8. Endocrine Glands, Hormones, and Target Cells Chapter 32 Capillary Hormone enters bloodstream Hormone distributed throughout body Endocrine cells release hormone Receptor en la Célula blanco Hormone- receptor Complex Tejido muscular esquelético: Hay unión, aparecen efectos hormonales Tejido nervioso: no hay unión, no hay efectos hormonales
13. The Thyroid and Parathyroid Glands Chapter 32 Dietary iodine insufficiency can lead to goiter
14. Retroalimentación Negativa en la función de la Glándula Tiroides Chapter 32 6. Una temperatura corporal más alta inhibe a las células del hipotálamo 1. Una temperatura corporal baja o tensiones estimulan células neurosecretoras del hipotálamo para que secreten una hormona liberadora 2. Esa hormona activa la liberación de hormona estimuladora de la tiroides( TSH ) de la pituitaria anterior 3. TSH estimula a la tiroides para que libere tiroxina 4. La tiroxina eleva la actividad metabólica de casi todas las células del cuerpo, lo que genera calor 5. Los niveles altos de tiroxina en la sangre inhiben a las células productoras de TSH 1 2 3 4 5 6 Thyroid Anterior Pituitary
15. The Pancreas Controls Blood Glucose Levels Chapter 32 hunger eating low blood glucose Células productoras de glucagon glucagon Eleva la glucosa sanguínea Convierte glucógeno en glucosa insulin-producing cells high blood glucose Convierte glucosa en glucógeno insulin Las células del cuerpo queman glucosa Baja la glucosa sanguínea Las cèlulas del cuerpo queman grasa pancreas liver body cells body cells
Biology: Life on Earth (Audesirk) Chapter 32 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.
Biology: Life on Earth (Audesirk) Chapter 32 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.
Biology: Life on Earth (Audesirk) Chapter 32 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).
Biology: Life on Earth (Audesirk) Chapter 32 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.
Biology: Life on Earth (Audesirk) Chapter 32 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).
Biology: Life on Earth (Audesirk) Chapter 32 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.
Biology: Life on Earth (Audesirk) Chapter 32 (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.
Biology: Life on Earth (Audesirk) Chapter 32 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.
Biology: Life on Earth (Audesirk) Chapter 32 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.
Biology: Life on Earth (Audesirk) Chapter 32 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.
Biology: Life on Earth (Audesirk) Chapter 32 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.