Lecture Exam: Digestive System Flashcards
1
Q
Digestive system
A
the system that processes food and extracts nutrients from it and eliminates residue. Most nutrient we ingest can’t be used in existing form and broken down to smaller components. Once broken down can be used what has been eaten. Disassembly line breaking down nutrients and distributing it to other tissues
2
Q
Digestion occurs in two ways
A
: mechanical and chemical
3
Q
Mechanical-
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physical breakdown of food into smaller particles achieved by cutting and grinding of teeth and churning of stomach, which exposes more food surface area to action of digestive enzymes
4
Q
Chemical digestion-
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hydrolysis reactions break dietary macromolecules into monomers: polysaccharides into monosaccharides, proteins into amino acids, fats into monoglycerides and fatty acids, and nucleic acids into nucleotides. Salivary glands, pancreas, and small intestine
5
Q
five stages of digestion
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ingestion digestion absorption compaction defecation
6
Q
Ingestion:
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selective intake of food
7
Q
Digestion:
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mechanical and chemical breakdown of food into a form usable by the body
8
Q
Absorption:
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uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph
9
Q
Compaction:
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absorbing water and consolidating the indigestible residue into feces
10
Q
Defecation
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:elimination of feces
11
Q
Enteric nervous system and its two networks of neurons
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—nervous network in esophagus, stomach, and intestines that regulates digestive tract motility, secretion, and blood flow
Thought to have over 100 million neurons
Can function independently of central nervous system
But CNS usually exerts influence on its action
Often considered part of autonomic nervous system
submucosal
myenteric plexuses
12
Q
Submucosal(Meissner) plexus-
A
in the submucosa controlling glandular secretion of mucosa and movement of muscularis mucosa
13
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Myenteric(Auerbach) plexus-
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parasympathetic nerve ganglia located between muscularis externa layers controlling peristalsis, and other contractions of muscularis externa
14
Q
Regulation of the Digestive tract
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Motility and secretion of the digestive tract are controlled by neural, hormonal, and paracrine mechanisms. Telling digestive tract what to do in regards to motility and secretion of mucous layers all based on neural hormonal and paracrine secretion.
15
Q
chyme
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acid, soupy, or pasty mixture of digested food
16
Q
microscopic anatomy of the stomach
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stomach wall is covered in simple columnar glandular epithelium in mucosa w/ apical region filled w/ mucin that once secreted swells w/ contact w/ water becoming mucus. Mucosa and submucosa smooth when full, when empty contain longitudinal wrinkles gastric rugae. Muscularis externa has three layers- outer longitudinal, middle circular, and inner oblique. Gastric pits are depressions w/ same cells, w/ 2-3 tubular glands opening in the bottom of each called: cardial, pyloric, and gastric for secretion.
17
Q
gastric secretions:
A
hydrochloric acid pepsin-zymogens lipase intrinsic factor chemical factors
18
Q
hydrochloric acid
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activating pepsin and lingual lipase, liquefy and form chyme, converts iron to be absorbed, contributes to innate immunity by breaking down cell wall and destroying ingested pathogens.
19
Q
pepsin
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enzymes as inactive proteins converted to active by HCl, which cuts off amino acids. from chief cells digesting dietary protein to shorter peptide chains auto-catalytic effect once one activated activates more
20
Q
lipase
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chief cells and lingual lipase digests 10-15% of dietary fat digested in stomach w/ most in small intestine
21
Q
intrinsic factor
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by parietal cells is a glycoprotein used to absorb Vitamin B, which is needed to synthesize hemoglobin *only indispensable function of stomach.
22
Q
chemical messengers
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produce and release hormones into blood helping to stimulate distant cells paracrine and peptides in digestive and CNS for communication
23
Q
gastric motility
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food stimulates mechanoreceptors in pharynx transmitting to medulla oblongata and returned by vagus nerve relaxing stomach to accommodate more resist stretcher briefly then relaxes, then peristaltic contraction rhythm by pacemaker cells in longitudinal layers of muscularis externa tight constriction around middle and down getting stronger churning, mixing. Antrum waves and Pylorus end breaks up semi digested food w/ strongest pump to pyloric valve closing downward propulsion. Only small amount of chyme put through duodenum in time to stops the acid if overfilled inhibits gastric motility so not hurting small intestine and doesn’t digest food as well. four hours to empty from stomach less if more liquid higher for more fat meals.
24
Q
vomiting
A
Forceful ejection of contents from stomach and small intestine. Emetic center of medulla oblongata- caused by overstretching of stomach and duodenum, chemical irritants (alcohol, bacterial toxins), visceral trauma, intense pain, psychological and sensory stimuli. Preceded by nausea and retching. Abdominal contraction and rising thoracic pressure force upper esophageal sphincter open, esophagus and body of stomach relax, and chyme is driven out of stomach and mouth by strong abdominal contraction w/ reverse peristalsis of gastric antrum and duodenum. When it becomes chronic there are fluid, electrolyte, and acid-base imbalances damaging parts of mouth or teeth, esophagus, and parts of respiratory system
25
retching
thoracic expansion and abdominal contraction creating pressure difference dilating esophagus. Lower esophageal sphincter relax while stomach and duodenum contract spasmodically, w/ chyme entering esophagus and dropping back into stomach doesnt get past upper esophageal sphincter. Accompanied by Tachycardia, profuse salivation, and sweating
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projectile vomiting
sudden vomiting w/ no prior nausea or vomiting, neurological lesions or found in infants.
