Slide 1Endocrine SystemEndocrine SystemChemical Classification of HormonesHormones classified by SolubilityHormonesPrehormonesComparing Neurotransmitters with HormonesMechanism of action of Lipophilic hormonesMechanism of action of Lipophilic hormonesMechanism of action of Lipophilic hormonesMechanism of action of Lipophilic hormonesMechanism of action of Lipophilic hormonesMechanism of Steroid Hormone ActionMechanism of Steroid Hormone ActionMechanism of Thyroid Hormone ActionMechanism of Thyroid Hormone ActionMechanism of Thyroid Hormone ActionMechanism of Thyroid Hormone ActionMechanism of Thyroid Hormone ActionHormones that use Second MessengersAdenylate Cyclase-Cyclic AMP Second Messenger SystemAdenylate Cyclase-Cyclic AMP Second Messenger SystemAdenylate Cyclase-Cyclic AMP Second Messenger SystemAdenylate Cyclase-Cyclic AMP Second Messenger SystemPhospholipase C-Ca2+ Second Messenger SystemPhospholipase C-Ca2+ Second Messenger SystemPhospholipase C-Ca2+ Second Messenger SystemPhospholipase C-Ca2+ Second Messenger SystemPhospholipase C-Ca2+ Second Messenger SystemPhospholipase C-Ca2+ Second Messenger SystemTyrosine Kinase Second Messenger SystemTyrosine Kinase Second Messenger SystemPituitary GlandPituitary HormonesHormones of the anterior pituitaryHormones of the adrenohypophysisHormones of neurohyophysisHormones of neurohyophysisHypothalamic Control of the Posterior PituitaryHypothalamic Control of the Posterior PituitaryHypothalamic Control of the Anterior PituitaryReleasing and Inhibiting HormonesReleasing and Inhibiting HormonesContinuedAdrenal GlandsAdrenal GlandsFunctions of the Adrenal CortexFunctions of the Adrenal CortexFunctions of the Adrenal CortexConditions of Adrenal CortexConditions of Adrenal CortexAdrenal MedullaPhysiology Exam 2- Chapter 11Endocrine System•Endocrine glands lack the ducts that are present in exocrine glands. The endocrine glands secrete hormones into the blood.•Exocrine glands secrete chemicals through a duct that leads to the outside of a membrane, and thus to the outside of a body surface.•Both are developed in embryo in epithelia.Endocrine System•Epithelial tissue lining the inner surface of the trachea develops evagination (vagination of epithelium of trachea). Connection to the epithelial surface is cut off which forms the thyroid gland. To retain connection to epithelial surface, the salivary gland is formed.•The skin, stomach, heart, and liver are all endocrine glands that produce hormones.Chemical Classification of Hormones•Hormones can be divided into a few chemical classes.1. Amines: Hormones derived from the amino acids tyrosine and tryptophan. They include the hormones secreted by the adrenal medulla (epinephrine and norepinephrine).2. Polypeptides and proteins: Antidiuretic hormone (ADH) is a polypeptide, growth hormone is a protein, insulin (two polypeptide chains derived from a single, larger molecule).3. Glycoproteins: These molecules consist of a protein bound to one or more carbohydrate groups. Examples are follicle-stimulating hormone (FSH) and luteinizing hormone (LH).4. Steroids: Two basic types: Sex steroids produced by gonads and corticosteroids produced by the adrenal cortex.Hormones classified by Solubility•Hormones can be divided into those that are polar and water soluble and those that are nonpolar and insoluble in water.•Because the nonpolar hydrophobic hormones are soluble in lipids, they are called lipophilic hormones. They are active when taken orally and have a genomic action (can turn genes on or off). Lipophilic hormones are steroid hormones (contraceptive pills) and thyroid hormones (pills for people whose thyroid is deficient).•Polar hydrophilic, water soluble hormones include polypeptides, glycoproteins, and the monoamines (catecholamine hormones secreted by the adrenal medulla, epinephrine, and norepinephrine). These cannot be taken orally, cannot pass the plasma membrane of the target cell, goes through the signal transduction pathway (no genomic action) for hormone to have its effect on the target cell.Hormones•Hormone molecules that affect the metabolism of target cells are often derived from precursor molecules. In polypeptide hormones, the precursor may be a long chained prohormone that is cut and spliced together to make a hormone. Prehormones are sometimes used to indicate such precursors of prohormones.Prehormones•In some cases, the hormone secreted by the endocrine gland from the prehormone is actually inactive in target cells. To become active, the target cells must modify the chemical structure of the secreted hormone.•Prehormone Thyroxine (T4) is a principle hormone of the thyroid gland and must be changed into T3 within the target cells in order to affect the metabolism of those cells.Comparing Neurotransmitters with Hormones•Neurotransmitters do not travel in the blood as do hormones, instead, they diffuse across a narrow synaptic cleft to the membrane of the postsynaptic cell. Hormones are released by an endocrine gland.•However, the actions of neurotransmitters are very similar to the actions of hormones. In order to function as physiological regulation, they are both regulatory molecules that combine to receptor proteins and cause a specific sequence of changes in the target cell, which must have a mechanism to turn off the action of the regulator .Mechanism of action of Lipophilic hormones•The mechanism of action of lipophilic hormones include the steroid hormone family (sex steroids and corticosteroids) and the thyroid hormone family (thyroid hormones T3 and T4)Mechanism of action of Lipophilic hormones•Hormones are delivered by the blood to every cell in the body but only the target cells are able to respond to these hormones. In order to respond, a target cell must have specific receptor proteins for that hormone. Because the lipophilic hormones (steroids and thyroxine) can pass through the plasma membrane and enter their target cells, the receptor proteins for them are located within the cytoplasm and nucleus.Mechanism of action of Lipophilic hormones•Unlike water soluble hormones, the lipophilic steroid and thyroid hormones do not travel dissolved in the aqueous portion of the plasma, instead, they are transported to their target cells attached to plasma carrier proteins. These hormones must then dissociate from their carrier proteins in the blood in order to pass through the lipid component of the plasma membrane and enter the target cell,