Endocrine System

• Mammalian digestive system


  • Mouth
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
• Secondary organs


  • Salivary glands
  • Gallbladder
  • Liver
  • Pancreas
• Oral cavity


  • Teeth (mechanical digestion)
  • Parotid, sublingual, and submandibular glands (chemical digestion, salivary amylase)
  • Tongue forms a bolus and facilitates swallowing
• Pharynx


  Opening between oral cavity and esophagus
• Epiglottis


  Prevents food from entering trachea
• Esophagus


  Moves food from stomach through peristalsis
• Stomach


  • Major site for mechanical and chemical digestion
  • 3 layers of smooth muscle
  • Sets of cells secrete substances collectively termed gastric juice
• Gastric juice


  pH of 2, made of hydrochloric acid and pepsin, pepsin is a protease and turns proteins into smaller peptides
• Parietal cells


  • Secrete hydrogen and chloride cells
  • Smaller cavities and bumps in the stomach
• Pepsinogen


  Activated to pepsin when mixed with hydrochloric acid
• Mucus


  Protects the stomach lining from gastric juice
• Small intestine


  • Majority of nutrient absorption, especially water, amino acids, fatty acids, monosaccharides, vitamins, and minerals
  • Has villi on the intestinal wall to absorb
• Portions of small intestine


  • Duodenum (1st, digestion)
  • Jejunum (2nd, absorption)
  • Ileum (3rd, absorption, leads to large intestine)
• Pancreas


  • Secretions are exocrine (digestive) and endocrine (hormonal)
  • Exocrine - amylase, protease, lipase
  • Endocrine - insulin (beta cells), glucagon (alpha cells), regulates blood sugar
• Insulin


  Acts on nearly all body cells to stimulate glucose uptake from blood
• Gallbladder


  Stores bile from liver, bile emulsifies lipids
• Large intestine


  Recover the rest of the water
• Dentition


  • Animals' teeth, major adaptation of animals, diet affects teeth, non-mammalian vertebrates have less specialized teeth
• Ruminant digestion


  Food is first fermented by bacteria in the rumen after ingestion and then regurgitated for further chewing and enzymatic digestion, adaptation for herbivores
• Types of hormones


  • Polypeptides
  • Steroids
  • Amines
• Polypeptides and amines


  Water-soluble (hydrophilic)
• Steroids


  Lipid-soluble (hydrophobic)
• Hormone → hormone receptor


  Hormone only acts where there is a receptor
• Endocrine signaling


  • Primarily negative feedback to maintain homeostasis and mediate responses to stimuli
  • Positive feedback, to maintain homeostasis amplifies changes (oxytocin)
• Low ADH


  Eliminate water, low osmolarity, ADH goes to tubules, aquaporin allows water to leave
• High ADH


  Conserve water, high osmolarity
• Cellular signaling


  Stimulus - receptor - transduction - response
• Reception


  • Ligand binds to a receptor
  • G-protein
  • Intracellular receptor
  • Hormone receptor
  • Tyrosine kinase receptor
• Transduction


  Receptor activates signal transduction molecule - cascade, binds to DNA and turns it on
• Water soluble hormones


  Come out of secretory cell vesicle, fuse with plasma membrane, travel in bloodstream, bind to receptors and trigger response
• Lipid soluble hormones


  Diffuse across lipid bilayer, go into bloodstream, go to target cell, go into target cell and receptor is waiting in cytoplasm and nucleus, response
• Negative feedback


  Inhibits a response by reducing the initial stimulus, most hormones, we don't have enough so we need more
• Positive feedback


  Reinforces a stimulus to produce an even greater response, oxytocin, the more suckling that happens the more hormone is released, keeps releasing until suckling stops
• Endocrine system


  • Hypothalamus
  • Pituitary gland
  • Thyroids
  • Adrenal glands
  • Reproductive organs
  • Pancreas
• Hypothalamus


  Control center, secretes hormones that either stimulate or release other hormones, sends and receives neural signals, secretes into pituitary to tell pituitary when to secrete
• Posterior pituitary gland


  Secretes the hormones throughout the body, oxytocin and vasopressin (ADH)
• Anterior pituitary gland


  Hypothalamus secretes releasing hormones, hormones can go to other hormone glands to release other hormones
• Hypothalamic-Pituitary axis (HPA)


  Wired connections (neurons) or through blood vessels
• Neuroendocrine signaling - stimulate hypothalamus because hormone levels drop, learn more