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Absorption-
Absorb aspirin and lipid soluble drugs, alcohol absorbed by small intestine depending upon how empty.
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Protection of the Stomach-Stomach is protected in three ways from the harsh acidic and enzymatic environment it creates.
Mucous coat thick layer highly alkaline mucus resists breakdown.
Tight junctions prevent gastric juice from beneath
Epithelial cell replacement live 3-6 days slough off into chyme and digested w/ food, replaced by mitosis in gastric pits w/ new cell layers replacing old
Breakdown causing inflammation ulcer or breakdown of wall
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peptic ulcer
Caused by bacteria can damage cells in layers of protection, stress related
Most ulcers are caused by acid-resistant bacteria Helicobacter pylori, that can be treated with antibiotics and Pepto-Bismol. Risk factors- smoking, aspirin NSAIDS
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gastritis
inflammation of the stomach, can lead to a peptic ulcer as pepsin and hydrochloric acid erode the stomach wall.
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Regulation of Gastric Function- Gastric activity three stages:
By nervous and endocrine system.
cephalic
gastric
intestinal phases
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cephalic phase
controlled by brain responding to sight smell taste or thought of food sensory and mental input to medulla oblongata, via vagus nerve, stimulating secretion of gastrin 40% of acid secreted
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gastric phase
stomach takes over controlling itself food and semi digested proteins stretches stomach and activates myenteric and vagovagal reflexes stimulating gastric secretion. ½ acid, ⅓ total secretions. Raising pH of contents. Stretch activates short reflex myenteric and long vagal reflex. Gastric secretion stimulated by acetylcholine (parasympathetic of both reflexes) histamine (paracrine), gastrin (in pyloric glands) to secrete HCl and intrinsic factor pepsinogen in response to gastrin. Positive-feedback but below pH of 2 stomach inhibits parietal.
34
intestinal phase
chyme arrives into duodenum controlling rate of gastric emptying. Duodenum enhances gastric secretions stretching stimulate stomach releasing gastrin furthering stimulating stomach, secretin, cck, and then enterogastric reflex caused by fats and acids when too full inhibiting it while duodenum processes chyme sympathetic suppress gastric, vagal parasympathetic stimulation of stomach inhibited. Chyme stimulates duodenal enteroendocrine cells to release secretin and cholecystokinin stimulate pancreas and gallbladder suppressing gastric secretion and motility. Sphincter tightens decreasing admission. Gastric-inhibitory peptide preps Insulin- secreted to prepare for processing of nutrients absorbed by small intestine more absorbed overlap and occur at same time.
35
describe the microscopic anatomy of the liver
interior of liver houses hepatic lobules. Consists of central vein (hepatic portal vein from stomach, intestines, pancreas, release glycogen spleen) passing down core surrounded by radiating plates of cuboidal cells (hepatocytes) w/ several cells thick, sinusoids are blood channels filling spaces.
36
describe microscopic functions of liver
Cells absorb from glucose, amino acids, iron, vitamins, and other nutrients from blood for metabolism or storage. Remove and degrade hormones, toxins, bile pigments, and drugs. Secrete albumin, lipoproteins, clotting factors, angiotensinogen. Blood collected central vein flows into right and left hepatic vein into inferior vena cava.
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galbladder
pear-shaped sac on underside of liver store and concentrate bile, simple columnar epithelium, fundus projects beyond inferior portion of liver, neck leads into cystic duct into bile duct. Function is to receive, store, and concentrate bile by concentrating water and electrolytes.
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Bile-
yellow-green Made of minerals, cholesterol, neural fats, phospholipids, bile pigments, bile acids, and lipid-transport vesicles (micelles).
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billirubin
principal bile pigment formed from decomposition of hemoglobin bacteria in large intestine. Intestine metabolize bilirubin to urobilinogen (colorless) half reabsorbed in small intestine and excreted by kidneys converted to urobilin (yellow), when remain in small intestine converted to stercobilin (brown). Absence of bile, feces are gray white w/ streaks of undigested fat.
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bile acids
steroids synthesized from cholesterol aid in fat digestion and absorption. 80% reabsorbed and sent to liver 20% secreted in feces
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gallstone
all other components of bile wastes can become concentrated forming gallstones from fatty meals can cause blockages filling bile duct and overflowing into galbladder.
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pancreas
| structure and ducts
flattened, spongy, retroperitoneal gland posterior to greater curvature of stomach. Globose head encircled by duodenum, body, and blunt tapered tail. endocrine (pancreatic islets concentrated in tail) and exocrine portion (pancreatic juice). Acini have branched duct converting into pancreatic duct lengthwise through middle of gland joining bile duct at hepatopancreatic ampulla w/ sphincter controlling release of both bile and juice. Additional Accessory duct open indepently into duodenum to be released into duodenum w/out bile.
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Pancreatic juice-
Alkaline mixture of water, enzymes, zymogens, sodium bicarbonate (buffer Hcl) and other electrolytes. Secreting many protein enzymes, amylase, lipase, ribonuclease, and deoxyribonuclease.
