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Endocrine System Hormones AP Biology 2006-2007 Regulation Why are hormones needed? chemical messages from one body part to another communication needed to coordinate whole body homeostasis & regulation metabolism growth development maturation reproduction AP Biology growth hormones Regulation & Communication Animals rely on 2 systems for regulation endocrine system ductless gland which secrete chemical signals directly into blood chemical travels to target tissue slow, long-lasting response nervous system system of neurons, central nerve system transmits “electrical” signal to target tissue fast, short-lasting response AP Biology Regulation by chemical messengers Neurotransmitters released by neurons Hormones release by endocrine glands Endocrine gland Neurotransmitter Axon Hormone carried by blood Receptor proteins AP Biology Receptor proteins Target cell Insect metamorphosis Figure 45.1 AP Biology Is regulated by hormones Three Key Events in Hormone Function Three Key Events Reception Signal transduction Response AP Biology Classes of Vertebrate Hormones Three major classes of molecules function as hormones in vertebrates Proteins and peptides Amines derived from amino acids Steroids AP Biology Classes of Hormones Protein-based hormones polypeptides small proteins: insulin, ADH glycoproteins large proteins + carbohydrate: FSH, LH amines modified amino acids: epinephrine, melatonin Lipid-based hormones steroids modified cholesterol: sex hormones, aldosterone Non polar amines Modified nonpolar amino acids: thyroxine AP Biology How do hormones act on target cells Protein-based SECRETORY CELL Hormone molecule hormones VIA BLOOD Signal receptor TARGET CELL Signal transduction pathway OR Cytoplasmic response DNA Nuclear response NUCLEUS hydrophilic & not lipid soluble can’t diffuse across membrane trigger secondary messenger pathway activate cellular response enzyme action, uptake or secretion of molecules… AP Biology Action of protein hormones 1 Protein hormone activates enzyme G protein cAMP Receptor protein 3 2 ATP GTP activates enzyme activates enzyme cytoplasm AP Biology 4 Produces an action protein messenger cascade How do hormones act on target cells Lipid-based SECRETORY CELL hormones hydrophobic & lipid-soluble Hormone molecule VIA BLOOD diffuse across membrane & enter cells bind to receptor proteins in cytoplasm & nucleus bind to DNA as transcription factors AP Biology TARGET CELL Signal receptor Signal transduction and response DNA mRNA NUCLEUS Synthesis of specific proteins Action of lipid (steroid) hormones cytoplasm steroid hormone S S S 1 2 blood protein carrier receptor protein 4 S 3 DNA nucleus AP Biology mRNA 5 protein plasma membrane Multiple Effects The same hormone may have different effects on target cells that have AP Biology Different receptors for the hormone Different signal transduction pathways Different proteins for carrying out the response Action of epinephrine (adrenalin) liver cell 1 epinephrine activates adenylyl cyclase adrenal gland G protein cAMP receptor protein 2 3 ATP GTP activates protein kinase-A activates phosphorylase 4 cytoplasm AP Biology glycogen glucose released to blood Epinephrine: Multiple Effects The hormone epinephrine Has multiple effects in mediating the Different receptors different cell responses body’s response to short-term stress Epinephrine Epinephrine Epinephrine a receptor b receptor b receptor Glycogen deposits Vessel constricts (a) Intestinal blood vessel Figure 45.4a–c AP Biology Vessel dilates (b) Skeletal muscle blood vessel Different intracellular proteins Glycogen breaks down and glucose is released from cell (c) Liver cell different cell responses Benefits of a 2° messenger system 1 Signal molecule Receptor protein Activated adenylyl cyclase Not yet activated 2 Amplification 4 Amplification 3 GTP cAMP 5 G protein Protein kinase 6 Amplification Amplification! AP Biology Enzyme 7 Amplification Enzymatic product Paracrine Signaling by Local Regulators Paracrine signaling Various types of chemical signals elicit responses in nearby target cells Local regulators have various functions and include AP Biology Cytokines – important in immune response Growth factors – stimulate cell