Homeostasis in Fight or Flight - Essay Example

Institution : xxxxxxxxxxx Title : Homeostasis in fight or flight Tutor : xxxxxxxxxxx Course : xxxxxxxxxxx @2010 Homeostasis in fight or flight Introduction Homeostasis is the ability of a cell or an organism to control its internal conditions, usually through feedback controls, so as to stabilize functioning and health, in spite of the external changing conditions. Homeostasis is dependent on the integrative act of different body systems under the regulation of feedback systems. According to Klipper (2005), the feedback loops function with the aid of the endocrine and nervous systems which uses signals and hormones to maintain the stability of the body. Living cells depend on them movement of chemicals throughout the body. Chemicals like carbon dioxide and oxygen are transported in and out of the cell through the processes of osmosis and diffusion which depend on the salt and water balance of the body, a balance maintained by homestasis. Cells also depend on enzymes to speed up several chemical reactions that maintain their functioning and survival. These enzymes work at certain temperatures and PH and homeostasis is crucial for cells because it maintains a constant PH and body temperature. Fight or flight response The fight or flight response is the natural reaction of the body and a type of defense strategy to a possible danger or threat. The functioning and systems of our bodies shift during a threatening situation. When the brain receives a danger or threat, signals are transmitted to the autonomic nervous system which then stimulates the adrenal gland of the kidney to secrete chemicals like adrenaline. The autonomic nervous system consists of two sub sections known as the sympathetic nervous system and parasympathetic nervous system. The sympathetic nervous system is the real system that liberates energy and prepares the body to act. The body usually restores back to its stability through the action of parasympathetic nervous system which acts as a stabilizer (Schulkin, 2006). The stress response characterized by sympathetic stimulation takes place in three phases namely, an initial flight or fight response that mobilizes the body for quick action, a slower resistance reaction and the exhaustion stage. Fink (2005) argues that when a stressor incites the flight or fight response, the pituitary gland and hypothalamus transmits a nerve signal from the brain to the sympathetic region of the autonomic nervous system. The impulses convey energy to the organs and muscles required for survival and away from those not required for survival. For instance, the reproductive, urinary, and digestive systems are shut down or become impaired. The resistance reaction phase is instigated by the hypothalamic activation of the adrenal gland secrete hormones such as cortisol and adrenaline which provides the energy needed for fight of flight. In most occasions, these two phases suffice to push the body through frightening situations but at times they do not, making the body to move into the exhaustion phase in which it persists to produce large quantities of stress hormones. Prolonged exposure of body to these stress hormones, especially cortisol can result to devastating health effects. Prolonged and higher levels of cortisol in the blood stream lead to negative effects such as repressed thyroid function, decreased muscle tissue, impaired cognitive function, and blood sugar imbalances like hyperglycemia. Klipper (2005) notes that in order to generate a flight or fight response, the hypothalamus activates the adrenal cortical system and the sympathetic nervous system. The adrenal cortical system utilizes the blood stream while the sympathetic nervous system uses neural pathways to instigate reactions in the body. When there is a threat or stress the sensory nerve cells in the hypothalamus receives the signal transmits the perception of the stress or threat from the surrounding to the autonomic nervous system which in turn activates the adrenal glands in the kidney to release stress hormones like adrenaline or cortisol into the blood stream. These models of chemical release and nerve cell firing cause the body to undergo a sequence of dramatic changes. When adrenaline is released into the blood stream, it causes changes in the body so as to make it more effective for flight or fight. Adrenaline functions by binding to several adrenergic receptors. It is a non selective agonist of adrenergic receptors like alpha 1, alpha 2, beta 1, beta 2 and beta 3 receptors. The binding of adrenaline to these receptors activates several metabolic changes. The binding of adrenaline to alpha receptors hinders secretion of insulin from the pancreas, activates glycogenolysis in the muscle and liver, and activates glycolysis in muscles. Binding of adrenaline to beta adrenergic receptors stimulates secretion of glucagon in the pancreas, increased secretion of adrenocorticotrophic hormone by the pituitary gland and increased lipolysis in the adipose tissue. These effects contribute to increased fatty acids and blood glucose, providing substrates needed for production of energy in cells throughout the body. Cortisol or hydrocortisone raises blood sugar levels through gluconeogenesis, suppress the immune system, and assist in carbohydrate, fat, and protein metabolism. Cortisol also decreases sensitivity to pain and increases memory functions. Pupils dilate in order to perceive as much light as possible and smooth muscles relaxes so allow increased flow of blood to the lungs. Bell & Rhoades (2009) note that adrenaline also causes the shutting down of nonessential systems like the immune and digestive systems in order to provide more energy for emergency purposes. The cardiovascular activation by sympathetic nervous system generates an increase in heart rate and strength of the