The Endocrine System /biology/the-human- body/endocrine-system/

Introduction The endocrine system is the second part of the message-relaying system of the human body The endocrine system is the second part of the message-relaying system of the human body It is a system of glands that release chemical messengers into the bloodstream It is a system of glands that release chemical messengers into the bloodstream – These messengers are called hormones These messengers act much more slowly that the neurotransmitters of the nervous system These messengers act much more slowly that the neurotransmitters of the nervous system – They must travel through the blood stream to where they are needed – They do, however travel throughout the body

Glands of the Endocrine System

Hypothalamus Hypothalamus – A part of the brain that secretes hormones Tell the pituitary gland to either secrete or stop secreting Tell the pituitary gland to either secrete or stop secreting This provides a link between the nervous and endocrine system This provides a link between the nervous and endocrine system – Also produces hormones that regulate other body processes These hormones travel to the pituitary for storage until they are needed These hormones travel to the pituitary for storage until they are needed

Hormones of the Hypothalamus Antidiuretic Hormone Antidiuretic Hormone – Stimulates the kidneys to conserve water by producing more concentrated urine Oxytocin Oxytocin – Stimulates the contractions of childbirth, among other functions

Pituitary Gland (Master Gland) Pea-sized gland attached to the hypothalamus Pea-sized gland attached to the hypothalamus Posterior lobe stores hormones from the hypothalamus Posterior lobe stores hormones from the hypothalamus Front lobe secretes pituitary hormones Front lobe secretes pituitary hormones – Most of these control other glands

HormoneTargetEffect Adrenocorticotropic Hormone(ACTH) Adrenal GlandsStimulates the cortex of each adrenal gland to secrete its hormones Thyroid-stimulating Hormone (TSH) Thyroid GlandStimulates the thyroid gland to secrete thyroid hormone Growth Hormone (GH)Body CellsStimulates body cells to synthesize proteins and grow Follicle-Stimulating Hormone (FSH) Ovaries, TestesStimulates the ovaries to develop mature eggs; stimulates the testes to produce sperm Luteinizing Hormone (LH)Ovaries, TestesStimulates the ovaries and testes to produce sex hormones Prolactin (PRL)Mammary glandsStimulates the mammary glands to produce mile Hormones Produces by the Pituitary Gland

Other Endocrine Glands Thyroid Gland – in the neck Thyroid Gland – in the neck – Hormones increase the rate of metabolism in cells throughout the body – Control how quickly cells use energy and make proteins Parathyroid gland – located behind the thyroid Parathyroid gland – located behind the thyroid – Helps keep the level of calcium in the blood within a narrow range – Stimulates bone cells to dissolve calcium in bone matrix and release it into the blood

Other Endocrine Glands Pineal Gland – located at the base of the brain Pineal Gland – located at the base of the brain – Secretes the hormone melatonin which controls sleep-wake cycles and several other processes Pancreas – located near the stomach Pancreas – located near the stomach – Produces insulin and glucagon They work together to control blood sugar levels They work together to control blood sugar levels Insulin causes excess blood glucose to be taken up the by liver and store it as glycogen Insulin causes excess blood glucose to be taken up the by liver and store it as glycogen Glucagon stimulates the liver to break down glycogen into glucose and release it back into the blood stream Glucagon stimulates the liver to break down glycogen into glucose and release it back into the blood stream Also secretes digestive enzymes into the digestive tract Also secretes digestive enzymes into the digestive tract

Other Endocrine Glands Adrenal Glands – located above the kidneys Adrenal Glands – located above the kidneys – Outer portion secretes cortisol which helps the body deal with stress along with aldosterone which helps regulate mineral balance in the body – Inner portion secretes the fight-or-flight hormones Adrenalin – increases the among of oxygen and glucose going to the muscles Adrenalin – increases the among of oxygen and glucose going to the muscles es/horm8.cfm?coSiteNavigation_allTopic=1 es/horm8.cfm?coSiteNavigation_allTopic=1 es/horm8.cfm?coSiteNavigation_allTopic=1 es/horm8.cfm?coSiteNavigation_allTopic=1

Other Endocrine Glands Gonads – secrete sex hormones Gonads – secrete sex hormones – Testes secrete testosterone – Ovaries secrete estrogen These two hormones are responsible for the changes of puberty and the control of the production of gametes by the gonads These two hormones are responsible for the changes of puberty and the control of the production of gametes by the gonads

How do hormones work? They affect only certain cells called target cells They affect only certain cells called target cells – These target cells have specific receptors on their surface that create a matching combination with its hormone When the hormone binds to the receptor it causes a change within in the cell When the hormone binds to the receptor it causes a change within in the cell What happens depends upon if the hormone is a steroid or non-steroid What happens depends upon if the hormone is a steroid or non-steroid online.com/objects/ViewObject.aspx?ID=AP online.com/objects/ViewObject.aspx?ID=AP online.com/objects/ViewObject.aspx?ID=AP online.com/objects/ViewObject.aspx?ID=AP ture=related ture=related ture=related ture=related

Steroid Hormones Made of lipids like phospholipids and cholesterol Made of lipids like phospholipids and cholesterol – They are fat soluble so they can diffuse through the plasma membrane of target cells and bind with the receptors in the cytoplasm

Non-Steroid Hormones Made of amino acids Made of amino acids – They are not fat soluble so they can’t diffuse across the plasma membrane – When they bind the trigger enzymes within the cell membrane the active other molecules

Hormone Regulation Typically Controlled by feedback mechanisms Typically Controlled by feedback mechanisms – This is a loop in which a product (hormone) feeds back to control its own production Most involve negative feedback loops Most involve negative feedback loops – Keeps the concentration within a very narrow range

Negative Feedback be.com/watch?v=C Lv3SkF_Eag

Endocrine System Disorders Hypersecretion Hypersecretion – Too much Usually caused by a tumor Usually caused by a tumor Too much growth hormone leads to gigantism Too much growth hormone leads to gigantism Hyposecretion Hyposecretion – Too little Type I diabetes Type I diabetes

Hormone Resistance Normal amounts of hormone but target cells do not respond to the hormones Normal amounts of hormone but target cells do not respond to the hormones – Type II diabetes – Cells don’t take up glucose Need to follow a specific diet along with medication Need to follow a specific diet along with medication Insulin doesn’t work Insulin doesn’t work