The Endocrine System PDF

THE ENDOCRINE SYSTEM Chapter 9 ENDOCRINE VS. NERVOUS SYSTEM • Nervous System • Electrical impulses & neurotransmitters • Effect is localized & of short duration • Acts quickly • Endocrine System • Acts through chemicals/hormones • Effect is generalized & of long term duration • Takes longer to sp...

THE ENDOCRINE SYSTEM Chapter 9 ENDOCRINE VS. NERVOUS SYSTEM • Nervous System • Electrical impulses & neurotransmitters • Effect is localized & of short duration • Acts quickly • Endocrine System • Acts through chemicals/hormones • Effect is generalized & of long term duration • Takes longer to spring into action THE ENDOCRINE SYSTEM • Second messenger system of the body • Uses chemical messages (hormones) that are released into the blood • Hormones control several major processes • • • • • • Reproduction Growth and development Mobilization of body defenses Maintenance of much of homeostasis Regulation of metabolism and energy balance Regulation of electrolyte, water and nutrient balance ENDOCRINE VS. EXOCRINE GLANDS • Exocrine Glands • Have ducts • Excrete onto a surface • Endocrine Glands • Ductless • Hormones secrete directly into the blood stream WHAT ARE HORMONES? • Chemical substances secreted by the cells of an endocrine gland, into the extra-cellular fluids • Regulate metabolic activity of other body cells HORMONES • Hormones are produced by specialized cells • Cells secrete hormones into extracellular fluids • Blood transfers hormones to target sites • These hormones regulate the activity of other cells CHARACTERISTICS OF HORMONES • Two Types: Amino Acid based (proteins) • OR Steroids • Most hormones are Amino Acid based or protein derivatives • Proteins, peptides and amines • Each hormone has its own specific target cells or organs THE CHEMISTRY OF HORMONES • Amino acid-based hormones • Proteins • Peptides • Amines • Steroid Hormones – made from cholesterol • Prostaglandins – made from highly active lipids MECHANISMS OF HORMONE ACTION • Hormones affect only certain tissues or organs (target cells or organs) • Target cells must have specific protein receptors • Hormone binding influences the working of the cells • Steroid Hormone activates cell activity differently than Non-Steroid hormones EFFECTS CAUSED BY HORMONES • Changes in plasma membrane permeability or electrical state • Synthesis of proteins or regulatory molecules in the cell such as enzymes • Activation or inactivation of enzymes • Stimulation of mitosis • Promotion of secretory activity STEROID HORMONE ACTION DIRECT GENE ACTIVATION • Diffuse through the plasma membrane of target cells • Enter the nucleus • Bind to a specific protein receptor within the nucleus • Complex binds to specific sites on the cell’s DNA • Activate genes that result in synthesis of new proteins STEROID HORMONE ACTION PRESS TO PLAY STEROID HORMONE ANIMATION Figure 9.1a NON-STEROID HORMONE ACTION SECOND MESSENGER SYSTEM • Hormone binds to a membrane receptor • Hormone does not enter the cell – requires a second messenger system • This binding sets off a series of reactions that activates an enzyme • This enzyme catalyzes a reaction(s) that produces a second messenger molecule • This Molecule oversees additional intracellular changes to promote a specific response NON-STEROID HORMONE ACTION PRESS TO PLAY NONSTEROID HORMONE ANIMATION Figure 9.1b CONTROL OF HORMONE RELEASE The stimulus that triggers the release of hormones falls into 3 categories • Hormonal- a hormone stimulates an endocrine gland(EG) • Humoral- “humors” chemical levels in blood stimulate EG • Neural- direct nerve stimulation • Hormones are regulated by the negative feedback system THE NEGATIVE FEEDBACK SYSTEM • Hormone levels in the blood are maintained primarily by negative feedback mechanisms • A stimulus or low hormone levels in the blood triggers the release of more hormone • Hormone