From the body's perspective, activities that don't allow you to deal with the stressor at hand should be ignored until the acute stress has ended. For example, reproductive activity is decreased. As glucose is a crucial energy source for your cells, this also provides your body with extra energy to deal with the stressor.Īdditionally, cortisol acts during the experience of a serious stressor to inhibit processes that are deemed to be of lesser importance at the time. It acts to increase circulating levels of glucose in your blood as well. For example, it increases blood pressure and cardiac output, providing more blood to your skeletal muscles in case the stressor you're dealing with involves some sort of physical exertion (like running for your life). Watch this 2-Minute Neuroscience video to learn more about the HPA axis.Ĭortisol has a number of effects on the body that are thought to be carried out in order to help the body deal with a stressor that lasts longer than a few minutes. ACTH binds to receptors on the surface of the adrenal cortices, leading to a series of intracellular events that result in the adrenal glands secreting glucocorticoids like the hormone cortisol. The pituitary gland releases ACTH into the bloodstream, and the hormone travels down to the adrenal cortex, which is a term for the outer layer of the adrenal glands. CRH, however, also tells the pituitary gland to secrete a substance called adrenocorticotropic hormone (ACTH) (for more on how the hypothalamus and pituitary gland communicate, see this article). Corticotropin-releasing hormone (also known as corticotropin releasing factor or CRH or CRF for short) itself increases the activity of the sympathetic nervous system, perpetuating effects like elevated heart rate. The hypothalamus responds to signals like elevated norepinephrine levels by secreting corticotropin-releasing hormone into the bloodstream. This response occurs almost immediately, and results in the secretion of epinephrine and norepinephrine, both of which work to enact changes that you would generally expect if you felt stressed and/or frightened, like increased heart rate and perspiration.Ībout 10 seconds later, the HPA axis is stimulated. When something stressful happens to us, our initial response is mediated by the sympathetic nervous system. The main function generally attributed to the HPA axis involves the body's reaction to stress. What is the HPA axis and what does it do? The hypothalamus and pituitary gland are located just above the brainstem, while the adrenal glands are found on top of the kidneys. The hypothalamic-pituitary-adrenal axis, or HPA axis as it is commonly called, describes the interaction between the hypothalamus, pituitary gland, and adrenal glands. HPA axis activation, proceeding from the hypothalamus to the pituitary gland to the adrenal glands.
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