What mediates our emotions and instincts?

Luv2PlaGmz

Limbic system http://www.saras-autism-diet.freeservers.com/Literature/Brain-002.html [Link added March 23, 2008 -- Zbeckabee] Aug 22 00, 6:26 PM

zbeckabee

The amygdala itself is a highly complex collection of nuclei, so it could conceivably support different emotions in different areas -- as it does appear to do in the case of fear and anger. The amygdalae (members of the limbic system) send impulses to the hypothalamus for important activation of the sympathetic nervous system, to the reticular nucleus for increased reflexes, to the nuclei of the trigeminal nerve and facial nerve for facial expressions of fear, and to the ventral tegmental area, locus coeruleus, and laterodorsal tegmental nucleus for activation of dopamine, norepinephrine and epinephrine. The central nucleus mediates expression of conditioned fear responses. The "defensive response" to a threatening stimulus consists of elevated heart rate (mediated by the lateral hypothalamus) and a "freeze state" (mediated by the central gray), both of which receive input from the central nucleus of the amygdala. Lesions to the lateral hypothalamus eliminate the effect on heart rate, but not the "freeze state", whereas lesions to the central gray have the opposite effect. Both responses can be evoked by amygdala stimulation. The bed nucleus of the stria terminalis mediates the release of pituitary-adrenal stress hormone (Corticotropin-Releasing Hormone, CRH) in response to fear. CRH causes the adrenal gland to release epinephrine & cortisol. Chronic stress causes cortisol-induced release of epinephrine from the locus coeruleus to the amygdala -- creating a vicious cycle. http://ptsdtraumaonthebrain.blogspot.com/2007/08/drive-behind-traumatized-mind-part-2.html http://en.wikipedia.org/wiki/Amygdala Mar 23 08, 9:32 AM