Presentation on theme: "Endocrine Glands: Secretion and Action of Hormones"— Presentation transcript:
1 Endocrine Glands: Secretion and Action of Hormones Chapter 11 Part 1Endocrine Glands:Secretion and Action of Hormones
2 Classic Definition of a Hormone Hormone - Chemical messenger produced by a ductless gland or tissue and carried in the blood/lymph to a target organ where it effects a change in cellular activity.EffectorCell 1TargetCell 2Capillary
3 Endocrine Glands Testis in Male Adrenal Gland Hypothalamus Ovary KidneyPituitaryLocated atbase of brainThyroidParathyroidTestis inMale
4 Anterior & Posterior Pituitary Higher Centers of Brain Control All Hormonal FunctionsCerebrumHypothalamusThirdVentriclePinealBodyMedullaOblongataPituitary StalkAnterior & PosteriorPituitaryCerebellum
5 Anatomy of Cow Brain Infundibular Stalk Diaphragma sellae Pituitary Spenoid Bone
6 Control of Endocrine Gland Function Hypothalamic-Pituitary InterrelationshipsHypothalamusSecreting neurons: GnRH, CRH, TRH, GHRHNerve cells which releasepeptide hormones:Oxytocin, ADHSuperior HypophysealArteryHypophyseal Portal VesselsPituitary StalkPosterior Pituitary:NeurohypophysisNerve endings comedirectly from hypothalamusAnterior PituitaryAdenohypophysisnon-neural tissueRelease of LH, FSH,ACTH, PRL, GH, TSHRelease of Oxytocin or ADHinto circulation
7 Endocrine Glands and Hormones Secrete biologically active molecules into the blood.Lack ducts.Carry hormones to target cells that contain specific receptor proteins for that hormone.Target cells can respond in a specific fashion.Different from nervous system –Nervous system is fast, short-term reactionsEndocrine – longer duration, adaptation response.
8 Endocrine Glands and Hormones (continued) Neurohormone:Specialized neurons that secrete chemicals into the blood rather than synaptic cleft.Chemical secreted is called neurohormone.Hormones:Affect metabolism of target organs.Help regulate total body metabolism, growth, and reproduction.
9 Other forms of endocrine action 1) Paracrine - released from effector cell (E) interact with a different target cell (T1).2) Autocrine - secreted by E interact with original E cell or similar cell types.3) Juxtacrine -expressed on surface of E and interacts with target cell (T2) via direct cell-cell contact.4) Intracrine - is not secreted by E and interacts with an intercellular receptor.EET
10 EctocrineFlehmenPheromones: A chemical substance that is liberated by one animal and causes a relatively specific behavior modification in a recipient animal following its chemoreceptionLee-Boot effect: Crowded female mice become anestrous when no males are present.Bruce effect: A newly mated female mouse will abort if placed with a strange male (not the previous mate).Dormitory effect: menstrual synchrony in all-females living groups
11 Common Aspects of Neural and Endocrine Regulation APs are chemical events produced by diffusion of ions through neuron plasma membrane.Action of some hormones are accompanied by ion diffusion and electrical changes in the target cell.Nerve axon boutons release NTs.Some chemicals are secreted as hormones, and also are NTs.In order for either a NT or hormone to function in physiological regulation:Target cell must have specific receptor proteins.Combination of the regulatory molecule with its receptor proteins must cause a specific sequence of changes.There must be a mechanism to quickly turn off the action of a regulator.
16 Most hormones belong to one of 4 structural classes Peptides & Amines (E, NE % DA) are hyrophilicSteroids and eicosanoids are hydrophobic
17 Structural Classes Amines: Peptides, Polypeptides and Proteins Hormones derived from tyrosine and tryptophan.NE, Epi, T4.Peptides, Polypeptides and ProteinsPolypeptidesChains of < 100 amino acids in length.ADH.Ex: Adrenalcorticotropic Hormone (ACTH) – 39 amino acidsPeptide - Few - Several amino acidsEx: Gonadotropin Releasing Hormone (GnRH) - 10 amino acidsOxytocin - 8 amino acidsProtein hormones:Polypeptide chains with > 100 amino acids.Growth hormone, Insulin, ACTH.Prolactin amino acids
18 Structural ClassesGlycoprotein - Protein hormone with carbohydrate moleculesSome have large amount of sialic acid – FSHSteroidsLipids derived from cholesterolAre lipophilic (fat loving; can diffuse through plasma membrane) hormones.Ex – testosterone, estradiol, progesteone, and cortisol
19 Effects of [Hormone] on Tissue Response [Hormone] in blood reflects the rate of secretion.Half-life:Time required for the blood [hormone] to be reduced to ½ reference level.Minutes to days.Normal tissue responses are produced only when [hormone] are present within physiological range.Varying [hormone] within normal, physiological range can affect the responsiveness of target cells.
