ENDOCRINE SYSTEM Chapter 16

ENDOCRINE GLANDS Ductless glands that produce hormones that are released directly into the bloodstream and are transported throughout the body to regulate the metabolic function of other cells in the body. Types of hormones: Paracrine Autocrine

Chemical Nature of Hormones Amino-acid based hormones Amines=simple hormones derived from tyrosine (example: Epinephrine) Protein and peptides=chains of amino acids hooked together (example: ADH or Oxytocin) Steroid-based hormones Progesterone Testosterone Eicosanoids Hormone-like substances that act only on cells in the immediate vicinity (example: prostaglandin)

Functions of Hormones Integrative Homeostatic Growth

Mechanisms of Hormone Action Lipid-soluble hormones Diffusion occurs Binds to intracellular receptors Forms hormone-receptor complexes Hormone-receptor complex binds to specific receptor proteins on DNA Initiates transcription of certain genes

Mechanisms of Hormone Action Cyclic AMP signaling Hormone binds to cell membrane receptor Hormone-receptor complex binds to inactive G protein G protein becomes active by GTP to GDP G protein binds adenylate cyclase producing Cyclic AMP Cyclic AMP activates protein kinase enzymes

Mechanisms of Hormone Action PIP-calcium signaling Hormone binds to cell membrane receptor Hormone-receptor complex binds to inactive G protein G protein becomes active and binds to phospholipase Phospholipase splits to form IP3 and DAG which activate protein kinases and calcium

Control of Hormones Feedback Mechanisms Responsiveness to target cells Negative feedback Positive feedback Responsiveness to target cells Concentrations of hormones Number of receptors Interaction of other hormones

Control of Hormones

Major Endocrine Glands Pituitary Gland Thyroid Gland Parathyroid Gland Adrenal Gland Thymus Gland Pineal Gland Other endocrine tissue

Pituitary Gland (Hypophysis) Posterior lobe Oxytocin ADH Anterior lobe GH TSH ACTH FSH LH PRL MSH

Thyroid Gland Follicles and follicle cells Thyroglobulin Colloid Thyroxine (T4) Triiodothyronine (T3) Calorigenic effect Calcitonin produced by parafollicular cells

Parathyroid Gland Produces parathyroid hormone (PTH) Regulates calcium levels by targeting: Bones Intestine Kidneys

Adrenal Gland Adrenal Cortex Zona glomerulosa produces mineralcorticoids Zona fasciculate produces glucocorticoids Zona reticularis produces androgens or adrenal sex hormones

Adrenal Gland (continued) Adrenal Medulla Chromaffin cells Epinephrine Norepinephrine Associated with stress or “Fight or Flight” responses

Thymus and Pineal Gland Thymus Gland Thymosin stimulates T-cell maturation Immune system Pineal Gland Pinealocytes Melatonin

Pancreas Alpha Cells Beta Cells Delta Cells Acinar Cells Produce glucagon Glycogen>>Glugacon>>Glucose Beta Cells Produce insulin Enhances uptake of glucose by cells as well as inhibits glycogenolysis and gluconeogenesis Delta Cells Somatostatin Acinar Cells Produces pancreatic enzymes but are exocrine

Pancreas (continued)

Other Endocrine Tissues Ovaries=produce estrogen and progesterone Testes=produce testosterone and inhibin Placenta=produces HCG Heart=secretes ANP Kidneys=secrete erythropoietin Skin=produces choleocalciferol Adipose tissue=releases leptin Gastrointestinal tract=releases gastrin, secretin, serotonin, cholecystokinin and others

Homeostatic Imbalances Gigantism Acromegaly Progeria Pituitary dwarfism Galactorrhea Gynecomastia Myxedema Goiter Cretinism Grave’s disease Hyperparathyroidism Hypoparathyroidism Diabetes insipidus Diabetes mellitus Aldosteronism Addison’s disease Cushing’s disease Masculinization

Thyroid Gland (continued)

Thyroid Gland (continued)

Cushing’s Disease

Cushing’ Disease

Acromegaly

Gigantism and Pituitary Dwarfism

Addison’s Disease