How does a fright become a racing heart and sweaty hands? · Grey Matter

The central nucleus of the amygdala sends its output to the hypothalamus and the brainstem.

How does a fright become a racing heart and sweaty hands?

The central nucleus of the amygdala sends its output to the hypothalamus and the brainstem. The lateral hypothalamus and brainstem centres switch on the sympathetic nervous system within a second or two (faster heart, higher blood pressure, sweating, wide pupils, adrenaline from the adrenal medulla), while the paraventricular nucleus starts the slower hormonal arm, the HPA axis, that brings cortisol minutes later. The hypothalamus generates none of the thought about the threat; it translates the amygdala's verdict into the state of the body.