Behaviour, Physiology & Fear

In this paper I will be looking at the behavioural and physiological processes involved when an individual experiences 'fear'. I will be examining the conscious and unconscious processes entailed in experiencing dangerous situations. I will also consider the functional value of the autonomic and somatic nervous systems in a given situation, and the crucial link between the psychological and biological processes of an individual. The scenario is as follows: A person is walking through a forest when he is suddenly confronted by an angry bear. The person immediately runs for the nearest tree and climbs it. Half an hour later the forest rangers arrive to rescue him. When an individual is confronted with apparent danger, one of the first reactions is the 'fight or flight' response. In other words, whether the individual stays to confront the perceived threat, or runs away to avoid it. This is often considered to be a conscious decision, based on the individuals knowledge of particular situations or dangers, it is also assumed to be evolutionary, from a period when man encountered physical harm from other animals on a daily basis. However, it is now thought that, before a situation is carefully evaluated via the conscious mind, a split-second decision is made unconsciously. Information about a dangerous situation reaches the 'amygdala' (part of the limbic system) which is used in emotional responses. This information travels down two different pathways: the 'direct' pathway and the 'indirect' pathway. The 'direct' pathway is the subcortical pathway (passing under the cortex) and carries information unconsciously. The information travels from the eye to the thalamus and on to the amygdala. Because this pathway is shorter it registers any perceived danger more rapidly and responds far more quickly than the 'indirect' pathway. The disadvantage to this rapid response is that we sometimes react hastily to a perceived danger which is perhaps groundless, like jumping at a loud noise. However, the advantage is that we are capable of reacting with great speed to avoid sometimes genuinely dangerous situations. The 'indirect' pathway or cortical pathway (passing through the cortex) is slower than the 'direct' pathway. Information travels from the eye to the thalamus through the visual cortex to the amygdala. This pathway is thought to be used to assess the situation after the initial rapid response. It allows us to consciously consider, for example: how we should respond or whether or not the danger is genuine. Therefore, on witnessing a noisy bear approaching him our 'subject' is likely to react rapidly before he even consciously registers the existence of the bear. As he turns to run for the nearest tree, information via the 'indirect' pathway will consciously begin to register and he will be able to draw on his knowledge of dangerous situation. He may know that bears do not climb trees and his decision to head for the nearest tree may be based on this thought process. Alternatively, he may act purely on his emotional instinct to distance himself from the bear. He will now need to conserve energy from non-essential areas of the body to those which are required to physically remove him from the situation such as the brain, the heart and skeletal muscles. At this stage the 'sympathetic system' will begin to dominate the 'parasympathetic system' in order to provide a rapid response. The sympathetic axons of the ANS (the autonomic nervous system, which regulates internal organs) will begin to innervate the adrenal glands, which will subsequently release hormones into the blood. Hormones such as adrenalin and noradrenalin will begin to hasten his heart beat and so rapidly increase blood flow to the skeletal muscles. Whilst increasing vital activities the sympathetic system will start to close down all non-essential activities. As sympathetic axons of the ANS react, our 'subject' may not be consciously aware of all the changes taking place in his body - though he may detect an increased heart beat, and the adrenalin flow which now enables his enhanced mobility. As he runs towards the tree, he may start to reflect on his predicament and perhaps consider the possible outcome of his situation. Whilst his mind is continuously focussed on his dilemma, his somatic nervous system has already begun the process of innervating his skeletal muscles. Neurons in his primary motor cortex (part of his somatic nervous system) are receiving information from other cortical areas such as the somatosensory cortex. This information is then relayed from the neurons and interneurons of the motor cortex to the motor neurons via the midbrain, pons and medulla to the spinal cords. At the most basic neuronal level, cell bodies project their axons from the spinal cord (CNS) to the effector organs in the peripheral nervous system (PNS). The neurons fire by sending out electrical pulses along axons and releasing neurotransmitters at the axon terminals creating the synapse. This process activates the skeletal muscle, and our 'subject' is then able to run, and to climb the tree, using the related muscles in an attempt to escape from danger. Once he is settled in a place of relative safety the parasympathetic system may then take over from the sympathetic system and begin to calm processes in the body. The parasympathetic system may allow systems to return to normal levels if our 'subject' perceives that he is out of danger. However, if he still feels that he may be in danger, hormone levels may stay high and he will remain in a state of extreme anxiety. This level of anxiety may only be decreased once he is rescued by the forest rangers and he is able to re-evaluate his situation. It seems clear that 'fear' is something we have all experienced and view as a natural emotional response to danger. However, our reaction to fear, which to some extent, we tend to take for granted provokes major underlying physiological changes. These changes innervate functions that are sometimes clearly understood by our conscious mind, such as 'movement' to enable us to run from danger. But there are many others of which we are not aware, such as the unconscious processing of information to enable a rapid response to perceived danger.