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THE ENDOCRINE SYSTEM.
Term Paper ID:30653
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Essay Subject:
Discusses functions of this group of glands.... More...
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4 Pages / 900 Words
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Paper Abstract:
Discusses functions of this group of glands. Main function to secrete hormones into the bloodstream. Control of various bodily functions such as growth, glucose control, blood pressure regulation, development of secondary sexual characteristics. Actions of the pituitary gland.;feedback mechanism. Effect of hormones on organs and glands. Examples of feedback control.
Paper Introduction:
The Endocrine System
The endocrine system is a group of glands whose function is to secrete hormones directly into the bloodstream (Berkow, Beers and Fletcher, 1997). Hormones are substances which serve as messengers which control the various functions of the body such as growth and development, glucose control, salt and water regulation, red cell production, bone formation, blood pressure regulation, development of secondary sexual characteristics, and support pregnancy. The major endocrine organs are the pituitary, hypothalamus, thyroid, parathyroids, pancreas, adrenals, testes and ovaries. The hypothalamus secretes several hormones which stimulate the pituitary gland, which then releases certain of its hormones in response. It secretes others which suppress release of pituitary hormones.
Text of the Paper:
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MCH can rapidly reduce plasma thyroid stimulating hormone (TSH) whengiven intracerebroventricularly. The results also indicated that FSHsecretion is controlled by a feedback system in which the feedforward arm(FSH-inhibin B) is less robust than the feedback loop (inhibin B-FSH). References Berkow, R., Beers, M. Theother testis was taken on day 44. A., & Bloom, S. Melanin-concentrating hormone (MCH) is an orexigenic peptide encodedin the pre-pro MCH gene (Kennedy et al (2 1). They looked at the rapid and delayed feedback systems to determinethe type of glucocorticoid receptor mediating the rapid and delayedfeedback responses. Some of the hormones the pituitary secretes act directly ontissues, and others stimulate the other endocrine glands to secrete theirown hormones. Hormone secretion is regulated by a feedback system controlling thepituitary and hypothalamus (Berkow, Beers and Fletcher, 1997). This studydemonstrates the specificity of receptors necessary for the feedbackcontrol of hormones in the endocrine system. MCH has also been shown to reduce thyroidreleasing hormone-stimulated TSH from pituitary cells in culture,indicating it disrupts the pituitary-thyroid axis. (2 1). For instance, the brain producesmany hormones which are distributed in the nervous system only. They found that the effects of corticosteroids on bothrapid and delayed feedback inhibition of ACTH release by the pituitary aremediated by type II glucocorticoid receptors, and that both types ofdelayed feedback require the synthesis of new mRNA and protein. A., Abbott, C. The second testis showed an increase innumber of all germ cells more mature than undifferentiated spermatogoniaand a sustained increase in FSH secretion was noted. Dynamics of follicle-stimulating hormone (FSH)-inhibin B feedbackloop and its role in regulating spermatogenesis in the adult male Rhesusmonkey (Macaca mulatta) as revealed by unilateral orchidectomy.Endocrinology, 141, 18-27. (pp. R. Dayanithi and Antoni (1989) showed that glucocorticoid hormonesuppresses the release of adrenocorticotrophic hormone (ACTH) by theanterior pituitary by rapid feedback within 3 minutes of application, bydelayed feedback at one to two hours, and slow feedback after severalhours. For instance, prolactin production bythe pituitary is stimulated by the suckling of a baby and causes release ofmilk. Deletion of this genecauses a phenotype of hypophagia and leanness with an inappropriately highmetabolic rate. Hormones may have rapid or delayed effects on their target organs orglands. A very tight control is kept on circulating hormone levels in thisway. J. Using adelicate balance of releasing and inhibiting feedback controls, thefunctions of the body are finely tuned by the endocrine system through itsmaster gland, the pituitary. Some ofthe endocrine glands operate independently of the pituitary gland: theislets of Langerhans in the pancreas which secrete insulin in response torising blood sugar