1. Motility to propel and mix food; 2. Gland secretion to aid in digestion and absorption; 3. Digestion of food into absorable molecules; 4. Nutrient, electrolyte, and H2O absorption into bloodstream.
Refles initiated when food is detected by mechanoreceptors in oropharynx. 3 Pharyngeal constictor muscles contract in succession and upper esophageal sphincter relaxes, allowing bolus to be pushed into esophagus
Esophageal Phase
Muscular contractions of esophagus, called peristaltic waves, push bolus down into the stomach.
Gastroesophageal Reflux Disease
Heartburn; defined by mucosal damage to the esophagus duw do stomach acid reflux.Complications: Chronic esophagitis, difficulty swallowingCauses: Caffeine, stress, alcohol, fatty food, obesity, smoking, and tight clothing. Acid inhibitor treatment
Stomach
enlarged segment of digestive tract in left superior part of abdomen; contains additional inner oblique muscle layer
Gastric Pits
In stomach; invagination of simple columnar epithelial cells.
4 Cell types of Gastric Pits
Mucus cells(secrete HCO3-, protects stomach from acid), chief cells (secrete pepsin, break down proteins), endocrine cells (secrete gastrin), parietal cells (produce HCL and intrinsic factor, activates Pepsin).
Intrinsic Factor
Binds Vitamin B12 making it more readily absorbed by small intesting. B12 is critical for DNA synthesis and RBC production.
Both __ and __ mechanisms regulate gastric secretion
neural and hormonal
Cephalic stage of Stomach secretion
first stage; anticipatory; taste, smell of food activate parasympathetic NS, stimulating stomach secretions, particulary gastrini which acts on parietal cells for HCL production
Gastric Phase of stomach secretion
greatest gastric secretion; reflex initiated by distention of the stomach
Intestinal phase of stomach secretion
inhibits gastric secretion, presence of chyme in duodenum initiate neural and hormonal resoponses
Neural:
Chemoreceptors in duodenum detect HCl or lipids, sent dignals to medulla to inhibit parasympathetic activity
Peptic Ulcer
Results from erosive and digestive actions of H+ and Pepsin.
Major causative factor of Peptic Ulcers
Helicobactor pylori infection, secretes cutotoxins, damage mucosal layer, secrete enzyme called urease, which alkinalizes the local enviro.
lobules by connective tissue septa, have portal triads at corners
Triads
Consist of hepatic portal veins, hepatic arteries, and hepatic ducts.
Bile
produced by liver, secreted into duodenum, contains amphipathic ile salts, which emulsify fats in the duodenum
Bile secreted by
CCk
CCK Response
released by endocrine cells in response to chyme from stomach. cck travels to gallbladder where it causes contraction.
Cirrhosis
refers to damage and death of hepatocytes and replacement by connective scar tissue. Treatment seeks to slow progression
Pancreas
posterior to stomach in left upper quatrant of abdomen. Composed of exocrine and endocrine tissues
endocrine tissue
composed of acinar glands
pancreatic juice
rich in HCO3- which neutralize acidic chyme. contain pancreatic proteases, such as trypsin, pancreatic amylase which breaks down starchinto disaccharides and pancreatic lipase which breaks down lipids into glycerol and fatty acids
pancreatic juice secretions
in response to neural and hormonal activity
Large Intestine
cecum colon rectum anal canal.
cecum
proximal end of LI, SI AND LI meet at ilocecal junction.
colon
longest part of LI consisting of ascendind, transverse, descending and sigmoid segments, mucosal lining contains crypts which contain goblet cells
colon functions
converts chyme into feces, absorbs water& salts, mucus secretion & activity of bacteria.
mass movements
propel feces long distances through the colon, occur every 8-12 hours
defecation reflex
distention of rectal wall, parasympathetic response causes strong peristaltic contractions and relaxation of internal anal sphincter
Irritable bowel syndrom
abdominal pain, twice as common in adult females, highly correlated with stress or depression. treated by stress management, increased fiber, or anxiety drugs.
Types of digestion
Mechanical: breaking food into smaller particles. Chemical: breaking of covalent bonds in nutrients by digestive enzymes
Carbohydrate digestion
begins in oral cavity.
Carbohydrate absorption
Absorbed as monosaccharides. Apical membrane transport; glucose and galactose cotransported with NA; secondary active transport driven by NA, K, ATPase on basal membreane. enter capillaries of intestinal villi and are transported to liver via hepaticportv
Protein digestion
Proteases digest protein and polypeptides into smaller polypeptides. Brush border peptidases break down small polypeptides into absorbable forms, Tripeptides, Dipeptides and amino acids.
Protein absorption
amino acids, dipeptides or tripeptides. apical membrane transport. amino acids cotransported with NA secondary driven by Na, K, ATPase on basal membrane.
