anterior pituitary gland an endocrine gland located in the brain. Pituitary gland is also called ‘master gland’, as it controls the secretion of other endocrine glands in the body. On stimulation by CRH, anterior pituitary secretes Adrenocorticotropin Hormone (ACTH). According to Scantamburlo et al., arginine vasopressin modulates the effect of CRH on ACTH secretion .
ACTH released from anterior pituitary gland in response to CRH stimulates adrenal glands located on the kidneys. There are two parts of adrenal - the outer part called cortex and the inner part known as medulla.
ACTH stimulates adrenal cortex to release corticoids (glucocorticoids and mineralocorticoids). The major function of glucocorticoids is to release energy, which is required to cope with the ill effects of stressor. The energy is released by conversion of glycogen into glucose (glycogenolysis) and also by breakdown of fats into fatty acids and glycerol (lipolysis). In addition to this corticoids have several other functions such as: increased urea production, appetite suppression, suppression of immune system, exacerbation of gastric irritation, associated feeling of depression and loss of control. These are the symptoms generally seen in a person under stress. Mineralocorticoid (aldosterone) promotes Na+ retention and elimination of K+. It increases blood pressure by increasing blood volume. The medulla part of the adrenal gland secretes epinephrine and norepinephrine. The functions of these hormones are the same as that of those secreted from nerve endings of sympathetic nervous system. These hormones secreted by adrenal medulla, reinforce the functions of sympathetic nervous system. The release of these hormones from adrenal medulla acts as a backup system to ensure the most efficient means of physical survival. The effects brought out by epinephrine and norepinephrine from the sympathetic nervous system may be termed as immediate effects and the effects brought out by those of adrenal medulla are intermediate effects.
The basic function of vasopressin or ADH synthesised by hypothalamus and released by posterior pituitary is to regulate fluid loss through urinary tract. This is achieved by reabsorption of water. In addition, ADH also has a prominent role on regulation of blood pressure during stress when the homeostasis of the body is disturbed in addition to release of energy second major change occurring during stress is distribution of energy to a particular organ that needs it most. This is achieved by increasing blood pressure. This occurs either through enhanced cardiac output or through constriction of blood vessel.
In addition to HPA axis some other hormones such as Growth Hormone (GH) and thyroid hormones also play significant role in stress. Growth hormone is a peptide hormone, released from anterior pituitary gland. GH is a stress hormone that raises the concentration of glucose and free fatty acids . It has been observed that, in human beings psychological stimuli increase the concentration of thyroid hormones [4,5]. Thyroid releases thyroxin and triiodothyronine. These hormones also have some significant function in stress . The main function of thyroid hormones is to increase overall metabolic rate or Basal Metabolic Rate (BMR). Thyroxin also increases heart rate and also the sensitivity of some tissues to catecholamines.
Though, serotonin and melatonin are not considered as stress hormones yet they are associated with mood. A decrease in the levels of these hormones is thought to be related to depression.
IMPACT OF STRESS ON THE BODY
Effect on digestive system
Extreme stress can also be associated with diabetes. This is because excessive cortisol can affect the activity of insulin. The body can also become resistant to insulin. This can lead to diabetes.
Effect on circulatory problems
Suppression of immune system
The high levels of stress hormones suppress the release of cytokines chemicals secreted by Th cells (T helper cells- a type of T lymphocytes). Cytokines regulate both cell-mediated and humoral immune response in the body. Two types of cytokines are released from Th cells. Th1 cytokines stimulate cytotoxic T cells and Natural Killer cells, cells that are involved in direct killing of target intracellular pathogens (cell mediated immune response) while Th2 cytokines stimulate B cells to produce antibodies (Humoral immune response). Chronic stress may dysregulate Th1 and Th2 cytokines that can lead to suppression of both cell mediated and humoral immune response . In addition to Th1 and Th2 chronic stress also affects proinflammatory cytokines, cytokines involved in inflammatory process. According to Miller stress may continue to promote proinflammatory cytokine production indefinitely. Proinflammatory cytokines feed back to the CNS and produce symptoms of fatigue, malaise, diminished appetite, and listlessness, which are the symptoms usually associated with depression .
Studies have also been carried out to study the association of stress with AIDS. Leserman et al., found that faster progression to AIDS was associated with higher cumulative stressful life events use of denial as a coping mechanism lower satisfaction with social support and elevated serum cortisol . According to Ko?odzie stress or stressful life events are considered important in terms of impacting the key biological markers of the disease viral load and CD4 cell count .
Some other effects of stress hormones
Stress also interferes with reproductive system both in men and women. Since sex life depends on fitness of both body and mind, chronic stress may decrease libido and may even cause erectile dysfunction or impotence in man. In case of chronic stress testosterone levels can drop to an extent that can interfere spermatogenesis (sperm production). In women stress can affect menstrual cycle. It can lead to irregular, heavier or more painful periods.
In addition to its direct effect on health, stress also produces some behavioural changes. People living in stressful environments are more prone to smoking which could lead to respiratory disorders and may even lead to cancer. Similarly stressed people are more vulnerable to alcohol consumption which has its own consequences.
The first step in managing stress is to identify the factors which cause the stress. The factors are not same in all individuals but vary from person to person. For example, ‘planning for a new job’ may cause stress to some people but not to others. For most of the students examinations come with lot of stress. Some people have the habit of taking things very seriously and this may be the reason for stress in their lives. Family conflicts are a major cause of stress. Similarly, many people are very much afraid of facing any type of challenges in life and find themselves in trouble whenever they are given any challenging task. Some people find it difficult when they have to travel or even when they have to attend some party or function. So it is very important to know what causes stress in your life. Once you identify the sources, then you can plan to manage them. You can manage your stress level by making some little changes in your daily routine and sparing some time on yourselves. Some of the life style changes are:
Check your diet
Make regular exercise a part of your life
A little time for meditation and yoga
Yoga is an important method of improving your body and mind. Regular practice of yoga relieves muscle tension, lowers blood pressure and decreases cholesterol levels. It is an excellent stress relieving practice. You can practice yoga when and wherever you get time.
Have a good social network
Always be positive
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Citation: Sharma DK (2018) Physiology of Stress and its Management. J Med Stud Res 1: 001.
Copyright: © 2018 Dushyant Kumar Sharma, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.