2. What are the major hormones and nervous pathways that play a role in primate (including humans) stress reactions?

Epinephrine (also known as adrenaline) and norepinephrine (also known as noradrenaline)

Explanation:

The hypothalamic-pituitary-adrenal axis (HHA axis) is a complex set of direct influences and feedback interactions between the hypothalamus, the pituitary gland, and the adrenal gland. The fine homeostatic interactions (Homeostasis) between these three organs constitute the HHA axis, an essential part of the neuroendocrine system that controls reactions to stress and regulates various processes in the body such as digestion, the immune system, emotions, sexual behavior and energy metabolism.

Adrenaline (or also epinephrine) is synthesized and stored in the adrenal medulla and released into the systemic circulation. Noradrenaline (or norepinephrine) is synthesized and stored not only in the adrenal medulla, but also in the peripheral sympathetic nerves. Epinephrine, among other things, increases the heart rate. Norepinephrine constricts blood vessels and extends the length of sympathetic nervous system activation.

The autonomic nervous system (ANS) is a control system that acts unconsciously and regulates heart rate, digestion, breathing rate, pupil response, urination and sexual response. It is one of the major neural pathways which has a role in the response to stress and is divided into the sympathetic nervous system (SNS), and the parasympathetic nervous system (PNS). During stress, the SNS contributes to the "fight or flight" response, a physiological response to the perception of harm, attack, or threat to survival. The response begins in the amygdala body, which triggers a neural response in the hypothalamus, the initial response is followed by activation of the pituitary gland and secretion of the hormone ACTH (adrenocorticotropic hormone). The adrenal gland is activated almost simultaneously and releases the neurotransmitter epinephrine. The release of chemical messengers results in the production of the hormone cortisol, which increases blood pressure, blood glucose concentration, and suppresses the immune system. The initial reaction and subsequent responses are initiated in an effort to increase energy, which is achieved by the binding of epinephrine to liver cells and the subsequent release of glucose. In addition, cortisol converts fatty acids into available energy, preparing muscles throughout the body for the reaction. The hormones catecholamines, such as epinephrine or norepinephrine, facilitate immediate physical responses associated with preparation for violent muscular action.