ENDOCRINE SYSTEM Honors Biology

Introduction Glands that transmit chemical messengers throughout the body Hormones: chemical messengers –Circulate through body –Affect many body cells

GLAND TYPES Gland: organ made of cells that secrete materials –Exocrine glands: secrete nonhormonal chemicals into ducts and transport to locations inside and outside the body; i.e. sweat, mucous, saliva, digestive –Endocrine glands: ductless and throughout body; secrete hormones into bloodstream through fluid surrounding cells

HORMONE TYPES Hormones: –Compounds that are secreted into bloodstream and affect activity of distant cells –Diffuse into blood 2 Categories –Amino acid-base hormones: derived from amino acids (epinephrine) –Steroid hormones: lipids derived from cholesterol (estrogen and testosterone)

HORMONE ACTION Each hormone only affects certain cells called target cells

PROSTAGLANDINS Group of hormone like lipids Regulate cell activities Not made by specific endocrine glands Made by cells throughout body Made and travel locally

ENDOCRINE GLANDS JIGSAW ACTIVITY –Pituitary Glands –Thyroid Gland –Adrenal Gland –Gonads –Pancreas (done for you)

OTHER ENDOCRINE GLANDS Thymus Gland: –Located beneath sternum and between lungs –Development of immune system and T cells Pineal Gland: –Near base of brain –Secretes melatonin; cycle regulate sleep patterns

OTHER ENDOCRINE GLANDS Parathyroid Glands –4 parathyroid glands –Back of thyroid gland –Secrete parathyroid hormone: Increase concentration of calcium ions in blood Digestive (in walls) –Gastrin: stimulates release of digestive enzymes –Secretin: in small intestine; stimulates release of digestive enzymes from pancreas and bile from liver

FEEDBACK MECHANISMS Last step of a series controls the first step –Negative: shuts off –Positive: makes more (going into labor!) Homeostasis –Insulin and glucagon work together to balance blood glucose –Antagonistic hormones

FEEDBACK MECHANISMS

NEGATIVE FEEDBACK Final step inhibits first step; thermostat Example: –Hypothalamus secretes LH releasing hormone –Stimulates LH from anterior pituitary –LH released into blood and transported –LH binds to target cells in tests –Stimulate cAMP production –Stimulate testosterone secretion –Testosterone binds to target cells –If high testosterone concentration; LH releasing hormone is inhibited