A&P Endocrine

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CHAPTER 15
The Endocrine System
 
NOTES
 
1. Name 4 ways cells communicate with each other and name important characteristics of each. Answers
a. gap junctions: really fast, nondirectional, part of nervous system b. neurotransmitters: fast, directional, specific, limited effects, part of nervous system c. paracrines: local tissue fluids, nondirectional, limited effects d. hormones: slower in onset, systemic in bloodstream, sustained effects 2. The area of the brain that is involved in regulating “primitive” functions like water balance, appetite, etc is the hypothalamus. It has both anatomic and functional connections to the pituitary gland or hypophysis by a narrow stalk, the infundibulum. The adenohypophysis or anterior pituitary derives  froman embryological pouch of the  pharynx while the neurohypophysis or posterior pituitary is part of the brain. A unique blood supply, the hypophyseal portal system, connects the hypothalamus directly to the anterior pituitary. The posterior pituitary is connected to the hypothalamus by axons with nerve cell bodies located in the hypothalamus.  3. With regard to the anterior pituitary, neurons in the hypothalamus secrete a group of compounds called releasing hormones that are absorbed into the primary capillaries. These compounds in turn effect the secretion of stimulating hormones  into the secondary capillaries to take them all over the body by the blood. Some of these from the anterior pituitary are called tropic  hormones because they stimulate specific endocrine glands. The two targeting the reproductive organs are called gonadotropins. Secretion of most tropic hormones is achieved by negative feedback of the target gland hormones acting on the hypothalamus. The non-tropic hormone from the anterior pituitary is GH. 4. List of the releasing hormones, the stimulating hormones they control and the final target organs. Know what each abbreviation stands for. RH                                  SH                                  Target TRH                                TSH, PRL                         thyroid, mammary glands CRH                                ACTH                              adrenal cortex GnRH                              FSH, LH                           testis, ovary PRH                                PRL                                 mammary glands GHRH                              GH                                  soma PIH                                 inhibits PRL                      Somatostatin                    inhibits GH & TSH             5. Know the specific actions of the anterior pituitary hormones. Answers

FSH:
-         ovary: development of the follicles (estrogen) and egg within -         testis: sperm production
LH:
-         ovary: ovulation & development of the corpus luteum (estrogen & progesterone) -         testis: secretion of testosterone from interstitial cells TSH: thyroid gland growth & thyroid hormone secretion

ACTH: (corticotropin): adrenal cortex secretion of corticosteroids PRL:
-         females: milk production
-         males: sensitizes interstitial cells to LH GH:
-         increases tissue growth, especially cartilage, bone , muscle, fat -         causes liver to make somatomedins or insulin-like growth factors; IGF-I stimulates bone growth at epipheseal plates -         increases amino acid transport into cells to support growth -         breaks down fat to spare glucose (ATP) & amino acids (protein) as energy sources There are 3 “axis” of action from the releasing hormones, all with negative feedback to hypothalamus: TRH à TSH à thyroid

GnRH à LH,FSH à          gonads
CRH à ACTH à adrenal cortex                      6. With regard to the posterior pituitary, name the two hormones produced, the target tissues and the signal for posterior pituitary hormone release. ADH

-         nerve cell bodies in the supraoptic nucleus        -         target = kidney:...
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