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Physiology 2: Nutrition
Transcript of Physiology 2: Nutrition
Each organ of the tract is seperated from eachother by muscular sphincters that prevent mixing of material
Food is digested in two ways:
physical- large pieces are broken into smaller pieces.
chemical- enzymes disrupt bonds between monomers Nutrition Fungi Plants Animals Overview The Mammalian Digestive System Mouth Esophagus Stomach Accessory Glands Large Intestine Control Adaptations Overview Roots Adaptations Plant Nutrients Soil Structure Symbiosis Nutritional Symbiotic Most fungi are saprophytic (they eat dead things). Some fungi are parasitic Exercise caution when thinking about eating fungi. With the exception of Carbon Dioxide and Oxygen, plants recieve most nutrients from the soil Hydroponic techniques are utilized to determine the effects of specific nutrient deficiencies on plant growth. While all organisms require SPONCH to live, plants are particularly sensitive to Potassium deficiencies as well, Soil is a complex mixture of organic and inorganic compounds of both biological and physical origin.
Soil is produced and replenished through natural processes including deposition, weathering and decomposition.
There is a directionality to typical soil production, with newer, nutrient-rich soil being deposited in the top horizon. The "Dustbowl" in the American Midwest: An example of accelerated soil depletion due to human ignorance combined with natural drought cycles. Contour farming: one example of a practice that can slow erosion due to farming. Plant roots are the structures responsible for soil nutrient absorption.
Root Hairs: Major absorptive surface of roots. Cation Exchange Protons are pumped out of plant roots into the soil.
The protons displace nutritive cations (K+, Mg++, etc.) in the soil, which are then absorbed into the roots.
Nutrients move in to roots via diffusion, mostly. Plants rely upon bacteria and fungi to provide them with some nutrients in the soil. Bacteria Fungi Bacteria play a major role in the Nitrogen Cycle The action of nitrogen-fixing bacteria in the soil converts atmospheric nitrogen into biologically useful forms, which can be incorporated from soil into amino acids and nucleotides by plants.
This is how all nitrogen enters the food chain.
Legumes: plants that have specialized root-nodule adaptations that contain populations of nitrogen-fixing bacteria. Mycorrhizae: Symbiotic fungal-root associations.
Increase nutrient absorption by roots. Development & Structure of Root Nodules "Carnivorous" Plants Live in nutrient-poor soils.
Adapted to catch and digest small animals as a supplementary source of soil nutrients (particularly nitrogen). Epiphytes Plants that live on other plants.
Typical in rainforests and other soil-poor areas.
Can be mutualistic, commensal, or parasitic. Parasites There are many different plant parasites of other plants, with a wide diversity of parasitic adaptations. Animal nutrition involves four phases:
Ingestion: Intake of food
Digestion: Breakdown of food macromolecules
Absorption: Transfer of nutrients into the body
Elimination: voiding of undigested materials Diploblastic animals (cnidarians) utilize a gastrovascular cavity for nutrition.
The "Bag" plan: The mouth of the animal is also the anus. Triploblastic animals (everything else) utilize a gastrointestinal ("GI") tract for nutrition.
The "tube" plan: The mouth is at one end of the tract and the anus is at the other end. The evolution of a gastrointestinal tract allows for compartmentalization of the digestive system and increased efficiency & control of nutrition.
Peristalsis: involuntary contractions of smooth muscle that line the gastrointestinal tract and move food through the tube. There are a wide variety of strategies used by animals to accomplish this process Nutritional Requirements Animals need to aquire all nutrients from their environment.
This includes macromolecules, vitamins and minerals.
