Exercise catecholamine release

The increase of FFA mobilization from adipose tissue is observed in a variety of conditions involving catecholamine release, such as adaptation to extrauterine. life, adaptation to upright posture, physical exercise, cold or psychological stress. 

The second factor that exerts control on heart rate is the release of the catecholamines, epinephrine and norepinephrine, from the adrenal medulla. Circulating catecholamines have the same effect on heart rate as direct sympathetic stimulation, which is to increase heart rate. In fact, in the intact heart, the effect of the catecholamines serves to supplement this direct effect. In a denervated heart, circulating catecholamines serve to replace the effect of direct sympathetic stimulation. In this way, patients who have had a heart transplant may still increase their heart rate during exercise. 

At the onset of exercise, signals from the cerebral cortex are transmitted to the vasomotor center in the medulla of the brainstem. This central command inhibits parasympathetic activity and also initiates the mass sympathetic discharge associated with exercise. Sympathetic activity (including release of catecholamines from the adrenal medulla) increases proportionally with the intensity of exercise. 

Epinephrine and norepinephrine, hormones called catecholamines, are released from the adrenal medulla during exercise. Epinephrine and, to a lesser extent, norepinephrine stimulate effects in muscles and the liver similar to those produced by glucagon. Epinephrine activates adenylate cyclase, resulting in such events as the breakdown of glycogen and fatty acids. 

Norepinephrine and epinephrine are hormones in the class called catechoiami nes. The catecholamines are synthesized and stored in the adrenal gland. With exercise, nerve impulses stimulate the adrenal gland to release the hormones into the bloodstream. Elevated levels of the plasma catecholamines, in turn, induce the contraction or dilation of specific arteries, and the synthesis of cAMF in various cells. Norepinephrine and epinephrine are stored in and released by nerve endings and, for this reason, these hormones are also classed as neurotransmitters. The catecholamine biosynthetic pathway begins with tyrosine (Figure 9.85). 

The catecholamine hormone epinephrine (also called adrenaline) is the fight, fright, and flight hormone. Epinephrine and the structurally similar hormone norepinephrine are released from the adrenal medulla in response to a variety of immediate stresses, including pain, hemorrhage, exercise, hypoglycemia, and hypoxia. Thus, as Ann O Rexia begins to jog, there is a rapid release of epinephrine and norepinephrine into the blood. 

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