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Homeostasis Through Chemistry The Endocrine System Topic 6.6 Comparing NS & ES • Animals have two systems of internal communication and regulation • The nervous system • Response time: • Fast, quick • Signals: • electrical • Specialized cells: • neurons • The endocrine system • Response time: • slower, longer • Signals: • chemical • Specialized glands: • endocrine glands Figure 32.9 (a) Signaling by hormones (b) Signaling by neurons Stimulus Stimulus Endocrine cell Cell body of neuron Nerve impulse Hormone Axon Signal travels to a specific location. Signal travels everywhere. Blood vessel Nerve impulse Axons Response © 2014 Pearson Education, Inc. Response Hormones • Three major classes of molecules – Proteins and peptides – Amines derived from amino acids – Steroids Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Water-Soluble Hormones • Hydrophobic or hydrophilic? • Can hydrophilic molecules cross the plasma membrane? • Receptors: • Binding: • Effect: • Different receptors for the hormone • Different signal transduction pathways • Different proteins for carrying out the response SECRETORY CELL Hormone molecule VIA BLOOD Signal receptor TARGET CELL Signal transduction pathway OR Cytoplasmic response DNA Nuclear response NUCLEUS • The major human endocrine glands Hypothalamus Pineal gland Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pancreas Ovary (female) Testis (male) Figure 45.6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hypothalamus and pituitary gland Hypothalamus and pituitary gland • integrate and control many functions of the endocrine system • Hypothalamus: • region o/t brain • sexual dimorphism • estrogen receptor distribution in Neurosecretory males,females cells of the • result of neonatal steroid exposure hypothalamus • neurosecretory cells Posterior pituitary • some produce direct-acting hormones • stored & released in posterior pituitary • tropic hormone cells • “tropic?” • (see next slide) HORMONE TARGET Hypothalamus Axon Anterior pituitary ADH Oxytocin Kidney tubules Mammary glands, uterine muscles Hypothalamic tropic hormones • secreted into the blood and transported to the anterior pituitary Neurosecretory cells of the hypothalamus Tropic Effects Only FSH, follicle-stimulating hormone LH, luteinizing hormone TSH, thyroid-stimulating hormone ACTH, adrenocorticotropic hormone 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 FSH and LH Testes or ovaries Pituitary hormones (blue dots) ACTH Prolactin MSH Endorphin Adrenal cortex Mammary glands Melanocytes Pain receptors in the brain TSH Thyroid Endocrine cells of the anterior pituitary Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Growth hormone Liver Bones Endocrine IB Understandings • Insulin & Glucagon • ß and å cell respectively • control blood glucose concentration • Insulin: gets glucose in (into the cells) • Glucagon: if glucose is gone, signals liver to release glucose (into the blood) Diabetes Mellitus • Diabetes mellitus, perhaps the best-known 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 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Type I diabetes mellitus (insulin-dependent diabetes) – Is an autoimmune disorder – immune system destroys the beta cells of the pancreas – treated: insulin added to the blood • Type II diabetes mellitus (non-insulin-dependent diabetes) – either deficiency of insulin or, – more commonly, by reduced responsiveness of target cells due to some change in insulin receptors – treated: insulin and lifestyle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Control & effect of thyroid hormones • Two negative feedback loop ex.: • Effect of T3 & T4 • Stimulate metabolism • Influence development and maturation • Too much: Hyperthyroidism • Graves Disease Graves Disease 45.10 Melatonin • Secreted by pineal gland; regulates sleep cycle • Can reduce effects of Jet Lag (induces earlier sleep cycle) Leptin • Secreted by cells in adipose tissue • acts on hypothalamus: • inhibits appetite
