Answer
The hypothalamus is considered the master structure/ organ in charge of our response to stress. The limbic system and the prefrontal cerebral cortex play important roles in the initial perception and response to certain kinds of stressors, but the hypothalomo-pituitary -adrenal axis is the major system by which we respond to and regulate our response to stress (the general adaptation syndrome).
The response to acute stress-- the flight or fight response of Canon--, is initiated by stimuli sent by the hypothalamus to the adrenal medulla. The adrenal response releases catecholamines , mainly, epinephrine. These have the effect of increasing muscle tone, increasing heart rate, and blood pressure, and respiratory rate. This increase in serum epinephrine also has the effect of increases pupil diameter. Later, an increase of cortisol mediated through the H=P=A system, begins to play a role in this response.
Work Step by Step
In the resistance reaction, pituitary hormone releasing factors( hormones) released from the hypothalamus cause the release of increased amounts of thyrotropin, ACTH, and human growth hormone (hGH). These hormones stimulate the secretion and release of increased amounts of thyroid hormone, and cortisol. These hormones have the effect of increasing the levels of glucose and ATP available to the body. This provides the energy necessary to support the resistance to long term stress.
In both the fight or fight response, and the resistance reaction, the hypothalamus has plays a vital role.
