Nutrition Chapter 3 - Lecture notes 1 PDF

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Kate Yerxa was the professor, and these are the notes I took during lecture. ...

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The Body’s Cells ● Body composed of trillions of cells ● Body needs nutrients ● Cells: self contained, living entities ○ Depend on one another ○ Basic needs ■ All cells need energy, oxygen, nutrients (essential), and water ● Cells die at varying rates Genes Control Functions ● A gene is a blueprint that directs the production of one or more proteins ○ Affect how body handles nutrients ● Different genes are active in different cells ● Gene variations (or mutations) ○ Inborn error of metabolism ○ Influence of nutrients Cells, Tissues, Organs, and Systems ● Cells organized into tissues ● Perform specialized tasks ● Tissues grouped together to form organs ● Organs work together as part of body systems Body Fluids ● Body fluids deliver energy, oxygen, nutrients, and water to cells ○ Body’s circulating fluids: Blood ● Deliver nutrients to all the body's cells and carry waste materials away from them ● Travels in arteries, veins, and capillaries Lymph ● Travels in its own vessels How the Body Fluids Circulate Around Cells ● Extracellular fluids: fluid surrounding cells and derived from blood in capillaries ● Plasma: circulates around cells white and red blood cells ● Intracellular fluids: where all cell reactions take place, helps cells hold its shape Blood Circulation ● Blood circulates to the lungs ○ Picks up oxygen ○ Releases carbon dioxide ● Blood returns to heart ○ Pumped to rest of body

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Blood passes through digestive system ○ Picks up nutrients ■ Fat travels via lymph ○ Routed directly to liver ○ Cleansed of wastes in the kidneys The Hormonal System ● Hormones ○ Chemical messengers ○ Secreted and released directly into blood by glands ○ Stimulate organs to take action ● Glands monitor conditions in the body ○ Pancreas ■ Insulin and Glucagon The Nervous System ● Nervous System’s role is coordinated by the brain ● The brain’s cortex sense hunger and appetite ● The hypothalamus monitors many body conditions, including nutrients and water availability ● The fight or flight reaction (stress response) is activated when danger is sensed

Immune Defenses ● Tissues cooperate with each other to maintain defenses ○ Physical barriers –– skin ○ Lungs and digestive tract are lined with membranes that resist microbes (b []\acteria, viruses, fungi that cause disease) ○ Antigens- Microbe or substance that is foreign to the body– immune system responds to defend the body Immune Defense– White Blood Cells ● Phagocytes ○ First to engulf pathogens and foreign particles ○ Leave a chemical trail that helps other immune cells to destroy the source of the infection ● Lymphocytes 1. T cells ○ Killer T cells, read and remember the chemical messages from phagocytes ○ Seek and destroy all foreign particles with the same identity ○ Helper T cells– does not attack, but helps other immune cells 2. B cells– secrete antibodies and help other WBC eliminate pathogens Antibodies: proteins made by cells of the immune system

Inflammation ● Response to cell injury or irritation ● Increased white blood cells, redness, heat, pain, and swelling ● Normal, healthy response ● Problem with chronic inflammation ● Low level chronic inflammation has been discovered to be associated with heart disease, diabetes, and severe arthritis The Digestive System ● Five basic chemical tastes ○ Sweet, sour, bitter, salty, and umami ● Other factors affect our experience of food flavor as well ● Sweet, salty, and fatty foods ○ Almost universally desired ○ Can lead to overeating of these substances The Digestive Tract ● Flexible, muscular tube ○ Extends from mouth to anus ○ Total length: about 26 feet ● Human body surrounds digestive canal ● Function of the digestive tract ○ Breaks down food to its components;, absorbs and excretes ○ Ready to digest at all times ● Works mechanically and chemically The Mechanical Aspect of Digestion ● Begins in the Mouth ○ Chewing- saliva moistens food for easier swallowing ● Stomach and small intestine ○ Peristalsis- wavelike muscular squeezing of the digestive tract that pushes contents along ○ Chyme- travels through pyloric valve (end of stomach) ● Large intestine (colon) ○ Role: reabsorb water and absorb nutrients ● Digestion is virtually continuous The Chemical Aspect of Digestion ● Organs that secrete digestive juices: ○ Salivary glands, stomach, pancreas, liver, and small intestine 1. Mouth ● Digestion begins in the mouth

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Saliva breaks down starches and fat ○ Contains salivary amylase that initiates the breakdown of CHO Maintains tooth health  Stomach Gastric juice include hydrochloric acid ○ Initiates protein digestion ○ Don't digest stomach lining because those cells are protected by mucus Small intestine- primary organ of digestion and absorption The gallbladder sends bile into the intestine ○ Bile is not an enzyme ○ Breaks up large particles of fat The pancreas sends ○ Bicarbonate to neutralize stomach acid (chyme) that entered small intestine ○ The largest number and variety of digestive enzymes to act on chemical bonds that hold the large nutrients together Intestinal cell walls also have digestive enzymes on their surfaces ○ Regenerate every 3 days Absorption of carbs, fat, proteins, vitamins, and most minerals occurs Water, fiber, and minerals remain in the tract

Pancreatic Enzymes (Pancreatic Juice) ● Pancreatic amylase ○ Helps digest carbs ● Pancreatic proteases ○ Trypsin and Chymotrypsin ○ Help digest proteins ● Pancreatic lipases ○ Helps digest fat Microbes in the digestive tract ● Some fiber is broken down by resident bacteria (microbiota) ○ Collective mix of species of a community–– or the human digestive tract ● Small fat fragments released from bacterial fermentation of the fiber provide a tiny bit of energy for colon cells ● Bacteria break down undigested protein or unabsorbed amino acids, releasing ammonia and other compounds Typical Digestive System Transit Times 1. Food is in the mouth for less than a minute 2. Food is in the stomach for about 1-2 hours 3. Food is in the small intestine for about 7-8 hours 4. Food is in the large intestine for about 12-14 hours Absorption and Transport of Nutrients

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Nutrient molecules transverse intestinal lining ○ Water soluble components ○ Fat soluble components Cells of small intestine are selective

Intestines absorbing surface: ● Villi and microvilli ● Increase the absorbing surface area of the small intestine Nutrient Transport ● Lymph vessels ○ Transport most of the products of fat digestion and fat soluble vitamins and delivers them to the bloodstream ● Blood vessels ○ Carry the products of carb and protein digestion, most vitamins and minerals from the digestive tract to the liver ● Nourishment of digestive tract ○ Long term lack of fiber, protein, or carbs in the food that reaches the small intestine, the absorptive surface of the small intestine will decrease Excretory System ● Organs involved in waste removal ○ Lungs, liver, and kidneys ● Kidneys ○ Waste materials are dissolved in water ■ Excreted ○ Working units–– nephrons ○ Urine stored in bladder Nutrient Storage ● Cells need nutrients 24 hours a day ● The body’s major storage sites for nutrients are the liver, muscles, and fat cells What Happens to Extra Nutrients? 1. Nutrients from the digestive system arrive at the liver 2. Liver processes nutrients 3. Excess nutrients are converted to glycogen (a carb) or fat a. Liver glycogen can sustain cell activities when the time between meals is long 4. Muscle cells make and store glycogen for their own use 5. Fat made in the liver is shipped to body cells for energy and excess is stored in adipose tissue...