The Physiology Of The Fear Response - Essay Example

Running Head: The fear response THE PHYSIOLOGY OF THE FEAR RESPONSE The physiology of the fear response The physiological response to fear produces external symptoms such as increased heart rate, sweating and shaking and trembling of the limbs. These reactions serve to prepare the body for a fight or flight response. However, such responses may also be linked to the emotional state of the individual. The differences in intensity of response may be caused by the differences in the unconscious memories that exist in various individuals. An assessment of these physiological responses to fear also offers material for the study of anxiety disorders. Introduction: When an individual experiences fear, there is an automatic fight or flight response that is stimulated in him or her. The body responds to the sensation of fear with an increase heart rate, faster breathing and muscle tension which results in the body breaking out into shaking or trembling. This allows the individual experiencing the fear to either stay on and fight or to run away from the source of the danger and fear causing stimulus. However, this initial physiological response is followed by a deeper psychological assessment of the fear generating circumstances, during which time the individual becomes conscious of feeling afraid. When an individual receives a visual or other kind of stimulus that indicates a potentially dangerous situation, neurons in the body send a signal directly to the amygdale, a specific region of the brain. The amygdala picks up on stimuli that appear dangerous and sends out powerful panic signals which produce the concomitant physical responses such as increased heart rate, shaking and trembling of the body and sweating.(Helmuth, 2003). The amygdale plays a vital role in processing the bodily reaction to fear and producing the external physical symptoms such as increased heart beat, trembling of the limbs and sweating. The study of brain activity shows that it is the prefrontal cortex which is responsible for the assessment of danger, because the cortex is the learning center in the brain which helps to interpret sensory stimuli and consciously assess the levels of danger. After the amygdale is alerted, the signals pass on to the cortex where the sensory information is examined to assess the levels of threat and based upon whether or not this is real, the amygdale is stimulated to either abort the reaction to the stimulus or to put forward the necessary physical reactions to respond to the fear generating situation. Research: Some researchers have linked the physiological response of fear to emotions. According to Joseph Ledoux, the physiological reactions to fear are caused as a result of the unconscious memories that are stored in the region of the brain called the amygdale, by wiring through synapses that participate in the formation of that memory.(Defries, 2002). As a result, the level and intensity of the physiological response to fear may depend upon the kind of unconscious memories a person has, which may serve to explain why individuals respond to different kinds of fear generating stimuli with different levels of intensity, or even why different individuals may react to the same dangerous stimulus with varying levels of intensity. It is the unconscious memories that are linked in an individual’s mind with the stimuli generated by the dangerous activity which are likely to also condition the degree and intensity of the individual’s physiological response to it. Compte and Postlewaite(2004) examined the effect of emotions upon performance and have pointed out that three is ample evidence to show that emotions may affect an individual’s reactions and performance. The physical reactions induced in the body in the presence of strong emotion like fear or anger may not necessarily serve to prepare the body to face up to a stressful condition. In some instances, it could impair performance. Compte and Postlewaite (2004) point out that fears induced in some cases, such as the fear of the possibility of failing in an examination, may in fact generate outer physical symptoms such as shaking and a loss of concentration which could result in an impairment of the performance of the individual in school or in sports. They also point out that there is a tendency for humans to suppress the memories of unpleasant, fear generating events, while pleasant memories of successes are more often present in the conscious memory of the individual. The unconscious suppression of unpleasant memories may be associated with the physiological response to fear. The action of the amygdala is in bringing these unconscious memories and the unpleasant sensations associated with them surging up into a person’s mind, thereby generating a physical response that tries to prepare an individual to tackle the fear stimulus and allow the individual to take flight if necessary. The physiological response to fear which manifests as increased heart rate, trembling and shaking is due to the action of the amygdala, which intercedes between emotion and attention by focusing the attention of the individual away from the more mundane images to the fear-generating stimuli. The amygdale also receives signals not only from higher visual areas, but also from crude visual pathways where communication is fast and images can be processed through the cortex in a much speedier manner.(Helmuth, 2003). The amygdala then reacts by producing cortico tropin releasing hormone (CRH) which in turn triggers the pituitary gland to release adenocorticotropic hormone (ACTH). This in turn stimulates the adrenal gland which secretes cortisol into the blood stream, and the result of this is an increased production of glucose which provides the levels of energy for the brain and muscles to cope with stress and danger. (Defries, 2002). The amygdala functions to bring about a fast and concentrated response to the fear inducing stimulus, even before the cortex can accurately assess the level of danger in the situation, as a result of which an individual is likely to experience the physiological symptoms of fear induced stress even when it is a false alarm.