BIOL 1080 Final Exam

• Zeitgebers


  Cues from the environment as to how to synchronize activities
• Gastrointestinal Tract


  • Tube view
  • Things are moving in and out of the "tube"
  • If you got holes in the tube (GI tract), an abundance of microbes will invade the inside of your body in massive numbers – this is called sepsis
  • Tube is not perforated; however, it is selectively penetrable (does not allow microbes to pass through)
  • Separated up into zones, which are separated by 6 valves (sphincters)
  • Only two are part of the somatic (voluntary) nervous system. (the upper esophageal sphincter and the external anal sphincter)
  • Lower esophageal sphincter, pyloric sphincter, ileocecal valve, and the internal anal sphincter are all controlled by the autonomic (involuntary) nervous system
  • 4 basic processes that occurs all the time: Motility, Secretion, Digestion, Absorption
  • Intestinal epithelium separates the inside and outside of the body
• The GI tract always sends things to the liver
• Unique Properties of the GI 'Tube'

  • Gi tract is about 28 ft. long
  • It has a luminal surface area between 200-400 square meters – thus the invagination depth/villus-microvillus height and densities of the mucosal layer are extensive in certain zones
  • It has a highly variable 'transit-time' for an ingested meal with a marker (30-80 hours) of which around 5-8 hours is for normal passage through the stomach and small intestine
  • Senses and expels noxious substances – diarrhea and vomiting
  • Continuously interacts with the gut microbiome that protects against pathogenic microbes that enter the tract
  • The GI microbiome is a subset of the total human microbiome
  • It is individually unique, no two people's gut microbiomes are identical
• Types of Breathing


  • The diaphragm separates the thoracic (lungs, above the diaphragm) cavity from the abdominal (below the diaphragm) cavity
  • Relaxed breathing: Shoulders stay at the same height, chest does not rise or fall, belly balloons out, aids in the function of the GI tract
  • Excited breathing: Shoulders raise when you breathe in and chest will puff out, abdominal wall stays contracted, 'shuts down' the GI tract because it happens when our fight or flight is triggered, and blood flow is directed somewhere else
• Peristalsis


  Movement from top to bottom (mouth to anus), moves things down except for acid reflux and vomiting
• Segmentation


  Movement in both directions in the small intestine, allows for greater mixing
• Sphincters


  • Lower esophageal sphincter: Esophagus to stomach
  • Pyloric sphincter: Stomach to duodenum
  • Ileosequal valve: Small intestine to large intestine
  • Internal anal sphincter: Inside the rectum
  • External anal sphincter: Around the outside of the anal canal
• Diseases and Disorders of GI Motility

  • GERD (Gastroesophageal Reflux Disease)
  • Gastroparesis
  • SBBOS (Small Bowel Bacterial Overgrowth Syndrome)
  • Chronic Constipation
• Secretion


  • Occurs constantly into the lumen but also from the lumen
  • From glands: Saliva, Acid, Bicarbonate, Pancreatic juice, Bile
  • From individual cells in the epithelium: Mucus, Defensins, Secretory IgA
  • Secretion happens in all directions, ranges in size/type from massive movement of water and/or electrolytes to single hormone secretions
• Bulk Fluid Secretion and Fluid Flow

  • 2500 mL of blood plasma in an adult
  • Water is lost as: Urine, Feces, Sweat
  • Use thirst as a marker for how much water you need
  • Taking diuretics requires you to drink more water (caffeine, alcohol)
• Diseases and Disorders of GI Secretion

  • Cystic Fibrosis
  • Inflammatory and secretory diarrhea
  • Achlorhydria
  • Xerostomia
• The Second Brain


  Supplies nerves to the mucosa
• Preconditions that determine the outcome of food and the 'meal eating experience'

  • Motivation to eat: Homeostatic hunger, Hedonic hunger
  • Nutritional Status: Deficiency, Adequacy, Excess
• Any environment that has an abundance of highly varied foods is considered an obesogenic environment due to its irresistibility
• What Happens When We Eat?

