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Transcript
Structure and Function of Endocrine System 1 Identify and describe the structure and function of important biochemical compounds, including protein and steroid hormones (314-3) Analyze homeostatic phenomena to identify the feedback mechanisms involved (317-2) •Name the parts of the endocrine system and discuss the function of each part •Discriminate the functions of each endocrine hormone secreted by same endocrine glands •Analyze the action of each hormone and demonstrate its contribution in maintaining homeostasis •Classify hormones according to its molecular structure and actions 2 The Endocrine System •Regulates many bodily functions •Maintains homeostasis by regulating the production of chemicals that affect most functions of the body •Secretes substances that aid the nervous system •Important regulator of growth and development •Endocrine glands are ductless glands, unlike exocrine glands that secrete substances into ducts. 3 Feedback Maintaining homeostasis hormone 1 gland lowers body condition high specific body condition low raises body condition gland hormone 2 Negative Feedback Response to changed body condition ◦ if body is high or low from normal level signal tells body to make changes that will bring body back to normal level ◦ once body is back to normal level, signal is turned off hormone 1 gland lowers body condition high specific body condition Regulation How we maintain homeostasis ◦ nervous system nerve signals control body functions ◦ endocrine system hormones chemical signals control body functions Hormones Why are hormones needed? ◦ chemical messages from one body part to cells in other parts of body ◦ communication needed to coordinate whole body ◦ maintaining homeostasis growth hormones Endocrine System Endocrine system releases hormones ◦ glands which secrete (release) chemical signals into blood chemicals cause changes in other parts of body growth hormones sex hormones response hormones metabolism hormones and more…. Responding to hormones Lock and key system ◦ hormone fits receptor on “target” cell target cell secreting cell can’t read signal nontarget cells can’t read signal II. Endocrine System vs Neuronal System 1. Neural & Hormonal communication a. Similarities i. Chemicals are stored and released ii. Release of chemicals is due to stimulation iii. Many different hormones & neurotransmitters iv. Both systems react w/specific receptors v. Second messenger involved in both (The first messenger reacts to the initial signal - like an ionotropic receptor, found in CNS only) 2. Second messenger reacts to a signal from a first messenger (like a metabotropic receptor) and affects intracellular functioning; it is a complex intracellular response that affects functioning. b. Differences i. In nervous system, neurons communicate with adjacent neurons; in hormones messages are sent long distances ii. Neural messages induce rapid response compared to hormones which have slower messages iii. Neural messages follow the all or none principle; hormonal messages are graded in strength iv. Neural messages can be directed as observed in behavior; hormonal messages are primarily involuntary (cannot be directed) 2. Three types of hormones a. Protein hormones – effect is on receptors within the membrane, binds to the receptors on the outside of membrane; its effects are the most rapid of all the hormones i. Oxytocin – involved in development of relationships ii. Adrenocorticotrophin – protein hormone; chains of amino acids b. Amine hormones – same relatively fast receptor response as protein hormones i. Epinepherine ii. Norepinepherine iii. Thyroid hormones iv. Melatonin c. Steroid hormones – binds to the intercellular receptors; slow actions i. Gonadal hormones 1. Estrogen, progesterone, androgens ii. Adrenal hormones 1. Glucocorticoids, mineralocorticoids Major Glands of the Endocrine System Hypothalamus Pituitary Thyroid Adrenal Gonads: Ovaries & Testes The Endocrine System Consists of: glands secrete into hormones bloodstream to target tissues 21 hypo hyper Homeostasis exists when there is a balance of substances. Endocrine conditions are due to either hypo (too little) or hyper (too much) secretions of substances (hormones). 22 Hypothalamus •Part of the nervous system. Also serves as an endocrine gland because it releases hormones that regulate pituitary hormones •Hormones released have either a releasing or an inhibiting factor 23 Pineal Gland •Located superior and posterior to the pituitary gland •Releases melatonin, a hormone affect sleep and gonad functioning believed to 25 Pituitary Anterior Pituitary - derived during embryological development from the roof of the mouth - connected to the hypothalamus by a portal system (hypothalamic-pituitary portal system) - most of the hormones are released from the anterior pituitary Posterior Pituitary - derived from nervous tissue - two protein hormones released: oxytocin & vasopressin _________________________________ Two Important