(Defries, 2002). This suggests that the physiological symptoms that are produced in the body are an automatic, speedy reaction by the body which serves to alert the individual to the fear generating situation and to prepare the defenses of the body to cope with the fear that is generated as a result. The physiological response of the body is the result of the emotional state which is induced upon contact with the fear generating stimulus and serves to focus and direct the body’s attention to the clear and present danger, based upon the unconscious memories of the individual which loudly proclaim the threat in the situation. The onset of these physiological symptoms is controlled and moderated by the amygdale, in a fast, timely manner in order that the individual can take necessary action. Alternatively, in some instances, the physiological symptoms that are induced could also lead to a freezing up or deterioration in performance due to the fear. Hence, the amygdala plays a vital role in individual response to fear, and the physiological response to the fear generating stimulus often results in the individual becoming physically prepared to either fight the dangerous stimulus or to flee from it. The increased heart rate and trembling in the limbs place the individual in a state of high alert so that he or she is able to respond at a moment’s notice to the dangerous stimulus. The manner in which this is achieved is by concentrating the attention of the individual full scale on the fear generating stimulus, allowing the individual to ignore the stimuli from other sources which are less important in terms of facing up to the dangerous situation. Stein et al (2007) observed the effects of amygdala reactivity while the body is coping with the effects of emotional stimuli such as fear or anger in patients who suffered from anxiety disorders and social phobia. The subjects of their research study were 32 physically healthy subjects in the age range of 18 to 21 years, of whom 16 were placed in the high anxiety range and 16 in the median anxiety range. The subjects participated in a test which was known to engage the amygdale and the associated limbic activity such as shaking and trembling and increased heart rate. The study noted that there was increased amygdale reactivity during the processing of fear stimuli in the participants who had anxiety disorders. Individuals in the high anxiety range exhibited greater levels of amygdala and insulin activation as compared to the less anxious groups. This study therefore indicates that measuring amygdala activity could provide valuable insight into diagnosing those individuals who are suffering from anxiety disorders. However, this study was not able to arrive at a definitive conclusion as to whether such a heightened level of amygdale activity is specific to people with anxiety disorders or whether it is a general reaction that may be observed in all those individuals who are anxious by temperament. The authors point out that the results of their study do not substantiate a finding that an altered amygdale function is disorder specific; however they recommend that functional differences in amygdale functioning in individuals may be observed and this could form the basis to assess what other characteristics they share in common. Directions for future research: The study of the physiological response to fear and stress offers enormous potential in terms of diagnosis of anxiety disorders. Since anxiety disorders are the most prevalent form of mental disorders in the United States (Kessler et al, 2005) and often produce a decreased standard and quality of living, apart from also setting the stage for future disorders related to depression, it is useful to be able to identify those individuals who have an abnormal physiological reaction to fear. The normal physiological response of the body is stimulated by the action of the amygdala and produces increased heart rate, sweating, shaking and trembling of the body, which is the normal fear conditioning which individuals experience. The amygdale therefore plays a crucial role in fear conditioning and any kind of irregularity in the normal functioning of the amygdale is likely to be a causative factor in the generation of anxiety disorders.(Rauch et al, 2003) Detailed research on the nature and degree of the physiological response to stress could also help to clarify the role of amygdala in generation of anxiety. Can the intensity of the physical response be reduced through regulation of levels of amygdala in the brain, in order to render the individual more calm and rational in a fear generating situation? Alternatively, could it help in improving performance by alleviating the paralysis that often accompanies the onset of fear and hinders performance? The results of such studies would be very useful in understanding how exactly individuals are fear conditioned and what differentiates individual responses to fear and stress as manifested through the outer physical symptoms such as increased heart rate, sweating and trembling. Future studies can also examine the relation between level of stimulation of amygdala and the production of cortisol and consequently the increased supply of glucose available within the body’s bloodstream to face up to the fear generating stimulus. The intensity of the external physiological symptoms offer a valid set of measures to examine differing levels of response in human beings, for example, heart rates, intensity of shaking, etc can all be measured. When combined with studies that evaluate unconscious memories that are present in individuals, this could shed considerable light on the mechanism of response to fear that takes place in individuals. References: * Defries, Claudia, 2002. “A conversation with Joseph LeDoux: taking a clinical look at human emotions.” The New York Times, October 8, 2002. Accessed October 15, 2007 from: http://query.nytimes.com/gst/fullpage.html?res=9404E0DA133BF93BA35753C1 A9649C8B63 * Helmuth, Laura, 2003. “Fear and trembling in the amygdala” Science 300 (5619):568-570 * Kessler RC, Chin WT, Demler O. Walters EE, 2005. “Prevalence, severity, and comorbidity of 12-month DSM-IV disorders in the National Comorbidity Survey Replication”. Archives of General Psychiatry, 62:617-627 * Rauch SL. Shin LM. Wright Cl, 2003. “Neuroimaging studies of amygdala function in anxiety disorders”, Annals of the New York Academy of Sciences, 985:389-410 * Stein, Murray B, Simmons, Alan N, Feinstein, Justin S and Paulus, Martin P, 2007. “Increased amygdale and insulin activation during emotion processing in anxiety prone subjects.” The American Journal of Psychiatry, 164(2): 318-28 Read More