Presentation on theme: "Integration and Control:"— Presentation transcript:
1 Integration and Control: THE ENDOCRINE SYSTEMCampbell & Reece Chapter 45
2 EndocrineHormones: substances produced by particular tissues of the body carried by the bloodstream to "target cells," upon which they exert special effects*Hormones are secreted by glands, made mostly of epithelial tissueExocrine glands: secrete into ducts (sweat glands, digestive glands)Endocrine glands: secrete hormones (into bloodstream) "ductless glands"Endocrine Gland--->hormone--> Bloodstream------> target organ/tissue
3 Active in very small quantities Controlled by: Hormones may be:SteroidsPeptides/proteins;Amino acidsActive in very small quantitiesControlled by:Negative FeedbackRapid degradation by the bodyHormonal communication
5 Mechanisms of Action of Hormones: 2 Main ways that Hormones Effect Target Cells:Intracellular receptor molecules- steroids, thyroid hormonesMembrane receptor molecules- amino, peptide, protein hormonesA. Intracellular ReceptorsSteroid hormones and thyroid hormones are soluble in lipids and pass freely through cell membranes; must contact receptor site with in a cellThis changes a cell’s actions (protein synthesis, etc.)B. Membrane ReceptorsCombine with receptors on or in the membrane target cellsOnce combined, send a second messenger inside ? to the nucleus (cyclic AMP)May simply increase/decrease a cell’s permeability to substancesAction of Steroid Hormones
6 The Hypothalamus-Pituitary Axis: Pituitary was once considered the "master gland" until it was learned that it was under control of the hypothalamus (brain region)The hypothalamus makes several hormones which travel to and are released by the pituitary lobes.Target tissues are stimulated by (or inhibited by) release of these hormones into the bloodstream.
7 HormoneMajor Target Organ(s)EffectsAnterior PituitaryGrowth hormone (GH)Liver, adipose tissuePromotes growth (indirectly), control of protein, lipid and carbohydrate metabolismThyroid-stimulating hormone (TSH)Thyroid glandStimulates secretion of thyroid hormonesAdrenocorticotropic hormone (ACTH)Adrenal gland (cortex)Stimulates secretion of glucocorticoidsProlactin (PRL)Mammary glandMilk productionLuteinizing hormone (LH)Ovary and testisControl of reproductive functionFollicle-stimulating hormone (FSH)Posterior PituitaryAntidiuretic hormone (ADH)KidneyConservation of body waterOxytocinStimulates milk ejection and uterine contractions
8 The Hypothalamus-Pituitary Axis: About the size of a kidney beanDivided into three lobes: Anterior, posterior, intermediate
9 Anterior PituitarySomatotropin = growth hormone (GH), stimulates protein synthesis, growth of muscle and boneDeficit: midgetExcess: giantism (acromegaly)Affects glucose metabolism; inhibits uptake and oxidation of glucose by cells, stimulates breakdown of fatty acid for energy (conserves glucose)Prolaction (PRL) –stimulates the secretion of milk in mammalscontrolled by inhibiting hormone in hypothalamuscontinued by nerve impulses from suckling; hypothalamus (supply upon demand)
10 Intermediate Pituitary Lobe Melanocyte- stimulating Hormone (MSH)(Wikipedia) ...stimulate the production and release of melanin (melanogenesis) by melanocytes in skin and hair.MSH is also produced by a subpopulation of neurons in the hypothalamus.MSH released into the brain by these neurons has effects on appetite and sexual arousal.More important for color change in reptiles, etc.