20 Percent of Carbohydrate and Size of Protein Effects Half-Life in Blood Equine ChorionicGonadotropin -45% CarbohydrateeCG% inBloodAfterInjectionHuman ChorionicGonadotropin -30% CarbohydrateFollicle Stimulating Hormone8% CarbohrydrateGnRHOxytocinLuteinizing Hormonelittle sialic acidTime required to remove or clear half of the dose from the blood
21 Chemical Classification of Hormones (continued)
23 Hormone Synthesis Protein Hormones Synthesized at ribosomes as large precursor proteinsPreprohomrone converted to prohormone within rough ERGolgi apparatus – packages prohormone and converts it to hormoneStored in secretory granulesUpon stimulation – get exocytosisRequires:1. ATP2. Ca
24 The flow of genetic information in a typical cell
25 b a Anterior Pituitary Hormones Such as LH, FSH and TSH (Thyroid Stimulating Hormone) have Two ChainsAlpha - aBeta - bbSSaa chain is identical between FSH, LH and TSH.b chain gives the hormone its specific action.Need both chains together for biological activity
27 Synthesis of Steroid Hormones Ex: glucocorticoids, mineralocorticoids, sex steroidsFormed from cholesterol – which is used immediately or stored in cellType of steroid hormone produced depends on presence of specific enzymesEX: adrenal cortex cell – contain enzymes needed for production of glucocorticoids or mineralocorticoidsSteroid hormones secreted immediately from cell after formationRate of steroid hormone secretion controlled by rate of production
28 Cholesterol C27 Pregnenolone C21 Androgens C19 Glucocorticoids C21 Mineralocorticoids, glucocorticoids and steroids are synthesized from cholesterolCholesterol C27Pregnenolone C21Glucocorticoids C21Mineralocorticoids C21Androgens C19Estrogens C18
29 Chemical Classification of Hormones (continued) Hormones can also be divided into:Polar:H20 soluble.Nonpolar (lipophilic):H20 insoluble.Can gain entry into target cells.Steroid hormones and T4.Pineal gland secretes melatonin:Has properties of both H20 soluble and lipophilic hormones.
30 Prohormones and Prehormones Precursor is a longer chained polypeptide that is cut and spliced together to make the hormone.Proinsulin.Preprohormone:Prohormone derived from larger precursor molecule.Preproinsulin.Prehormone:Molecules secreted by endocrine glands that are inactive until changed into hormones by target cells.T4 converted to T3.
32 Hormonal Interactions Synergistic:Two hormones work together to produce a result.Additive:Each hormone separately produces response, together at same concentrations stimulate even greater effect.NE and Epi.Complementary:Each hormone stimulates different step in the process.FSH and testosterone.
33 Hormonal Interactions (continued) Permissive effects:Hormone enhances the responsiveness of a target organ to second hormone.Increases the activity of a second hormone.Prior exposure of uterus to estrogen induces formation of receptors for progesterone.Antagonistic effects:Action of one hormone antagonizes the effects of another.Insulin and glucagon.
34 Effects of [Hormone] on Tissue Response (continued) Priming effect (upregulation):Increase number of receptors formed on target cells in response to particular hormone.Greater response by the target cell.Desensitization (downregulation):Prolonged exposure to high [polypeptide hormone].Subsequent exposure to the same [hormone] produces less response.Decrease in number of receptors on target cells.Insulin in adipose cells.Type 2 diabetesPulsatile secretion may prevent down regulation.
35 Mechanisms of Hormone Action Hormones of same chemical class have similar mechanisms of action.Similarities include:Location of cellular receptor proteins depends on the chemical nature of the hormone.Events that occur in the target cells.GH and Prolactin (Trophic hormones - increase in growth)To respond to a hormone:Target cell must have specific receptors for that hormone (specificity).Hormones exhibit:Affinity (bind to receptors with high bond strength).Saturation (low capacity of receptors).