  • Within 48hrs, food to support growth maintenance and repair of the body is "processed"
  • Major 'zones' of nutrition: Amino acids (protein), Monosaccharides (carbohydrates), Fatty acids (fats), Vitamins, Minerals
• Essential nutrients


  Do not exist in the body and every ounce and molecule we use needs to come from outside sources (e.g. iron, vitamin A)
• Conditionally essential nutrients


  Nutrients that are not always required from the diet
• Non-essential nutrients


  Nutrients that can be synthesized by the body
• The Cephalic Phase of Digestion and Absorption


  • The cephalic phase is triggered by the brain when we see, smell, or think of food
  • Initiates the digestive process by secreting saliva and gastric juices
  • Under autonomic control
• Taste


  • There is no tongue map
  • The tongue and nasal cavity work together to transmit flavour and smell information to the CNS
  • It also stimulates salivary glands to aid with digestion
  • 5 tastes: Sweet, Sour, Salty, Bitter, Savoury/umami
  • Taste is DETECTED on the surface of the taste bud cells, but it is PERCIEVED in the brain
• The Gastric Phase of Digestion and Absorption


  • Muscular stomach churns the food
  • Glandular stomach secretes enzymes to help with digestion
  • Alcohol is partially absorbed through the stomach
  • Aspirin inhibits signalling molecules that maintain healthy functionality of the stomach
  • The bulk of digestion and absorption occurs in the small intestine
• The Accessory Organs of the Small Intestine

  • Release substances into the duodenum: Liver, Gallbladder, Exocrine pancreas
  • Sphincter of Oddi: The sphincter that allows the secretions of the liver, gallbladder and exocrine pancreas into the duodenum
  • If the epithelial cells of the duodenum detect fats, they signal to the gallbladder to release bile
• The microvilli as specialized absorptive structures


  • Villa structures: Finger-like structures that protrude into the intestinal cavity to increase surface area and improve absorption
  • There is a capillary bed in EACH villa structure
  • Fat is transported via the lymphatic system until it can safely enter the blood supply
  • All water-soluble chemicals go into the venous system which goes to the liver
• Nutrient Absorption After Digestion

  • Carbohydrates: Polysaccharides broken down into monosaccharides (glucose and fructose)
  • Proteins: Proteases break down proteins into peptides, peptidases break down peptides into amino acids
  • Fat: Bile salts break up fat globules, lipases break down into fatty acids and monoglycerides, transferred into the lymph system
  • Vitamins and minerals: Do not have special enzyme secretions to help with digestion
• The Large Intestinal Phase of Digestion and Absorption


  • What goes into the large intestine from the ileum: Unabsorbed nutrients, Hormones and chemical messengers, Soluble fibre, Plant cell wall material, Insoluble fibre, Microbes, Cellular debris, Excretion products from the liver
  • What happens in the large intestine: Colonic epithelium absorbs water and ions, Resident microbes digest and absorb prebiotics, Resident microbes produce vitamins and gases, New microbes seek to get a foothold, Microbes cooperate and/or compete
  • For something to get into our body, it must pass through the mucus layer and epithelial cells
  • The microbes that are part of our microbiome live under the mucus layer in close association with the epithelial cells
• Gastric bypass surgery


  • Roux-en Y Procedure: A small pouch is created in the upper stomach and attached directly to the small intestine, bypasses most of the stomach and duodenum, reduces appetite-controlling hormones
  • Lap Banding Procedure: A silicone band containing saline is placed around the upper stomach
• End-products


  Can have hormone-like activity
• Microbiome activity


  1. Resident microbes produce gases during digestion and consumption of ileal chyme

  2. Newly arriving live microbes seek to get a foothold and multiply

  3. Microbes cooperate and/or compete
• Entering the body


  1. Must pass through thick mucus layer

  2. Then through epithelial cells

  3. Then out the back end into the bloodstream
• Microbiome


  Microbes that live under the mucus layer in close association with the epithelial cells
• Gastric bypass surgery types

  • Roux-en Y Procedure
  • Lap Banding Procedure
• Roux-en Y Procedure


  • A small pouch is created in the upper stomach and attached directly to the small intestine
  • Bypasses most of the stomach and duodenum
  • Appetite-controlling hormones (PYY and ghrelin) reduce appetite
  • The change in the hormones could contribute to the success of this surgery
• Lap Banding Procedure


  • A silicone band containing saline is placed around the upper stomach
  • It is placed under the skin and is easily inflated
  • Prevents the stomach from expanding due to large meals, therefore forcing an individual to eat smaller meals
• Both gastric bypass procedures result in 40-50% weight loss within a year of surgery
• The stomach is targeted because the smaller your stomach is, and the less it can expand, the less food you will eat
• After both gastric bypass surgeries, the microbiome changes and creates more positive biomarkers
• The overall effect of gastric bypass surgery is to force individuals to consume less food by 'shrinking' the stomach
• Energy Distribution System


  Homeostatically control the primary fuels in the blood plasma and extracellular fluid
• Primary fuels


  Used for precursors for biosynthetic pathways and combustion and harvesting of energy as ATP