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Endocrines:. Types of glands. b. Ex: thyroid hormones, adrenaline. c. d. Endocrine Glands. Different endocrine glands:. Hormones Chemical messenger-Secreted by endocrine gland. Specific to target organs elsewhere in body. Activate cellular change.
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Hormones • Chemical messenger-Secreted by endocrine gland. • Specific to targetorgans elsewhere in body. • Activate cellular change. • Control/coordinate widespread processes: • Homeostasis. • Reproduction. • Growth & Development. • Metabolism. • Response to stress.
Classes of Hormones 1. Peptides and proteins -Glycoproteins 2. Amino acid derivatives -Catecholamines -Thyroid hormones -Melatonin 3. Steroids -Sex steroids -Corticosteroids
Regulation of Hormone secretion • Feed back secretion • Neural control • Rhythmic control: Episodic: GnRH Diurinal: ACTH, melatonin, cortisol Periodic: Gonadal hormones Developmental: growth Seasonal: mainly in birds • Humoral and chemical control
Control of Endocrine Function • Positive • or Negative Feedback mechanisms Self-regulating system
A. Positive Feedback • Not common • Classic example: Action of OXYTOCIN on uterine muscle during birth.
B. Negative Feedback • Most common control mechanism • Level of hormone in blood or body shuts off loop at hypothalamus and pituitary
Second messenger • 1) adenylcyclase- c AMP system • 2) membrane phospholipase- phospholipid system • 3) gyanylcyclase- c GMP system • 4) transcription of m RNA
Hypothalamus: Master of endocrine orchestra Is the portion of the anterior end of the diencephalon. It is divided in to a variety of nuclei and nuclear area.
The Hypothalamus and Endocrine Regulation 1.Coordinating centers in the hypothalamus (master gland) regulate the NS and endocrine system activities by 3 different mechanisms: • Secreting regulatory hormones that control endocrine cells in the adenohypophysis (anterior lobe) of the pituitary gland. • Releasing hormones (RH) stimulate production of one or more hormones. • Inhibiting hormones (IH) prevent the synthesis and secretion of specific pituitary hormones
2) The hypothalamus acts as an endocrine organ: Releasing the hormones ADH and Oxytocin. 3) The hypothalamus contains autonomic centers that have direct neural control over the endocrine cells of the suprarenal medullae. when the sympathetic division is activated, the suprarenal medullae release hormones into the bloodstream
HYPOTHALAMUS Anterior Pituitary regulating hormones Posterior Pituitary hormones Others
Anterior Pitutiary regulating hormones • Releasing hormones Growth hormone releasing hormone (GHRH) Thyrotrophic releasing hormone (TRH) Gonadotropin releasing hormone (GnRH) Corticotropin releasing hormone (CRH) Prolactin releasing hormone (PRH) Melanocyte stimulating hormone releasing hormone (MSH RH).
Inhibiting hormones Prolactin inhibitory hormone(PIH) Somatostatin (GHIH). Melanocyte stimulating hormone inhibiting hormone.MSH IH).
Posterior Pitutiary hormones • Anti Diuretic Hormone • Oxytocin
Others • Neuropeptide Y • Orexins increase food intake • Melanin Concentrating hormone • Cocaine and amphetamine decrease food regulating transcript. Intake.
HYPOTHALAMUS Anterior Pituitary Posterior Pituitary Hypothalamo- hypophyseal portal system Hypothalamo-hypophyseal tract