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Activation of Pancreatic Enzymes in the Small Intestine
Acetylcholine- vagus and enteric nerves stimulate acini to secrete during cephalic phase. Cholecystokinin (CCK)- mucosa of duodenum in response to fats in small intestine and allowing bile to be released into duodenum. Secretin- small intestine stimulates duct of liver and pancreas to secrete solution flushing enzyme buffering in response to chyme
45
duodenum
retroperitoneal Begins at pyloric valves of stomach, arcs around head of pancreas ending at duodenojejunal flexure. w/ major and minor duodenal papilla wrinkles receiving pancreatic duct and its accessory. Receives stomach contents, pancreatic juices, and bile. Stomach acid is neutralized Fats are physically broken up by emulsification by bile acids. Pepsin inactivated by high pH, pancreatic enzymes protect from stomach acid do chemical digestion.
46
jejunum
first 40% of small intestine beyond duodenum, large tall closely spaced folds begins in upper left quadrant of abdomen w/in umbilical region w/ thick muscular walls, rich blood supply, w/ most digestion and absorption occurring here.
47
Illium-
forms 60% post-duodenal, hypogastric region and pelvic cavity. thinner less muscle and vasculature, w/ prominent lymphatic nodules Pyers patches along mesenteric attachment points. Ileocecal junction end of illium meet w/ cecum of large intestine. Muscularis is thickened forming Ileocecal valve regulating passage of food residue prevents backup
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Circulation of small intestine
all supplied by superior mesenteric artery, branches to arteries to villi where it picks up absorbed nutrients to superior mesenteric vein to splenic vein into hepatic portal system.
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intestinal villi
w/in small intestine have villi tiny projections largest in duodenum smaller in distal parts containing lacteal in the middle for fat absorption helping w/ secretions and movement of stuff throughout intestine. And microvilli increase surface area absorption of nutrients, contact digestion, and push stuff along. Lower half have dividing stem cells pushing cells up crypt to be sloughed off and digested aiding in immune function as well.
50
circular folds
largest of internal folds transverse spiral ridges mucosa and submucosa slow progress of chyme flowing on spiral path increasing contact more thorough mixing and absorption begin in duodenum, tallest in jejunum, end in ileum. help push and mix nutrients w/in further exposing them to greater surface area
51
intestinal motility
purpose of segmentation is to mix, churn bringing it into contact for digestion and absorption, move things along. Segmentation- stationary ring like constriction along intestine contract and then knead and churn slow different cells form rhythm of segmentation. When most absorbed and not a lot left, segmentation declines and just peristalsis begins or waves of contractions pushing towards colon starting in duodenum and food in stomach form gastroileal reflex enhance segmentation in ileum relaxing valve. As cecum fills pressure pinches valve shut prevents reflux of cecal contents into ileum
52
carbohydrates
about 50% of dietary starch is digested before it reaches the small intestine. Pancreatic amylase resumes starch digestion in intestine. Starches- most digestible dietary carbohydrate first to be. Cellulose- indigestible. Beginning in mouth amylase digests it, it is then denatured by stomach acid and broken down by pepsin before it even reaches small intestine. Small intestine releases pancreatic amylase and further broken down. Absorbed by sodium-glucose transporter 80% of sugar absorbed as glucose carrying by solvent drag out.
53
lactose intolerance
In people without lactase, lactose passes undigested into large intestine. Still consume yogurt and cheese because bacteria breaks it down and not stomach.
Increases osmolarity of intestinal contents
Causes water retention in the colon and diarrhea
Gas production by bacterial fermentation of the lactose
54
protein digestion and absorption
pancreatic enzymes take over protein digestion in small intestine by hydrolyzing polypeptides using pepsin turning them into shorter oligopeptides doing most of it. Amino acids absorbed by small intestine come from 3 different sources: dietary proteins, digestive enzymes digested by each other, sloughed epithelial digested. Endogenous and exogenous amino acids (essential and nonessential). Proteases digests any protein or enzyme including itself. Pancreatic enzymes trypsin etc. take over further hydrolyzing then peptidases occuring at brush border enzymes.
Brush border enzymes finish task, producing free amino acids that are absorbed into intestinal epithelial cells
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Lipids: Fat Digestion and Absorption-
Hydrophobic digestion and absorption complicate matters using lipases released lingual by intrinsic salivary of tongue, and stomach (gastric) handful lipids before duodenum most there on. Stomach digestion occurs from contraction turning chyme breaking into emulsification droplets. exposing more surface area so easier. Mix w/ pancreatic juices further digesting fat. liver release certain bile acids. bile phospholipid and cholesterol diffuse into center of bile acids and are absorb fat solulble lipids, cholesterol, and monosaccharides, transport lipids to surface of small intestine. Bile acids also bind to droplets in duodenum breaking them up to be further digested. Absorption depends on micelles, bile acid components that allow the transport of broken down lipids into the center to facilitate transport to enterocytes. Some pass through plasma membrane of cells, and some fats are used or continued on to be digested later or excreted. transported through blood by chylomicron
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Minerals (iron)
absorbed along entire length of small intestine. Iron taken up by transferrin into blood where it goes to bone marrow for hemoglobin synthesis, muscular tissue for myoglobin synthesis, and liver for storage. Excess is bound to ferritin and passed. Liver hormone- Hepcidin inhibits intestinal absorption and mobilization of iron. excess binds to ferritin until passed.
57
calcium absorption
only 40% absorbed by transcellular route in calcium channels sodium-calcium pumpin duodenum, the rest passed. Parathyroid hormone secreted in response to drop in calcium, stimulates kidneys to synthesize vitamin D increases calcium channels in apical membrane of duodenum, increases amount of albindin in cytoplasm, and number of calcium-ATPase pumps in basal membrane most actually absorbed in jejunum and ileum but by paracellular where diffusion through epithelial cells and not controlled. Most absorbed from meat and dairy w/ fat retarding.
