Ciencias Biológicas 2 © 2006 Teresa Audesirk Gerald Audesirk Bruce E. Byres

Control químico del organismo animal: El sistema endocrino Biology: Life on Earth (Audesirk) Capítulo 2: Hormonas Control químico del organismo animal: El sistema endocrino Chapter 32

Hormonas Animales Clases de hormonas: Hormonas peptídicas Hormonas basadas en aminoácidos Hormonas esteroideas Prostaglandinas Funciones de las hormonas Se unen a receptores en la superficie de las células blanco Atraviesan la membrana plasmática de la célula blanco y se unen a receptores en el citoplasma La acción hormonal generalmente se regula por retroalimentación negativa

Principales glándulas endocrinas en los seres humanos Complejo hipotálamo - pituitaria Glándulas tiroides y paratiroides La tiroides produce tiroxina y eleva la tasa metabólica Hipertiroidismo El páncreas como glándula endocrina La insulina y el glucagón regulan la glucosa en la sangre Los defectos en la producción, liberación o recepción de insulina producen diabetes mellitus Los órganos sexuales secretan hormonas esterioideas Desempeñan un papel clave en la pubertad, basado en las características sexuales secundarias Producen gametos

Principales glándulas endocrinas en los seres humanos Glándulas suprarrenales (1 en cada riñón) Médula suprarrenal Produce adrenalina y noradrenalina Estas hormonas se liberan en respuesta a tensiones, preparan al cuerpo para acciones de emergencia

Principales glándulas endocrinas en los seres humanos Corteza suprarrenal Produce glucocorticoides Hormonas esteroideas que regulan el metabolismo de la glucosa Los glucocorticoides y la medicina del deporte Produce aldosterona Hormona esteroidea que regula el contenido de sodio en la sangre Una excesiva síntesis de testosterona causa masculinización en las mujeres

Biology: Life on Earth (Audesirk) Principales glándulas endocrinas en los seres humanos hipotálamo Pituitaria o hipófisis tiroides timo Haga click en el recuadro para una visión expandida The major mammalian endocrine glands are the hypothalamus-pituitary gland complex, the thyroid and parathyroid glands, the pancreas, the sex organs (ovaries in females, testes in males), and the adrenal glands. Other organs that secrete hormones include the pineal gland, thymus, kidneys, heart, and parts of the digestive tract. glándulas suprarrenales (una en cada riñón) Páncreas (islotes de Langerhans) gónadas testículo ovario Chapter 32

El sistema endocrino en los mamíferos Glándulas exocrinas B. Glándulas endocrinas

Glándulas endocrinas, Hormonas, y Células Blanco Biology: Life on Earth (Audesirk) Glándulas endocrinas, Hormonas, y Células Blanco La hormona entra al torrente sanguíneo Células endocrinas liberan hormona La hormona se distribuye por el cuerpo Endocrine glands consist of hormone-producing cells embedded in a network of capillaries. These cells secrete hormones into the extracellular fluid, from which they diffuse into the capillaries. Each hormone is transported around the body by the bloodstream but binds to (and influences) only those cells that contain specific receptors for the hormone. Muscle cells but not neurons have receptors for the particular hormone shown here. Receptor en la célula blanco Capilar TEJIDO NERVIOSO no hay unión, no hay efectos hormonales TEJIDO MUSCULAR ESQUELÉTICO: hay unión, aparen efectos hormonales Complejo Hormona-receptor Chapter 32

Hormonas peptídicas y de aminoácidos Biology: Life on Earth (Audesirk) Hormonas peptídicas y de aminoácidos 1) Peptide and amino-acid hormones, which are not soluble in lipids, bind to a receptor on the outside of the target cell’s plasma membrane. 2) Hormone-receptor binding triggers the synthesis of cyclic AMP (cAMP). 3) Cyclic AMP activates enzymes that 4) promote specific cellular reactions, producing new products. This cAMP “cascade” may generate a variety of responses, such as an increase in glucose synthesis (induced by epinephrine) and an increase in estrogen synthesis (induced by luteinizing hormone). Chapter 32

Hormonas peptídicas y de aminoácidos Biology: Life on Earth (Audesirk) Hormonas peptídicas y de aminoácidos 1) Peptide and amino-acid hormones, which are not soluble in lipids, bind to a receptor on the outside of the target cell’s plasma membrane. 2) Hormone-receptor binding triggers the synthesis of cyclic AMP (cAMP). 3) Cyclic AMP activates enzymes that 4) promote specific cellular reactions, producing new products. This cAMP “cascade” may generate a variety of responses, such as an increase in glucose synthesis (induced by epinephrine) and an increase in estrogen synthesis (induced by luteinizing hormone). Chapter 32

