21.5
시상하부-뇌하수체 축
스트레스에 대한 반응(물리적, 심리적, 급성 또는 만성)은 시상하부-뇌하수체-부신축(hypothalamic-pituitary-adrenal axis; 줄여서 HPA axis)의 활성화와 관련이 있습니다. HPA축은 뉴런과 호르몬의 의사소통을 모두 포함하기 때문에 신경내…
스트레스에 대한 반응은육체적이든 심리적이든 뇌에서신경내분비계, 즉 시상하부 뇌하수체 부신(HPA)축의 활성화로 시작된다시상하부(H)가 부신 피질 자극 호르몬을 내는호르몬(CRH)를 방출하는데, 이는그 축에서 뇌하수체(P)를 활성화 한다이 신경내분비계 샘이 많은 기능을 하지만스트레스 상황에서는 부신 피질 자극 호르몬ATCH를 혈액으로 방출한다ACTH는 부신피질 A를 자극하는데, 이는신장 표면에 있는 작은 조직이다부신은 두 유형의 호르몬을 분비한다첫째는 노르에피네프린과 에피네프린인데이 두 교감 신경 흥분 복합체는신체가 행동하도록 자극하는데방법은 교감 신경을 끌어들여서심장 박동과 혈류를 증가시키는 것이다둘째는 글루코코르티코이드, 구체적으로 코티솔이다이는 스트레스 반응을 유지하도록 고안된몸의 시스템을 활성화 하는데방법은 포도당 생성 증가 및중요하지 않은 면역 시스템 같은 과정을억제하는 것이다코티솔 레벨이 높아지면뇌하수체와 시상하부에 대한부정적인 피드백 순환이 시작된다이 반응은 ACTH와 CRH의 방출을 멈추게 하고스트레스 반응에 종지부를 찍는다
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Q1: What is the hypothalamic-pituitary-adrenal axis and why does it activate during stress?
The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system that regulates the body's response to stress by coordinating neuronal and hormonal communication. During stress, the hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH then signals the adrenal glands to release stress hormones that prepare the body for action and mobilize energy reserves.
Q2: What hormones does the adrenal gland release during the stress response?
The adrenal gland releases two types of stress hormones. The adrenal medulla releases epinephrine and norepinephrine, which activate the sympathetic nervous system, increasing heart rate and blood flow. The adrenal cortex releases glucocorticoids, primarily cortisol, which mobilizes glucose reserves and temporarily suppresses non-vital processes like immune function to sustain the stress response.
Q3: How do epinephrine and norepinephrine affect the body during stress?
Epinephrine and norepinephrine are sympathomimetic compounds that activate the sympathetic nervous system, causing increased heart rate, blood flow, and respiration. These hormones prepare the body for immediate action by promoting states of alertness and arousal, enabling rapid physical responses to stressors.
Q4: What role does cortisol play in the stress response?
Cortisol, the primary glucocorticoid in humans, mobilizes energy by promoting glucose production through the breakdown of fatty acids and proteins. It also temporarily inhibits immune and inflammatory responses to prioritize resources for stress management. When cortisol levels rise sufficiently, it triggers a negative feedback loop that deactivates the HPA axis and terminates the stress response.
Q5: How does negative feedback terminate the stress response?
When blood cortisol levels reach a certain threshold, they trigger a negative feedback loop that inhibits both the hypothalamus and pituitary gland. This stops the release of CRH and ACTH, effectively deactivating the HPA axis and ending the stress response, allowing the body to return to homeostasis.
Q6: What are the long-term effects of chronic HPA axis activation?
Chronic stress or repeated acute stress can lead to continuous HPA axis activation, eventually depleting cortisol reserves. This depletion disrupts cortisol's multiple functions during both stress and non-stress periods, potentially causing chronic pain, depression, infertility, and may contribute to substance abuse and addiction.
Q7: How does the HPA axis maintain homeostasis during stress?
The HPA axis regulates metabolic, cardiovascular, and immune systems to maintain homeostasis during stress. Epinephrine and norepinephrine increase cardiovascular activity for immediate response, while cortisol mobilizes energy reserves and temporarily suppresses immune function. This coordinated hormonal response enables the body to sustain stress reactions while preserving critical functions.