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water absorption controlled by
Water absorbed thorugh salts and dietary minerals. Diarrhea occurs when large intestine absorbs too little water if it is irritated by bacteria and passes too quickly w/ not enough water absorbed. Feces hard- constipation goes too slow too much reabsorbed.
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timing of excretion
36-48 hours to reduce meal to feces spending 24 hours in transverse colon reabsorbing water and electrolytes. Feces: 75% water 25% solids (30% bacteria, 30% undigested fiber, 10-20% fat from bacteria), bacteria smaller proteins, sloughed epithelial cells, salts, mucus.
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Haustral contractions and mass movements
30 minutes distention of haustrum w/ feces stimulates it to contract, churning and mixing residue promoting water and salt absorption and passing residue distally. Mass movements 1-3 times a day w/ filling of stomach stimulating motility of colon.
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Neural Control of Defecation-
Urge to defecate soon after a meal, intrinsic defecation reflex weak responses starts stretch signals to muscular layer contract and internal anal sphincter to relax. Parasympathetic reflex- stretch signals to Spinal cord rectum and spinal cord, pelvic nerves return w/ increase perstaltisand relax internal sphincter. Only occur if both sphincters and rectal muscles that must be relaxed. . Rectalis muscles must be realxed as well. Valsalva Maneuver increase contractions for defecation.
1. Filling of the rectum
2. Reflex contraction of rectum and relaxation of internal anal sphincter
3. Voluntary relaxation of external sphincte
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metabolism and nutrition
provides matter needed for cell division, growth, and development
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nutrition
starting point and the basis for all human form and function
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metabolism
chemical change that lies at the foundation of form and function
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weight
determined by the body’s energy balance, if energy intake and output are equal stabilizes gaining if intake exceeds output and vice versa stable over years w/ homeostatic set point for each personfrom hereditary (30-50%) and environmental influences (exercise and sleep)
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gut-brain peptides
chemical signals form gastrointestinal tract to brain several hormones that control weight.
short and long term
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ghrelin
secreted by parietal cells in gastric fundus, when stomach is empty producing sensation of hunger and stimulates hypothalamus to secrete GHRH priming body to take advantage of nutrients to be absorbed ceasing hour after eating.
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PYY
peptide YY hormone is secreted by enteroendocrine cells in ileum and colon, sense food arrives as it enters stomach based on quantity of calories consumed signaling satiety and terminate eating elevated after meal ileal brake preventing stomach from emptying too quickly prolong sensation of satiety
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CCK
cholecystokinin secreted by enteroendocrine cells in duodenum and jejunum stimulates secreiton of bile and pancreatic enzymes, stimulates brain and sensory fibers of vagus nerves, appetite-suppressant effect
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Short-term gut-brain peptides
minutes to hours, making one feel hungry, eating, and satiated
gherkin, PYY, CCK, amylin
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long-term gut brain peptides
regulate appetite, metabolic rate, and body weight over longer term governing caloric intake and energy expenditure over weeks to years. Adipostiy signals how much has for adding or reducing
insulin and leptin
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insulin
secreted by pancreatic beta cells, stimulates glucose and amino acid uptake and promotes glycogen and fat synthesis index of body’s fat stores w/ weaker effect on appetite
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leptin
secreted by adipocytes throughout body, proportional to fat stores telling brain how much fat we have. Inhibits secretion of appetite stimulants endocannabinoids. Leptin deficiency- hyperphagia overeating and obesity. Leptin insensitivity- in humans receptor defect not hormone deficiency more common
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arcuate nucleus of hypothalamus and the two neural networks involved in hunger
all peptides have receptors in this location as well as target cells, w/ two neural networks involved in hunger: neuropeptide Y- appetite stimulant (ghrelin stimulate its, insulin, PYY and leptin inhibit), melanocortin- inhibits eating (leptin stimulates)
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neurotransmitters affecting hunger
Norepinephrine stimulates appetite for carbohydrates, galanin for fatty foods, and endorphins for protein
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obesity risks and causes
shortens life expectancy and increases person’s risk of atherosclerosis, hypertension, diabetes mellitus, joint pain and degeneration, kidney stones, and gallstones; cancer of breast, uterus, liver of women, and colon, rectum, and prostate in men. Thoracic fat impairs breathing and results in increased blood PCO2, sleepiness, and reducedvitality. Causes are hereditary, environmental (too much stored based on metabolism nad evolution), overfeeding in infancy and childhood (increasing adipocyte size and number)
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calories
good nutrition requires more complex foods that simultaneously meet need for proteins, lipids, vitamins, and other nutrients breaking these down.