Major Ingested Lipids
Triglycerides ( can be saturated or unsaturated), phospholipids ( recall major constituent of cell membrane), steroids (cholesterol and hormones), fat-soluble vitamins such as vitamin E
Lipid Digestion
Emulsification: Amphipathic bile salts break large lipid droplets into much smaller droplets
Absorption of Lipids
Occurs when micelles containing products of lipid digestion feely diffuse across apical surface of intestinal cells
Lipid Digestion
Emulsification: Amphipathic bile salts break large lipid droplets into much smaller droplets
Absorption of Lipids
Occurs when micelles containing products of lipid digestion feely diffuse across apical surface of intestinal cells
Lipoproteins transport
Triglycerides and Cholesterol.
LDL
Low Density Lipoproteins;; transport cholesterol from liver to tissues for use by clls. High cholesterol content and low protein content.
HDL
High Density Lipoproteins transport cholesterol from tissues to liver where its metabolized or excreted in bile.
about __L of H20 enters GItract daily
9
92% of water absorbed by
SI
7% of water absorbed by
LI
1% of water
lost in feces
water moving across GI Tract
Passive, direction determined by osmotic gradient
Electroltes such as NA, K, Ca are __ across intestinal epithelium
actively transported
Ca2 absorption requires
Vitamin D. Acts on intestinal epithelial cells to increase synthesis of a Ca binding portien called Calbindin.
Diarrhea
Major cause of Death worldwide. responsible for 18% of childhood deaths. Loss of fluid >> loss of extracellular fluid>> low blood volume >> low BP > death.
secretory diarhhea
Vibrio cholerae. cholera toxin released, causes crypt cells to secrete large amounts of fluid>> can be fatal within hours. Easily treated by replacing fluid and electrolytes.
Nutrients
Ingested chemicals.
Major classes of nutrients
carbohydrates, lipids, proteins, vitamins, minerals, water
Essential nutrients
ex: linoleic acid must be ingested. important for blood clotting. Nonessenial are necessary but can be synthesized from esential nutrients.
Benefits of a healthy diet
reduction in heart and chronic diseases
Caloric restriction
Restrict calories by 10-25%. decrease in heart disease, diabetes, and cancer shown (in rats) monkeys less likely to develop Alzheimer's. Increased insulin sensitivity and reduced LDL cholesterol. Humans: lower BP and cholesterol, possibly lifespan.
Glucose
Principal energy source for cells. Glycolysis yeilds ATP. help build DNA and RNA.
When Glycogen stores are full...
The liver converts excess glucose to riglycerides which are exported to adipose tissue for long term storage.
Insulin
Released from Beta cells of pancreas in response to a raise in blood sugar; promotes uptake and storage of glucose as well as fats and proteins.
Insulin uptake & storage
Binds to receptor>intracellular phosphorylation of proteins> insertion of GLUTs in cell membrane > increased glucose Uptake
Glucagon
hormone of starvation. During periods of fasting, raises glucose levels. triggered by low blood glucose levels.
Glucagon release
Breakdown of glycogen> glucose in lover, break down of fats in adipose tissue and breake down of amino acids from muscle; all enter bloodstream.
Gluconeogenesis
Liver can synthesize glucose from other nutrient sources such as amino acids and glycerol in triglycerides
Insulin dependent diabetes mellitus
cause by distruction of beta cells in pancreas so body produces no insulin
Characterization of Type 1 diabetes
hyperglycemia, osmotoic diuresis, bypotension treated by administration of synthetic insulin
non insulin dependent diabetes mellitus (type 2)
caused by increased resistance of target tissues to insulin. assoc. w. obesity. Caloric and cab restriction and drugs
Carb. restriction
Atkins;; Utilization of glycogen stores, gluconeogenisis keeps these people alive
glycemic index
predicts whether absorbed carbs are used for immediate energy needs or sent to long term storage: Low value indicates slower digestion higher = quicker
factors which affect glycemic indes
type of starch, physical entrapment of starch, presence of fat and protein, organic acids such as vinegar
high glycemic index foods
promotes storage as fat; reduces insulin sensitivity
nutrient timing
popular in athletic training; involves significant carb intake during periods before or after intense physical activity. outside of that small window, carb intake is restricted
Fatty acids are classified by..
degree of saturation
saturated
carbon chain has all single bonds. each c atom in chain is saturated with hydrogen atoms
unsaturated
carbon chain has one or more double bonds.
Monounsaturated
unsaturate; one double bond
polyunsaturated
unsaturated; more than 1 double bond
sources of each fatty acid.
Sat: meat, dary, eggs, nutsMono:olive, canola, certain nuts/seedsPolyunsat: fish, safflower, certain nuts/seeds
Homeostasis
maintenence of a relatively stably environment with respect to a given variable
which substances can freely diffuse across CM?
Lipids and other hydrophobic molecules (CO2 and 02 both can) an exception: water CAN freely diffuse
osmosis
diffusion of water across a membrane from high to low concentration
diffusion
movement of molecules across a membrane from high to low concentration
how are substances movs across CM against concentration gradient? classic example?
active transport: proteins.
How is the body able to produce different cell types?
