Anatomy Study Guide Endocrine System Together the nervous and endocrine systems are responsible for integration and coordination to maintain homeostasis Endocrine system is chemical slow to react seconds to days most tissues in body continues for days stimulates inhibits neurons Nervous system is electrochemical very fast milliseconds only muscles glands ends quickly may stimulate hormone release Plays a major role in growth and development full body metabolism and reproduction Hormones are mostly controlled by negative feedback sometimes positive blood clotting oxytocin paracrine local hormones secrete their fluids into the tissues of nearby cell autocrine affect itself Transport of Hormones endocrine glands are highly vascularized release hormones into extracellular fluid via exocytosis hormones travel in blood vessels and are transported to target organ Hypothalamus and Pituitary have a closely integrated relationship Hypothalamus major link between the nervous and endocrine systems hormones control the pituitary derived from neural tissue part of diencephalon of cerebrum hormones are produced in 2 nuclei paraventricular and supraoptic Hypothalamic Hormones Anterior Pituitary Growth hormone releasing hormone GHRH Growth hormone inhibiting hormone GHIH Corticotropin releasing hormone CRH Thyrotropin releasing hormone TRH Gonadotropin releasing hormone GNRH Prolactin releasing hormone PRH Prolactin inhibiting hormone PIH Posterior Pituitary Oxytocin produced in paraventricular nucleus Anti diuretic hormone ADH produced in supraoptic nucleus Pituitary master endocrine gland suspended from hypothalamus by infundibulum together they have 16 different hormones that regulate growth development metabolism and homeostasis anterior pituitary adenohypophysis derived from glandular epithelium 5 types of cells 3 produce tropic hormones 1 Corticotropes Adrenocorticotropic hormone ACTH targets adrenal cortex promotes the growth of adrenal cortex and the secretion of glucocorticoids regulates glucose protein and fat metabolism 2 Thyrotropes Thyroid Stimulating Hormone TSH targets thyroid gland promotes growth of thyroid and secretion of thyroid hormone 3 Gonadotropes Follicle Stimulating Hormone FSH secretion of estrogen and sperm and Luteinizing Hormone LH both target ovaries and testes ovulation secretion of testosterone 2 produce effects on non endocrine tissues 1 Sometropes Growth Hormone GH targets liver bone cartilage muscle and fat Widespread tissue growth 2 Lactotropes Prolactin PRL targets mammary glands and testes female milk synthesis male increased luteinizing hormone sensitivity posterior pituitary neurohypophysis derived from neural tissue 2 hormones are synthesized in hypothalamus transported to Posterior pituitary where they are stored until they are released on demand travel down hypothalamic hypophyseal tract as a nerve impulse from the the hypothalamus released into ECF then capillaries 1 Oxytocin targeted to uterus and mammary glands labor contractions and milk release 2 Antidiuretic Hormone ADH targets kidneys water retention hypothalamic hypophyseal tract nerve tract connecting to posterior pituitary hypophyseal portal system vascular connection to anterior pituitary primary capillary plexus hypophyseal portal vein secondary capillary plexus Thyroid Largest gland located on neck above trachea 2 winglike lobes connected by an isthmus very large blood flow only gland to store hormones in large quantity 3 months worth major metabolic hormone of body primarily increases metabolic rate affects virtually every cell except adult brain spleen testes uterus and thyroid gland Follicular cell hormones thyroid hormones formed from iodine and thyroglobin transported by thyroxin binding globulin T3 3 iodines most active thyroid hormone T4 4 iodines aka thyroxin most abundant but converted to T3 once absorbed by target cells Calcitonin produced in parafollicular cells promotes deposition of calcium into bone matrix decreases blood Calcium levels and stimulates osteoblasts promotes bone growth Parathyroid Glands at least two pairs on back of thyroid gland secretes Parathyroid Hormone PTH which counteracts calcitonin raise blood calcium levels and inhibits osteoclasts Thymus Gland Large and conspicuous in children diminishes through adulthood plays a role in endocrine lymphatic and immune system secretes T cells T lymphocytes which play a large role in immunity affected during AIDS Thymosin and thumopoietin regulate and activate the T cells Adrenal Glands Structurally and functionally two glands Major function is to help body cope with stress Adrenal Cortex surrounds the medulla produces more than 25 steroid hormones known collectively as corticoids all synthesized from cholesterol Mineralcorticoids produced in zona golerulosa regulate body s electrolyte balance Aldosterone is a mineralcorticoid that maintains blood volume and pressure Glucocorticoids produced in zona fasiculata regulate the metabolism of glucose and other organic fuels Cortisol aids in chronic stress excess of cortisol effects immune system Gonadocorticoids produced in zona reticularis various developmental reproductive functions Androgen sex hormones Adrenal Medulla made of cells that are modified postganglionic neurons no axons sympathetic innervation hormones prolong the effects of sympathetic stimulation epinephrine 80 norepinephrine 20 Pancreas an elongated spongy gland located below and behind the stomach mainly an exocrine digestive gland but 1 2 of pancreatic cells are endocrine Islets of Langerhans very important in regulation of blood glucose concentration Alpha cells secrete glucagon between meals when blood glucose concentration falls Beta cells secrete insulin during and after a meal when blood nutrient levels are rising Delta cells secrete somatostatin inhibits growth hormone concurrently with the release of insulin inhibits some digestive enzyme secretion and nutrient absorption Gonads testes and ovaries estrogen and progesterone predominantly secreted by females testosterone predominantly secreted by males Pineal Gland has both nervous system and endocrine system functions Produces melatonin which regulates sleep wake cycles changes in response to light cycles possible role in sexual maturation Endocrine Functions of Other Organs Stomach Small Intestine secretes enteric hormones which coordinate digestion Kidney calcitrol affects calcium handling erythropoietin stimulates RBC production Heart atrial