There are 8 major endocrine glands 1.Pituitary gland 2.Thyroid gland 3.Thymus 4.Pancreas 5.Gonads (testis/ovaries) 6.Adrenal gland 7.Parathyroid gland.

There are 8 major endocrine glands 1.Pituitary gland 2.Thyroid gland 3.Thymus 4.Pancreas 5.Gonads (testis/ovaries) 6.Adrenal gland 7.Parathyroid gland 8.Pineal gland Critical Thinking The nervous and endocrine systems are responsible for maintaining what? 2 a. Nervous system: acts through electrical impulses and neurotransmitters To cause muscle contraction and glandular secretion Effect: short duration, measured in seconds, localized b. Endocrine system: acts through chemical messengers (hormones) Hormones influence growth, development, and metabolic activities Action is measured in minutes, hours, or weeks and is more generalized 3 Comparison of the Endocrine and Nervous Systems Critical Thinking What is the difference in an exocrine gland and an endocrine gland? 4 Comparison of Exocrine and Endocrine Glands 1.Exocrine glands: have ducts that carry their secretory product to a surface Examples: sweat, sebaceous, and mammary glands and glands that secrete digestive enzymes 2.Endocrine glands: secrete hormones directly into the into blood which carries them throughout body, they have no ducts 5 Critical Thinking What are hormones made up of? 6 Characteristics of Hormones Chemical classification a.Proteins: make up most of the hormones in the body Difficult to administer orally Inactivated by acid and pepsin in stomach Must be given by injection (example: insulin) b.Steroids: make up sex hormones and hormones secreted by the adrenal cortex May be given orally 7 Characteristics of Hormones The specific cells that respond to a given hormone have receptor sites for that hormone Lock and key mechanism If a hormone fits the receptor site: there will be an effect If a hormone and a receptor site do not match: there is no reaction 8 Characteristics of Hormones Target tissue: a tissue (cells) that responds to a particular hormone because it has receptor sites for that hormone May be localized in a single gland or organ May be diffuse and scattered throughout body Many areas are affected 9 Endocrine Glands 10 The Pituitary Gland The Master Gland Small-size of a pea Connected to hypothalamus by a slender stalk: infundibulum Two regions a.Adenohypophysis: anterior portion b.Neurohypophysis: posterior portion 11 Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotrophic hormone (ATCH) Gonatrophic hormone Follicle stimulating hormone (FSH) Leutinizing hormone (LH) Prolactin hormone (PRH) 12 Hormones of the Anterior Lobe (Adenohypophysis) 1. Growth hormone (GH) Stimulates growth of bones, muscles, and other organs Influences height Too little GH in a child: pituitary dwarf of normal proportions but small stature Excess of GH in a child: individual becomes exceptionally tall After ossification is complete (bone length no longer possible) Excess GH in adult causes enlargement in the diameter of the bones: acromegaly bones of the hands and face become abnormally large 13 Hormones of the Anterior Lobe (Adenohypophysis) 2. Thyroid-stimulating hormone (TSH) Causes glandular cells of thyroid to secrete thyroid hormone Hypersecretion of TSH: thyroid gland enlarges and secretes too much thyroid hormone Hyposecretion of TSH: results in atrophy of thyroid gland and too little thyroid hormone HINT: this is not the same hormone that is produced by the thyroid gland! 14 Hormones of the Anterior Lobe (Adenohypophysis) 15 Thyroid Gland Vascular organ: located in neck Consists of two lobes: one on each side of trachea Thyroxine and Triiodothyronine Thyroid hormone consists of: Thyroxine: 95% Triiodothyronine: 5% Requires iodine for synthesis Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 16 Thyroid Gland Iodine and the Thyroid Gland Iodine is required for synthesis of thyroid hormone Iodine deficiency: thyroid cannot make sufficient hormone and the thyroid gland increases in size in an attempt to produce more thyroid hormone. Known as simple goiter or iodine deficiency goiter Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 17 Thyroid Gland Help to regulate the metabolism of carbohydrates, proteins, and lipids Increases rate at which cells release energy from carbohydrates Enhances protein synthesis Necessary for normal growth and development Stimulates nervous system Do not have a single target organ Affect most of the cells in the body Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 18 Hypothyroidism Deficiency of thyroid hormone a.Cretinism: in a child Mentally retarded dwarf with abnormal skeletal features Tx: thyroid hormone therapy b.Myxedema: in an adult Lethargy, weight gain, loss of hair, low metabolic rate Thyroid hormone therapy: usually alleviates symptoms 19 Hyperthyroidism Enlarged thyroid gland that produces too much hormone Symptoms: High metabolic rate, hyperactivity, insomnia, nervousness, irritability, chronic fatigue Exophthalmos: protruding eyes due to swelling in tissues behind the eyes Treatment: removal or destruction of a portion of the thyroid gland 20 Graves Disease Thyroid Gland Calcitonin Secreted by thyroid gland Reduces the calcium level in the blood by: Reducing rate at which calcium is released from bone Increasing rate of calcium excretion by kidneys Reducing calcium absorption in intestines Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 21 Parathyroid Glands 22 1.Four small masses of epithelial tissue located on the posterior surface of the thyroid glands 2.Secrete parathyroid hormone (PTH) 3.When blood calcium levels become low the PTH is released to increase levels 4.Vitamin D is necessary for dietary calcium to be absorbed in intestines Parathyroid PTH has opposite effect of calcitonin from the thyroid gland Hypoparathyroidism: insufficient secretion of PTH can cause increased nerve excitability due to low blood calcium levels