Endocrine System

Function? Regulates functioning of the body to maintain homeostasis

Major players Endocrine glands which secrete substances called hormones Hormones diffuse into the bloodstream and act on target cells Some local hormones affect only neighboring cells Exocrine glands secrete outside the body through tubes or ducts that lead to the surface

Steroid Hormones Formed from cholesterol Insoluble in water; soluble in lipids Can diffuse into cells relatively easily and may enter any cell in the body Ex. Estrogen, testosterone, aldosterone, cortisol

Once steroid hormone meets target cell… 1.It diffuses through the cell membrane 2.It binds with a receptor protein 3.Hormone-receptor complex binds with nuclear DNA and activates transcription of specific genes into mRNA 4.mRNA leaves nucleus and enters cytoplasm 5.mRNA associates with ribosomes to direct synthesis of specific proteins

Nonsteroid Hormones amines, peptides, and proteins Soluble in water Target cells must receive a continuous signal Ex. Epinephrine, growth hormone, antidiuretic hormone

Once nonsteroid hormone meets target cell… 1.Hormone (first messenger) binds to its receptor 2.Resulting hormone-receptor complex activates a protein called a G protein 3.G protein activates an enzyme called adenylate cyclase 4.Activated adenylate cyclase catalyzes the circularization of ATP in the cytoplasm into cAMP

5.cAMP, or cyclic adenosine monophosphate, is the second messenger and activates another set of enzymes called protein kinases 6.Protein kinases transfer phosphate groups from ATP to their substrate molecules (phosphorylation) 7.Substrate molecules’ shapes are altered and activated 8.Activated proteins then alter various cellular processes

Drawings Steroid hormones p. 279 Non-steroid hormones p. 280 List events of each

Prostaglandins Lipids synthesized from a fatty acid in cell membranes Act more locally than hormones Potent and present in small quantities Ex. Relax/contract smooth muscle, stimulate/inhibit hormone secretion, help regulate blood pressure

Control of Hormonal Secretions 1.Hypothalamus regulates the anterior pituitary gland’s release of hormones that stimulate other endocrine glands to release hormones

2.Nervous system stimulates glands directly 3.Glands respond directly to changes in the composition of the internal environment

Negative Feedback System Gland senses conc. of a substance it regulates When the conc. reaches a certain point, it inhibits the gland As the gland secretes less hormone, the controlled substance also decreases

Pituitary Gland Located at the base of the brain 1 cm in diameter Activities controlled by the brain

Thyroid Gland Lies just below the larynx on either side and in front of the trachea

Parathyroid Glands (4) Located on the posterior surface of the thyroid gland

Adrenal Glands A gland sits atop each kidney like a cap Embedded in a mass of adipose tissue

Pancreas Elongated, flattened organ posterior to the stomach and behind the parietal peritoneum

Pineal Gland Small structure located deep between the cerebral hemispheres, where it attaches to the upper portion of the thalamus

Growth Hormone Stimulates an increase in the size and division rate of body cells giantism

Prolactin Sustains milk production after birth

Thyroid-stimulating Hormone Controls secretions of hormones from thyroid gland An underactive thyroid gland (hypothyroidism) can cause symptoms such as weight gain, tiredness, dry skin, constipation, a feeling of being too cold, or frequent menstrual periods. An overactive thyroid (hyperthyroidism) can cause symptoms such as weight loss, rapid heart rate, nervousness, diarrhea, a feeling of being too hot, or irregular menstrual periods

Follicle-stimulating hormone In females, responsible for the development of egg-containing follicles in ovaries and stimulates follicular cells to secrete estrogen; in males, stimulates production of sperm cells tests

Luteinizing hormone Promotes secretion of sex hormones, plays a role in releasing an egg cell in females More info

Antidiuretic Horomone Causes kidneys to conserve water; in high concentration, increases blood pressure

Oxytocin Contracts muscles in the uterine wall; contracts muscles associated with the milk-secreting glands Trust?

Thyroxine Increases rate of energy release from carbohydrates; increases rate of protein synthesis

Calcitonin Lowers blood calcium and phosphate ion concentrations by inhibiting release of calcium and phosphate ions from bones and by increasing excretion of these ions by kidneys

Aldosterone Helps regulate the concentration of extracellular electrolytes by conserving sodium ions and excreting potassium ions

Cortisol Decreases protein synthesis, increases fatty acid release, and stimulates glucose synthesis from noncarbohydrates Positive effects: A quick burst of energy for survival reasons, Heightened memory functions; A burst of increased immunity; Lower sensitivity to pain; Helps maintain homeostasis in the body Negative effects: Impaired cognitive performance; Suppressed thyroid function; Blood sugar imbalances such as hyperglycemia; Decreased bone density; Decrease in muscle tissue; Higher blood pressure; Lowered immunity and inflammatory responses in the body; Increased abdominal fatblood pressureimmunity

Epinephrine Increases heart rate, increases force of cardiac muscle contraction, increases breathing rate, elevates blood pressure, increases blood glucose, and decreases digestive activity

Glucagon Stimulates liver to break down glycogen into glucose, raising blood sugar concentration

Insulin Stimulates the liver to form glycogen from glucose and inhibits conversion of noncarbohydrates into glucose Diabetes

Melatonin Helps regulate circadian rhythms, helps regulate the female reproductive cycle