Block 3

• Endocrine system vs. Nervous system


  nature of message:

  nervous- APs and NTs

  endocrine- hormones

  
  

  Message characteristics:

  nervous- very quick

  endocrine- longer to activate and longer lasting
• exocrine glands


  secrete products into ducts or lumens or outer surface of body
• endocrine glands


  secrete products into ISF or blood
• local hormones


  hormones that act in immediate vicinity
• paracrine hormones


  neighboring cells
• autocrine hormones


  act on cell from which hormone was released
• lipid soluble hormones


  bound to transport proteins for transport in bodily fluids
• water soluble hormones


  free dissolved in body fluids
• circulating hormones


  travel throughout body
• hormone function


  released from glands in response to internal/external changes

  produce wide-reaching coordinated effects

  regulate organ system function
• Mechanism for circulating hormones


  To be a target cell for a hormone, a cell must possess a receptor for that hormone

  cells can have surface receptors or internal receptors
• hepatocytes


  insulin stimulates glycogen synthesis
• steroid hormone action


  -water-soluble

  1. leave secretory cell by diffusion

  2. require transport proteins

  3. diffuse into target cells to target intracellular receptors

  4. changes level of specific gene expression
• adipocytes


  insulin stimulates triglyceride synthesis
• peptide hormone action


  -lipid-soluble

  1. leave secretory cell by exocytosis

  2. DO NOT require transport proteins

  3. bind to cell surface receptors

  4. evoke changes in activity of existing proteins through second messengers
• hypothalamus


  receives info from other organs

  provides a link between internal and external environment and endocrine system
• tropic hormones


  hormones that regulate the function of endocrine cells or glands
• hypothalamic control of anterior pituitary

  1. secretes releasing and/or inhibiting hormones which act on cells in anterior pituitary

  2. anterior pituitary secretes a tropic hormone into blood for circulation
• somatotrophs


  secrete human growth hormone
• thyrotrophs


  secrete thyroid stimulating hormone
• lactotrophs


  secrete prolactin
• gonadotrophs


  secrete follicle stimulating hormone ad luteinizing hormone
• corticotrophs


  secrete adrenocorticotropic hormone and melanocyte stimulating hormone
• human growth hormone


  increases synthesis of insulin-like growth factors

  -decrease glucose use by most body cells

  -increased cell division and growth
• regulation of hGH


  -released in bursts

  -regulated by GHRH or GHIH
• stimuli for GHRH


  hypolgycemia, deep sleep, decreased fatty acids and increased amino acids
• stimuli for GHIH


  hyperglycemia, REM sleep, increased fatty acids and decreased amino acids, high levels of hGH
• follicle stimulating hormone


  GnRH stimulates gonadotrophs to produce FSH

  females: stimulates secretion of estrogen and initiates formation of follicles in ovaries

  males: stimulates sperm production in testes
• Luteinizing Hormone


  GnRH stimulates gonadotrophs to produce LH

  females: secretion of estrogen and progesterone, ovulation

  males: secretion of testosterone
• prolactin


  PRH and PIH (dopamine) act on lactotrophs to produce prolactin

  function: causes breast milk production

  during breast feeding, prolactin levels rise higher
• melanocyte-stimulating hormone


  CRH causes corticotrophs to release MSH

  PIH (dopamine) inhibits MSH release

  function: increases skin pigmentation
• adrenocorticotropic hormone


  CRH stimulates corticotrophs to release ACTH

  ACTH release also sitmulated by hypoglycemia, physical trauma, IL-1

  function: stimulates release of glucocorticoids (mainly cortisol) from adrenal cortex

  cortisol inhibits release of CRH and ACTH
• thyroid stimulating hormone


  TRH causes thyrotrophs to produce TSH

  function: stimulates the synthesis and secretion of T3 and T4, metabolic rate increases
• posterior pituitary gland


  hypothalamus releases hormones directly into circulation through posterior pituitary
• antidiuretic hormone and oxytocin


  made in hypothalamus and stored in posterior pituitary until triggered for release
• antidiuretic hormone


  -synthesized by cells in the supraoptic nucleus

  -made in response to signals from osmoreceptors

  function: decreased urine production by stimulating renal water reabsorption, prevents water loss in sweat glands, constriction of arterioles
• diabetes insipidus


  caused by lack of ADH or nonfunctional ADH receptors

  excessive urination bc of inability of kidneys to conserve water
• oxytocin


  produced by paraventricular nucles

  positive feedback loop during labor causes uterine contractions

  negative feedback loop after delivery: oxytocin causes smooth muscle contraction and milk ejection
• follicular cells of thyroid


  produce thyroid hormones T3 and T4
• formation of T3 and T4


  T3 and T4 bound and transported by thyroxine binding globulin