Physiology G Endocrine

2/28/18

Introduction

• Endocrine system works with nervous system to coordinate body functions - Nervous system uses impulses and Endocrine System neurotransmitters - Endocrine system uses hormones • Many cells have receptors for both Chapter 24 neurotransmitters and hormones and can be regulated by both chemicals

Comparing Endocrine and Introduction Nervous System Functions

• Exocrine glands: Secrete products into ducts that open into body cavities - Sudoriferous: Secrete sweat - Sebaceous: Secrete oil - Ceruminous: Secrete ear wax • Endocrine glands - Secrete hormones directly into bloodstream - Ductless glands

Major Endocrine Glands Anatomy

• Hypothalamus • Pituitary • Pineal • Thyroid • Parathyroids • Adrenals • Pancreatic islets • Ovaries • Testes • Hormones

From Koeppen BM: Berne & Levy Physiology, Updated Edition, ed 6, St. Louis, 2010, Mosby.

1 2/28/18

Physiology Hormones and Regulation

• Hormone production and secretion • Chemical messengers that regulate the • Regulation of metabolism physiologic activity of other cells • Stress adaptation • Have potential to come in contact with every • Chemical composition and fluid volume cell type regulation - Target cells are chemically compatible with • Reproductive process regulation corresponding hormone(s) - Lock together with receptor sites

Hormonal Control Mechanisms Negative Feedback Regulation

• Types are: • Movement reverses deviations from - Negative feedback regulation homeostasis - Hormonal regulation • Glands respond to information - Neural regulation - Secrete more or less hormone • Positive feedback systems also regulate hormones

Hormonal Regulation Neural Regulation

• Hormone from one endocrine gland binds to • Neural impulses stimulate release of receptor sites on another endocrine gland hormones • Tropic hormones stimulate other endocrine • Epinephrine and norepinephrine maintain glands fight-or-flight response - Most are secreted by anterior pituitary • These systems have a faster response than other regulation systems

2 2/28/18

Hypothalamus Hypothalamic Hormones

• Regulates the autonomic nervous system and • Stimulatory controls many behaviors - Thyrotropin-releasing hormone, gonadotropin- • Links nervous system to endocrine system releasing hormone, growth hormone-releasing through pituitary gland hormone, prolactin-releasing hormone, and corticotropin-releasing hormone • Stimulates or inhibits pituitary hormones • Inhibitory - Growth hormone-inhibiting hormone - Prolactin-inhibiting hormone

Pituitary Pituitary Hormones

• Lies in sella turcica of sphenoid bone • Consists of: - Anterior lobe: Constitutes 75% of entire gland - Posterior lobe: Regulated by the nervous system

Anterior Pituitary Hormones Anterior Pituitary Hormones

• Adrenocorticotropic hormone (ACTH) • Luteinizing hormone (LH) - Stimulates hormones of adrenal cortex, especially - Women: Stimulates estrogens and progesterone, cortisol ovulation, and corpus luteum development • Growth hormone (GH) - Men: Stimulates testosterone production - Stimulates protein synthesis for muscle and bone growth maintenance, repair, and metabolism • Prolactin (PRL) - Promotes milk production in the breasts • Thyroid-stimulating hormone (TSH) - Stimulates secretion of thyroid hormones • Melanocyte-stimulating hormone (MSH) • Follicle-stimulating hormone (FSH) - Increases skin pigmentation - Women: Stimulates estrogen production and development of ovarian follicle - Men: Stimulates sperm production in the testes

3 2/28/18

Posterior Pituitary Hormones Pineal Gland

• Antidiuretic hormone (ADH) • Located posterior aspect of the diencephalon - Decreases urine production • Pine nut-shaped - Raises blood pressure by vasoconstriction • Chief hormone secreted is melatonin • Oxytocin (OT) - Controls biorhythms - Stimulates uterine contraction - Levels remain elevated for 12 hours - Stimulates milk expression

Thyroid Thyroid Hormones

• Located below the larynx and around the • Triiodothyronine (T3) and thyroxine (T4) front and sides of the trachea - Collectively called thyroid hormones (TH) • Contains two lobes connected at center by - Regulates metabolism the isthmus - Affect growth and development - Cannot be made without iodine - Occasionally, a third lobe will arise

Thyroid Hormones Thyroid and Parathyroid Glands

• Calcitonin (CT) - Decreases blood calcium levels (hypocalcemic) by stimulating osteoblast activity - Decreases with advancing age

From Christensen BL: Adult Health Nursing, ed 6, St. Louis, 2010, Mosby.

