Gastrointenestinal and MSK Review Flashcards
Functions of the GI tract
Digestion, absorption excretion, endocrine
Mouth releases what proteins? What do they break down?
Salivary amylase - CHO/starch into maltose
Lingual lipase - fats into smaller fats
Gastric gland mucosal/neck cells secrete what?
Mucus
G cells produce gastrin
Function of gastrin?
Stimulate hydrochloric acid secretion from parietal cells
Stimulate gastric motility
Chief cells in the gastric glands produce what?
Pepsinogen
Parietal cells in the gastric glands secrete what? Functions?
Hydrochloric acid - activate pepsinogen, destroy bacteria
Intrinsic factor - absorb Vit B12
Mast cells in the gastric glands secrete?
Histamine
Food + gastric secretions =
Chyme
The presence of chyme in the small intestine causing S-cells in the duodenum to release? what does it do?
Secretin - stim pancreatic acinar cells to release bicarb and water, decrease gastric motility
Bicarbonate-rich mucus is secreted by what in the duodenum?
Brunner’s glands
Function of bicarbonate mucus?
Neutralize gastric acid in SI and make pH alkaline (protection)
Presence of fat in duodenum stimulates release of what from the I-cells of the duodenum? Function?
CCK - gallbladder contractin, sphincter of Oddi to relax, bile excretion into duodenum, stimulates pancreatic secretion of pancreatic amylase
Function of pancreatic amylase
Breakdown starch into maltose
Maltase breaks down maltose into?
2 molecules of glucose
Lactase breaks down glucose into?
Glucose and galactose
Sucrase breaks down sucrose into?
Glucose and fructose
Lactase, sucrase, maltase are found where in the enterocyte?
Brush border
Glucose is ACTIVELY transported into intestinal cells by?
Na+-G carrier
Digest fat is absorbed into central lacteals which drain where? Everything else goes where?
The Thoracic Duct
The liver
Fat breakdown products in the SI?
Fatty acids, glycerol
Starch, sucrose, lactose breakdown products in the SI?
Glucose, fructose, galactose
Protein breakdown products in the SI?
Amino acids
Exocrine cells in the pancreas are arranged into?
Acini
Exocrine cells of the pancreas secrete? which do?
Trypsinogen - activated to trypsin by enterokinase from enterocytes in the small intestine
Chymotryspin, carboxypolypeptidase, proelastase
Pancreatic amylase aids in digestion of starch to produce maltose
Lipase breaks down fat into fatty acids and glycerol
Endocrine cells in the pancreas are located where?
Islets of langerhans
Endocrine cell secretions from which cell type?
Glucagon - alpha cells
Insulin - beta cells
Somatostatin - delta cells
Where is most of the water absorbed in the GI tract?
Large intestine
Bacteria in the large intestine produce what Vitamin?
Vitamin K
Large intestine goblet cell secrete what? Why?
Mucus, aid in passage of feces
Fat soluble vitamins are?
ADEK
Water soluble vitamins enter enterocytes via 2o active transport using Na+-amino acid co-transporters except!!!
B12
How do water soluble vitamins exit enterocytes?
Diffusion into portal circulation
Folic acid and iron are absorbed where?
Jejunum
Iron + apotransferrin in blood =
Transferrin
Transferrin carries iron to where?
Liver, spleen, bone marrow
In the liver, spleen, bone marrow iron is bound to what?
Apoferritin
Iron + apoferritin =
Ferritin
B12 attaches to what to be delivered to the terminal ileum?
Intrinsic factor
B12 is bound to what in the terminal ileum?
Cubilin
B12 diffuses out of enterocytes into?
Portal vein
Roles of the liver
CHO, protein, lipid metabolism
Store glycogen, Vitamins A, D, B12
Detoxifies hormones, drugs, poison (alcohol)
Makes bilirubin, antibodies, steroid hormones, clotting factors, RBC in fetus
Immune system - Kupffer cells
Bilirubin is a byproduct of?
RBC breakdown in the spleen
Old RBCs (>120 days) are broken down into?
Heme, globin
Heme in bilirubin metabolism is broken down into?
