Endocrine system power point 2022-1 (1).pptx

UNIVERSITY OF BELIZE COURSE CODE – ALHL2021 FACULTY OF HEALTH SCIENCES ENDOCRINE SYSTEM WEEK 1 PATRICIA LOPEZ TIME FRAME (75 MINUTES) Copyright© 2020 University of Belize. All rights reserved Not to be reproduced or disseminated without permission from the University of Belize. Objectives • St...

UNIVERSITY OF BELIZE COURSE CODE – ALHL2021 FACULTY OF HEALTH SCIENCES ENDOCRINE SYSTEM WEEK 1 PATRICIA LOPEZ TIME FRAME (75 MINUTES) Copyright© 2020 University of Belize. All rights reserved Not to be reproduced or disseminated without permission from the University of Belize. Objectives • State differences between hormonal and neural controls • List major endocrine organs and their locations • Distinguish between circulating hormones and local hormones • Classify hormones • Describe major mechanisms by which hormones bring about effect on target cells • Explain how hormone release is regulated • Name the hormones secreted by each endocrine organ and explain the effects of each. Differences between nervous and endocrine system Nervous • Regulate muscles, glands • Via impulses • Responds in milliseconds • Response can be short Endocrine • Affect metabolic activities of cells • Via hormones • Response after lag period or days • Response may be prolonged Major characteristics 1 • Organs are scattered • Lack ducts • Hormones released into surrounding fluids • Affect target cells • Have rich vascular and lymphatic drainage Major characteristics 2 • Endocrine glands—pituitary, thyroid, adrenal, pineal, thymus • Hypothalamus has both neural functions and produce hormones • Pancreas and gonads have both endocrine and exocrine functions • Other tissues and organs producing hormones Major endocrine glands Hormones • Hormones – chemical substances secreted by cells into the extracellular fluids • Regulate the metabolic function of other cells • Have lag times ranging from seconds to hours • Tend to have prolonged effects Action of hormones • Hormones produce one or more of the following cellular changes in target cells • • • • • Alter plasma membrane permeability Stimulate protein synthesis Activate or deactivate enzyme systems Induce secretory activity Stimulate mitosis Hormone action • Hormones alter target cell activity by one of two mechanisms • Second messengers involving: • Regulatory G proteins • Direct gene activation involving steroid hormones • The precise response depends on the type of the target cell Classification of hormones • Amino acid-base (simple amino acid derivatives, peptides, proteins) • Steroids (cholesterol base) Amino acid-base hormone action (second messenger cAMP) • Hormone (first messenger) binds to its receptor, which then binds to a G protein • The G protein is then activated as it binds GTP, displacing GDP • Activated G protein activates the effector enzyme adenylate cyclase • Adenylate cyclase generates cAMP (second messenger) from ATP • cAMP activates protein kinases, which then cause cellular effects Amino acid-base hormone action (second messenger cAMP Steroid-base hormone action • Steroid hormones and thyroid hormone diffuse easily into their target cells • Once inside, they bind and activate a specific intracellular receptor • The hormone-receptor complex travels to the nucleus and binds a DNA-associated receptor protein • This interaction prompts DNA transcription to produce mRNA • The mRNA is translated into proteins, which bring about a cellular effect Steroid base hormone action Hormone action Target cell activation depends on • Blood level of the hormone • Number of receptors for that hormone on target cell • Strength of the bond between hormone and receptor Control of hormone release • Humoral stimuli—release in response to change in blood ions and nutrients • Neural stimuli—nerve fiber stimulate release • Hormonal—release in response to other hormones Removal of hormones • Hormones are removed from the blood by: • Degrading enzymes • The kidneys • Liver enzyme systems The pituitary • Pituitary gland – two-lobed organ that secretes nine major hormones • Neurohypophysis – posterior lobe (neural tissue) and the infundibulum • Receives, stores, and releases hormones from the hypothalamus • Adenohypophysis – anterior lobe, made up of glandular tissue • Synthesizes and secretes a number of hormones Structure of the pituitary Adenohypophysis hormones • The six hormones of the adenohypophysis: • Are abbreviated as GH, TSH, ACTH, FSH, LH, and PRL • Regulate the activity of other endocrine glands • In addition, pro-opiomelanocortin (POMC): • Has been isolated from the pituitary • Is a prohormone (precursor for ACTH) Activity of adenohypophysis • Controlled by the hypothalamus • Hypothalamic hormones either stimulate or inhibit release of hormones • The tropic hormones that are released are: • • • • Thyroid-stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Growth hormone • Produced by somatotropic cells of the anterior lobe that: • Stimulate most cells, but target bone and skeletal muscle • Promote protein synthesis and encourage the use of fats for fuel • Most effects are mediated indirectly by somatomedins • Antagonistic hypothalamic hormones regulate GH • Growth hormone–releasing hormone (GHRH) stimulates GH release • Growth hormone–inhibiting hormone (GHIH) inhibits GH release Effects of growth hormone • Anabolic (tissue building) • Promotes protein synthesis • Stimulate the use of fats for fuel instead of glucose • Stimulate body cells to increase (targets bones and skeletal muscles) Thyroid stimulating hormone • Tropic hormone that stimulates the normal development and secretory activity of the thyroid gland • Triggered by hypothalamic peptide thyrotropin-releasing hormone (TRH) • Rising blood levels of thyroid hormones act on the pituitary and hypothalamus to block the release of TSH Adrenocorticotropic hormone • Stimulates the adrenal cortex to release corticosteroids • Triggered by hypothalamic corticotropin-releasing hormone (CRH) in a daily rhythm • Internal and external factors such as fever, hypoglycemia, and stressors can trigger the release of CRH Gonadotropins • Gonadotropins – follicle-stimulating hormone (FSH) and luteinizing hormone (LH) • • • • Regulate the function of the ovaries and testes FSH stimulates gamete (egg or sperm) production Absent from the blood in prepubertal boys and girls Triggered by the hypothalamic gonadotropin-releasing hormone (GnRH) during and after puberty Functions of gonadotropins • In females • LH works with FSH to cause maturation of the ovarian follicle • LH works alone to trigger ovulation (expulsion of the egg from the follicle) • LH promotes synthesis and release of estrogens and progesterone • In males • LH stimulates interstitial cells of the testes to produce testosterone • LH is also referred to as interstitial cell-stimulating hormone (ICSH) Prolactin (PRL) • In females, stimulates milk production by the breasts • Triggered by the hypothalamic prolactin-releasing hormone (PRH) • Inhibited by prolactin-inhibiting hormone (PIH) • Blood levels rise toward the end of pregnancy • Suckling stimulates PRH release and encourages continued milk production Posterior pituitary and hypothalamic hormones • Posterior pituitary – made of axons of hypothalamic neurons, stores antidiuretic hormone (ADH) and oxytocin • ADH and oxytocin are synthesized in the hypothalamus • ADH influences water balance • Oxytocin stimulates smooth muscle contraction in breasts and uterus