11 Posterior Pituitary Lobe Hypothalamus releases Oxytocin and antidiuretic hormone (ADH) and stores it here, released by posterior pituitaryOxytocin- "milk let down" hormone, stimulates uterine contractions, smooth muscle contraction (BP regulation)Antidiuretic Hormone (ADH)- a.k.a. vasopression (increase BP) decreases excretion of water by kidneys. Increases permeability of water in nephrons
12 Regulation of The Other Glands: Regulation: negative feedback system involving a gonadotropic (gonad-stimulating) hormoneLH (luteinizing hormone): produced by ant. pituitaryIn males:LH is carried by blood to stimulate testesas blood level of testosterone increases, LH production decreasesIn females:rise in LH stimulates ovulationFSH (follicle-stimulating hormone):In males: acts upon the sertoli cells of the testes, important for spermatogenesisIn females: stimulates maturation of germ cells, sets mentrual cycleHigh concentrations of LH cause germ cells to produce an inhibitor, "inhibin", which will then lower LH levels
14 Testes Androgens- the "male sex hormones" Testosterone (steroid) is one type. Produced in the testes necessary for sperm production and secondary sex characteristics:genitalslarnyx (voice change)skeletal enlargementmuscle tissueacne
15 The Ovaries Estrogens- the "female sex hormones" Different kinds of estrogen hormones: estriol, estrone, and estradiol (most important)Produced by ovaries by stimulation of FSH from pituitaryStimulate development of secondary sex characteristics (breast development, genital development, distribution of body fat)Progesterone- maintenance of pregnancy, uterus(estrogen, progesterone interaction= menstrual cycle)estrus cycle diagram, showing hormone fluctuations in the mare
16 Prostaglandins Hormone-like chemicals differ from other hormones: Fatty acids (formed by oxygenation of Arachidonic Acid)Produced by cell membranes of most organs (as opposed to specific glands)Often exert effects on the tissues that produce themThe target tissue may be that of another person (e.g. in semen, for fertilization)More patent than hormones (needed in smaller amounts)Effects- stimulation of smooth muscle (uterus- menstruation labor); blood vessel dilation/constriction (BP down, up); inflammatory response by T-cells
17 Adrenal GlandsAdrenal Cortex- outer layer of adrenal glands; major source of steroid hormonesAdrenal glands lie on top of kidneys ("ad-renal")Humans: two major groups of adrenocortical steroidsGlucocorticoidsMineralocorticoids
18 Adrenal Cortex: Glucocorticoids Glucocorticoids- used to suppress inflammation (medical)Cortisol- (most important) mainly the formation of glucose from fats and proteins. Inhibit up take of glucose by most cells (except brain and heart). Release increases during excitement etc.; work with sympathetic nervous system.Secreted in response to Adrenocorticotropic Hormone (ACTH), secreted by Ant. Pituitary ("master gland") which is stimulated by hormone released from Hypothalamus
19 Adrenal Cortex: Mineralocorticoids Affect the ion concentration in the blood; water loss/retention.Aldosterone- (example) regulation of ions (K+, Na+)Affect the transport of ions across membranes of the NEPHRONSDeficiency leads to Na+ ion loss (via urine) = loss of water = lowers blood pressureSince adrenal cortex is source of androgens (male and female) sex hormones, a tumor can increases male secondary sex characteristics (e.g. bearded ladies)
20 Adrenal MedullaCentral portion of adrenal made up of neurosecretory cells (rather than epithelial)Adrenaline and Noradrenalin- increase rate and strength of heartbeat; raise BP; dilate resp. passages (act as enforcer of sympathetic N.S.)
21 Pancreatic Hormones: "Islets of Langerhans" Insulin: secreted in response to rise in blood sugar or AA concentration. It lowers blood sugar by stimulating up take of glucose (conversion of glucose to glycogen by liver)Glucagon: increases blood sugar by breakdown of glycogen glucose in liver and breakdown of fats/proteinsSomatostatin: synthesis of insulinFive different sugar-regulating hormones (growth hormone, cortisol, insulin, adrenalin, glucagon)Diabetes- insulin too lowHypoglycemia- insulin too high
22 Thyroid Gland: Located on top of Larynx Controlled by "hypothalamus- pituitary axis" - TSH (thyroid-stimulating hormones a.k.a. "thyrotropin"A. ThyroxineAccelerates rate of cellular respiration (metabolism)differs from androgens, estrogens, corticosteroids because it is an amino acid with 4 iodine atoms (T4), also T3B. Calcitonin: inhibits release of calcium ions [Ca2+ ions] from bones. Secretion is controlled by Ca ion conc. in fluid around thyroid cells.
23 Thyroid diseasesGoiter is a swelling of the thyroid gland, results from low iodine in dietHyperthyroidism: (overproduction) weight loss, nervousness, fatigue. Most common cause in Grave's Disease.Hypothyroidism: (underproduction) dwarfism in infants (Cretinism) low energy, low brain cell development, can be caused by insufficient iodine in dietautoimmune disease of thyroid : Hashimoto's thyroiditis
24 Parathyroid Glands:Located below thyroid, pea- size, smallest endocrine glandParathormone: essential in mineral metabolism, regulation of Calcium and Phosphate ions in bloodstimulates release of Ca?? ions from bones; secreted in response to low blood [Ca2+](Calcium = blood coagulation, muscle contraction, nerve function)
25 The Pineal Gland Small lobe in forebrain, near center Involved in "photoperiodism"- seasonal enlargement of ovaries etc.Secretes hormone: Melatonin (up/down, day/night)Melatonin: causes pigment cells to open/close "biological clock"