![]() 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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