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Transcript
5/9/2014 The Endocrine System 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 1 Hormone Overview 2 The Chemistry of 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 Amino acid-based hormones Steroids hormones - made from cholesterol Ex: Proteins 3 Mechanisms of Hormone Action 4 Effects Caused by Hormones 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 5 Changes in plasma membrane permeability or electrical state Synthesis of proteins, such as enzymes Activation or inactivation of enzymes Stimulation of mitosis 6 1 5/9/2014 Steroid Hormone Action Steroid Hormone Action Diffuse through the plasma membrane of target cells Enter the nucleus Bind to a specific protein within the nucleus Bind to specific sites on the cell’s DNA Activate genes that result in synthesis of new proteins PRESS TO PLAY STEROID HORMONE ANIMATION Figure 9.1a 8 7 Nonsteroid Hormone Action Nonsteroid Hormone Action Hormone binds to a membrane receptor Hormone does not enter the cell Sets off a series of reactions that activates an enzyme Catalyzes a reaction that produces a second messenger molecule Oversees additional intracellular changes to promote a specific response PRESS TO PLAY 9 Figure 10 9.1b Endocrine Glands – may be activated by other hormones Control of Hormone Release NONSTEROID HORMONE ANIMATION Hormone levels in the blood are maintained by negative feedback 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 11 Figure 12 9.2a 2 5/9/2014 Endocrine Glands - may be activated by the nervous system Location of Major Endrocrine Organs Nerve impulses stimulate hormone release Most are under control of the sympathetic nervous system Figure 13 9.2c Figure 14 9.3 Hormones of the Pituitary – Growth Hormone (GH) Hormones of the Pituitary 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 Figure 15 9.4 Functions of Pituitary Hormones Stimulates follicle development in ovaries Stimulates sperm development in testes Luteinizing hormone (LH) Triggers ovulation Causes ruptured follicle to become the corpus luteum Stimulates testosterone production in males Regulates endocrine activity of the adrenal cortex Thyroid-stimulating hormone (TSH) Follicle-stimulating hormone (FSH) Stimulates and maintains milk production following childbirth Adrenocorticotropic hormone (ACTH) Functions of Pituitary Hormones Prolactin 16 Influences growth and activity of the thyroid 17 18 3 5/9/2014 Functions of the Pituitary Hormones Oxytocin Thyroid Gland Stimulates contractions of the uterus during labor Causes milk ejection Antidiuretic hormone (ADH) Can decrease urine production (less water in urine) In large amounts, causes increased blood pressure Found at the base of the throat Consists of two lobes and a connecting isthmus Produces two hormones Thyroid hormone Calcitonin 19 Thyroid Hormone 20 Thyroid hormone - Calcitonin Thyroxin - major metabolic hormone Decreases blood calcium levels by depositing Ca in bone Opposite of parathyroid hormone Figure 22 9.9 21 Parathyroid Glands Adrenal Glands Tiny masses on the posterior of the thyroid Secrete parathyroid hormone Two glands At the top of the kidneys Stimulate bone cells to remove calcium from bone Stimulate the kidneys and intestine to absorb more calcium Raise calcium levels in the blood 23 24 4 5/9/2014 Hormones of the Adrenal Glands Pancreatic Islets Produce sex hormones The pancreas produces: Produce cortisone and cortisol Promote normal cell metabolism Help resist long-term stressors Insulin – allows glucose to pass through cell membranes into cells Glucagon – allows glucose to enter the blood from cells Insulin and glucagon hormones maintain blood sugar homeostasis 25 Pancreatic Hormones and Blood Sugar 26 Pineal Gland Secretes melatonin Helps establish the body’s wake and sleep cycles Figure 27 9.14 Thymus Hormones of the Ovaries Located posterior to the sternum Largest in infants and children Produces thymosin 28 Estrogens Matures some types of white blood cells Important in developing the immune system 29 Stimulates the development of secondary female characteristics Matures female reproductive organs Helps prepare the uterus to receive a fertilized egg Helps maintain pregnancy Prepares the breasts to produce milk 30 5 5/9/2014 Hormones of the Ovaries Hormones of the Testes Progesterone Produced by the corpus luteum Acts with estrogen to bring about the menstrual cycle Helps in the implantation of an embryo in the uterus Testosterone Responsible for adult male secondary sex characteristics Promotes growth and maturation of male reproductive system Required for sperm cell production 31 32 This image cannot currently be display ed. The Endocrine System and Aging The Placenta Produces hormones that maintain the pregnancy Some hormones play a part in the delivery of the baby Produces HCG in addition to estrogen, progesterone, and other hormones 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 33 34 Effect of growth hormone Endocrine organs (review) 35 Greatest production occurs during childhood Lack of GH- pituitary dwarfism Excess - giantism 36 6 5/9/2014 Abnormalities of the thyroid Cretinism- abnormal thyroid development; short, stocky body type. Severe hypothyroidism causes mental retardation Myxedema - Hypothyroidism in adults-lethargy, weight gain, loss of hair. Grave’s disease- hyperthyroidism; causes exophthalmic goiter-edema behind eyes 37 causes bulging; hyperactivity, arrythmias. Addison’s disease ACTH accumulates causing stimulation of melanocytes (bronze skin color). Without cortisol, there is no mobilization of glucose under stress; can be life-threatening. Hyposecretion of aldosterone-most serious, causes hyperkalemia (low blood potassium) 39 leading to cardiac arrest Acromegaly Excess production of GH; the growth plates of bone have closed so no increased growth in height. Feet, hands, and face become “heavy” in appearance 38 Cushing’s syndrome Hypersecretion of the adrenal cortex hormone, cortisol is primary problem. Results in Diabetes mellitus from increased blood glucose; Subcutaneous fat deposited in midsection; High blood pressure 40 7