Points: Hormones released from the posterior pituitary are synthesized in the hypothalamus. Hormones released from the anterior pituitary are dormant unless directed to be released by the hypothalamus via Releasing Factors. Pituitary & all Hormones are Under the Control of the Hypothalamus Hypothalamus RF Anterior Pituitary Hormone Posterior Pituitary Hormone SH Target Organs RF = Releasing Factor Hormone Target Organs SH = Stimulating Hypothalamic Hormones: Corticotropin Gondotropin RF RF (CRF) Thyrotropin Growth Hor RF RF Prolactin RF Pituitary Hormones: Thyrotropin SH Adrenocorticoptropin Luteinizing Hor. Hormone (ACTH) Follicle SH & Growth Hormone Prolactin Target Gland or Structure: Adrenal Gland Ovaries & Testes (cortisol) (androgens, estrogen) Cells of body Thyroid Gland (thyroxine) Bones, breasts & cells of body Adrenal Gland i. Adrenal cortex (outer) produces about 50 different chemicals including… 1. Mineralocorticoids (outer layer) 2. Glucocorticoids, cortisol (middle layer) 3. Sex hormones (inner most layer) a. Estrogen, progesterone androgens note: Congenital adrenal hyperplasia – too much testosterone produced by mother. This comes from dysfunction in adrenal gland. ii. Adrenal medulla (inner) 1. Dopamine Norepinepherine/Epinepherine Thyroid Gland 1. Too little thyroxin – hypothyroidism a. Depression (clinical or subclinical), attention & memory problems 2. Too much thyroxin – hyperthyroidism a. Agitation, irritability, & weight loss *Goiters – Growths on thyroid gland Gonads & Hormones LH & FSH Growth Hormone Cells of body in response to growth hormone i. During childhood GH is at maximum 1. Too little and we have a small person 2. Too much and we have gigantism, often accompanied by acromegaly (continued growth of extremities of bones) a. Makes hands, feet, jaw, nose, and eye sockets (orbits) enlarged Oxytocin The hormone involved in inducing labor during childbirth Hormone involved in bonding Hormone involved in relationships Might be deficient in Autism All hormones utilize feedback loops: Autocrine response – Same as the autoreceptors, both communicate and terminate release Note similarity to the CNS: Autoreceptors – in the CNS the receptors on presynaptic cell that are sensitive to its own NT Parathyroid Gland Thymus Gland •Four oval shaped glands located on the dorsal side of the thyroid •Regulates calcium and phosphate levels •Also part of the immune system •The hormones secreted stimulate the production of T and B cells Adrenal Glands •A pair of glands, each one situated on top of a kidney •Each gland has an outer portion (adrenal cortex) and inner portion (adrenal medulla) •Regulates electrolytes •Adrenal medulla secretes catecholamines (epinephrine and norepinephrine) in response to stress 43 Pancreas •Helps maintain proper blood glucose levels •Is both an endocrine and exocrine gland. The islets of Langerhans serve its endocrine functions •Two types of cells, alpha and beta are produced by the islets of Langerhans Elevated Blood sugar Insulin is released by the beta cells which stimulate the glucose to be sent to the body’s cells and convert unused glucose to glycogen Blood sugar Low Glucagon is released by the alpha cells which stimulate stored glycogen to be transformed into glucose again 46 Insulin and Glucagon Insulin Rise in blood glucose stimulates insulin secretion Promotes movement of glucose into certain cells Stimulates formation of glycogen from glucose In response to insulin, blood glucose drops toward normal (and inhibits insulin secretion) Artery In response to glucagon, blood glucose rises toward normal (and inhibits insulin secretion) Pancreas Drop in blood glucose stimulates glucagon secretion Glucagon Stimulates cells to break down glycogen into glucose Stimulates cells to convert non-carbohydrates into glucose 47 Ultimately,what controls the endocrine system? Our emotions Our perceptions Our cognitions Our experiences Our behavior Our response to the environment Higher Brain Areas Hypothalamus Pituitary Endocrine Glands Ovaries •Located in the female pelvic region one attached to the top of each fallopian tube •Produce the female hormones: -estrogen -progesterone Testes •Located in the scrotum, a sac outside the body •Produce spermatozoa which fertilizes the female ova •Produce male sex hormones: -testosterone 50 Combining Form Meaning aden(o) gland adren(o) adrenal glands gluc(o) glucose glyc(o) glycogen gonad(o) sex glands pancreat(o) pancreas parathyroid(o) parathyroid thyr(o) thyroid gland 51 Abbreviation Meaning ACTH adrenocorticotropic hormone ADH antidiuretic hormone CRH corticotropin-releasing hormone DM diabetes mellitus FSH follicle-stimulating hormone GH growth hormone GTT glucose tolerance test HCG human chorionic gonadotropin 52 Abbreviation Meaning IDDM insulin-dependent diabetes mellitus LH luteinizing hormone MSH melanocyte-stimulating hormone NIDDM noninsulin dependent diabetes mellitus PRL prolactin PTH parathyroid hormone, parathormone STH somatotropin hormone TSH thyroid-stimulating hormone 53