Biology, 9th ed, Sylvia Mader Chapter 42 Chapter 42 Hormones & the Endocrine System Hormones & the Endocrine System

The Human Endocrine System

Chemical Signals Pheromones Hormones Chemical signals that work at a distance between individuals A woman’s axillary extract can alter another woman’s menstrual cycle Hormones Chemical signals that work At a distance between organs, or Locally between adjacent cells

Target Cell Concept

Action of Hormones Hormones Chemical signals produced by one cell that regulate the metabolism of other cells Steroid Hormones Can cross cell membranes Peptide Hormones Most bind to receptor in plasma membrane First Messenger Causes internal release of cAMP Second Messenger

Peptide Hormone

Steroid Hormone

Human Endocrine System Endocrine glands Ductless glands that secrete hormones directly into the bloodstream Most endocrine hormones are peptides Only gonads and adrenal cortex produce steroid hormones Effects of hormones are moderated in two ways Negative feedback opposes release Antagonistic hormones oppose each other’s actions

Hypothalamus and Pituitary Gland Hypothalamus regulates internal environment Acts through autonomic system Also controls glandular secretions of pituitary gland Posterior Pituitary Antidiuretic Hormone (ADH) Controlled by negative feedback Oxytocin Controlled by positive feedback Anterior Pituitary Hypothalamus controls by producing Hypothalamic-releasing hormones, and Hypothalamic-inhibiting hormones

Hypothalamus and the Pituitary

Anterior Pituitary Hormones Anterior pituitary hormones that affect other glands: Thyroid-Stimulating Hormone (TSH) Adrenocorticotropic Hormone (ACTH) Gonadotropic Hormones Anterior pituitary hormones that do NOT affect other glands Prolactin (PRL) Melanocyte-Stimulating Hormone (MSH) Growth Hormone (GH)

Effect of Growth Hormone

Acromegaly

Composed of large number of follicles filled with Thyroid Glands Composed of large number of follicles filled with Triiodothyronine (T3), and Thyroxine (T4) Thyroid hormones increase metabolic rate Thyroid-induced abnormalities Simple goiter - Poor hormone production Cretinism - Poor thyroid development Myxedema - Hypothyroidism Exophthalmic goiter - Hyperthyroidism

Simple Goiter

Cretinism

Regulates blood calcium level (in part) Calcitonin Regulates blood calcium level (in part) Secreted by thyroid gland when blood calcium level rises Brings about deposit of calcium in the bones Low calcium level in blood stimulates the release of parathyroid hormone (PTH) Parathyroid hormone causes Phosphate level in blood to decrease, and Calcium level in blood to increase Insufficient production of parathyroid hormone leads to tetany

Regulation of Blood Calcium Level

Paired – One sits atop each kidney (ad-renal) Adrenal Glands Paired – One sits atop each kidney (ad-renal) Each consists of outer cortex and inner medulla Inner portion, the adrenal medulla Produces Epinephrine, and Norepinephrine Short-term response to stress (fight or flight) Outer portion, adrenal cortex Mineralocorticoids, and Glucocorticoids Long-term response to stress

Adrenal Glands

Glucocorticoids Cortisol Raises blood glucose level Promotes breakdown of muscle proteins to amino acids Promotes metabolism of fatty acids Counteracts inflammatory response

Atrial natriuretic hormone (ANH) is antagonistic to aldosterone Mineralocorticoids Aldosterone Promotes two renal functions: Absorption of sodium, and Excretion of potassium Renin-angiotensin-aldosterone system Raises blood pressure Angiotensin II constricts arterioles Aldosterone causes kidneys to reabsorb sodium (causing water retention) Atrial natriuretic hormone (ANH) is antagonistic to aldosterone

Regulation of Blood Pressure and Volume

Addison Disease

Cushing Syndrome

Made up up exocrine and endocrine tissue Pancreas Made up up exocrine and endocrine tissue Endocrine Portion of the Pancreas: Consists of pancreatic islets Produce and secrete Insulin Secreted during high blood glucose level Stimulates uptake of glucose by cells Glucagon Secreted during low blood glucose level Stimulates liver to break down glycogen Exocrine Portion of the Pancreas: Secretes enzymes and buffers into intestine

Regulation of Blood Glucose Level

Other Endocrine Glands Gonads Testes Produce testosterone Secondary sex characteristics Ovaries Produce estrogen and progesterone Reproduction

The Effects of Anabolic Steroid Use

Other Endocrine Glands Pineal Gland Produces melatonin Involved in Circadian rhythms Thymus Gland Secrete thymosins Aid in differentiation of lymphocytes Prostaglandins Produced within cells Not distributed in blood

Melatonin Production