2019 Biology 2 Chapter 26 Hormones and the

• The major role of hormones is to coordinate activities in different parts of the body – Hormones regulate energy use, metabolism, and growth – Hormones and other chemicals also maintain homeostasis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

THE NATURE OF CHEMICAL REGULATION 26. 1 Chemical signals coordinate body functions • Endocrine glands and neurosecretory cells secrete hormones – Hormones are regulatory chemicals that are carried by the blood and cause specific changes in target cells • All hormone-secreting cells constitute the endocrine system – It works with the nervous system to regulate body activities Endocrine system Nervous system Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Regulation of body activities and functions

• Hormone from an endocrine cell Copyright © 2003 Pearson Education, Inc. publishing

• Hormone from a neurosecretory cell Specialized nerve cell that can secret a hormone Blood vessel NEUROSECRETORY CELL Hormone molecules Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Target cell

• Local regulators produce changes in cells – Neurotransmitters – Prostaglandins – Interleukins (cytokine), NO, growth factor Muscle cell or endocrine cell Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

26. 2 Hormones affect target cells by two main signaling mechanisms Hormone receptor -Plasma-membrane receptor -Intracellular receptor -The only cell with specific receptors can respond to a hormone The hormones that bind to plasma-membrane receptors are all made from amino acids -Amine hormone: modified amino acid -Peptide hormone -Protein hormone Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

(1) A hormone binds to a receptor protein in the plasma membrane (2) The receptor protein activates a signal-transduction pathway in the cell (3) A series of relay molecules transmits the signal to a protein that carries out the cell’s response Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Steroid hormones bind to intracellular receptors – The steroid-receptor complex binds to DNA, turning specific genes on or off Steroid hormones -sex hormone (testosterone, estrogen) -hormones synthesized in the adrenal cortex (glucocorticoid) The receptors for thyroid hormones are intracellular ones Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

THE VERTEBRATE ENDOCRINE SYSTEM 26. 3 Overview: The vertebrate endocrine system • The vertebrate endocrine system consists of more than a dozen glands – The glands secrete more than 50 hormones • Only the sex glands and the adrenal cortex secrete steroids – The remaining glands secrete nonsteroid hormones Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Table 26. 3, part 2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin

• Pineal gland -Secretion of melatonin -Melatonin is involved in biological rhythm -Amine hormone -The target is the hypothalamus • Thymus gland -Secretion of thymosin -Thymosin stimulates T-cell development -Peptide hormone Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

26. 4 The hypothalamus, closely tied to the pituitary, connects the nervous and endocrine • Thesystems hypothalamus is the master control center of the endocrine system – It regulates the anterior pituitary gland by secreting releasing hormones and inhibiting hormones Information on internal and external environment Brain Hypothalamus Posterior pituitary Bone Anterior pituitary Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Posterior pituitary – Composed of nervous tissue – Stores and secretes hormones made in the hypothalamus • Anterior pituitary – Composed of glandular tissue – It synthesizes its own hormones, several of which control the activity of other endocrine glands Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Information on internal or external environments Nervous system Hypothalamus Releasing or inhibiting hormones Anterior pituitary Stimulating hormones Other endocrine glands Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Homeostasis is maintained by negative-feedback mechanisms coupled with environmental cues Copyright ©

• Neurosecretory cells extending from the hypothalamus into the posterior pituitary – synthesize oxytocin and antidiuretic hormone (ADH) – transmit nerve signals that trigger oxytocin and ADH release from the posterior pituitary Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Releasing and inhibiting hormones secreted by the hypothalamus control the anterior pituitary • The brain and anterior pituitary also produce endorphins Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

HORMONES AND HOMEOSTASIS 26. 5 The thyroid regulates development and metabolism • The thyroid gland produces two amine hormones (derived from Tyr) – T 3 and T 4 (Triiodothyronine and thyroxine containing iodine) – These regulate development and metabolism – Thyroid hormones are important in bone and nerve cell development in mammals – Thyroid hormones help maintain normal blood pressure, heart rate, muscle tone, digestion, and reproductive functions – The hormones increase the rate of cellular metabolism and oxygen consumption – Hypothyroidism, hyperthyroidism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Thyroid imbalance can cause cretinism, metabolic disorders, and goiter Copyright © 2003

26. 6 Hormones from the thyroid and parathyroids maintain calcium homeostasis • Blood calcium level is regulated by a tightly balanced antagonism between – calcitonin from the thyroid – parathyroid hormone from the parathyroid glands Ca 2+ -Bone development -Transmission of nerve signals, muscle contraction -Blood clotting -Solute transport across the membrane Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Calcium homeostasis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

26. 7 Pancreatic hormones regulate blood glucose levels • Blood glucose levels are controlled by two antagonistic hormones secreted by the pancreas Insulin -Synthesized in the beta cells of the pancreatic islet cells -Decrease the glucose levels in blood promote the uptake of glucose from the blood by the liver and skeletal muscle cells promote the conversion of glucose to glycogen in liver and muscle cells increase the glucose metabolism (glycolysis, TCA cycle) Promote the synthesis of proteins and fats from glucose Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Glucagon -Synthesized in the alpha cells of the pancreatic islet cells -Increase the glucose levels in blood Insuline Glucagon : antagonism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Glucose homeostasis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

26. 8 Connection: Diabetes is a common endocrine disorder • Diabetes mellitus is a serious hormonal disease – Body cells are unable to absorb glucose from the blood • There are two types of diabetes Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Type I (insulin-dependent) diabetes – Autoimmune disease in which pancreatic beta cells are destroyed and thus not enough insulin is produced – Often develops before age 15 – Patient requires insulin supplement, often by injection Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Type II (non-insulin-dependent) diabetes – Body cells fail to respond to insulin (due to malfunction insulin receptors on the cells) – Accounts for 90% of diabetes cases in the United States – Associated with obesity – Often develops after age 40 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

26. 9 The adrenal glands mobilize responses to stress • Hormones from the adrenal glands make stress response • Adrenal medulla – Nervous signals from the hypothalamus stimulate secretion of epinephrine (adrenaline) and norepinephrine – These quickly trigger the fight or flight response Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Adrenal cortex – Chemical signals (ACTH) stimulate secretion of corticosteroids, including glucocorticoids and mineralocorticoids – Corticosteroids boost blood pressure and energy in response to long-term stress Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• How the adrenal glands control our responses to stress Copyright © 2003

26. 10 The gonads secrete sex hormones • The gonads (testis, ovary) secrete sex hormones – Secretion is controlled by the hypothalamus and the pituitary • The steroid hormones are found in both sexes but in different proportions – Estrogens: e. g. , estradiol – Progesterone – Androgens: e. g. , testosterone Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Estrogen and progesterone – maintain the female reproductive system – stimulate the development of female characteristics • Androgens, such as testosterone, trigger the development of male characteristics Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings