Chapter 10 Endocrine System Endocrine glands are ductless releases hormones hormones released to target organs Exocrine glands have ducts 10-1

Chemistry of Hormones Steroid Hormones Nonsteroid Hormones derived from cholesterol sex hormones adrenal cortex hormones Nonsteroid Hormones amines proteins peptides glycoproteins most hormones 10-2

Actions of Steroid Hormones hormone crosses membranes hormone combines with receptor in nucleus synthesis of mRNA activated mRNA enters cytoplasm to direct synthesis of protein 10-3

Actions of Nonsteroid Hormones hormone binds to receptor on cell membrane adenylate cyclase activated ATP converted to cAMP cAMP promotes a series of reactions leading to cellular changes second messenger 10-4

Control of Hormonal Secretions primarily controlled by negative feedback mechanism 10-5

Negative Feedback 10-6

Major Endocrine Glands 10-7

Pituitary Gland Two distinct portions anterior pituitary (adenohypophysis) posterior pituitary (neurohypophysis) 10-8

Pituitary Gland Control Hypothalamic releasing hormones stimulate cells of anterior pituitary to release hormones Nerve impulses from hypothalamus stimulate nerve endings in the posterior pituitary gland to release hormones 10-9

Hypothalamic Hormones 10-10

Anterior Pituitary Hormones Growth Hormone (GH) stimulates increase in size and rate of body cells enhances movement of amino acids through membranes promotes growth of long bones secretion stimulated by growth hormone-releasing hormone slows carbohydrate catabolism; increases blood glucose levels Prolactin (PRL) sustains milk production after birth secretion inhibited by prolactin release-inhibiting hormone 10-11

Anterior Pituitary Hormones Thyroid Stimulating Hormone (TSH) controls secretions of hormones from the thyroid gland controlled by thyrotropin-releasing hormone Adrenocorticotropic Hormone controls secretions of some hormones of adrenal cortex controlled by corticotropin-releasing hormone 10-12

Anterior Pituitary Hormones Follicle-Stimulating Hormone (FSH) stimulates development of egg-containing follicles in ovaries stimulates follicular cells to secrete estrogen stimulates production of sperm cells controlled by gonadotropin-releasing hormone Luteinizing Hormone (LH) promotes secretions of sex hormones stimulates release of egg from ovary (ovulation) stimulates corpus luteum to produce progesterone controlled by gonadotropin-releasing hormone 10-13

Posterior Pituitary Hormones Antidiuretic Hormone (ADH) causes kidneys to reduce water excretion in high concentration, raises blood pressure controlled by hypothalamus in response to changes in blood water concentration and blood volume Oxytocin (OT) stimulates uterine contractions stimulates mammary glands to release milk controlled by hypothalamus in response to stretch in uterine and vaginal walls and stimulation of breasts 10-14

Thyroid Gland 10-15

Thyroid Gland Hormones Thyroxine (T4) and Triiodothyronine (T3) increases rate of energy release from carbohydrates accelerates growth stimulates activity in the nervous system controlled by TSH Calcitonin lowers blood calcium concentrations by inhibiting release of calcium from bones increases rate at which calcium isdeposited in bones 10-16

Thyroid Gland Disorders General Hyperthyroidism high metabolic rate hyperactivity weight loss protruding eyes Simple Goiter deficiency of iodine leads to deficiency of thyroid hormones gland enlarges 10-17

Parathyroid Glands 10-18

Parathyroid Hormone PTH increases blood calcium levels stimulates bone resorption by osteoclasts inhibits osteoblasts stimulates kidneys to retain calcium promotes calcium absorption into intestine 10-19

Adrenal Glands 10-20

Adrenal Cortex Hormones Aldosterone increases blood volume and pressure by promoting conservation of sodium ions and water 10-21

Adrenal Cortex Hormones Cortisol decreases protein synthesis increases fatty acid release stimulates glucose synthesis from noncarbohydrates controlled by CRH from hypothalamus and ACTH from anterior pituitary maintain normal blood pressure anti-inflammatory effect released during long term stress 10-22

Adrenal Medulla Hormones Epinephrine and Norepinephrine release controlled by sympathetic nervous system increases heart rate and blood pressure dilates respiratory airways promotes breakdown of glycogen increases metabolic rates 10-23

Adrenal Cortex Hormones Adrenal androgens supplement sex hormones from the gonads may be converted to estrogen female sexual drive 10-24

Pancreas 10-25

Pancreatic Hormones Glucagon secreted by alpha cells of pancreatic islets stimulates liver to break down glycogen stimulates liver to convert noncarbohydrates into glucose controlled by blood glucose concentrations Insulin secreted by beta cells of pancreatic islets promotes formation of glycogen from glucose enhances movement of glucose into adipose and muscle cells decreases blood glucose concentrations controlled by blood glucose concentrations 10-26

Other Endocrine Glands Reproductive Glands ovaries secrete estrogen and progesterone testes secrete testosterone placenta secretes estrogen, progesterone, and gonadotropins 10-28

Other Endocrine Glands Pineal Gland secretes melatonin regulates sleep/wake cycles may control onset of puberty helps regulate female reproductive cycle Thymus Gland secretes thymosins promotes development of certain lymphocytes 10-28

Clinical Application Growth Hormone Ups and Downs Gigantism - hypersecretion of GH in children Acromegaly – hypersecretion of GH in adults Dwarfism – hyposecretion of GH in children 10-29

Clinical Application Diabetes Mellitus 3 Cardinal signs polyuria polyphagia polydipsia 10-30