The Endocrine The Endocrine SystemSystem

Exocrine vs EndocrineExocrine vs Endocrine

Classified by location of secretionClassified by location of secretion

Exocrine- through tube or duct to a surfaceExocrine- through tube or duct to a surface

Endocrine- secrete into internal Endocrine- secrete into internal environmentenvironment

Endocrine GlandsEndocrine Glands

Can be cell, tissue, or organ (gland)Can be cell, tissue, or organ (gland)

Hormone- messenger secreted by glandHormone- messenger secreted by gland

Target cell- receives the messageTarget cell- receives the message– Receptor for hormoneReceptor for hormone– Hormone creates a responseHormone creates a response

Tropic hormones- hormone whose target Tropic hormones- hormone whose target cell is another endocrine glandcell is another endocrine gland

Other MessengersOther Messengers

““Local Hormones”- never reach Local Hormones”- never reach bloodstreambloodstream– Paracrine- affect neighboring cellsParacrine- affect neighboring cells– Autocrine- affect secreting cellAutocrine- affect secreting cell

Prostaglandins- lipids messenger usually Prostaglandins- lipids messenger usually affecting organ secreted inaffecting organ secreted in

Hormone ActionHormone Action

Steroid Hormone (derivative of Steroid Hormone (derivative of cholesterol)cholesterol)– Must be carried by plasma proteins through Must be carried by plasma proteins through

bloodstreambloodstream– Diffuse into any cellDiffuse into any cell– Binds to receptor in cell Binds to receptor in cell – Activates specific area of DNAActivates specific area of DNA– Protein synthesis is end resultProtein synthesis is end result– ExampleExample

Hormone Action (cont)Hormone Action (cont)

Nonsteriod hormone (amines, peptides, Nonsteriod hormone (amines, peptides, proteins)proteins)– Hormone (primary messenger) binds to Hormone (primary messenger) binds to

receptor on outside of cellreceptor on outside of cell– Binding causes activity center inside cell to Binding causes activity center inside cell to

activate a messenger (sometimes cAMP)activate a messenger (sometimes cAMP)– This second messenger cause the change in This second messenger cause the change in

the target cellthe target cell

Hormonal ControlHormonal Control

Stimulation of hormone releaseStimulation of hormone release– HypothalamusHypothalamus– Nervous systemNervous system– Changing internal environmentChanging internal environment

Inhibition of hormone releaseInhibition of hormone release– Negative feedback loopNegative feedback loop

HypothalamusHypothalamus

•Located deep inside the brain

•Releasing and inhibiting hormone secretion to anterior pituitary

•Direct innervation to posterior pituitary

Pituitary GlandPituitary Gland

•Located deep within the brain

•Divided into two sections

•Anterior Pituitary- glandular epithelium with many blood vessels

•Posterior Pituitary- nerve fibers and neuroglial cells

Tropic Hormones of the Anterior Tropic Hormones of the Anterior PituitaryPituitary

Thyroid-stimulating hormone (TSH)Thyroid-stimulating hormone (TSH)

Adrenocorticotropic hormone (ACTH)Adrenocorticotropic hormone (ACTH)

GonadotropinsGonadotropins– Follicle-stimulating hormone (FSH)Follicle-stimulating hormone (FSH)– Lutenizing hormone (LH)Lutenizing hormone (LH)

Thyroid-stimulating hormone Thyroid-stimulating hormone (TSH)(TSH)

Stimulation: Thyrotropin-releasing Stimulation: Thyrotropin-releasing hormone (TRH) from hypothalamushormone (TRH) from hypothalamus

Inhibition: Circulating thyroid hormones Inhibition: Circulating thyroid hormones decrease TSH and TRH secretiondecrease TSH and TRH secretion

Target Cell: Thyroid Target Cell: Thyroid

Action: Increase thyroid secretions Action: Increase thyroid secretions

Adrenocorticotropic hormone Adrenocorticotropic hormone (ACTH)(ACTH)

Stimulation: Corticotropin-releasing Stimulation: Corticotropin-releasing hormone (CRH) from hypothalamushormone (CRH) from hypothalamus