One calorie—amount of heat required to raise temperature of 1 g of water 1°C
1,000 calories is a kilocalorie (kcal) in physiology or a Calorie in dietetics
A measure of the capacity to do biological work
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nutrients and how many calories they provide food
Carbohydrates and proteins yield about 4 kcal/g
Sugar and alcohol (7.1 kcal/g) are “empty” calories
Provide few nutrients and suppress appetite
Fats yield about 9 kcal/g
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fuel
oxidized solely or primarily to extract energy from it w/ extracted energy usually used to make ATP transferring energy to other physiological processes
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Nutrients what are they and what are the classes
any ingested chemical used for growth, repair, or maintenance of the body
Six classes of nutrients
Water ,carbohydrates, lipids, and proteins
Macronutrients—must be consumed in relatively large quantities
Vitamins and minerals
Micronutrients—only small quantities are required
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carbohydrates how are they used and where do they come from
complex sugars oxidized rapidly taken in in greater amounts that any other nutrients w/ brain most often used. Come from plants: grains, legumes, fruit, and root vegetables
Well-nourished adult body has 440 g of carbohydrates
325 g of muscle glycogen, 90 to 100 g of liver glycogen, 15 to 20 g of blood glucose
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blood glucose
Blood glucose concentration carefully regulated because it has a structural component of many other molecules and fuel because if hypoglycemia for short periods can cause nervous system disturbance including weakness and dizziness
Interplay of insulin and glucagon
Regulate balance between glycogen and free glucose
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carbohydrates influence of other nutrients
Fats used as fuel when glucose and glycogen levels are low
| Excess carbohydrates are converted to fat
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monosaccharides
glucose, galactose, and fructose (both of which are turned into glucose by liver and small intestine) from digestion of starches
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disaccharides
(sucrose-table sugar, lactose, and maltose)
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polysaccharides
(starch, glycogen (rare in foods), and cellulose (not nutrient but is a fiber)
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fiber
Dietary fiber—all fibrous material of plant and animal origin that resists digestion
Cellulose, pectin, gums, and lignins
Fiber is important to diet—RDA is 30 g/day
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water-soluble fiber
(e.g., pectin)
Found in oats, beans, peas, brown rice, and fruits
Decreases blood cholesterol and LDL levels
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water-insoluble fiber
includes cellulose, hemicellulose, and lignin no effect on cholesterol or LDL but absorbs water and swells softening stool and increasing bulk stretching colon stimulating peristalsis quickening passage of feces reducing constipation and diverticulitis no effect on colorectal cancer. Excessive intake interferes w/ absorption of iron, calcium, magnesium, phosphorus, and other things.
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lipids
Average male 15% body fat; female 25% body fat
| Well-nourished adult meets 80% to 90% of resting energy needs from fat
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fat is superior to carbs for two reasons?
Carbohydrates are hydrophilic, absorb water, and expand and occupy more space, whereas fat is hydrophobic, and is a more compact energy storage substance
Fat is less oxidized than carbohydrates and contains over twice as much energy: 9 kcal/g for fat; 4 kcal/g for carbohydrates. Less than 30% of daily calorie intake, saturated fats and cholesterol limited. Most fatty acids created by body but some have to be intaken
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Function of lipids
structural & physiological including phospholipids, cholesterol components of plasma membranes and myelin; vitamins are fat-soluble and require fat to transport w/out they are not absorbed; cholesterol is important precursor of steroid hormones, bile acids, and vitamin D; thromboplastin, blood clotting factor is a lipoprotein; fatty acids arachidonic and linoleic acid (essential fatty acids) precursor for prostaglandins and eicosanoids protective and insulating functions
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lipoprotein processing and the 4 categories of serum lipoproteins
transported to all cells of body, yet don’t dissolve in blood plasma. Use lipoproteins, tiny droplets w/ a core of cholesterol and triglycerides and coating of proteins and phospholipids coating enables lipids to remain suspended in blood and recognition markers for absorbing cells. 4 categories of serum lipoproteins categorized by their density the higher the proportion of protein to lipid, the higher the density. Differ in composition and functions
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chylomicrons
form in absorptive cells of small intestine pass into lymphatic system and bloodstream, blood capillary endothelial cells have surface enzyme called lipoprotein lipase hydrolyzes chylomicron triglycerides into monoglycerides and free fatty acid, which then pass through capillary walls into adipocytes synthesized into storage triglycerides. Chylomicron remnants after extracted and degraded by liver
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3 other categories of serum lipoproteins in addition to chylomicrons
high-density lipoproteins- good cholesterol.
low-density lipoproteins- bad cholesterol
very low-density lipoproteins
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Cholesterol and Serum Lipoproteins
Most of the body’s cholesterol is endogenous—internally synthesized rather than dietary
Body compensates for variation in intake
High dietary intake lowers liver cholesterol production
Low dietary intake raises liver production
Lowering dietary cholesterol lowers level by no more than 5%
Certain saturated fatty acids (SFAs) raise serum cholesterol level
Moderate reduction in SFAs can lower blood cholesterol by 15% to 20%
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how does exercise affect blood cholesterol
Sensitivity of right atrium to blood pressure is reduced
Heart secretes less atrial natriuretic peptide and thus kidneys excrete less sodium and water
Raises blood volume
Dilution of blood lipoproteins causes adipocytes to produce more lipoprotein lipase
Adipocytes consume more blood triglycerides
VLDL particles shed some cholesterol which is picked up by HDL and removed by the liver
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what does high LDL mean?
indicates deposition in peoples arteries, elevated by saturated fat intake, smoking, coffee, and stress.
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what does high HDL mean?
beneficial cholesterol moved from arteries and transported to liver for disposal. Compensates for high bad cholesterol.
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what should the the ratio of HDL:LDL
High ratio of HDL:LDL by exercise: avoiding smoking, saturated fats, coffee, and stress
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dietary protein what is it normally? whaen should you have more? what happens if overload
take up 12-15% of body’s mass, 65% in skeletal muscles. Higher intake recommended under conditions of stress, infection, injury, and pregnancy. Overload of proteins can cause renal damage overloading w/ nitrogenous wastes.
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fibrous proteins
collagen, elastin, and keratin making up structure of bone, cartilage, tendons, ligaments, skin, hair, and nails
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globular proteins
antibodies, hormones, neuromodulators, hemoglobin, myoglobin, enzymes controlling cellular metabolism
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plasma proteins
albumin maintain blood viscosity and osmolarity, transport lipids and solutes. Buffer pH of body fluids contribute to resting membrane potential of cells
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where proteins come from
Animal proteins of meat, eggs, and dairy products are complete proteins
Closely match human proteins in amino acid composition
Plant sources are incomplete proteins and must be combined in the right proportions
Beans and rice are a complementary choice
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nutritional value of proteins
depends on amino acids proportions needed for building human proteins. 8 essential amino acids not produced by body need to take in by body 12 inessential not produced by body.
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how proteins are mad
Cells don't store amino acids for later use all must be present when synthesizing if one missing it cannot be made. High quality complete proteins provide all of the essential amino acids in necessary proportions for human tissue growth, maintenance, and nitrogen balance. Lower-quality incomplete proteins lack one or more essential amino acids
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net protein utilization
percentage of amino acids in protein that human body uses
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advantages of going vegetarian
plant food provide more vitamins, minerals, and fibers; less saturated fats, no cholesterol, and less pesticide
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Nitrogen Balance
rate of nitrogen ingested equals rate of nitrogen excreted
| Proteins are chief dietary source of nitrogen
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positive nitrogen balance
found in growing children because they ingest more than excrete retaining protein for tissue growth. Pregnant women and athletes in resistance training as well. Growth hormone and sex steroids promote protein synthesis.
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negative nitrogen balance
excretion exceeds ingestion, body proteins broken down and used as fuel. Proteins of muscle and liver more easily broken down so it is usually associated w/ muscle atrophy occur if carb and fat intake insufficient to meet need for energy. Glucocorticoids promote protein catabolism in states of stress.
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minerals
norganic elements that plants extract from soil or water and introduce into the food web. 4% of body mass ¾ are calcium and phosphorus in bones and teeth
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mineral salts
function as electrolytes and govern function of nerve and muscle cells, osmotically regulating content and distribution of water in body maintaining blood volume best sources are vegetables, milk, eggs, fish, shellfish, and other meats. Herbivores require more salt than carnivores and salt is associated w/ hypertension
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vitamins
small dietary organic compounds that are necessary for metabolism can be intaken by diet or from precursors
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water soluble
absorbed w/ water from small intestine, dissolve freely in body fluids quickly excreted by kidneys cannot be stored ex. Ascorbic acid/vitamin c (promote hemoglobin, collagen synthesis, connective tissue structure, antioxidant, reducing risk of cancer) and B vitamins (function as coenzymes or parts of coenzyme molecules help enzymes by transferring electrons from one metabolic reaction to other, possible for enzymes to catalyze these reactions)
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fat soluble
incorporated into lipid micelles in small intestine and absorbed w/ dietary lipids more varied function. Include vitamin A (visual pigments, proteoglycan synthesis and epithelial maintenance), vitamin D (promotes calcium absorption and bone mineralization), vitamin K (essential to prothrombin synthesis and blood clotting) A&E are antioxidants.
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carbohydrate metabolism
turns energy into ATP for glucose
Most dietary carbohydrates burned as fuel within hours of absorption
Oxidative carbohydrate metabolism is glucose catabolism
C6H12O6+ 6 O2®6 CO2+ 6 H2O
Function of this reaction is to transfer energy from glucose to ATP
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vitamins and minerals
Neither is used as fuel
| Both are essential to our ability to use other nutrients
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Glucose Catabolism and its three major processes
series of small steps controlled by separate enzyme releasing energy in small manageable amounts transferring it to ATP with the rest released as heat
glycolysis, anaerobic fermentation, aerobic respiration
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Describe the three major pathways of glucose catabolism
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Glycolysis
Glucose (6 C) split into two pyruvic acid molecules (3 C)
Anaerobic fermentation
Occurs in the absence of oxygen
Reduces pyruvic acid to lactic acid
Aerobic respiration
Occurs in the presence of oxygen
Oxidizes pyruvic acid to CO2and H2O
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Describe glucose catabolism. what does it require?
enzymes remove electrons as hydrogen atoms from intermediate compounds of these pathways, not binding but transferring to other coenzymes donating to other compounds later on in the pathway cant function w/out.
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Anaerobic Fermentation-
fate of pyruvate depends on whether or not oxygen. When it becomes available liver oxidizing it back to pyruvic acid, breathing more vigorously after exervise. In exercising demand for ATP may exceed supply of oxygen, wasteful, energy of glucose stuck in lactic acid, lactic acid is toxic but tolerated in skeletal muscle but not in heart.
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Aerobic Respiration and its two major steps
Most ATP generated in mitochondria, which requires oxygen as final electron acceptor
In the presence of oxygen, pyruvic acid enters the mitochondria and is oxidized by aerobic respiration
Two major steps: matrix reactions- controlling enzymes are in fluid of mitochondrial matrix
Membrane reactions- controlling enzymes are bound to membranes of mitochondrial cristae
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Glycogen Metabolism and the two processes involved
ATP quickly used after formed, energy-transfer molecule, not storage. Body converts excess glucose to other compounds better suited for energy storage, glycogen and fat. Glycogenesis stimulated by insulin chaining glucose monomers together in cells or outside of cells.