Some can be synthesized from raw materials, others must be consumed "pre-made" Vitamins: Organic, non-macromolecular, compounds Minerals: inorganic elements Data from an experiment (right) looking at the effects of invasive garlic mustard (left) on the ability of native plants to form mycorrhizal associations Disorders Deficiencies in nutritional requirements will have effects on the physiology of the organism Starvation results in digestion of the bodies stored nutrients. Lack of specific nutrients will have specific effects on physiology. Shown: Kwashiorkor, a protein deficiency Data showing a correlation between consumption of folic acid vitamin supplements and a decreased likelihood of neural tube birth defects in a sample of the female population of Great Britain. General Points: The human digestive system is a very typical example of the mammalian digestive system. Structure Functions Teeth, tongue, and salivary glands. Teeth: mechanically digest food.
Tongue: moves food into gastrointestinal tract.
Salivary Glands: Produce saliva which moistens food and contains amylase (chemically digests starches) Structure Functions A tube that connects the mouth to the stomach. Begins transport of food through the GI tract.
Pharynx: beginning of esophagus.
epiglottis: Prevents movement of food into the respiratory system Structure Functions A muscular pouch.
Capable of rapid expansion.
Filled with "gastric juice" (a mixture of pepsin and hydrochloric acid).
Processes food into chyme. Holds food.
HCl- Sanitizes food.
pepsin- chemicall digests protein Stomach Ultrastructure The walls of the stomach contain many "gastric pits"
Three cell types:
mucous cells: make a protective mucous coating for the stomach epithelium.
Parietal cells: Produce HCl
Chief cells: Produce the pepsin protein precursor pepsinogen
Pepsinogen is an example of a "zymogen", an inactive protein molecule that is converted into the active form in specific conditions
In the case of pepsinogen, HCl is needed to cleave it in to active pepsin.
Why is the pepsinogen/pepsin system necessary? Term refers to any organs that make secretions that are introduced into the GI tract. Liver Pancreas Makes bile which emulsifies fat (physical digestion).
Excess bile is stored in the gallbladder. Makes pancreatic fluid, which contains a variety of hydrolytic enzymes for all macromolecules
Carbohydrates- pancreatic amylase
Lipids- pancreatic lipase
Nucleic Acids- pancreatic nucleases
Proteins- trypsin, chymotrypsin, & carboxypeptidase
The pancreas also produces bicarbonate ions, which raise the pH of the chyme (pancreatic enzymes function in basic pH) Bile and Pancreatic fluid enter the GI tract through a common duct at the beginning of the small intestine (the "duodenum") Structure: 3 sections:
Duodenum: Digestive section.
Jejunum: Primary absorptive section (most nutrients)
Ileum: Final absorptive section (bile salts and some vitamins). Small Intestine Ultrastructure: The epithelium of the small intestine is adapted for absorption of nutrients.
Villi: projections of epithelial tissue. Each vilus is covered in microvilli (the "brush border").
A network of capilaries (circulatory system) and lacteals (lymph vessels) runs through each vilus, separated from the lumen (interior) of the small intestine by the brush border.
Nutrients diffuse through the brush border, into the circulatory/lymphatic system. Carbohydrates, amino acids, and other water-soluble molecules are absorbed into the circulatory system, while lipids are absorbed in to the lymphatic system.
Blood and lymph flow from the small intestine to the liver for detoxification of absorbed molecules. Function: Final stages of digestion and main area of absorption of nutrients Structure: A tube that holds undigested, unabsorbed digestive material.
Also holds a massive colony (~90 trillion cells) of symbiotic bacteria. Function: Small Intestine Reabsorption of water.
Production & absorption of vitamins by bacteria.
Storage and (usually) voluntary elimination of undigested food ("feces") Digestive Hormones There are several hormones involved in the digestive system.
The GI tract is under the control of an entire division of the autonomic nervous system (the "enteric" division), and is subject to several different regulatory feedback loops 2. Regulation of Blood-Glucose Level Controlled by 2 pancreatic hormones:
Insulin- removes excess glucose from the blood via storage in body cells and conversion to glycogen in the liver.
Glucagon- increases glucose level in the blood via glycogen breakdown and glucose release from the liver. 1. Digestion Control 1. The expansion of the stomach to accomodate incoming food trigers the release of gastrin, which stimulates production of gastric juice.