4 2/28/18

Parathyroid Adrenals

• Located on posterolateral surface of thyroid • Cortex is outer region lobes - Produces three steroid hormones: • Mineralocorticoids • Usually four in number • Glucocorticoids • Parathyroid hormone (PTH) • Sex hormones (adrenal estrogens and adrenal - Increases blood calcium levels (hypercalcemic) by androgens) stimulating osteoclastic activity • Medulla is the inner region - Increases calcium absorption in intestines - Produces epinephrine and norepinephrine

Adrenal Cortex and Adrenal Glands Adrenal Medulla Hormones

• Cortisol (Hydrocortisone) - Influences the metabolism of food molecules, such as carbohydrates, proteins, and fats - Has antiinflammatory effect in large amounts • Aldosterone maintains sodium levels in the blood • Epinephrine or adrenaline and norepinephrine or noradrenaline bind to receptors of sympathetic effectors

Pancreatic Islets Pancreatic Hormones

• Also called islets of Langerhans • Insulin • Contains: - Decreases blood glucose levels by moving - Alpha cells: Secrete glucagon glucose into cells - Beta cells: Secrete insulin - Secreted by pancreatic beta cells - Delta cells: Secrete somatostatin and pancreatic - Cannot be given orally polypeptides

5 2/28/18

Regulation of Blood Pancreatic Hormones Glucose by Pancreas

• Glucagon - Increases blood glucose levels by moving stored glucose to the blood - Secreted by pancreatic alpha cells

From Goodman CC: Pathology for the Physical Therapy Assistant, ed 1, St. Louis, 2011, Saunders.

Ovaries Ovarian Hormones

• Located in female abdominopelvic area • Estrogens • Secrete estrogens and progesterone - Responsible for secondary sex characteristics in • Regulate menstrual cycle and secondary sex females characteristics - Promote the proper sequence of events of the menstrual cycle • Other hormones are relaxin and inhibin • Progesterone - Maintains uterine lining for implantation and gestation - Slightly elevates temperature for incubating effect

Testes Testicular Hormones

• Located in male scrotum • Testosterone • Contains interstitial cells of Leydig - Stimulates sperm production - Produce androgens - Responsible for secondary sex characteristics in • Principal androgen is testosterone males - Involved in increasing libido

6 2/28/18

Organs That Possess Endocrine Cells Thymus: Hormones

• Kidneys • Thymosin and thymopoietin • Hormones - Stimulates T-cell maturation - Erythropoietin - Involved in immune responses • Secreted when blood oxygen levels decline • Stimulates production of additional red blood cells in bone marrow - Renin • Secreted when blood pressure in kidneys drops below a certain level • Stimulates a negative feedback system called the renin- angiotensin-aldosterone system, which increases blood pressure

Gastric and Intestinal Placenta: Hormones Mucosa: Hormones

• Human chorionic gonadotropin (HCG) • Gastrin - Pregnancy hormone, present in blood and urine of - Initiates secretion of bile, gastric juices, and pregnant women pancreatic enzymes - Stimulates ovaries to secrete estrogens and • Cholecystokinin progesterone - Stimulates gallbladder to release bile and - Decreases lymphocyte activity pancreas to secrete its enzymes • Relaxin • Secretin - Facilitates implantation by relaxing uterus - Stimulates pancreas to secrete alkaline liquid to - Softens connective tissue and dilates cervix for neutralize acidic chyme fetal delivery

Heart: Hormones Fat Cells: Hormones

• Atrial natriuretic hormone (ANH) • Leptin - Released when right atrium is overstretched - Regulates appetite and metabolism - Triggers urine production • Resistin • Decreases blood volume in attempt to reduce blood - Increases blood glucose levels by increasing pressure insulin resistance