The Endocrine System Human Physiology

Endocrine Functions: Hormones Come from endocrine glands Circulate in the blood stream Act on specific cells in the body

Endocrine System Characteristics Access to every cell Each hormone acts only on specific cells (target cells) Only specific cells have receptors for specific hormones Endocrine control slower than nervous system Endocrine and nervous systems interact

Steroid Hormone Action on a Target Cell Figure 13.2

Classification of Hormones: Steroid Steroid Hormones: Lipid soluble, chemically derived from cholesterol Enter target cells Activate specific genes to produce specific proteins Slower acting than nonsteroid hormones, minutes to hours

Nonsteroid Hormone Action on a Target Cell Figure 13.3

Classification of Hormones: Nonsteroid Nonsteroid hormones: Water soluble Bind to receptors on target cell membranes Work through intermediate mechanisms to activate existing enzymes Faster action than steroid hormones, seconds to minutes

Example of a Negative Feedback Loop: Homeostasis

Location of Major Endrocrine Organs Figure 9.3 Slide 9.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Hormones of the Pituitary Gland Table 13.1

Hypothalamus and the Anterior Pituitary Gland Figure 13.7

Hypothalamus and the Anterior Pituitary Gland Connection to hypothalamus: releasing and inhibiting hormones from hypothalamus travel to pituitary through pituitary portal system Hormones ACTH: stimulates adrenal cortex TSH: acts on thyroid gland FSH, LH, Prolactin: related to control of reproductive cycles and lactation Growth Hormone: widespread effects on body

Hypothalamus and the Posterior Pituitary Gland Connection to hypothalamus: hormones made in hypothalamus, stored in posterior pituitary Hormones: nonsteroidal Antidiuretic hormone (ADH): conserves water in kidneys, regulates water balance in body Oxytocin: causes uterine contractions during labor and milk ejection through neuroendocrine reflex

Pituitary Disorders Gigantism: hypersecretion of growth hormone Pituitary Dwarfism: hyposecretion of growth hormone

Pituitary Gigantism

Pancreas: Endocrine Functions Structures: islets of Langerhans Hormones: nonsteroidal Glucagon: made by alpha cells, raises blood sugar Insulin: made by beta cells, lowers blood sugar

Location of Major Endrocrine Organs Figure 9.3 Slide 9.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Roles of Insulin and Glucagon in Regulating Blood Glucose Figure 13.9

Location of Major Endrocrine Organs Figure 9.3 Slide 9.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Adrenal Glands: Cortex Adrenal cortex Secretion: mediated through hypothalamus-pituitary secretions Hormones: steroidal Glucocorticoids: cortisol – blood glucose regulation Mineralocorticoids: aldosterone – sodium/fluid/urine

Secretion of Cortisol Figure 13.10

Adrenal Glands: Medulla Adrenal medulla: neuroendocrine organ Secretion: sympathetic nervous system Hormones: nonsteroidal Epinephrine and Norepinephrine: enhance function of sympathetic nervous system (Fight or flight)

Roles of the Hypothalamus and Adrenal Glands in the Stress Response Figure 9.12 Slide 9.31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Thyroid Gland Secretion: mediated through hypothalamus-pituitary secretions Steroidal hormones: Thyroxine (T4) and Triiodothyronine (T3): both regulate production of ATP from glucose, affects metabolic rate Calcitonin: lowers blood calcium levels

Negative Feedback Control of Thyroxine Secretion Figure 13.13

Homeostatic Regulation of Blood Calcium Concentration Figure 13.15A

Homeostatic Regulation of Blood Calcium Concentration (cont.) Figure 13.15B

Parathyroid Glands Secretion: response to lowered blood calcium levels Hormone: Parathyroid hormone (PTH), nonsteroidal Removes calcium and phosphate from bone Increases absorption of calcium by the digestive tract Increases renal retention of calcium and excretion of phosphate

Location of Major Endrocrine Organs Figure 9.3 Slide 9.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Testes Hormone: testosterone (steroidal) Functions: Regulates development and normal functioning of sperm, male reproductive organs, male sex drive Development of male secondary sex characteristics

Ovaries Hormones (steroidal) and functions: Estrogen: initiates development of secondary sex characteristics, regulates menstrual cycle Progesterone: regulates menstrual cycle

Ovarian Cycle Figure 16.6

Disorders of the Endocrine System Thyroid Hypothyroidism: Children: cretinism Adults: myxedema Hyperthyroidism: Graves Disease Adrenal glands Addison’s Disease: failure of adrenal cortex, cortisol deficiency Cushing’s Syndrome: excessive cortisol

Grave’s Disease – overactive thyroid