2. As chyme moves in to the duodenum, the presence of amino acids and fatty acids trigers the release of CCK by duodenal cells, which causes the liver and pancreas to release secretions into the GI tract. The hormone secretin is also released by the duodenum which causes the pancreas to release bicarbonate ions to neutralize the acidic chyme.
3. Very fatty foods will cause a large amound of secretin and CCK to be released, which has an inhibitory effect on peristalsis and slows down the digestive process. 3. Satiety Satiety is the feeling of being "full".
Under the control of the hypothalamus in the brain.
Leptin, Insulin, and PYY are three hormones that decrease the hunger sensation.
Ghrelin increases the hunger sensation and decreases saitety.
These hormones work in an antagonistic fashion, similarly to insulin and glucagon. Data from an experiment in which ob mutant mice (genetically prone to obesity) were surgically joined to non-mutants.
ob mutants show decreased body mass gains when joined to non-mutant mice. While humans have a fairly typical digestive system, other mammals demonstrate various adaptations. Dentition Variation in tooth structure allows animals to adapt to particular sources of food. GI Tract Adaptations Many herbivores have highly adapted, elongated appendix structures ("Cecum"), which serve as locations for colonies of bacteria that can aid in cellulose digestion.
Carnivores do not have these structures. Ruminants Herbivores that possess highly adapted, expanded upper GI tracts.
Allow for maximized mastication of vegetable matter and prolonged exposure to symbiotic bacteria. Obesity Temporary obesity is frequently seen in animals to deal with environmental fluctuations and nutritional requirements of specific life stages. Disruptions in food cycles that animals have adapted to can lead to unintended obesity.
This is perhaps the major reason why there is currently an obesity "epidemic" in the United States. There are many disorders of the digestive system. Here are a few examples: "Upper GI" Disorders: "Lower GI" Disorders: Ulcers Acid Reflux Diarrhea/Constipation Irritable Bowel Disease Cause: Symptoms: Cause: Symptoms: Cause: Symptoms: Cause: Symptoms: A disruption of the protective mucus lining of the stomach.
Often caused by the Helicobacter pylori bacterium. Frequently stress-linked. Persistent "Burning sensation" in upper abdomen. Treatment: Antibiotics, diet modification, possible surgery. Movement of stomach contents through the lower esophageal sphincter. Transient "Burning sensation" in upper abdomen, particularly following meals. Treatment: Antacids, medications that reduce HCl production. Diarrhea: too much water in feces (decreased absorption by large intestine).
Constipation: too little water in feces (feces remains in large intestine longer than normal). Cramping (Diarrhea), Tenesmus (constipation) Treatment: Immediate: laxatives, indigestion aids (e.g. pepto bismol).
Long-term: Diet modification. Increased fiber intake. Decreased intake of fatty, sugary foods. Irritation and inflammation of the large intestine.
Ultimate etiology is unclear (stress? Autoimmune?) Irregular, spastic bowel movements. Discomfort, bleeding (severe cases) Treatment: Medication, Diet modification, surgery (extreme cases). Big Questions: Make Sure You Can: Why do organisms need to acquire nutrients?
How do organisms acquire nutrients?
What happens if organisms are unable to acquire nutrients? The Amanita muscaria mushroom causes liver failure and psychosis in animals "Nom Nom Nom" "Nom Nom Nom" Chemical Digestion: A summary Explain why organisms require nutrients, how they accomplish the processes involved in nutrition, and the consequences of malnutrition.
Compare and contrast plant and animal nutrition.
Explain the structure and function of all organs involved in plant and animal nutrition.
Describe the roles of symbiotic relationships in both plant and animal nutrition.
Describe the modes of hormonal regulation of mammalian nutrition.
Explain the causes, effects and treatments of various disorders of the human digestive system. "all that remains is a husk" Note:
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