heartbeat. This is vital in preparation for flight or fight because since it pumps blood more quickly to the required parts of the body. The crucial parts blood is instantly pumped to be the biceps, thighs, and other muscles that help in preparing for fight or flight. Blood is also pushed away from the digestive system, fingers and toes which results to tingling sensations and clammy hands in the toes and feet. The respiratory effect generated by the sympathetic nervous system has an important function. According to Bell and Rhoades (2009), the accelerated, deep breathing assists in the preparation for flight or fight by offering body tissues more oxygen required. This accelerated breathing results to choking sensations, tightness in the chest and smothering, dizziness because the supply of the blood to the head is decreased by heavy breathing. It can also cause a sense of derealization of a feeling of confusion or unreality. The flight or fight response system generates increased sweating to prevent the body from over heat during the action. The sweat also assists in making the skin harder and slippery to grab incase one is caught by the predator. The mental system is also influenced by the activation of flight or fight response so as to constantly alert the person to the threat or danger in the environment. The mind quickly alters attention and start focusing on its immediate environment for danger. As a result of this influence, a person experiencing a terror attack usually relate it during an attack, have a problem with memory, difficulty in concentrating and is distracted from responsibilities and chores. The relaxation response After a person perceives that the threat is over, the brain through the hypothalamus, activates the parasympathetic nervous system which switches off the flight or fight response. According to Martha, (2009), the stress hormones return back to their pre stress levels, reversing all physiological and biochemical responses. The parasympathetic nervous system starts operating when a signal has been responded to and after the action has taken place. It has the reverse effect to sympathetic action and allows the body to wind down and rebalance. The activation of parasympathetic nervous system promotes muscle relaxation, lowering blood pressure and slowing heart rate. It helps the breathing to go back to its normal rate, digestive juices are released and digestion restored, the functioning bowels and bladder is restored. The pupil constricts and immune functions like the synthesis of white blood cells are restored. The relaxation response stimulates the parasympathetic nervous system (Bell & Rhoades, 2009). In the relaxation response, norepinephrine is secreted from the nerve endings the synapses causing vasoconstriction. Nitric acid is then released and it induces vasodilatation through obstructing the response of the smooth muscles arteries to adrenaline. Nitric oxide hinders further synthesis and release of adrenaline. Nitric acid functions as a neurotransmitter by acting at the nerve end. As a consequence of Nitric oxide induced vasodilatation, the relaxation response decreases respiratory rate, oxygen consumption, blood pressure, and increases flow of blood to the muscles. The dilation of blood vessels results to warmer feet and hands and increased focus and alertness as a consequence of an increase in oxygen supply to the brain (Klipper, 2005). The hypothalamus neurons synthesize the oxytocin hormone and its release from the pituitary gland decreases the symphathetic nervous system and hypothalamic- pituitary- adrenal axis activity by hindering adrenocorticotrophic hormone and corticotrophin releasing hormone secretion and therefore decreasing the secretion of glucocorticoids and cortisol. The oxytocin rushes to the adrenal gland and repress the production of cortisol and its release to the blood stream. The hormone also rushes to the brain to round up every cortisol remnant which that made it in the hippocampus. The hormone escort remnants of the cortisol back to the kidneyland for a one way ride on the bladderhorn. This makes the body to reach metabolic equilibrium or homeostasis. Conclusion Homeostasis provides the body with the rights conditions required for the functioning and survival of cells. During fight or flight, the brain perceives the threat or danger signal and transmit it to the sympathetic nervous system which activates the adrenal gland to secrete stress hormones like cortisol and adrenaline. Consequently, these hormones lead to psychological and physical changes such as increased heart rate and generation of more energy which enable the body to cope with the threat. However, when the threat is over, the brain via the hypothalamus activates the parasympathetic nervous system which switches off the fight or flight response restores stress hormones to their normal levels, reversing all biochemical and physiological responses. The parasympathetic nervous system starts operating after a stimulus has been responded to and an action taken place. Activation of sympathetic nervous system promotes relaxation of muscles, decrease in blood pressure and heart rate. This results from secretion of norepinephrine from nerve endings causing vasoconstriction and the consequent release of Nitric oxide triggers vasodilatation by inhibiting the arterial smooth muscle response to adrenaline. Bibliography Schulkin, J, 2006, Rethinking Homeostasis: allostatic regulation in physiology and pathophysiology, MIT, Cambridge. Klipper, M, 2005, The relaxation response, HarperCollins, New York. Bell, D & Rhoades R, 2009, Medical physiology: principles for clinical medicine, Lippincott Williams & Wilkins, Philadelphia. Fink, G, 2005, Encyclopedia of stress, Oxford, UK. Martha, D, 2009, The Relaxation and Stress Reduction Workbook, New Harbinger, Pennsylvania.       Read More