Glycogenolysis- hydrolysis of glycogen
Gluconeogenesis- synthesis of glucose from noncarbohydrates, such as glycerol and amino acids
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lypolysis
breaking down fat for fuel. Hydrolysis of glyceride into glycerol and fatty acids stimulated by epinephrine, norepinephrine, glucocorticoids, thyroid hormone, and growth hormone. Glycerol is easily converted and enters pathway of glycolysis generating only half as much ATP as glucose. Fatty acids are catabolized into acetyl groups by beta oxidation can undergo ketogenesis (liver to produce ketone bodies) rapid or incomplete oxidation of fats raising ketone levels from mitosis leading to ketoacidosis, pH imbalance.
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protein synthesis
all amino acids absorbed by small intestine, half from diet, ¼ from dead epithelial cells, and dead enzymes digested each other. Some can be converted into others, free amino acids can be converted into glucose, fat, or directly used. As fuel. involving DNA, mRNA, tRNA, and ribosomes
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protein synthesis done by three processes
all reversible in case there is a need of amino acids
Deamination- removal of amino group
Amination- addition of NH2
Transamination- transfer of NH2 from one molecule to another.
Stimulated by growth hormone, thyroid hormone, and insulin
Requires an ample supply of all amino acids
Nonessential amino acids can be made by the liver from other amino acids or citric acid cycle intermediates
Essential amino acids must be obtained from the diet
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liver functions in metabolism
Liver plays a wide variety of roles in carbohydrate, lipid, and protein metabolism
Most of its functions are non digestive
Hepatocytes perform all functions, except phagocytosis
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Degenerative liver diseases
such as hepatitis, cirrhosis, and liver cancer are especially life-threatening
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hepatitis
inflammation of liver from virus B & C or results from alcohol abuse.
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cirrhosis its causes and symptoms
is number one symptom of alcohol abuse being irreversible inflammation of the liver. Others are hepatitis, gallstones, pancreatic inflammation. Developing slowing over a period of years, disorganized liver scar tissue making it lumpy or knobby and hardened last for years can lead to detrimental effects scarring and blockage of pathways causing rupture or necrosis of liver
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hepatitis A
common and mild can cause 6 months of illness, but most people recover and are permanently immune to it.
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Hepatitis E
water-borne epidemics in less economically developed countries
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Hepatitis B&C
transmitted sexually through blood and body fluids. Symptoms are fatigue, malaise, nausea, vomiting, and weight loss. Causing enlarged and tender liver, yellowing of skin (jaundice)- Hepatocytes are destroyed, bile passages blocked and accumulate in blood. Lead to chronic hepatitis progressing to cirrhosis or liver cancer,
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metabolism is regulated by:
regulated by insulin, in response to elevated blood glucose and amino acid levels in all cells except neurons, kidney cells, and erythrocytes having independent rates of uptake
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insulin has large effect on:
increasing cellular uptake of glucose 20-fold (causing blood glucose to fall); stimulates glucose oxidation, glycogenesis, and lipogenesis; inhibits gluconeogenesis; stimulates the active transport of amino acids into cells promoting protein synthesis; acts on brain as adiposity signal (index of fat stores
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high amino acid level does?
High amino acid level stimulates secretion of both insulin and glucagon supporting adequate level of glucose to meet needs of brain
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metabolism-
Your metabolism changes from hour to hour, Depending on how long since your last meal
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Absorptive (fed) state when does it occur and what is generally occurring?
About 4 hours during and after a meal, Nutrients are being absorbed, Nutrients may be used immediately to meet energy and other needs
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How is glucose used in absorptive state?
glucose is used for ATP synthesis as fuel and spares other fuels carbohydrates absorbed with sugars transported to liver by hepatic portal system, most glucose passes thorugh liver and becomes available to cells everywhere in the body. Glucose in excess is absorbed by liver and converted to glycogen or fat. Most fat synthesize in liver is released into circulation.
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How is fat used in absorptive state?
Fats enter lymphatic system as chylomicrons bypassing liver. Lipoprotein lipases removes fat from chylomicrons for uptake by tissues, adipose and muscular. Liver disposes of chylomicron remnants w/ fats primary energy substrate for hepatocytes, adipocytes, and muscle
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How is amino acids used in absorptive state?
circulate first to liver, pass through and become available to other cells for protein synthesis. Some removed by liver to be used for synthesis, deaminated and used for ATP synthesis fuel or fatty acid synthesis
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Post-absorptive fasting state when and what is it generally?
Prevails in the late morning, late afternoon, and overnight, Stomach and intestines are empty, Body’s energy needs are met from stored fuels.
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what regulates fasting state?
Regulated by cortisol (released in response to stress promoting fat and protein catabolism and gluconeogenesis) and growth hormone (in response to drop in glucose level in states of prolonged fasting opposes insulin raising blood glucose concentration. .
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metabolic rate-
the amount of energy liberated in the body in a given period of time (kcal/hr or kcal/day). Depending on physical activity, pregnancy, mental state, anxiety, fever absorptive or postabsorptive status, thyroid hormone, and other hormones higher in children declining w/ age.
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factors lowering metabolic rate
(apathy, depression, and prolonged starvation). As one reduces food intake, body reduces its metabolic rate to conserve body mass making weight loss more difficult
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Body Heat and Thermoregulation-
body temperature varies w/in 2-3 hour cycle. Low in morning high in afternoon.