Target Cell: Adrenal cortexTarget Cell: Adrenal cortex

Action: Increase adrenal cortex secretionsAction: Increase adrenal cortex secretions

Follicle-stimulating hormone Follicle-stimulating hormone (FSH)(FSH)

Stimulation: Gonadotropin-releasing Stimulation: Gonadotropin-releasing hormone from hypothalamushormone from hypothalamus

Target Cell: Gonads (testes in males and Target Cell: Gonads (testes in males and ovaries in females)ovaries in females)

Action:Action:– Female- maturation of egg; secretion of Female- maturation of egg; secretion of

estrogenestrogen– Male- development of spermMale- development of sperm

Lutenizing hormone (LH)Lutenizing hormone (LH)

Also called Interstitial cell stimulating hormone Also called Interstitial cell stimulating hormone (ICSH)(ICSH)Stimulation: Gonadotropin-releasing hormone Stimulation: Gonadotropin-releasing hormone from hypothalamusfrom hypothalamusTarget Cell: Gonads (testes in males and Target Cell: Gonads (testes in males and ovaries in females)ovaries in females)Action:Action:– Female- release of mature egg from ovary (ovulation)Female- release of mature egg from ovary (ovulation)– Male- development of interstitial cell; secretion of Male- development of interstitial cell; secretion of

male sex hormonesmale sex hormones

Other hormone of the Anterior Other hormone of the Anterior PituitaryPituitary

Growth Hormone (GH)Growth Hormone (GH)– Stimulation: GH-releasing hormone from Stimulation: GH-releasing hormone from

hypothalamushypothalamus– Inhibition: GH release-inhibiting hormoneInhibition: GH release-inhibiting hormone– Target Cell: Somatic cells Target Cell: Somatic cells – Action: enhances movement of amino acids Action: enhances movement of amino acids

across cell membrane; speeds up rate of across cell membrane; speeds up rate of carbohydrate utilizationcarbohydrate utilization

Other hormone of the Anterior Other hormone of the Anterior Pituitary (cont)Pituitary (cont)

Prolactin (PRL)Prolactin (PRL)– Stimulates breast development necessary for Stimulates breast development necessary for

lactationlactation– Stimulates breast to secrete milk after birthStimulates breast to secrete milk after birth

Posterior PituitaryPosterior Pituitary

Antidiuretic hormone (ADH)Antidiuretic hormone (ADH)– Stimulation: Nerve Impulse from hypothalamus when Stimulation: Nerve Impulse from hypothalamus when

osmoreceptors sense dehydrationosmoreceptors sense dehydration– Target Cell: kidneys Target Cell: kidneys – Action: kidneys produce less urine to conserve waterAction: kidneys produce less urine to conserve water

Oxytocin (OT)Oxytocin (OT)– Stimulates contraction of the pregnant uterusStimulates contraction of the pregnant uterus– Stimulates “let-down” of milkStimulates “let-down” of milk

ThyroidThyroid

•Location: attached to front of trachea

•Contains follicles

•Follicles have hollow center cavity filled with colloid

Thyroid (cont)Thyroid (cont)

Follicular cells secrete two hormonesFollicular cells secrete two hormones– Thyroxine (tetraiodothyronine)- TThyroxine (tetraiodothyronine)- T44

– Triiodothyronine- TTriiodothyronine- T3 3 (much more potent)(much more potent)– Increases metabolism of carbohydrates, Increases metabolism of carbohydrates,

lipids, and proteinslipids, and proteins

Extrafollicular cells secrete calcitoninExtrafollicular cells secrete calcitonin– Lowers blood calcium level by inhibiting Lowers blood calcium level by inhibiting

osteoclasts and making kidney secrete more osteoclasts and making kidney secrete more calcium in urinecalcium in urine

Parathyroid glandsParathyroid glands

Located on the thyroid in four patches of Located on the thyroid in four patches of highly dense secretory cellshighly dense secretory cells

