Passage
The adrenal glands are divided into two anatomically distinct regions, the adrenal medulla and the adrenal cortex. The adrenal medulla is a collection of irregularly shaped cells located in the interior portion of each adrenal gland. In response to changing serum levels of corticosteroid hormones, medullary cells synthesize and secrete the catecholamines norepinephrine and epinephrine. Norepinephrine and epinephrine are water-soluble compounds, and their actual secretion into the bloodstream is stimulated by acetylcholine (ACh) -mediated signaling in the sympathetic component of the autonomic nervous system. Figure 1 shows the enzyme-mediated synthesis of norepinephrine and epinephrine.
Figure 1The adrenal cortex is the outer portion of the adrenal gland and is composed of cells that synthesize and secrete lipophilic hormones derived from cholesterol. Hormones produced by the adrenal cortex include the principal glucocorticoid hormone (cortisol) and the mineralocorticoid hormone (aldosterone) .The hypothalamus and pituitary gland regulate and control the endocrine functions of the adrenal cortex (Figure 2) . Secretion of corticotrophin-releasing hormone (CRH) from the hypothalamus promotes the synthesis and release of adrenocorticotrophic hormone (ACTH) by the pituitary gland. ACTH acts on adrenal cortex cells to promote the growth of cortical tissue and to increase the synthesis and secretion of glucocorticoids. In addition to its body-wide functions as the principal stress hormone, cortisol also regulates adrenal activity by inhibiting CRH release from the hypothalamus and ACTH release from the pituitary.
Figure 2
-Hormones secreted by the adrenal medulla most likely influence energy metabolism by:

Question

Passage
The adrenal glands are divided into two anatomically distinct regions, the adrenal medulla and the adrenal cortex. The adrenal medulla is a collection of irregularly shaped cells located in the interior portion of each adrenal gland. In response to changing serum levels of corticosteroid hormones, medullary cells synthesize and secrete the catecholamines norepinephrine and epinephrine. Norepinephrine and epinephrine are water-soluble compounds, and their actual secretion into the bloodstream is stimulated by acetylcholine (ACh) -mediated signaling in the sympathetic component of the autonomic nervous system. Figure 1 shows the enzyme-mediated synthesis of norepinephrine and epinephrine.

Figure 1The adrenal cortex is the outer portion of the adrenal gland and is composed of cells that synthesize and secrete lipophilic hormones derived from cholesterol. Hormones produced by the adrenal cortex include the principal glucocorticoid hormone (cortisol) and the mineralocorticoid hormone (aldosterone) .The hypothalamus and pituitary gland regulate and control the endocrine functions of the adrenal cortex (Figure 2) . Secretion of corticotrophin-releasing hormone (CRH) from the hypothalamus promotes the synthesis and release of adrenocorticotrophic hormone (ACTH) by the pituitary gland. ACTH acts on adrenal cortex cells to promote the growth of cortical tissue and to increase the synthesis and secretion of glucocorticoids. In addition to its body-wide functions as the principal stress hormone, cortisol also regulates adrenal activity by inhibiting CRH release from the hypothalamus and ACTH release from the pituitary.

Figure 2
-Hormones secreted by the adrenal medulla most likely influence energy metabolism by:

Quizplus · Accepted Answer

11ecba2d_0ffd_f909_a3bf_3d388932a6e6_MD0008_00 Energy metabolism refers to the cellular processes by which an organism stores or utilizes sources of energy. During periods of stress, hormones secreted by the adrenal gland influence energy metabolism by promoting energy utilization and inhibiting energy storage. Hormones secreted by the adrenal gland regulate energy metabolism as follows: Glucocorticoids (eg, cortisol) released by the adrenal cortex act on the liver to stimulate the synthesis of glucose from other molecules (ie, gluconeogenesis) and the breakdown of fats into fatty acids (ie, lipolysis). Both glucose and free fatty acids are forms of cellular energy that can be readily utilized. Norepinephrine and epinephrine are released by the adrenal medulla to modulate the metabolism of glycogen, the storage form of glucose. In addition, both hormones promote the breakdown of glycogen into glucose monomers in a process known as glycogenolysis. By inhibiting the enzymes that mediate glycogen synthesis, norepinephrine and epinephrine also inhibit glycogenesis (the formation of glycogen from glucose). (Choice B) Water-insoluble hormones (eg, steroid hormones) can diffuse across the plasma membranes of cells to bind cytosolic receptors. However, as stated in the passage, the adrenal medulla secretes the water-soluble hormones norepinephrine and epinephrine. Water-soluble hormones cannot diffuse across the plasma membrane and instead influence cellular activity by binding extracellular surface receptors to initiate a second messenger cascade. (Choice C) In order for triglycerides (the storage form of fatty acids) to be utilized as a source of energy, the fatty acid chains must be released from their glycerol backbone in a reaction facilitated by lipases. Because medullary hormones promote energy utilization, they would be expected to increase lipase activity, thereby increasing the use of fats as a source of energy. (Choice D) Increasing the activity of proteins that inhibit gluconeogenesis would decrease glucose synthesis and decrease available energy. In addition, adrenal gland hormones promote gluconeogenesis such that the serum level of glucose rises. Educational objective: Energy metabolism refers to the processes by which the body manages cellular energy stores. The adrenal gland increases the body-wide level of free cellular energy sources by releasing glucocorticoids, norepinephrine, and epinephrine.

Passage The Adrenal Glands Are Divided into Two Anatomically Distinct Regions