release stops once an appropriate level in the blood is reached HORMONAL STIMULI OF ENDOCRINE GLANDS • Endocrine glands activated by other hormones Figure 9.2a HUMORAL STIMULI OF ENDOCRINE GLANDS • Changing blood levels of certain ions stimulate hormone release Figure 9.2b NEURAL STIMULI OF ENDOCRINE GLANDS • Nerve impulses stimulate hormone release • Most are under control of the sympathetic nervous system Figure 9.2c CONTROL OF HORMONE RELEASE LOCATION OF MAJOR ENDOCRINE ORGANS Figure 9.3 HYPOTHALAMUS • Major link between Nervous System & Endocrine System • Manufactures hormones • Some are stored in the posterior lobe of pituitary gland (2) • Some trigger the anterior pituitary to release other hormones PITUITARY GLAND • Size of a grape • Hangs by a stalk from the hypothalamus • Protected by the sphenoid bone • Has two functional lobes • Anterior pituitary – glandular tissue • Posterior pituitary – nervous tissue PITUITARY - HYPOTHALAMUS RELATIONSHIP • Release of hormones is controlled by releasing and inhibiting hormones produced by the hypothalamus • Hypothalamus produces two hormones that are transported to neuro-secretory cells of the posterior pituitary • The posterior pituitary is not strictly an endocrine gland, but does release hormones PITUITARY GLAND • Adenohypophysis- anterior lobe of pituitary gland • Regulated by inhibiting and releasing hormones from the hypothalamus • It manufactures its own hormones • Neurohypophysis- posterior lobe of the pituitary gland • Regulated by nerve stimulation • Its hormones are manufactured by the hypothalamus HORMONES OF THE ANTERIOR PITUITARY • Six anterior pituitary hormones • Two affect non-endocrine targets (GH and prolactin) • Four stimulate other endocrine glands (tropic hormones) • Characteristics of all anterior pituitary hormones • Proteins (or peptides) • Act through second-messenger systems • Regulated by hormonal stimuli, mostly negative feedback HORMONES OF THE ANTERIOR PITUITARY GLAND • Growth hormone GH • Thyroid Stimulating Hormone TSH • Adrenocorticotropic Hormone ACTH • Follicle-stimulating Hormone FSH • Luteinizing Hormone LH • Prolactin HORMONES OF THE ANTERIOR PITUITARY Figure 9.4 GROWTH HORMONE (GH) • General metabolic hormone • Major effects are directed to growth of skeletal muscles and long bones • Causes amino acids to be built into proteins • Causes fats to be broken down for a source of energy while sparing glucose thus maintaining blood sugar levels Effects of Growth hormone age 9 age 16 age 33 age 52 Fig. 13.7, p. 268 FUNCTIONS OF OTHER ANTERIOR PITUITARY HORMONES • Prolactin (PRL) • Stimulates and maintains milk production following childbirth • Function in males is unknown • Adrenocorticotropic hormone (ACTH) • Regulates endocrine activity of the adrenal cortex • Thyroid-stimulating hormone (TSH) • Influences growth and activity of the thyroid FUNCTIONS OF OTHER ANTERIOR PITUITARY HORMONES Gonadotropic hormones • Regulate hormonal activity of the gonads • Luteinizing Hormone (LH) • Triggers ovulation • Stimulates testosterone production in males • Follicle-stimulating hormone (FSH) • Stimulates follicle development in ovaries • Stimulates sperm development in testes POSTERIOR PITUITARY • Does not MAKE the hormones • Stores 2 hormones made by the hypothalamus • Responds to nervous stimuli HORMONES OF THE POSTERIOR PITUITARY GLAND • Anti-Diuretic Hormone (ADH) (Vasopressin) • Promotes the re-absorption of water by the kidneys • Thus leads to an increase in BP, vasoconstriction and decrease urine output • Oxytocin • Causes uterine contraction during labour & ejection of milk from the breast in nursing women HORMONES OF THE POSTERIOR PITUITARY Figure 9.5 THYROID GLAND • Found at the base of the throat • Consists of two lobes and a connecting mass (isthmus) • Produces two hormones • Thyroid hormone (T4, T3) • Calcitonin THYROID GLAND HORMONES • Thyroxine T4 & Triiodothyronine T3 • • • • • • 1st is most active of the two Made and stored in follicles Both require iodine for synthesis Affect metabolism Control the rate that glucose is used Every body cell is a target cell! • Calcitonin • Reduces calcium levels in the blood THYROID CONDITIONS • Goiters: • Lack of Iodine leads to gland enlargement THYROID CONDITIONS • Cretinism: • Lack of Thyroxine due to lack of TSH stimulation during early childhood • Dwarfism with Childlike proportions • Head and Trunk are 1 ½ the length of legs • Often developmentally challenged • Skin and Hair abnormalities Myxedema GRAVES’ DISEASE • Hyperthyroidism • Gland enlargement • Exophthalamus • Weight loss • Anxiety/Agitation • Tachycardia Thyroid Gland Figure 9.6 CALCITONIN • Decreases blood calcium levels by causing deposition in bone • Antagonistic to parathyroid hormone • Uses Humoral stimulation Figure 9.9 PARATHYROID GLAND • Found on posterior surface on thyroid gland • Tiny masses on the posterior of the thyroid • Parathyroid hormone (PTH) • Increases blood calcium levels • Opposes Calcitonin • Under humoral control ADRENAL GLANDS & ADRENAL CORTEX • Adrenal glands are found sitting on top of the kidneys • Each gland has an inner(adrenal medulla) & an outer(adrenal cortex) component • Adrenal cortex is stimulated by ACTH and is glandular tissue • Adrenal medulla is neural tissue ADRENAL CORTEX • Has 3 distinct layers • Makes 3 types of steroid hormones (corticosteroids) • Made from cholesterol • where as other hormones are proteins made from amino acids • IE. Aldosterone, cortisol, Testosterone, progesterone, ADRENAL CORTEX & HORMONES Stimulated by Adrenocorticotropic hormone (ACTH). • 1) Mineralocorticoids • Aldosterone promotes Na+ reabsorption in kidney tubules – humoral and hormonal control • Work to regulate mineral/salt content • Target the kidney tubules. Increase Aldosterone increase reabsorption of Na+ (& H2O) and secrete K+ • 2) Glucocorticoids • Cortisol increases blood glucose levels & helps to counteract inflammatory response • 3) Sex hormones - small amounts HORMONES OF THE ADRENAL CORTEX • Mineralocorticoids (mainly aldosterone) • Produced in outermost adrenal cortex • Regulate mineral content in blood, water, and electrolyte balance • Target organ is the kidney tubules • Production stimulated by Renin/Angiotension II and ACTH (from the pituitary gland) and direct humoral stimulation • Production inhibited by atrial natriuretic peptide ADRENAL CORTEX - ALDOSTERONE Figure 9.10 HORMONES OF THE ADRENAL CORTEX • Glucocorticoids (including cortisone and cortisol) • Produced in the middle layer of the adrenal cortex • Promote normal cell metabolism • Help resist long-term stressors • Primary method is to increase blood glucose levels • Released in response to increased blood levels of ACTH HORMONES OF THE ADRENAL CORTEX • Sex hormones • Produced in the inner layer of the adrenal cortex • Small amounts throughout life • Androgens (male) and some estrogen (female) HOMEOSTATIC IMBALANCES • Addison’s Disease: • Hyposecretion of all Adrenal Cortex Hormones • Bronze skin tone • Water and Electrolyte imbalances • Muscle weakness, inability to cope, hypoglycemia, weakened immunity Hyperaldosteronism Masculinization • Excessive Water and salt retention • Hypersecretion of the sex hormones • HTN • Inner layer of the cortex affected • Edema • Potassium deficiency leading to heart arrhythmias or nervous system disruptions • More noticeable in females with increase hair pattern and growth HOMEOSTATIC IMBALANCES Cushing’s Syndrome • Middle cortex area affected • Excessive glucocorticoids • • • • • Swollen face Buffalo Hump HTN, Hyperglycemia Bone weakening Severe Immune sys depression HORMONES OF THE ADRENAL MEDULLA • Stimulated by the Sympathetic Nervous system • Produces two similar hormones (catecholamines) • Epinephrine (Adrenaline) • Norepinephrine (Noradrenaline) • These hormones prepare the body to deal with short-term stress ADRENAL MEDULLA & HORMONES • Epinephrine (adrenalin) & norepinephrine (noradrenalin) prepare the body for strenuous activity or stress • Effect is similar to the Sympathetic Nervous System but lasts up to 10X longer • Steroidal or Non-steroidal? • What are the effects on the body? HYPOTHALAMUS AND ADRENAL GLANDS DURING THE STRESS RESPONSE Figure 9.12 PANCREATIC HORMONES • Pancreas is both an exocrine & an endocrine gland • Exocrine secrete into ducts, endocrine secrete into blood • Pancreatic islets are the endocrine portion of the gland • Alpha cells produce glucagon which increases blood glucose • Beta cells produce insulin which decreases blood glucose • Delta cells produce somatostatin • F-cells secrete pancreatic polypeptide PANCREATIC ISLETS Figure 9.13 PANCREATIC HORMONES AND BLOOD SUGAR Figure 9.14 PINEAL GLAND • Found on the third ventricle of the brain • Secretes melatonin • Helps establish the body’s wake and sleep cycles • May have other as-yet-unsubstantiated functions THYMUS • Located posterior to the sternum • Largest in infants and children • Produces Thymosin • Matures some types of white blood cells • Important in developing the immune system HORMONES OF THE GONADS: OVARIES & TESTES • Estrogens • Sex characteristics & Secondary sex characteristics in females • Progesterone • Prepares uterus for fertilized egg • Androgens testosterone • adult male sex characteristics • Growth & maturation of reproductive system HORMONES OF THE OVARIES • Estrogens • Development of sex characteristics (reproductive system) • Stimulates the development of secondary female characteristics • Matures female reproductive organs • Helps prepare the uterus to receive a fertilized egg (menstrual cycle) • Helps maintain pregnancy • Prepares the breasts to produce milk • Stimulated Hormonally – Gonadotropic hormones from the Anterior Pituitary Gland HORMONES OF THE OVARIES • Progesterone • Acts with estrogen to bring about the menstrual cycle • Helps in the implantation of an embryo in the uterus • Helps prepare for lactation • Stimulated Hormonally – Gonadotropic hormones from the Anterior Pituitary Gland HORMONES OF THE TESTES • Interstitial cells of testes are hormone-producing • Produce several Androgens • Testosterone is the most important • Responsible for adult male secondary sex characteristics • Promotes growth and maturation of male reproductive system • Required for sperm cell production • Secretion is hormonally controlled – Gonadotropins form the Anterior Pituitary ENDOCRINE FUNCTION OF THE PLACENTA • Produces hormones that maintain the pregnancy • Some hormones play a part in the delivery of the baby • Produces Human Chorionic Gonadotropin (hCG) in addition to estrogen, progesterone, and other hormones OTHER HORMONE-PRODUCING TISSUES AND ORGANS • Parts of the Stomach and small intestine • Kidneys (Erythropoietin) • Heart (Atrial Natriuretic Peptide) • Placenta (Human Chorionic Gonadotropin) • Adipose Tissue • Many other areas have scattered endocrine cells PROSTAGLANDINS • Hormone-like molecules, produced by the plasma membranes of most cells • Affect smooth muscle contraction • Affect blood clotting • Promote inflammatory response • Produced PRN • Effect is immediate, short-term & localized (not transported in blood) DEVELOPMENTAL ASPECTS OF THE ENDOCRINE SYSTEM • Most endocrine organs operate smoothly until old age • Menopause is brought about by lack of efficiency of the ovaries • Problems associated with reduced estrogen are common • Growth hormone production declines with age • Many endocrine glands decrease output with age • See textbook page 328-329 Table 9.1 for summary details of major endocrine glands and hormones • See textbook page 331 for Table 9.2 for summary details of other hormone producing organs