Homeostasis, alostasis y estrés Versión imprimible
De Dolopedia
- Enlaces de interés : Conceptos a tener en cuenta a la hora de comprender los mecanismos del dolor
HOMEOSTASIS
Although the term homeostasis commonly connotes adjustment to achieve balance, McEwen asserts that homeostasis strictly applies to a limited set of systems concerned with maintaining the essentials of the internal milieu. The maintenance of homeostasis is the control of internal processes truly necessary for life such as thermoregulation, blood gases, acid base, fluid levels, metabolite levels, and blood pressure. McEwen’s strict distinction means that homeostasis does not contribute to adaptation; rather, adaptation protects homeostasis. Failure to sustain homeostasis is fatal. Generic threats to homeostasis include environmental extremes, extreme physical exertion, depletion of essential resources, abnormal feedback processes, aging, and disease. Environmental perturbations can threaten homeostatic regulation at any time. The stress response exists to sustain homeostasis.
ALOSTASIS Y ESTRÉS
Three interdependent systems contribute to the preservation of homeostasis when injury occurs: Neural, endocrine, and immune . Adaptive response involves substantial autonomic activity and the connectivity of humoral messenger substances that also serve as mediators and determinants of neural regulatory processes, particularly hormones, neurotransmitters, peptides, endocannabinoids, and cytokines. The term for the physiological protective, coordinated, adaptive reaction in the service of homeostasis is allostasis , Allostasis ensures that the processes sustaining homeostasis stay within normal range. Stress is the resource-intensive process of mounting allostatic responses to challenges that occur in the external or internal environment. A stressor is any event that elicits a stress response. It may be a physical or social event, an invading micro-organism, or a signal of tissue trauma. Selye first described this response as a syndrome produced by “diverse nocuous agents.” He characterized the stress response as having 3 stages: Alarm reaction, resistance, and if the stressor does not relent, exhaustion. The normal stress responses of everyday consist of the alarm reaction, resistance and recovery. The primary features of stressors are intensity, duration and frequency. The impact of a stressor is the magnitude of the response it elicits. This impact involves cognitive mediation because it is a function of both the predictability and the controllability of the stressor. Allostasis is the essence of the stress response because it mobilizes internal resources to meet the challenge that a stressor represents. Stressors may be multimodal and complex or unimodal and simple. When a stressor, such as tissue trauma, persists for a long period of time, or when repeated stressors occur in rapid succession, allostasis may burn resources faster than the body can replenish them. The cost to the body, or burden, of allostatic adjustment, whether in response to extreme acute challenges or to lesser challenges over an extended period of time, is allostatic load.