proliferation and differentiation Nitric oxide – (NO) relaxes neighboring smooth muscles causing vasodialation Prostaglandins – important in semen and in immune response promote fever and inflammation Fig. 11-5ab Local signaling Electrical signal along nerve cell triggers release of neurotransmitter Target cell Secreting cell Local regulator diffuses through extracellular fluid (a) Paracrine signaling AP Biology Neurotransmitter diffuses across synapse Secretory vesicle Target cell is stimulated (b) Synaptic signaling The major human endocrine glands Hypothalamus Pineal gland Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pancreas Ovary (female) Testis (male) Figure 45.6 AP Biology Major human endocrine glands and some of their hormones Table 45.1 AP Biology Major human endocrine glands and some of their hormones Table 45.1 AP Biology Endocrine & Nervous system links Hypothalamus = “master control center” nervous system receives information from nerves around body about internal conditions regulates release of hormones from pituitary Pituitary gland = “master gland” AP Biology endocrine system secretes broad range of hormones regulating other glands Relation Between the Hypothalamus and Pituitary Gland The hypothalamus, a region of the lower brain Contains different sets of neurosecretory cells AP Biology Relation Between the Hypothalamus and Pituitary Gland Some of these cells produce direct-acting hormones That are stored in and released from the posterior pituitary, or neurohypophysis Hypothalamus Neurosecretory cells of the hypothalamus Axon Posterior pituitary HORMONE Figure 45.7 AP Biology TARGET Anterior pituitary ADH Kidney tubules Oxytocin Mammary glands, uterine muscles Other hypothalamic cells produce tropic hormones That are secreted into the blood and transported to the anterior pituitary or adenohypophysis Tropic Effects Only FSH, follicle-stimulating hormone LH, luteinizing hormone TSH, thyroid-stimulating hormone ACTH, adrenocorticotropic hormone Neurosecretory cells of the hypothalamus Nontropic Effects Only Prolactin MSH, melanocyte-stimulating hormone Endorphin Portal vessels Nontropic and Tropic Effects Growth hormone Hypothalamic releasing hormones (red dots) HORMONE TARGET Figure 45.8 AP Biology FSH and LH Testes or ovaries TSH Thyroid Endocrine cells of the anterior pituitary Pituitary hormones (blue dots) ACTH Prolactin MSH Endorphin Adrenal cortex Mammary glands Melanocytes Pain receptors in the brain Growth hormone Liver Bones The anterior pituitary Is a true-endocrine gland The tropic hormones of the hypothalamus AP Biology Control release of hormones from the anterior pituitary Hypothalamus Thyroid-stimulating Antidiuretic Hormone Posterior hormone (TSH) pituitary (ADH) Thyroid gland Anterior pituitary Kidney tubules Muscles of uterus Adrenal cortex Gonadotropic hormones: Folliclestimulating hormone (FSH) & luteinizing hormone (LH) Melanocyte in amphibian Bone and muscle AP Biology Testis Ovary Mammary glands in mammals Negative Feedback Model hormone 1 lowers body condition gland high specific body condition low raises body condition AP Biology gland hormone 2 2005-2006 Nervous System Control Body Temperature Feedback nerve signals brain sweat dilates surface blood vessels high body temperature low brain constricts surface shiver blood vessels AP Biology nerve signals 2005-2006 Endocrine System Control Blood Sugar Feedback insulin liver stores sugar body cells take up sugar from blood pancreas high reduces appetite liver blood sugar level low triggers hunger AP Biology liver releases sugar liver pancreas glucagon 2005-2006 Body cells take up more glucose. Insulin Maintenance of glucose homeostasis Beta cells of pancreas are stimulated to release insulin into the blood. Liver takes up glucose and stores it as glycogen. STIMULUS: Rising blood glucose level (for instance, after eating a carbohydraterich meal) Blood glucose level declines to set point; stimulus for insulin release diminishes. Homeostasis: Blood glucose level (about 90 mg/100 mL) Blood glucose level rises to set point; stimulus for glucagon release diminishes. Figure 45.12 AP Biology Liver breaks down glycogen and releases glucose into blood. STIMULUS: Dropping blood glucose level (for