Endocrine SystemHarliansyah Dept BiochemistryUniversity of YARSI

Hormones are chemical substances, involved in cell to cell communication, that promote the maintenance of homeostasis.

Hormones are blood borne substances involved in regulating a variety of processes.

The word hormone is derived from the Greek hormaein which means to exciteor to stir up.

The endocrinology is the branch of physiology concerned with the descriptionand characterization of processes involved in the regulation and integration of cells and organ systems.

The Endocrine System forms an important communication system that serves toRegulate, Integrate and Coordinate a variety of different physiological processes

The process that hormones regulate fall into four areas:The digestion, utilization and storage of nutrientGrowth and development3. Ion and water balance4. Reproductive function

General CharacteristicsGlands that secrete chemical signals (hormones) into circulatory systemHormone characteristicsProduced in small quantitiesSecreted into intercellular spaceTransported some distance in circulatory systemActs on target tissues elsewhere in bodyRegulate activities of body structuresLigands: more general term for chemical signals

4 Classes of HormonesPeptide/ ProteinSteroidAmineEicosanoid

Protein/Peptide HormonesHydrophilicLargeCan't fit through membraneSecond messenger mechanism of actionMost hormonesExample: Insulin

Steroid HormonesSmallHydrophobic/LipophilicTravel in blood w/carrierCytoplasmic or nuclear receptorschange protein synthesisExample: estradiol

AmineSynthesized from a single amino acidMelatonin from tryptophanThyroid hormone from tyrosineCatecholamines (EPI, DA) from tyrosine

EicosanoidProduced from 20-carbon fatty acid, arachadonic acidProduced in all cells except RBCs2nd messengerProstaglandins and leukotrienesinflammation

Hormone + Receptor

SteroidHormoneMechanism

Regulation of Activities: Comparison of Endocrine and Nervous SystemsEndocrine: amplitude modulated signals. Amount of hormone determines strength of signalOnset within minutes of secretion of hormoneNervous: frequency-modulated signals. Frequency of action potentials produced by neurons determines strength of signal.Onset within millisecondsTwo systems actually inseparableNervous system secretes neurohormones into circulatory systemNervous system uses neurotransmitters and neuromodulators as ligandsSome parts of endocrine system innervated directly by nervous system

Intercellular Chemical SignalsHormones: type of intercellular signal. Produced by cells of endocrine glands, enter circulatory system, and affect distant cells; e.g., estrogenAutocrine: released by cells and have a local effect on same cell type from which chemical signals released; e.g., prostaglandinParacrine: released by cells and affect other cell types locally without being transported in blood; e.g., somatostatinPheromones: secreted into environment and modify behavior and physiology; e.g., sex pheromones Neurohormone: produced by neurons and function like hormones; e.g., oxytocinNeurotransmitter or neuromodulator: produced by neurons and secreted into extracellular spaces by presynaptic nerve terminals; travels short distances; influences postsynaptic cells; e.g., acetylcholine.

HypothalamusGRHTRHCRHDopaminePRF, PIFGnRHGHTSHACTHLPH-EndorphinPRLFSHLHMSHAnterior pituitaryGrowth of bone, body tissues; carbohydrate and protein metabolism; production of IGFsHyperglycemic effectsThyroid hormonesLiverThyroidAdrenal cortexMammary glandOvaryTestisCorticosteroids-EndorphinAnalgesiaSkin darkeningTestisCell development, lactationDevelopment of follicles, estradiolGrowth of seminal tubules and spermatogenesisOvaryOvulation, corpus luteum, progesteroneInterstitial cell development, testosteroneGH-Growth hormone, TSH-Thyrotropin, ACTH-Adrenocorticotropic hormone, LPH-Lipotropin,MSH-Melanocyte stimulating hormone, PRL-Prolactin, FSH-Follicle stimulating hormone, LH-Luteinizing hormone

CNSLimbic systemHypothalamusAnterior pituitaryAdrenal glandEnvironmental stressA single stressor (change in temperature, noise, trauma)Electrical-chemical signalElectrical-chemical signalCorticotropin releasing hormone (CRH) in ng, t1/2 minutesAdrenocorticotropic hormone (ACTH) in g, increased t1/2Cortisol in mg, t1/2 hoursThe glucocorticoid receptors in different cellsPortal systemThe corticotrophic cellsSystemic effectsCRH-ACTH-Cortisol

CNSLimbic systemHypothalamusAnterior pituitaryTarget glandEnvironmental or internal signalElectrical-chemical signalElectrical-chemical signalReleasing hormones (ng)Anterior pituitary hormone (g)Ultimate hormone (mg)Systemic effectsThe gonads, the thyroid gland, the adrenal cortexHormonal cascade Signal amplification

CNSLimbic systemHypothalamusAnterior pituitaryTarget glandReleasing hormonesAnterior pituitary hormonesUltimate hormoneSystemic effectsShort feedback loopLong feedback loopHormonal cascade Negative feedback system

Control Pathways and Feedback LoopsThere are three types of hormonal control pathways

***********