1Chapter 12 Key Terms

HormonesMelatoninHomeostasisAldosteroneThymus GlandHyperglycemiaHypophysisHypothalamusInfundibulumAcidosisAdrenal GlandAlpha CellsBeta CellsChief CellsInsulin

AndrogensOvariesTestes

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ANATOMY & PHYSIOLOGYCHAPTER 12: ENDOCRINE SYSTEM

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Introduction

PurposeHomeostasis: maintaining the body’s internal environment

within certain narrow ranges Involves growth, maturation, metabolism, and reproduction

Works closely with the nervous systemHypothalamus sends chemical signals (neurotransmitters)

to the endocrine system Endocrine Glands

Ductless glands that secrete hormones directly into bloodstream

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Hormones

Negative feedback loopMechanism by which hormones function

3 chemical categoriesModified amino acidsProtein hormonesSteroid hormones

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Hypothalamus

Controls the pituitary gland Infundibulum

Funnel shaped extension from hypothalamus to pituitary gland

Produces chemical signalsReleasing hormonesReleasing inhibitory hormones

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Endocrine Glands

Pituitary Gland (A) Thyroid Gland (B) Parathyroid Gland Adrenal Gland (C) Testes (D) Ovaries (E) Pancreas (F) Thymus Gland (G) Pineal Gland (H)

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Pituitary Gland

Also known as the Hypophysis, and also the “Master Gland”

Divided into two lobesAnterior Pituitary GlandPosterior Pituitary Gland

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Anterior Pituitary Gland

Growth Hormone (GH)Stimulates cell growth and divisionStimulates bone and muscle growthPituitary Dwarfism: result of too little GHGigantism: result of too much GH

Thyroid Stimulating Hormone (TSH)Stimulates thyroid to release its hormone

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Anterior Pituitary Gland

Adrenocorticotropic Hormone (ACTH)Stimulates adrenal cortex to secrete its hormone

(Cortisol)Helps reduce inflammation

Melanocyte-stimulating Hormone (MSH)Stimulates production of melanin in the skin

Follicle-stimulating Hormone (FSH)Stimulates the production of sperm in malesStimulates development of follicles in ovaries

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Anterior Pituitary Gland

Luteinizing Hormone (LH)Stimulates production of progesterone and ovulation

in ovaryStimulates production of testosterone in males

Lactogenic Hormone (LTH)AKA ProlactinStimulates milk production in a pregnant femaleMay cause decrease in male sex hormones

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Posterior Pituitary Gland

Antidiuretic Hormone (ADH)AKA VasopressinMaintains body’s water balance by promoting water

reabsorption in the kidneys Oxytocin

Stimulates contraction of smooth muscles in the uterus

Sometimes given to help induce labor if the uterus does not contract sufficiently on its own during childbirth

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Thyroid Gland

Consists of two lobes connected by a smaller band called the isthmus

Stimulated by TSH from the Pituitary Gland Requires Iodine to function properly

Iodine deficiency causes goiters

Releases T3 and T4

Contain 3 and 4 Iodine atoms Regulate metabolism of carbs, fats, proteins for

proper growth and development

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Thyroid Gland

CalcitoninLowers calcium and phosphate concentrations in the blood Inhibits release of ions from bones, and increases

excretion of ions by the kidneys Hypothyroidism

Low levels of thyroid hormonesCretinism

HyperthyroidismToo much secretion of thyroid hormones

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Parathyroid Gland

4 small glands on posterior surface of thyroid gland Made of chief cells and oxyphil cells Releases Parathyroid Hormone (PTH)

Raises blood calcium levels by causing bone matrix to break down, releasing calcium and phosphate ions into bloodstream

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Adrenal Gland

Located on top of the kidneys Adrenal Medulla

Epinephrine (adrenaline) and Norepinephrine (noradrenaline)

Released as a response to signals of the autonomic nervous system

Fight or flight hormonesCauses a breakdown of glycogen to glucoseStimulates release of fatty acids from fat cells

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Adrenal Cortex

AldosteroneRegulates Na reabsorption and K excretion by kidneysReleased by outer layer of cortex

Cortisol (Hydrocortisone)Helps maintain blood glucose levels between mealsSynthesizes glucose from amino acids

CortisoneSteroid often give as medication to reduce

inflammation

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Adrenal Cortex

AndrogensPromotes development of male characteristics

Addison’s diseaseNot enough hormones secreted by adrenal cortexCauses change of electrolyte balance in blood

Cushing’s syndromeBlood glucose concentrations remains high, causing

puffy skin and obesity because of excess tissue fluid

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Pancreas

Part of digestive and endocrine systems Alpha Cells

Secretes GlucagonRaises blood sugar level

Beta CellsSecretes InsulinLowers blood sugar level

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Diabetes Mellitus

Deficiency in insulin production Type 1

Previously called juvenile diabetesBody does not produce insulin5% of diabetics

Type 2Body does not use insulin properly (insulin resistance)Previously called adult onset diabetes

Balanced diet, exercise, proper body weight

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Testes and Ovaries

OvariesReleases estrogen and progesteronePromote development of female characteristicsControl menstrual cycle

TestesReleases testosteronePromotes development of male reproductive

structures and male characteristics Both controlled by LH and LTH from Pituitary gland

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Thymus Gland

Located in the mediastinum Helps in development of the immune system Thymosin

Promotes production of T lymphocytes

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Pineal Gland

MelatoninSecreted directly into cerebrospinal fluid Inhibits secretion of LH and LTHRegulates circadian rhythms (feeling of tired and

onset of sleep)Bright light inhibits secretion of melatonin

SerotoninActs as neurotransmitter and vasoconstrictorStimulates smooth muscle contractions