Chapter 16 - The endocrine system (part b), this chapter describe structural and functional relationships between the hypothalamus and the pituitary gland; list and describe the chief effects of anterior pituitary hormones; discuss the structure of the posterior pituitary, and describe the effects of the two hormones it releases;. | 16 The Endocrine System: Part B The Posterior Pituitary Contains axons of hypothalamic neurons Stores antidiuretic hormone (ADH) and oxytocin ADH and oxytocin are released in response to nerve impulses Oxytocin Stimulates uterine contractions during childbirth by mobilizing Ca2+ through a PIP2-Ca2+ second-messenger system Also triggers milk ejection (“letdown” reflex) in women producing milk Plays a role in sexual arousal and orgasm in males and females Antidiuretic Hormone (ADH) Hypothalamic osmoreceptors respond to changes in the solute concentration of the blood If solute concentration is high Osmoreceptors depolarize and transmit impulses to hypothalamic neurons ADH is synthesized and released, inhibiting urine formation Antidiuretic Hormone (ADH) If solute concentration is low ADH is not released, allowing water loss Alcohol inhibits ADH release and causes copious urine output Homeostatic Imbalances of ADH ADH deficiency—diabetes insipidus; huge output of urine and intense thirst ADH hypersecretion (after neurosurgery, trauma, or secreted by cancer cells)—syndrome of inappropriate ADH secretion (SIADH) Thyroid Gland Consists of two lateral lobes connected by a median mass called the isthmus Composed of follicles that produce the glycoprotein thyroglobulin Colloid (thyroglobulin + iodine) fills the lumen of the follicles and is the precursor of thyroid hormone Parafollicular cells produce the hormone calcitonin Figure Thyroid Hormone (TH) Actually two related compounds T4 (thyroxine); has 2 tyrosine molecules + 4 bound iodine atoms T3 (triiodothyronine); has 2 tyrosines + 3 bound iodine atoms Thyroid Hormone Major metabolic hormone Increases metabolic rate and heat production (calorigenic effect) Plays a role in Maintenance of blood pressure Regulation of tissue growth Development of skeletal and nervous systems Reproductive capabilities Synthesis of Thyroid Hormone Thyroglobulin is synthesized and discharged into the follicle lumen Iodides (I–) are . | 16 The Endocrine System: Part B The Posterior Pituitary Contains axons of hypothalamic neurons Stores antidiuretic hormone (ADH) and oxytocin ADH and oxytocin are released in response to nerve impulses Oxytocin Stimulates uterine contractions during childbirth by mobilizing Ca2+ through a PIP2-Ca2+ second-messenger system Also triggers milk ejection (“letdown” reflex) in women producing milk Plays a role in sexual arousal and orgasm in males and females Antidiuretic Hormone (ADH) Hypothalamic osmoreceptors respond to changes in the solute concentration of the blood If solute concentration is high Osmoreceptors depolarize and transmit impulses to hypothalamic neurons ADH is synthesized and released, inhibiting urine formation Antidiuretic Hormone (ADH) If solute concentration is low ADH is not released, allowing water loss Alcohol inhibits ADH release and causes copious urine output Homeostatic Imbalances of ADH ADH deficiency—diabetes insipidus; huge output of urine and intense .
