Numerous physiological changes are associated with the stress response that enables the animal to adapt to aversive stimuli. Short-term activation of the HPA axis results in changes in metabolic responses such as rapid mobilization of energy stores for initiation of the fight-or-flight response. In the long run, suppression and changes in other physiological responses such as anabolic processes, energy stores, and the immune system have negative consequences. Stress results in mobilization of energy stores to maintain normal brain and muscle function while increasing glucose utilization, which are essential to maintaining physiological stability. Cardiovascular output and respiration are enhanced during stress to mobilize glucose and oxygen for the tissues. The gastrointestinal tract during acute stress is inhibited. Many of these changes are associated with stressful events that prepare the animal for fight or flight. These precise physiological changes are geared to alter the internal milieu in order to increase survivability, but if activated frequently and for too long, the results can be detrimental.
The immune response and processes involving cellular growth and reproduction are temporarily inhibited during stress to allow the animal to utilize biological resources for other purposes (such as flight). Long-term stress can cause disruptions in reproductive physiology and sexual behavior. Stress modulates the immune system. Acute or short-term stress may suppress, enhance, or have no effect on the immune system. Chronic or long-term stress can suppress the immune system, thus making it more difficult for the animal to fight disease effectively. Glucocorticoids and other components may contribute to stress-induced immunosuppression, but can also serve as a protective mechanism against stress. In addition, feed intake, appetite, and other catabolic and anabolic processes are altered in response to stress. Physiological responses to stressful situations are critical to the adaptability of the animal, but repeated exposure to stressors or a massive single stressful experience may lead to pathological consequences.
stress for a prolonged period of time or is in a state in which behavioral adjustments are no longer adequate that other physiological processes are affected, leading to a prepathological state or development of pathology. It is this point in which behavioral adjustments are no longer adequate to return to homeostasis.
The central state of the brain orchestrates the behavioral responses in anticipation of and in adaptation to environmental events. Behavioral responses to stress involve neuronal systems in which peptides function as neurotransmitters. It has been suggested that CRH coordinates behavioral responses to stress such as feed intake, anxiety-like behaviors, arousal, learning, and memory just to name a few. CRH is a critical mediator of stress-related behaviors and its influence on behavior is dependent on the baseline arousal state of the animal. In nonstressed animals under low levels of arousal, CRH is behaviorally activating while under stressful conditions, exogenous CRH causes enhanced behavioral responses. Neuropeptides prepare the animal to perceive stimuli and cause an animal to behave a certain way, which enables it to respond appropriately to environmental changes. Other neuropeptides are probably involved in the behavioral responses to stress, but few have been described at this time.
Was this article helpful?