Stress is one of the many factors that affect the autonomic nervous system. The autonomic nervous system is branched into two divisions: the parasympathetic nervous system and the sympathetic nervous system (Kardong, 2015). In fact, stress has a more serious effect on the sympathetic division. Stress is classified as a non-specific response of a living organism to any demand and/or need. Further, the stressor itself is any factor that leads to stress, which in turn triggers an organism’s response. An organism’s relationship with its environment is affected by many psychological elements, and those features depend on the organism’s response to those stressors (Sadeghi et al., 2013).
According to Garfinkel and colleagues (2014), the internal state of the body influences one’s perceptions, cognitions and emotions. Although the main neural mechanisms have yet to be determined, the theories of emotion highlight the significance of bodily responses to experiences of emotion (Seth, 2013). Furthermore, emotional feeling is hypothesized to arise from the physiological changes in the body (Garfinkel et al., 2014).
Bodily states of arousal are predominantly relevant to fear and anxiety. When the body is in a state of fear, the fear response is strongly coupled to sympathetic nervous system activation. The sympathetic nervous system is commonly known as the “fight-or-flight” system (Kardong, 2015). Similarly, highly anxious individuals manifest enhanced autonomic nervous system activity, as they have a higher sensitivity to psychological threat. Highly anxious individuals also have superior detection of internal sensations, notably their heart beat (Garfinkel et al., 2014).
Clinical manifestations of anxiety have been known to be coupled with autonomic nervous system imbalance. This type of imbalance can be noted in numerous forms and is characterized by heart rate variability (Knepp et al., 2015). In an elementary explanation of the autonomic nervous system, it is viewed and known as an antagonist and a reciprocal. Specifically, as the autonomic nervous system increases its activity, the sympathetic division decreases activity, and vice versa. In a more complex explanation, the autonomic nervous system controls nine modes of activity that allow flexibility in the system. This flexibility is what permits the variability in the heart rate control system. Fear and anxiety can be thought of as a continuum ranging from the early state variable of fear (Knepp et al., 2015).
In this study, heart rate fluctuations will be observed while the subject is in a state of fear or anxiety. Specifically, the present study at hand will be analyzing and observing fear bradycardia. The expected outcome is that the subjects heart rate will notably decrease while being in a state of fear. This mechanism of fear bradycardia is common among other animal species. For example, a passive defense mode that is activated in a threatening environment, is known as freezing. Freezing is a state of attentive immobility which serves to avoid predators in many species. This freezing behavior is associated with deceleration of heart rate, otherwise known as fear bradycardia (Hermans et al., 2012). This autonomic response is dominated by the parasympathetic (rest and digest) division of the nervous system, which is antagonized by the flight-or-fight response (Fanselow, 1994). Although little is known about freezing in humans, it is thought that its focus on life-threatening situations contributes to a cycle where emotional disturbance triggers an attentional preference for threatening information, and vice versa (Fox et al., 2001). The present study will examine whether heart rate rises or falls when presented undesirable film footage that will cause fear or anxiety. If the video elicits a fear response, it is hypothesized that fear bradycardia will result.