instance, after skipping a meal) Alpha cells of pancreas are stimulated to release glucagon into the blood. Glucagon 2005-2006 Diabetes Mellitus Diabetes mellitus, perhaps the bestknown endocrine disorder Is caused by a deficiency of insulin or a decreased response to insulin in target tissues Is marked by elevated blood glucose levels AP Biology 2005-2006 Types of Diabetes Type I diabetes mellitus (insulin-dependent diabetes) Is an autoimmune disorder in which the immune system destroys the beta cells of the pancreas Type II diabetes mellitus (non-insulindependent diabetes) Is characterized either by a deficiency of insulin or, more commonly, by reduced responsiveness of target cells due to some change in insulin receptors AP Biology 2005-2006 Adrenal Hormones: Response to Stress The adrenal glands Are adjacent to the kidneys Are actually made up of two glands: the adrenal medulla and the adrenal cortex AP Biology 2005-2006 Adrenal Hormones: Response to Stress The adrenal medulla secretes epinephrine and norepinephrine AP Biology Hormones which are members of a class of compounds called catecholamines 2005-2006 Adrenal Hormones: Response to Stress These hormones Are secreted in response to stressactivated impulses from the nervous system Mediate various fight-or-flight responses AP Biology 2005-2006 Adrenal Hormones: Response to Stress Hormones from the adrenal cortex Also function in the body’s response to stress Fall into three classes of steroid hormones AP Biology 2005-2006 Adrenal Hormones: Response to Stress Glucocorticoids, such as cortisol Influence glucose metabolism and the immune system Mineralocorticoids, such as aldosterone Affect salt and water balance Sex hormones AP Biology Are produced in small amounts 2005-2006 Stress and the adrenal gland Stress Spinal cord (cross section) Nerve signals Hypothalamus Releasing hormone Nerve cell Anterior pituitary Blood vessel Adrenal medulla secretes epinephrine and norepinephrine. Nerve cell Adrenal cortex secretes mineralocorticoids and glucocorticoids. ACTH Adrenal gland Kidney (a) Short-term stress response Effects of epinephrine and norepinephrine: 1. Glycogen broken down to glucose; increased blood glucose 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate Figure 45.13a,b AP Biology 5. Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity (b) Long-term stress response Effects of mineralocorticoids: 1. Retention of sodium ions and water by kidneys 2. Increased blood volume and blood pressure Effects of glucocorticoids: 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose 2. Immune system may be suppressed 2005-2006 Endocrine System Control Blood Osmolarity Feedback ADH increased water reabsorption pituitary increase thirst nephron high blood osmolarity blood pressure adrenal gland low increased water & salt reabsorption nephron renin aldosterone AP Biology angiotensinogen angiotensin 2005-2006 Homology in hormones What does this tell you about these hormones? same gene family prolactin mammals milk production AP Biology birds fat metabolism fish amphibians salt & water balance metamorphosis & maturation growth hormone growth & development Regulating metabolism Hypothalamus TRH = TSH-releasing hormone Anterior Pituitary TSH = thyroid stimulating hormone Thyroid produces thyroxine hormones metabolism & development AP Biology bone growth mental development metabolic use of energy blood pressure & heart rate muscle tone digestion reproduction tyrosine iodine thyroxine Goiter Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine AP Biology Regulating blood calcium levels Thyroid Low blood Ca++ – Negative feedback Increased absorption of Ca++ from intestine due to PTH activation of Vitamin D AP Biology Parathyroids Parathyroid hormone (PTH) Reabsorption of Ca++ & excretion of PO4 Increased blood Ca++ Osteoclasts dissolve CaPO4 crystals in bone, releasing Ca++ Feedback Female reproductive cycle egg matures & is released (ovulation) estrogen builds up uterus lining corpus luteum ovary progesterone FSH & LH maintains uterus lining fertilized egg (zygote) HCG yes pituitary gland pregnancy GnRH AP Biology hypothalamus no corpus luteum breaks down progesterone drops menstruation corpus luteum progesterone maintains 2005-2006 uterus lining