The Endocrine System chemical messages hormones that are

The Endocrine System § chemical messages (hormones) that are released into the blood § Hormones control several major processes § Reproduction - gametogenesis, sexual desire § Growth and development § Maintenance of homeostasis - salts, water, blood pressure, RBCs § Regulation of metabolism - digestion, stress responses Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Endocrine System Characteristics § Access to every cell § Each hormone acts only on specific cells (target cells) that have matching receptors § Endocrine control slower than nervous system § Endocrine and nervous systems interact Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Classification of Hormones: Steroid § Steroid Hormones: § Lipid soluble, derived from cholesterol § Enter target cells § Activate specific genes to produce proteins § Slower acting: minutes to hours Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Steroid Hormones: How does a steroid hormone cause changes in cells? Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Hormones: Nonsteroid § Amino acid-based hormones proteins, peptides, amines § Water soluble § Bind to receptors on target cell surface § Work via second messengers to activate existing enzymes § Faster action: seconds to minutes Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Non-Steroid Hormones: How does a non-steroid hormone cause changes in cells? Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Control of Hormone Release § Hormone levels are maintained by negative feedback § Low hormone levels or a stimulus triggers the release of more hormone § Hormone release stops once an appropriate level in the blood is reached Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

1. Hormonal Stimulus § Endocrine glands are activated by other hormones § Most common signalcoordinates response of several glands Figure 9. 2 a Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

2. Humoral Stimulus § Changing blood levels of certain ions stimulate hormone release § PTH - to raise Ca++ § Calcitonin - to decrease Ca++ § Insulin - to decrease glucose Figure 9. 2 b Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

3. Neural Stimulus § Nerve impulses stimulate hormone release § Usually by sympathetic nervous system Figure 9. 2 c Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Location of Major Endocrine Organs Figure 9. 3 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Pituitary - Hypothalamus Relationship § Release of anterior pituitary hormones is controlled by hormones from hypothalamus § Hypothalamus produces two hormones that are stored in the posterior pituitary § posterior pituitary releases hormones when neurally stimulated by hypothalamus Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Hormones of the Posterior Pituitary § Oxytocin § Stimulates contractions of the uterus during labor § Causes milk ejection § Antidiuretic hormone (ADH) § Can inhibit urine production § In large amounts, causes vasoconstriction Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Hormones of the Anterior Pituitary §Six anterior pituitary hormones; common characteristics: §Proteins (or peptides) §Act through secondmessenger systems §Regulated by hormonal stimuli, mostly negative feedback Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Growth Hormone (GH) § General metabolic hormone § Major effects are directed to growth of skeletal muscles and long bones § Causes amino acids to be built into proteins § Causes fats to be broken down for a source of energy Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Functions of Other Anterior Pituitary Hormones § Prolactin (PRL) § Stimulates milk production following childbirth § Function in males is unknown § Adrenocorticotropic hormone (ACTH) § Regulates the adrenal cortex (affects salt, glucose levels) § Thyroid-stimulating hormone (TSH) § Influences thyroid gland Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Functions of Other Anterior Pituitary Hormones § Gonadotropic hormones - appear at puberty § Follicle-stimulating hormone (FSH) § Stimulates follicle development (ovaries) and sperm development (testes) § Luteinizing hormone (LH) § Triggers ovulation § Stimulates testosterone production in males Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Thyroid Gland § Found at the base of the throat § Produces two hormones § Thyroid hormone controls metabolism § Calcitonin - affects Ca++ levels in blood Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Calcitonin § Decreases blood calcium levels by causing calcium deposition in bone (in children) § Antagonistic to PTH, parathyroid hormone Figure 9. 9 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Adrenal Glands § Two glands § Cortex – outer glandular region in three layers § Medulla – inner neural tissue region § Sits on top of the kidneys Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Hormones of the Adrenal Cortex § Mineralocorticoids (mainly aldosterone) § Regulate mineral content in blood, water, and electrolyte balance via kidney action § Glucocorticoids (cortisone, cortisol) § Promote normal cell metabolism § Help resist long-term stressors § depress inflammatory response § Androgen, estrogen Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Hormones of the Adrenal Medulla § Produces two similar hormones (catecholamines) § Epinephrine § Norepinephrine § prepare the body to deal with short-term stress Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Roles of the Hypothalamus and Adrenal Glands in the Stress Response Figure 9. 12 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Pancreatic Islets §pancreas is a mixed gland §islet cells produce hormones: §Insulin – allows glucose to cross plasma membranes into cells §Glucagon – allows glucose to enter the blood §Somatostatin Figure 9. 13 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Diabetes § Diabetes mellitus - “sweet siphon” § Type I - lack of insulin § juvenile § Type II - resistant to effects of insulin § Adult onset Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Other Hormone Sources § Thymus: thymosin and thymopoietin, assist maturation of T lymphocytes § Pineal gland: melatonin § Heart: atrial natriuretic hormone (ANH) § Digestive system: gastrin, secretin, cholecystokinin § Kidney: erythropoietin, renin Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings