Class notes - Nutritional Physiology

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Samenvatting - Class notes - Nutritional Physiology

  • 1468360800 Mass flow of nutrients

  • Once you swallow your food, you have hardly any influence on the fate of the food. this is all regulated by the body; you can't control this. Your metabolism is balancing the nutritional input with the physiological output. It is like a factory; your food comes in and it will be mixed and grinded with enzumes and water to digest it. Your food will be transformed into monomeres, so they can be absorpted. Particles in the food that can't be digested, are waste products and leave the body.
  • True or false? Fermentation in the colon by microbiota of non-digestible products can lead to small sugars and fatty acids, but not to amino acids. Those will only be derived from your food.
    True
  • Nutritional input (intake, meal size, pattern, composition)
    Post Prandial Phase
    Physiological output (physiological status, health status, environment)
    Post-Absorptive Phase
    Metabolism (metabolic pathways, energetic efficiencies, body composition, waste products)    
    Waste
  • What is the breakdown of protein called and what is needed to accomodate this breakdown?
    It is called proteolysis. This will cost a lot of energy without enzymes; enzymes lower the activation energy. Enzymes are stored as inactive pro-enzymes.
  • Mucus protects the walls of organs from digestion of human cells (autodigestion).
  • In what form are amino acids, glucose and glycerol+fatty acids stored?
    Subsequently protein, glycogen and triglycerides (neutral fat). They are all linked to degradation/catabolism ultimately leading to the citric acids cycle.
  • Eating a meal has thermogenic effects. In general, protein produces the most heat, than carbohydrates and than fat, by the post-prandial metabolism (PPM). Metabolisable Energy (ME) is depicted on food labels; these are not corrected for energetic costs of PPM.
  • How many of the total glucose production is used by the brain in a 24 hours time span?
    More than two-third of the production.
  • Homeostasis is the ability of an organism to counteract (within limits of the metabolic flexibility) factors that disturb vital functions. In the body there is a conflict of interest in homeostasis between the body and the metabolism; glucose concentrations are desired to be stable, but body temperature too.
  • What does the nutritional paradox mean?
    It means that the food and your body are no natural allies; in fact food isn't meant for you to use as best as possible; most food isn't natural. Only human breast milk that's given to you as a baby is.
  • The small intestine is divided into three functional regions; the duodenum (25cm), jejunum (2m) and ileum (3m). There is a clear distinction in what kind of nutrients are being absorbed in what part of the instine. In the whole intestine segmentation (mixing of your chyme) and peristalsis (movement of the bolus to the different parts) take place.
  • What is the function of the villi, enterocytes and goblet cells in the wall of the small intestine?
    Villi increases the surface area to enhance digestion and absorption of the food. Villi has enterocytes on it, which absorb the monomers passing by. In between the enterocytes are goblet cells, that produces mucus to protect the villi.
  • The colon and rectum (1,5m) have multiple functions:
    • The absorption of water
    • Bacterial fermentation
    • Storage --> The body tries to contain most of the energy from the food as possible, therefore it stays a long time in the colon)
    • Elimination
  • Name all parts where a villi consists of.
    - A villi has a wall with enterocytes and goblet cells.
    - Inside the fingerlike foldings of the cell membrane is a lacteal that is in connection with the lymphatic drainage. This lacteal takes care of the uptake of lipids. 
    - In the villi are also small blood arteries that takes care of blood supply and venous drainage to absorb the monomers taken up by the enterocytes.
  • Enterocytes are renewed. Old ones are shed at the tip of the villus to be degraded in the lumen.
  • Name the four different layers of the GI-tract and their function
    1. Mucosa -> enterocytes which facilitates secretion and absorption
    2. Submucusa -> vascular layer for the blood supply
    3. Muscularis -> muscle layer to move and mix the food in the tract constantly.
    4. Serosa -> protective layer to keep the intestine intact.
  • Inbetween the four layers of the wall of the GI-tract is the Enteric Nervous System (ENS) located. This system senses, by signals of enterocytes, what food is in the intestine to give a signal to the muscularis in what intensity they should contract. The ENS also gives signals to the enterocytes to excrete specific hormones.
  • Enterocytes not only absorb and release nutrients to the bloodstream, they also store some nutrients. This is called gut retention, explain what this means for the digestion of protein.
    Amino acids are taken up and next they contribute to the intracellular acid pool. Then they can be converted into other amino acids or they can be used for protein synthesis. For instanse for specific enzymes needed for cellular metabolism of the enterocytes. They can also be released into the bloodstream. This means that the presence of amino acids in the lumen and its presence in the blood takes quite some time before you see those being available in the portal vein. There is a delay in having the acids in your lumen and having them truly available for instance for the liver or muscle. This also relates to tri-glycerides.
  • Villi has enterocytes which have microvilli; fingerlike foldings of the cell membrance also indicated as the 'brush border' (plasma membrane of the enterocytes). The total absorptive area is 250-300 m2.
  • Gut stimuli evoke digestive responses via the enteric and the central nervous systems. The nervus fagus integrates the brain area with your GI-tract. There is a constant communication between them. Three mechanisms of communication response in the GI-tract, name them and their function.
    1. Endocrine system -> a sensor cell releases hormones for a specific target cell to act upon it.
    2. Neurocrine system -> neurones release a neurotransmitter and target cells respond.
    3. Paracrine system -> a specific cell senses one of the compounds and its releases a mediator so the neighbouring cells are immediately affected to for instance releasing enzymes or acids.
  • Transit time depends highly on the energy content and the macronutrient composition (fat stays longer in the stomach). The transit time in the stomach, small intestine and large intestine is subsequently 1-5 hours, 1,5 hours and 1-2 days.
  • Your body is constantly integrating its repsonses to each single meal, from the mouth untill the colon. Constantly it is communicating and taking care of the most efficient way of digesting the food.
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Voorbeelden van vragen in deze samenvatting

True or false? Fermentation in the colon by microbiota of non-digestible products can lead to small sugars and fatty acids, but not to amino acids. Those will only be derived from your food.
1
What is the breakdown of protein called and what is needed to accomodate this breakdown?
1
In what form are amino acids, glucose and glycerol+fatty acids stored?
1
How many of the total glucose production is used by the brain in a 24 hours time span?
1
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