Hormonas peptídicas y de aminoácidos Biology: Life on Earth (Audesirk) Hormonas peptídicas y de aminoácidos 1) Peptide and amino-acid hormones, which are not soluble in lipids, bind to a receptor on the outside of the target cell’s plasma membrane. 2) Hormone-receptor binding triggers the synthesis of cyclic AMP (cAMP). 3) Cyclic AMP activates enzymes that 4) promote specific cellular reactions, producing new products. This cAMP “cascade” may generate a variety of responses, such as an increase in glucose synthesis (induced by epinephrine) and an increase in estrogen synthesis (induced by luteinizing hormone). Chapter 32

Hormonas peptídicas y de aminoácidos Biology: Life on Earth (Audesirk) Hormonas peptídicas y de aminoácidos 1) Peptide and amino-acid hormones, which are not soluble in lipids, bind to a receptor on the outside of the target cell’s plasma membrane. 2) Hormone-receptor binding triggers the synthesis of cyclic AMP (cAMP). 3) Cyclic AMP activates enzymes that 4) promote specific cellular reactions, producing new products. This cAMP “cascade” may generate a variety of responses, such as an increase in glucose synthesis (induced by epinephrine) and an increase in estrogen synthesis (induced by luteinizing hormone). Chapter 32

Hormonas esteroideas lipo-solubles Biology: Life on Earth (Audesirk) Hormonas esteroideas lipo-solubles 1) Lipid-soluble steroid hormones diffuse readily through the plasma membrane into the target cell and into the nucleus, where they combine with a protein receptor molecule. 2) The hormone-receptor complex binds to DNA and facilitates the binding of RNA polymerase to promoter sites on specific genes, accelerating 3) the transcription of DNA into messenger RNA (mRNA). 4) The mRNA then directs protein synthesis. In hens, for example, estrogen promotes the transcription of the albumin gene, causing the synthesis of albumin (egg white), which is packaged in the egg as a food supply for the developing chick. Chapter 32

Hormonas esteroideas lipo-solubles Biology: Life on Earth (Audesirk) Hormonas esteroideas lipo-solubles 1) Lipid-soluble steroid hormones diffuse readily through the plasma membrane into the target cell and into the nucleus, where they combine with a protein receptor molecule. 2) The hormone-receptor complex binds to DNA and facilitates the binding of RNA polymerase to promoter sites on specific genes, accelerating 3) the transcription of DNA into messenger RNA (mRNA). 4) The mRNA then directs protein synthesis. In hens, for example, estrogen promotes the transcription of the albumin gene, causing the synthesis of albumin (egg white), which is packaged in the egg as a food supply for the developing chick. Chapter 32

Hormonaas esteroideas lipo-solubles Biology: Life on Earth (Audesirk) Hormonaas esteroideas lipo-solubles 1) Lipid-soluble steroid hormones diffuse readily through the plasma membrane into the target cell and into the nucleus, where they combine with a protein receptor molecule. 2) The hormone-receptor complex binds to DNA and facilitates the binding of RNA polymerase to promoter sites on specific genes, accelerating 3) the transcription of DNA into messenger RNA (mRNA). 4) The mRNA then directs protein synthesis. In hens, for example, estrogen promotes the transcription of the albumin gene, causing the synthesis of albumin (egg white), which is packaged in the egg as a food supply for the developing chick. Chapter 32

El hipotálamo controla a la pituitaria Biology: Life on Earth (Audesirk) El hipotálamo controla a la pituitaria Pituitaria Hipotálamo Células neurosecretoras Neurosecretory cells of the hypothalamus control hormone release in the anterior lobe of the pituitary by producing releasing hormones (left). These cells secrete their hormones into a capillary network that carries them to the anterior pituitary. There, each releasing hormone stimulates endocrine cells with appropriate receptors to secrete that hormone while leaving other types unaffected. The posterior lobe of the pituitary (right) is an extension of the hypothalamus. Neurosecretory cells in the hypothalamus have cell endings on a capillary bed in the posterior lobe, where the cells release oxytocin or antidiuretic hormone (ADH). Hormona liberadora Lóbulo anterior Lóbulo posterior Chapter 32

Biology: Life on Earth (Audesirk) Hormonas y Lactancia Se secreta oxitocina The control of milk letdown by oxytocin during breastfeeding is regulated by feedback between a baby and its mother. The mammary gland is an exocrine gland. There, clusters of milk-producing cells surround hollow bulbs, where milk collects in lactating women. The bulbs are surrounded by muscle that can expel the milk through the nipple. Milk is expelled when suckling stimulates nerve endings that send a signal to the mother’s hypothalamus, causing the posterior pituitary to secrete oxytocin into the bloodstream. When oxytocin reaches the muscles that surround the milk ducts, it causes them to contract and expel milk through the nipple. This cycle continues until the infant is full and stops suckling. With the nipple no longer being stimulated, oxytocin release stops, the muscles relax, and milk flow ceases. (3)Los músculos se contraen (1) La succión estimula terminaciones nerviosas que envían una señal al hipotálamo (4) Se libera leche Chapter 32

