Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 45 Hormones and the Endocrine System

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 45.1: The endocrine system and the nervous system act individually and together in regulating an animal’s physiology Animals have two systems of internal communication and regulation: the nervous system and the endocrine system The nervous system conveys high-speed electrical signals along specialized cells called neurons The endocrine system secretes hormones that coordinate slower but longer-acting responses

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overlap Between Endocrine and Nervous Regulation The endocrine and nervous systems function together in maintaining homeostasis, development, and reproduction Specialized nerve cells known as neurosecretory cells release neurohormones into the blood Both endocrine hormones and neurohormones function as long-distance regulators of many physiological processes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Control Pathways and Feedback Loops There are three types of hormonal control pathways: simple endocrine, simple neurohormone, and simple neuroendocrine A common feature is a feedback loop connecting the response to the initial stimulus Negative feedback regulates many hormonal pathways involved in homeostasis

LE 45-2a Target effectors Response Simple endocrine pathway Glycogen breakdown, glucose release into blood Liver Blood vessel Pancreas secretes glucagon ( ) Endocrine cell Low blood glucose Receptor protein Stimulus Pathway Example

LE 45-2b Target effectors Response Simple neurohormone pathway Stimulus Pathway Example Suckling Milk release Smooth muscle in breast Neurosecretory cell Blood vessel Posterior pituitary secretes oxytocin ( ) Hypothalamus/ posterior pituitary Sensory neuron

LE 45-2c Target effectors Response Simple neuroendocrine pathway Stimulus Pathway Example Milk production Blood vessel Hypothalamus Sensory neuron Mammary glands Endocrine cell Blood vessel Anterior pituitary secretes prolactin ( ) Hypothalamus secretes prolactin- releasing hormone ( ) Neurosecretory cell Hypothalamic neurohormone released in response to neural and hormonal signals

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 45.2: Hormones and other chemical signals bind to target cell receptors, initiating pathways that culminate in specific cell responses Hormones convey information via the bloodstream to target cells throughout the body Three major classes of molecules function as hormones in vertebrates: – Proteins and peptides – Amines derived from amino acids – Steroids

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Signaling by any of these hormones involves three key events: – Reception – Signal transduction – Response

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell-Surface Receptors for Water-Soluble Hormones The receptors for most water-soluble hormones are embedded in the plasma membrane, projecting outward from the cell surface Animation: Water-Soluble Hormone Animation: Water-Soluble Hormone

LE 45-3 SECRETORY CELL Hormone molecule Signal receptor VIA BLOOD VIA BLOOD TARGET CELL TARGET CELL Signal transduction pathway OR Cytoplasmic response DNA NUCLEUS Nuclear response Receptor in plasma membraneReceptor in cell nucleus DNA NUCLEUS mRNA Synthesis of specific proteins Signal transduction and response Signal receptor Hormone molecule SECRETORY CELL

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm or a change in gene expression The same hormone may have different effects on target cells that have – Different receptors for the hormone – Different signal transduction pathways – Different proteins for carrying out the response

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The hormone epinephrine has multiple effects in mediating the body’s response to short-term stress

LE 45-4 Different receptors different cell responses Epinephrine  receptor Epinephrine  receptor Epinephrine  receptor Vessel constricts Vessel dilates Intestinal blood vessel Skeletal muscle blood vessel Liver cell Different intracellular proteins different cell responses Glycogen deposits Glycogen breaks down and glucose is released from cell

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Intracellular Receptors for Lipid-Soluble Hormones Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes Animation: Lipid-Soluble Hormone Animation: Lipid-Soluble Hormone

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Paracrine Signaling by Local Regulators In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells Types of local regulators: – Neurotransmitters – Cytokines and growth factors – Nitric oxide – Prostaglandins

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prostaglandins help regulate aggregation of platelets, an early step in formation of blood clots

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The hypothalamus and the pituitary gland control much of the endocrine system Concept 45.3: The hypothalamus and pituitary integrate many functions of the vertebrate endocrine system

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

LE 45-6 Testis (male) Ovary (female) Adrenal glands Pancreas Parathyroid glands Thyroid gland Pituitary gland Pineal gland Hypothalamus

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Relation Between the Hypothalamus and Pituitary Gland The hypothalamus, a region of the lower brain, contains neurosecretory cells The posterior pituitary, or neurohypophysis, is an extension of the hypothalamus Hormonal secretions from neurosecretory cells are stored in or regulate the pituitary gland

LE 45-7 Mammary glands, uterine muscles Hypothalamus Kidney tubules Oxytocin HORMONE TARGET ADH Posterior pituitary Neurosecretory cells of the hypothalamus Axon Anterior pituitary

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Other hypothalamic cells produce tropic hormones, hormones that regulate endocrine organs Tropic hormones are secreted into the blood and transported to the anterior pituitary, or adenohypophysis The tropic hormones of the hypothalamus control release of hormones from the anterior pituitary

LE 45-8 Neurosecretory cells of the hypothalamus Endocrine cells of the anterior pituitary Portal vessels Pituitary hormones (blue dots) Pain receptors in the brain EndorphinGrowth hormone Bones Liver MSH Melanocytes Prolactin Mammary glands ACTH Adrenal cortex TSH Thyroid Testes or ovaries FSH and LH TARGET HORMONE Hypothalamic releasing hormones (red dots) 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 Nontropic and Tropic Effects Growth hormone

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Posterior Pituitary Hormones The two hormones released from the posterior pituitary act directly on nonendocrine tissues Oxytocin induces uterine contractions and milk ejection Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Anterior Pituitary Hormones The anterior pituitary produces both tropic and nontropic hormones

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tropic Hormones The four strictly tropic hormones are – Follicle-stimulating hormone (FSH) – Luteinizing hormone (LH) – Thyroid-stimulating hormone (TSH) – Adrenocorticotropic hormone (ACTH) Each tropic hormone acts on its target endocrine tissue to stimulate release of hormone(s) with direct metabolic or developmental effects

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nontropic Hormones Nontropic hormones produced by the anterior pituitary: – Prolactin – Melanocyte-stimulating hormone (MSH) –  -endorphin

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prolactin stimulates lactation in mammals but has diverse effects in different vertebrates MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals Endorphins inhibit pain

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Growth Hormone Growth hormone (GH) has tropic and nontropic actions It promotes growth directly and has diverse metabolic effects It stimulates production of growth factors