Secrete Parathyroid hormone (PTH)Secrete Parathyroid hormone (PTH)– Raises blood calcium levelsRaises blood calcium levels– Inhibits osteoblasts, stimulates osteoclasts, Inhibits osteoblasts, stimulates osteoclasts,

makes kidneys conserve calcium, increase makes kidneys conserve calcium, increase absorption of calcium in intestineabsorption of calcium in intestine

Adrenal glandsAdrenal glands

Adrenal CortexAdrenal Cortex

Three layers: outer, middle, and innerThree layers: outer, middle, and inner

Closely packed masses of epithelial tissueClosely packed masses of epithelial tissue

Outer Layer of CortexOuter Layer of Cortex

Outer (glomerulosa)Outer (glomerulosa)– Mineralocorticoid (MC)- regulate mineral Mineralocorticoid (MC)- regulate mineral

electrolyteselectrolytesAldosteroneAldosterone

– Stimulated by decrease in blood levels of sodium, Stimulated by decrease in blood levels of sodium, increase in potassium in blood levels, or decrease in increase in potassium in blood levels, or decrease in blood pressureblood pressure

– Cause kidneys to retain sodium and secrete potassium Cause kidneys to retain sodium and secrete potassium into urineinto urine

– Indirectly water will be retained as wellIndirectly water will be retained as well

Adrenal Cortex (cont)Adrenal Cortex (cont)

Middle (fasciculata)Middle (fasciculata)– Glucocorticoids- affects glucose metabolismGlucocorticoids- affects glucose metabolism

Cortisol or hydrocortisoneCortisol or hydrocortisone– Increase gluconeogenisisIncrease gluconeogenisis– Inhibition of protein synthesisInhibition of protein synthesis– Promotion of fatty acid release from adipose tissuePromotion of fatty acid release from adipose tissue– Produce state of stressProduce state of stress

Adrenal Cortex (cont)Adrenal Cortex (cont)

Inner (reticularis)Inner (reticularis)– Sex hormones Sex hormones

Produces androgen hormonesProduces androgen hormones

Can be used to synthesize female sex hormones Can be used to synthesize female sex hormones like estrogenslike estrogens

Adrenal MedullaAdrenal Medulla

Composed of modified neuronsComposed of modified neuronsSecrete epinephrine (adrenaline) and Secrete epinephrine (adrenaline) and norepinephrine (noradrenaline)norepinephrine (noradrenaline)

““Fight or Flight” responseFight or Flight” response

Directly innervated by sympathetic Directly innervated by sympathetic nervous systemnervous system

Pancreatic Islets (Islets of Pancreatic Islets (Islets of Langerhans)Langerhans)

Alpha cellsAlpha cells– GlucagonGlucagon

Accelerates process of gylcogenolysisAccelerates process of gylcogenolysis

Beta cellsBeta cells– InsulinInsulin

Increeases movement of glucose inside of cells for Increeases movement of glucose inside of cells for metabolismmetabolism

Stimulates liver to produce glycogenStimulates liver to produce glycogen

ThymusThymus

•Located in mediastinum cavity

•Hormones called thymosins

•Important function in development of immune system

Pineal glandPineal gland

Releases melatoninReleases melatonin

– Regulates body clock and sleep cycleRegulates body clock and sleep cycle

Female Sex GlandsFemale Sex Glands

OvariesOvaries

Ovarian Ovarian follicles follicles

Corpus Corpus luteumluteum

Male sex glandsMale sex glands

TestesTestes

– Interstitial cells produce testosteroneInterstitial cells produce testosterone

– Testosterone stimulates sperm productionTestosterone stimulates sperm production

PlacentaPlacenta

•Chorionic gonadotropins

•Pregnancy tests test for this hormone

•Prevents dissolution of corpus luteum

Other hormonesOther hormones

Wall of Atria in HeartWall of Atria in Heart– Atrial Natriuretic hormone- regulates fluid and Atrial Natriuretic hormone- regulates fluid and

electrolyte balance by increasing removal of electrolyte balance by increasing removal of sodium and watersodium and water

Various Digestive GlandsVarious Digestive Glands

KidneysKidneys– Erythropoietin- red blood cell growth hormoneErythropoietin- red blood cell growth hormone