Hyperparathyroidism: excessive secretion of PTH Excess calcium in the blood: May precipitate in abnormal locations Causes kidney stones Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 23 3. Adrenocorticotropic hormone (ACTH) Reacts with receptor sites in the cortex of adrenal gland To stimulate secretion of cortical hormones (cortisol) Affects melanocytes in the skin: increases pigmentation 24 Hormones of the Anterior Lobe (Adenohypophysis) Adrenal Glands (Suprarenal) Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc Paired glands: one located near upper portion of each kidney 2.Divided into 2 regions: a.Adrenal cortex: outer region b.Adrenal medulla: inner region Hormones of the Adrenal Cortex 1. Mineralocorticoids: Regulate the concentration of mineral electrolytes in the blood (Aldosterone) 2. Glucorticoids: Produce cortisol which helps to maintain glucose levels and counteract inflammation 3. Gonadocorticoids: Sex hormones Androgens: Males Estorgens: Females 4. Addisons disease: hyposecretion 5. Cushings syndrome: hypersecretion 26 27 Hormones of the Adrenal Medulla 1. Epinephrine and Norepinephrine 2. Prepares body for strenuous activity Sometimes called fight-or-flight hormones 3. Effect on body: increased heart rate, increased respiratory rate, increased blood supply to skeletal muscles Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 28 4. Gonadotropic hormones React with receptor sites in the gonads (ovaries and testes) To regulate development, growth, and function of these organs Follicle-stimulating hormone (FSH) Stimulates development of eggs in the ovaries and sperm in testes Stimulates estrogen production in female 29 Hormones of the Anterior Lobe (Adenohypophysis) Luteinizing hormone (LH) Female: causes ovulation, production and secretion of female sex hormones 1) Progesterone 2) Estrogen Male: sometimes called interstitial cell-stimulating hormone (ICSH) Stimulates interstitial cells of testes 1) To produce and secrete testosterone (male sex hormone) Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 30 Hormones of the Anterior Lobe (Adenohypophysis) Without gonadotropins: Ovaries and testes decrease in size Ova and sperm are not produced Sex hormones are not secreted Prolactin (PRL) Promotes development of glandular tissue in female breast during pregnancy Stimulates milk production after birth of infant Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 31 Hormones of the Anterior Lobe (Adenohypophysis) Hormones of the Posterior Lobe (Neurohypophysis) 1. Antidiuretic hormone (ADH) Promotes reabsorption of water by the kidney tubules Less water is lost as urine Conserves water for the body Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 32 Hormones of the Posterior Lobe (Neurohypophysis) b. When not enough ADH is produced there is excessive water loss in urine Large amounts of dilute urine: known as diabetes insipidus c. Large amounts of ADH: cause blood vessels to constrict Increases blood pressure ADH sometimes called vasopressin Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 33 Hormones of the Posterior Lobe (Neurohypophysis) 2. Oxytocin Causes contraction of smooth muscle in wall of uterus Stimulates ejection of milk from lactating breast Pitocin: commercial preparation of this hormone Used to induce labor Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 34 Endocrine Glands and Their Hormones Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 35 Pancreas Islets of Langerhans Long, soft organ Located posterior to stomach Exocrine portion: secretes digestive enzymes Carried through a duct to duodenum Endocrine portion: secretes hormones into blood Alpha cells: secrete glucagon Beta cells: secrete insulin Glucagon & insulin regulate blood glucose levels Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 36 Glucose Primary energy source for nervous system If glucose levels too low nervous system does not function properly If glucose levels too high kidneys produce large volumes of urine that can lead to dehydration Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 37 Pancreas Glucagon Secreted by alpha cells in pancreatic islets In response to low concentration of glucose in blood Action: raises blood glucose levels Stimulates liver to break down glycogen into glucose Prevents hypoglycemia from occurring Between meals When glucose is being used rapidly Given in response to severe hypoglycemic episodes in injection form Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 38 Insulin Secreted by beta cells in pancreatic islets In response to a high concentration of glucose in blood Action of insulin: decreases blood glucose level (opposite or antagonistic to glucagon) Promotes cellular uptake and use of glucose for energy Stimulates liver and muscle to remove glucose from blood Stores it as glycogen Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 39 Pancreas When the liver has stored all the glycogen possible: Glucose is converted to fat Hypoactivity of insulin Insufficient insulin secretion Insufficient receptor sites on target cell membranes Defective receptor sites that do not recognize insulin Leads to diabetes mellitus (abnormally high blood glucose) Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 40 Gonads Primary reproductive organs Testes: male secrete androgens Ovaries: female secrete estrogen and progesterone Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 41 Gonads (Testes and Ovaries) Pineal Gland Extends from third ventricle of brain Synthesize melatonin Secrete it directly into cerebrospinal fluid: takes it into blood High levels: secreted at night Low levels: secreted during day Regulation of circadian rhythms Example: sleepiness/wakefulness cycle Increased plasma melatonin levels (night): associated with sleepiness Plays a role in hunger/satiety cycles, mood changes, and jet lag Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 42