I am wondering why the HPA mediated cortisol response only peaks after 20 minutes whereas SNS is quick acting. Is this because SNS is nervous system mediated and HPA is endocrine pathway mediated?
Hello
When you ask WHY, it is because living organisms need a very fast-responding system for fight or flight situation. It is sympathetic system.
If you want to know HOW SNS works so quickly, it is because it is a nervous system. When an organism release a fight or flight situation, it lasts very short (within seconds) that a nervous massage created for HPA activation.
But, for cortisol release, ACTH must released from hypothalamus to reach adrenal glands via circulation; it takes time. And this response is more long lasting compared to SNS to provide demanded energy for coping with the stressful situation.
I agree with Seyyed. The neurohumoral response of the HPA-axis by glucocorticoids via CRH and ACTH requires more time than the direct preganglionic sympathetic neural control of the andrenal medulla. HPA-axis contributes therefore to the longer-term control of stress response, in contrast to the immediate response of the sympathetic nervous system.
Thank you. The responses are very helpful. I realize I meant to ask "how" rather than "why". So in simple terms, since SNS is neural based it is faster whereas HPA being a neuroendocrine response takes longer due to the various steps involved.
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