Biology: Life on Earth (Audesirk) Las glándulas tiroides y paratiroides Una dieta deficiente en yodo puede producir bocio (a) The thyroid and parathyroid glands wrap around the front of the larynx in the neck. (b) Goiter, a condition in which the thyroid gland becomes greatly enlarged, is caused by an iodine-deficient diet. Chapter 32

Retroalimentación negativa en la función de la glándula tiroides Biology: Life on Earth (Audesirk) Retroalimentación negativa en la función de la glándula tiroides El frío estimula al hipotálamo a secretar la hormona liberadora 6 1 Esa hormona activa la liberación de la hormona estimuladora de la tiroides (TSH) Pituitaria anterior 1) Low body temperature or stress stimulates neurosecretory cells of the hypothalamus to secrete a releasing hormone. 2) That hormone triggers the release of thyroid-stimulating hormone (TSH) from the anterior pituitary. 3) TSH stimulates the thyroid gland to release thyroxine. 4) Thyroxine causes an increase in the metabolic activity of most body cells, generating heat. 5) Higher thyroxine levels in the blood inhibit the TSH-producing cells. 6) Higher body temperature inhibits the hypothalamic cells. La TSH estimula a la tiroides para que libere tiroxina 2 Tiroides La tiroxina eleva la actividad metabólica, lo que genera calor 5 Los niveles altos de tiroxina en la sangre inhiben a las células productoras de TSH Una temperatura corporal más alta inhibe a las células del hipotálamo 3 4 Chapter 32

El páncreas controla los niveles de glucosa en la sangre Biology: Life on Earth (Audesirk) comer hambre células productoras de insulina glucosa sanguínea alta páncreas glucosa sanguínea baja El páncreas controla los niveles de glucosa en la sangre células productoras de glucagon glucagon The pancreatic islet cells contain two populations of hormone-producing cells: one producing insulin; the other, producing glucagon. These two hormones cooperate in a two-part negative feedback loop to control blood glucose concentrations. High blood glucose stimulates the insulin-producing cells and inhibits the glucagon-producing cells; low blood glucose stimulates the glucagon-producing cells and inhibits the insulin-producing cells. This dual control quickly corrects high or low blood glucose levels. insulina células del cuerpo las células del cuerpo queman grasa glucosa en la sangre Hígado Convierte glucosa en glucógeno convierte glucógeno en glucosa Baja la glucosa sanguínea eleva la glucosa sanguínea Chapter 32

Las glándulas suprarrenales Biology: Life on Earth (Audesirk) Las glándulas suprarrenales Corteza suprarrenal Médula suprarrenal Produce: glucocorticoides, testosterona, aldosterona. Produce: adrenalina, noradrenalina Atop each kidney sits an adrenal gland, which is a two-part gland composed of very dissimilar cells. The outer cortex consists of ordinary endocrine cells that secrete steroid homones. The inner medulla, derived from nervous tissue during development, secretes epinephrine and norepinephrine. riñón Chapter 32

Otras glándulas endocrinas Glándula Pineal – produce la hormona melatonina Riñones Producen la hormona erytropoyetina En respuesta a una baja de oxígeno en la sangre Estimula la producción de glóbulos rojos en la médula ósea Producen renina En respuesta a una presión arterial baja Activa la producción of angiotensina, la cual eleva la presión arterial, constriñendo las arteriolas

Otras glándulas endocrinas Corazón Produce el péptido natriurético atrial (PNA) Disminuye la presión sanguínea Aumenta la producción de sal y agua por los riñones Estómago Produce diversas hormonas peptídicas que ayudan a regular la digestión

La Tiroxina controla la metamorfo-sis de los anfibios Biology: Life on Earth (Audesirk) renacuajo metamorfosis tratar el renacuajo con tiroxina adicional rana miniatura La Tiroxina controla la metamorfo-sis de los anfibios embrión The life cycle of the frog begins with fertilization of the eggs (bottom). The fertilized eggs develop into an aquatic, fishlike tadpole, which grows and ultimately metamorphoses into an adult frog. Metamorphosis is triggered by a surge of thyroxine from the tadpole’s thyroid gland. If injected with extra thyroxine, a young tadpole will metamorphose ahead of schedule into a miniature adult frog. rana adulta huevos Chapter 32

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