Chapter 2 The Endocrine System

Introduction The endocrine system includes the organs of the body that secrete hormones directly into body fluids such as blood Regulates chemical reaction in cells and therefore control functions of the organs, tissues, and other cells bloodstream to hormones Glands into secrete target tissues

Hormones Endocrine glands Ductless Release hormones Directly into target tissues Into bloodstream to be carried to target tissues Hormones – chemicals secreted by a cell that affect the functions of other cells

Hormones (cont.) Many are derived from steroids that easily cross the cell membrane Examples of steroid hormones Estrogen Progesterone Testosterone Cortisol hormones

Hypothalamus Hormones Oxytocin Antidiuretic hormone (ADH) Hormones transported to the posterior pituitary for storage Directs posterior pituitary to release hormones Glands

Pituitary Gland Controlled by the hypothalamus Located at the base of the brain Two lobes Anterior lobe Posterior lobe

Pituitary Gland (cont.) Growth hormone Prolactin Stimulates milk production Stimulates increase in size of muscles and bones Anterior Lobe Thyroid-stimulating Luteinizing Stimulates the thyroid gland to release its hormones Females: stimulates ovulation and estrogen production Males: stimulates testosterone production Follicle-stimulating Adrenocorticotropic Females: stimulates estrogen production and maturation of the ova Males: stimulates sperm production Stimulates the adrenal cortex to release its hormones

Pituitary Gland (cont.) Oxytocin Posterior Lobe Females: causes contraction of the uterus and ejection of breast milk Males: stimulates contraction of the prostate and vas deferens during sexual arousal Antidiuretic hormone (ADH) Stimulates the kidneys to conserve water

Thyroid Gland and Parathyroid Glands Located below the larynx Divided into follicles that store some of the hormones Major hormones Calcitonin Thyroid hormones T3 T4 Stimulate protein synthesis and increase cellular energy production Lowers blood calcium levels by activating osteoblasts that build new bone tissue Glands

Thyroid Gland and Parathyroid Glands (cont.) Four located on the posterior surface of the thyroid gland Secrete parathyroid hormone (PTH) Agonist to calcitonin by raising blood calcium levels through activation of osetoclasts (dissolve bone) As bone dissolves, calcium levels in blood increase Glands

Adrenal Glands Located on top of each kidney Divided into the adrenal medulla and adrenal cortex Adrenal medulla Central portion Hormones Epinephrine Norepinephrine Same effects as sympathetic nervous system Glands

Adrenal Glands (cont.) Adrenal cortex Outermost portion Secretes many hormones, but main ones are Aldosterone Stimulates body to retain sodium and water Important in maintaining BP Cortisol Released when stressed Decreases protein synthesis, resulting in slowed tissue repair Decreases inflammation

Pancreas Located behind the stomach Both exocrine gland and endocrine gland Exocrine – secretes digestive enzymes into a duct leading to the small intestine Endocrine – secretes hormones into bloodstream Glands

Pancreas (cont.) Insulin Glucagon Islets of Langerhans secrete hormones into bloodstream Alpha cells secrete glucagon Beta cells secrete insulin Insulin Glucagon Blood glucose concentrations Blood glucose concentrations Protein synthesis Protein synthesis

Other Hormone-Producing Organs Pineal body Small gland Located between cerebral hemispheres Melatonin Regulates circadian rhythms May play a role in onset of puberty Thymus gland Located between lungs Thymosin Promotes production of T lymphocytes Glands

Other Hormone-Producing Organs (cont.) The gonads Ovaries Estrogen Progesterone Testes Testosterone Stomach Gastrin Small intestine Secretin Cholecystokinin Heart Atrial natriuretic peptide – regulates BP Kidneys Erythropoietin – stimulates blood cell production Glands

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Common Diseases and Disorders Disease/Disorder Description Acromegaly Too much growth hormone produced in adults; enlargement of bones and thickened skin Addison’s disease Adrenal gland fails to produce enough corticosteroids Cretinism Extreme form of hypothyroidism present prior to or soon after birth Cushing’s disease Hypercortisolism; over-production of cortisol Diabetes insipidus Kidneys fail to reabsorb water, resulting in excessive urination; hyposecretion of ADH

Common Diseases and Disorders (cont.) Disease/Disorder Description Diabetes mellitus Type I Type II Gestational Chronic disease characterized by elevated blood glucose levels Insulin-dependent diabetes mellitus; usually develops in childhood Noninsulin-dependent diabetes mellitus; primarily in adults but increased incidence in teens Occurs during pregnancy; usually temporary Dwarfism Too little growth hormone (somatotropin) produced during childhood

Common Diseases and Disorders (cont.) Disease/Disorder Description Gigantism Too much growth hormone produced during childhood Goiter Enlargement of thyroid gland, causing swelling in neck; deficiency of iodine in diet Grave’s disease Hyperthyroidism; antibodies attach to thyroid gland, causing it to produce too much thyroid hormone Myxedema Thyroid gland produces inadequate amounts of thyroid hormone; common in females over 50