Epinephrine stress response

People suffering from PTSD frequently have abnormal levels of the hormones that are involved in the body s response to stress. Studies have shown that baseline cortisol levels in people with PTSD are lower than normal, and epinephrine and norepinephrine levels are higher than normal. However, it is not known whether these differences in hormones and neurotransmitters involved in the bod/s stress response precede or follow the development of the disorder. It is important to note that the neurotransmitter and hormone changes seen with PTSD are separate from, and actually opposite to, those seen in major depression. In major depression, cortisol levels are elevated and epinephrine and norepinephrine levels are low. The distinctive profile associated with PTSD is also seen in individuals who have both PTSD and depression. One hypothesis is that people who cannot mount a robust stress... 

In addition to regulating the synthesis and release of ACTH from the pituitary, neurons in the PVN also project to areas in the brainstem that control the output of the sympathetic branch of the PNS. Activation of PVN neurons at the onset of a stress response thus leads to increased sympathetic outflow, resulting in release of norepinephrine from sympathetic nerve terminals and epinephrine from the adrenal medulla. The effects of these catecholamines are responsible for the behavioral syndrome known as the fight-or-fhght response. 

As described, the secretion of epinephrine in response to stress, trauma, extreme exercise, or hypoglycemia causes a rapid mobilization of energy stores, that is, glucose from the liver and fatty acids from adipose tissue. The reaction in which NE is methylated to form E is mediated by the enzyme phenylethanolamine-N-methyltransferase (PNMT). Although the enzyme occurs predominantly in the chromaffin cells of the adrenal medulla, it is also... 

In contrast, there are several causes of neutrophilia (increased numbers of circulating neutrophils) that are unrelated to immune status. Neutrophilia can be part of a corticosteroid-mediated stress response (increased release of mature neutrophils from marrow and decreased egress to tissues), or an epinephrine-mediated physiologic response (demargination) due to excitement or fear. Neutrophilia can also be seen with hemorrhage or hemolysis which accelerates red blood cell production. This is thought to be due to generalized bone marrow stimulation and, in the case of hemolysis, cell destruction may result in increased demand for neutrophils (Latimer et al.,... 

The sympathetic or adrenergic nervous system operates in juxtaposition to the parasympathetic nervous system to maintain homeostasis in response to physical activity and physical or psychological stress. Sympathomimetic neurotransmission is generally mediated by norepinephrine [51-41 -2] (1), CgH NO, released from presynaptic storage granules upon stimulation. A second endogenous sympathomimetic agent, epinephrine [51-43-4] (2),... 

Adrenal medulla. On the one hand, release of epinephrine elicits cardiovascular effects, such as increases in heart rate und peripheral vascular resistance. On the other, it evokes metabolic responses, such as glycogenolysis and li-polysis, that generate energy-rich substrates. The sensation of hunger is suppressed. The metabolic state corresponds to that associated with physical exercise - silent stress . 

Skeletal muscle glycogen delivers glucose primarily as a response to contractile stress. Regulation occurs through both modification of the enzyme phosphorylase, primarily by the action of epinephrine-adrenaline and allosteric regulation of phosphorylase related to a demand for ATP. 

Few studies have examined noradrenergic function in patients with phobic disorders. In patients with specific phobias, increases in subjective anxiety and increased heart rate, blood pressure, plasma NE, and epinephrine have been associated with exposure to the phobic stimulus (Nesse et al. 1985). This finding may be of interest from the standpoint of the model of conditioned fear, reviewed above, in which a potentiated release of NE occurs in response to a reexposure to the original stressful stimulus. Patients with social phobia have been found to have greater increases in plasma NE in comparison to healthy controls and patients with panic disorder (Stein et al. 1992). In contrast to panic disorder patients, the density of lymphocyte a-adrenoceptors is normal in social phobic patients (Stein et al. 1993). The growth hormone response to intravenous clonidine (a marker of central a2-receptor function) is blunted in social phobia patients (Tancer et al. 1990). 

The ultimate effects of sympathetic stimulation are mediated by release of norepinephrine from nerve terminals, which then activates adrenoceptors on postsynaptic sites (see Chapter 6). Also, in response to a variety of stimuli such as stress, the adrenal medulla releases epinephrine, which is transported in the blood to target tissues. In other words, epinephrine acts as a hormone, whereas norepinephrine acts as a neurotransmitter. 

Catecholamines produced in the brain and in other neural tissues function as neurotransmitters, but epinephrine and norepinephrine are also hormones, synthesized and secreted by the adrenal glands. Like the peptide hormones, catecholamines are highly concentrated within secretory vesicles and released by exocytosis, and they act through surface receptors to generate intracellular second messengers. They mediate a wide variety of physiological responses to acute stress (see Table 23-6). 

Compounds that stimu late insulin secretion One that decreases insulin secretion A rise in blood glucose is the most important signal for increased insulin secretion. Plasma amino acid levels and the intestinal peptide secretin also stimulate insulin secre tion. Its synthesis and release are decreased by epinephrine, which is secreted in response to stress, trauma, or extreme exercise. 

Epinephrine A hormone synthesized primarily in the adrenal medulla, mimicking the peripheral effects of norepinephrine. Epinephrine is involved in the sympathetic nervous system response to stress and is especially effective in stimulating cardiovascular function (SYN adrenaline). 

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