Gene Regulation controls which cells get made my regulating which cells get copied, or transcribed
Action Potential (1)
a Ligand binds to a ligand gated Na+ channel, releasing a bunch of Na+. This floods the cell because of how much more Na is on the outside. This strongly depolarizes the cell. This reaches the threshold potential needed to open the voltage gated Na
AP(2)
Channels, releasing more Na, making the membrane go up to +40mV. Finally, the slower-opening K+ channels open, causing K+ to rush out of the cell, repolarizing it.
Steps of Neurotransmission
current is detected by voltage gated Ca2+ channels, which open allowing Ca2+ to move down its conc. gradient. Ions flow into vessicle and associate with vessicles containing neurotransmitters. vessicles fuse with CM, releasing 10000s of neurotransmitter
Neurotrans (2)
molecules into extracellular space. difuse across synapse and bind specific receptors. leads to channel opening and depolarization of postsynaptic membrane.
how is touch sensation detected and transmited to somatosensory cortex
planning in premotor area, primary motor cortex initiates signals which result in movement; lower motor neurons project to skeletal muscle fibers;
how brain initiates skeletal muscle movement
planning in premotor area, primary motor cortex initiates signals which result in movement; lower motor neurons project to skeletal muscle fibers;
2 divisions of ANS and functions neurotransmitters released from each
Sympathetic: fight of flight norepiParasympathetic: resorative or vegetative body functions ach
2 divisions of ANS and functions neurotransmitters released from each
Sympathetic: fight of flight norepiParasympathetic: resorative or vegetative body functions ach
motor unit
all muscle fibers a single lower motor neuron innervates.
motor unit
all muscle fibers a single lower motor neuron innervates.
motor unit
all muscle fibers a single lower motor neuron innervates.
intercellular events occuring during muscle contraction and relaxation
release of Ca2+ cells, opens voltage gated Ca channels, in SR, Ca is released into sarcoplasm, allows myosin to bind to actin, myosin binds and unbinds, pulling a little each time and burning one ATP each time. called cross bridge cycling. Ca is pumpedbac
intercellular events occuring during muscle contraction and relaxation
release of Ca2+ cells, opens voltage gated Ca channels, in SR, Ca is released into sarcoplasm, allows myosin to bind to actin, myosin binds and unbinds, pulling a little each time and burning one ATP each time. called cross bridge cycling. Ca is pumpedbac
electrical conduction through heart
release of Ca2+ cells, opens voltage gated Ca channels, in SR, Ca is released into sarcoplasm, allows myosin to bind to actin, myosin binds and unbinds, pulling a little each time and burning one ATP each time. called cross bridge cycling. Ca is pumpedbac
electrical conduction through heart
initiated in SAnode, right A wall, Left A wall, AV node, AV bundle, Ventricles, Purkinje fibers
electrical conduction through heart
initiated in SAnode, right A wall, Left A wall, AV node, AV bundle, Ventricles, Purkinje fibers
drop in atrial pressure, less barometric stretch, info sent to cv center; sympathetic response., efferent fibers project to sa node and vent. muscle, release norepi, sa increases HR, ventricles contract more forcefully raising bp, raises arterial pressure
diaphragm contraction causes increase in thorassic pressure, ^ pleural cavity volume, V pleural pressure, expansion of lungs, lowered pressure drives air in. Expiration is natural, lungs have recoil naturally
how 02 and c02 are exchanged in pulmonary and systemic capillaries
partial pressures drive the gasses between alveoli and pulmonary capillaries. hemoglobin in systemic capillaries.
how do kidneys handle Na & main site of reabsorption & how handling relates to blood volume
kidneys can alter serum levels of sodium salts; proximal tubule, more Na, higher BP
Hormone which determines wheter urine is dilute or concentrated by altering water permeability of distal renal tubule
ADH
good fats
Poly and mono unsaturated: Decresase LDL and increase HDL
bad fats
Saturated fats raise LDL and HDL. Really bad fats are transfats, Raise LDL and lower HDL.
1g TG yeilds
as much caloric energy as 2gs FA.
ketosis
excess ketones in blood
vitamins
organic molecules that exist in minute quantities in food that are essential to a normal metabolism
minerals
inorganic nutrients that are essential for normal metabolic function
role of Mineral, Calcium
builds n maintains bones and teeth; neurotransmission, heart rhythm, muscle contraction, blood clotting.
osteoperosis
results from deficiency in dietary calcium; causes bones to be porous and fragile. prevention includes excercise, vit D, sun exposure
Vit D
facilitates absorption of dietary calcium in intestinal epithelium.
healthy bones
not calcium but vitamin d
folate, Vitamin B9
plays an important part in nucleic synthesis and replacement. important for RBC synthesis. deficiency can cause spina bifida in unborn babies;
folate, VB6 VB12
may reduce risk of CVD and/or stroke by reducing homocysteine which causes CVD and Stroke.
Folate lowers risk of
colon and breast cancer; unless preexisting, when it may make them worse!
Ch.18 LTI-MA 509