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how is body heat maintained
Enzymes that control our metabolism depend on an optimal, stable working temperature
To maintain this, heat loss must match heat generation
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what happens if body heat is not maintained
Low body temperature (hypothermia)can slow metabolism and cause death
High body temperature (hyperthermia)can disrupt coordination of metabolic pathways and cause death
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core body temperature
of organs in cranial, thoracic, and abdominal cavities best to measure w/ rectal thermometer. Adults vary from 99-99.7
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shell tempertature
temperature closer to surface skin and oral temperature. 97.9-98. Hard exercise as high as 104, fluctuates in response to processes that that serve to maintain stable core temperature
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thermoregulation
the balance between heat production and loss. Heat generated from: joint friction, blood flow. Most heat: generated by organs such as brain, heart, liver, and endocrine glands. Skeletal contributes 20-30% of resting heat and vigorous 30-40%.
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radiation
the emission of infrared (IR) rays by moving molecules. Emission of these- Heat means molecular motion, which create infrared rays increasing molecular motion and temperature to those nearby that receive it removing from source to things around it. We end up losing more heat this way than we can gain. Metal on body transferring it to it.
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conduction
transfer of kinetic energy between molecules as they collide, body heat is conducted from skin to any cooler than it. Can gain if body is contacting something warmer than it.
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convection
transfer of heat to a moving fluid (blood, air, or water). Heat from metabolism is carried by convection to body surface warming adjacent air at skin surface. As it rises is replaced by cooler air from below. Natural convection- temperature change. Forced convection- other force acting on it
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evaporation
change from a liquid to a gaseous state, cohesion of water hampering vibrations in response to heat input, temperature water raises sufficiently great enough to break free taking heat with it when it evaporates like sweat. forced convection can increase evaporative heat lose. Extreme conditions someone can lose 2L of sweat per hour. Nude body at 70F loses 60% radiation, 18% conduction, and 22% evaporation. Once it is higher evaporation only means of heat loss as the others add to it
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thermoregulation
is achieved through several negative feedback loops, heat loss sensor senses blood temperature is too high activating heat-losing mechanisms
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when temperature is high?
Ex. is cutaneous vasodilation increasing blood flow to body shell promoting heat loss can trigger sweating if necessary and inhibit heat-promoting centers.
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when temperature is low?
When temperature is low heat-promoting center activated mechanisms to conserve body heat or generate more by vasoconstriction by sympathetic nervous system w/ Warm blood retained deep in body. If still cant restore enough causes shivering, thermogenesis spinal reflex to contract tiny alternating muscles antagonistic releasing heat from ATP consumption increasing body heat production by four.
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non shivering thermogenesis
longer-term mechanism for generating heat, thyroid hormone sympathetic nervous system raises metabolic rate during colder times after several weeks as much as 30%, more nutrients are burned as fuel w/ more appetite in winter. Behavioral regulation- add more clothes
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low core body temp.
Core body drops below 91 temperature, metabolic rate drops so low that heat production cannot keep pace w/ heat loss, and temperature falls even more death below 90 degrees because of cardiac fibrillation. Dangerous to give alcohol to someone w/ hypothermia giving an illusion of warmth but accelerates heat loss by dilating cutaneous blood vessels.
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hypothalamic thermostats
the preoptic area of the hypothalamus functions as the body’s thermostat
Monitors temperature of the blood
Receives signals from peripheral thermoreceptors in the skin
Sends appropriate signals to nearby centers:
Heat-loss center: a nucleus in the anterior hypothalamus
Heat-promoting center:a nucleus near the mammillary bodies of the brai
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alcohol and alcoholism effects on nervous system
Low doses of alcohol provide euphoria and giddiness. W/ higher doses nerves less responsive to neurotransmitters: impaired coordination, slurring speech, and slower reaction time. Can destroy liver cells faster than they can regenerate cirrhosis, inflammation. scarring and can go into hepatic coma and jaundice caused by damage to liver
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alcohol and alcoholism effects on circulatory system
portal hypertension, and hypoproteinemia destroying livers function to make enough proteins causing the organs to weep serous fluid into peritoneal cavity causing ascites (swelling of the abdomen) making it extremely distended. Hypertension and impaired clotting (lack of albumin) leads to hemorrhaging, hematemesis- vomiting blood as enlarged veins of esophagus hemorhage. Destroy myocardial tissue, reduce contractility of heart causing cardiac arrhythmia.
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alcohol-
mind-altering drug, empty calories, addictive drug, and a toxin
Rapidly absorbed from GI tract
10% in stomach and 90% in small intestine
Carbonation increases rate of absorption
Food reduces absorption
Easily crosses blood–brain barrier to exert intoxicating effects on the brain
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alcohol addiction
high risk of addiction and overdose similar to barbiturates in effects and detox
Alcohol is the most widely available addictive drug in America
Similar to barbiturates in toxic effects
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alcoholism
involves: potential for tolerance, dependence, and risk of overdose
Physiological tolerance of high concentrations requiring more to get same feeling
Impaired physiological, psychological, and social functionality
Withdrawal symptoms when intake is reduced or stopped: delirium tremens (DT)
Restlessness, insomnia, confusion, irritability, tremors, incoherent speech, hallucinations, convulsions, and coma
Has 5% to 15% mortality rate
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two types of alcoholism
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Type I (more common) sets in after age 25—usually associated with life stress or peer pressure
Type II is addicted before 25—partially hereditary unusual EEG brain waves and levels in blood when drinking predisposed to it
Sons of other type II alcoholics
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