levels, the parathyroid cells which respond tocirculating calcium and phosphate levels, and the adrenal medulla whichresponds directly to parasympathetic stimulation by the nervous system.Some organs also secrete hormones and hormone-like substances, but are notconsidered part of the endocrine system. Thehypothalamus secretes several hormones which stimulate the pituitary gland,which then releases certain of its hormones in response. In Merck Manual of Medical Information. S., & Plant, T. These twoglands respond to circulating hormone levels and release hormones whichstimulate specific glands when the levels hormones produced by those glandsare low in the bloodstream, and release hormones which inhibit these glandsfrom producing their hormones when the levels in the bloodstream are toohigh. R., McNeilly, A. Adecrease in the inhibin B feedback signal resulted in a sustained increasein FSH secretion that drove the testes toward their spermatogenic maximum. The Endocrine System The endocrine system is a group of glands whose function is to secretehormones directly into the bloodstream (Berkow, Beers and Fletcher, 1997).Hormones are substances which serve as messengers which control the variousfunctions of the body such as growth and development, glucose control, saltand water regulation, red cell production, bone formation, blood pressureregulation, development of secondary sexual characteristics, and supportpregnancy. R., Small, C.J., Ghatei, M. Rapid as well as delayedinhibitory effects of glucocorticoid hormones on pituitaryadrenocorticotrophic hormone release are mediated by type II glucocorticoidreceptors and require newly synthesized messenger ribonucleic acid as wellas protein. It secretesothers which suppress release of pituitary hormones. Endocrinology, 125, 3 8-313. The stimulus for FSHsecretion was presumed to be the 5 percent decrease in circulating inhibinB following unilateral orchidectomy. Ramaswamy, S., Marshall, G. Profiles of circulating concentrations of FSH, LH, testosterone,inhibin B, and pro-?-C were monitored in blood samples before, on the dayof, and at various times after unilateral orchidectomy for 43 days. M.(2 ). Certain hormones are produced at varying times, such as the hormonesinvolved with pregnancy and lactation, which are only secreted when needed(Berkow, Beers and Fletcher, 1997). Another example of feedback control in the endocrine system wasinvestigated by Ramaswamy, Marshall, McNeilly and Plant (2 ). Endocrinology, 142, 3265-3268. H., & Fletcher, A. These data suggest thatMCH has a role in the control of energy homeostasis through inhibition ofthe thyroid-pituitary axis. A. Kennedy, A. R., Todd, J. 693-696).Whitehouse Station, NJ: Merck Research Laboratories. Dayanithi, G., & Antoni, F. This study suggests that sperm output by the monkeytestis is regulated by circulating FSH concentrations, and that inphysiological situations, FSH concentrations are unable to stimulatespermatogenesis to its maximum. (1997). The hypothalamic- pituitary-thyroid axis is important inenergy homeostasis and starvation leads to profound suppression of thisaxis. The major endocrine organs are the pituitary, hypothalamus,thyroid, parathyroids, pancreas, adrenals, testes and ovaries. The production of corticosteroids and growth hormone is the highestearly in the morning and the lowest in mid-afternoon. The pituitary, in turn, is controlled by a feedbackmechanism, responding to circulating levels of the other hormones. The above data show how the feedback control system works in theendocrine system to control the release of hormones from the pituitary andthus the secretion of hormones by the other endocrine organs. F., Stanley, S. The pituitary is the major controlling gland which coordinates many ofthe functions of the other endocrine glands (Berkow, Beers and Fletcher,1997). Theylooked at the dynamics of the follicle-stimulating hormone (FSH)-inhibin Bfeedback loop and its role in the regulation of spermatogenesis in Rhesusmonkeys. Endocrine systemand hormones. Transient changes were seen in LH andtestosterone levels. Melanin-concentrating hormone(MCH) suppresses thyroid stimulating hormone (TSH) release, in vivo and invitro, via the hypothalamus and the pituitary. The study was carried out to document the morphological changesin the seminiferous epithelium that underlie the compensatory testicularhypertrophy seen in response to unilateral orchidectomy, and to describethe response in the endocrine feedback loop controlling testicularfunction. (1989).
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