Bilirverdin and iron
Biliverden is converted to? Carried in blood attached to what?
Bilirubin
Albumin
Bilirubin is insoluble or soluble in water? lipids?
Insoluble in water
Soluble in lipids
The liver conjugates bilirubin with? By what
Glucuronide
UDPG transferase
Conjugation does or does not make bilirubin soluble in water?
It does :D
Conjugated bilirubin is secreted into? Stored in? Excreted by?
Biliary tract
Gallbladder
Gallbladder
Bile in bilirubin saponifies fat making is more or less accessible to pancreatic lipase?
More
Bilirubin in the gut is converted by bacteria into?
Urobilinogen
Most of urobilinogen goes where? Where else?
90% into blood stream, some into urine (urobilin = yellow), or converted to stercobilinogen in gut where it oxidizes and makes stool brown
Role of gallbladder?
Store 50 cc and concentrate bile
excrete bile when fat is in duodenum and prescence of CCK
Bile is made of?
Water, bile salts, phospholipids, cholesterol, bilirubin
K cells in the Small Intestine secrete?
Gastric inhibitory peptide
Glucagon-like peptide
Function of GIP
Inhibit effect of gastrin on parietal cells
Decrease gastric acid secretion
Glucagon-like peptide function?
Inhibits gastric emptying
Ghrelin is secreted by?
P cells in the stomach
Motilin is secreted by? Stimulated by?
M cells in the duodenum
Fasting
The sarcomere lies between two _ lines which bisect the I band
Z lines
The A band contains?
Actin and myosin
The M line bisects?
The H band
The H band contains?
Myosin - thick filaments
The I band contains?
Actin, troponin, tropomyosin - thin filaments
What part of the sarcomere remains the same length in contraction?
A band
What part of the sarcomere disappears with full contraction?
H band
Differences between Troponin C, T, I?
C: binds to calcium ions
T: binds to tropomyosin and prevents X binding
I: binds to actin and inhibits interaction between actin and myosin
Actin and myosin at what ratio in skeletal muscle?
2:1
Describe the neuromuscular junction and how messages are sent to the muscle?
Alpha motor neurons connected to motor end plates via a bouton filled with vesicles that release ACh when stimulated and Ca2+ flows into bouton and ACH is released goes through presynaptic membrane into synaptic cleft and diffuses to nicotinic ACH receptor on muscle and cause an end plate potential to cause contraction of the skeletal muscle and acetylcholinesterase in the synaptic cleft breaks down ACH and choline is reabsorbed and combined w/acetyl CoA in presynaptic vesicles
Describe the sliding filament model
Na+ into sarcolemma generating action potential to T tubules which release Ca2+ from cisterna of sarcoplasmic reticulum and Ca2+ binds to Troponin C which changes shape displacing tropomyosin so myosin can break down ATP and form a X bridge with actin and pull actin closer to middle and it detaches when ATP binds during relaxation Ca2+ pumped back into sarcoplasmic reticulum by Ca2+ pump
Slow twitch type 1 vs fast twitch type 2
I: red, more in long distance runners, smaller fiber size, less glycogen, more mitochondria increase aerobic metabolism, more myoglobin, resistant to fatigue
II: white, more common in sprinters, large fiber sie for greater contraction, large glycogen stores, few mitochondria for increased anaerobic glycolysis, less myoglobin, easily fatigued
Types of contraction: Isometric Isotonic Isokinetic Concentric Eccentric
Isometric: fibers lengths don’t change (push against wall)
Isotonic: load remains the same (flex elbow w/fixed weight)
Isokinetic: speed of contraction same
Concentric: muscle shortens in contraction (flex elbow w/weight in hand)
Eccentric: muscle lengthened in contraction (ext elbow slowly with weight in hand)
Describe smooth muscle contraction:
Influx of Ca+ into sarcoplasm, Ca2+ binds to calmodulin which activates myosin light chain kinase, phosphorylates myosin so myosin-P binds to actin and causes contraction, when myosin-P is dephosphorylated relaxation occurs
Ratio of actin to myosin in smooth muscle?
20:1
Describe the flexor withdrawal reflex?
Painful stimulus along afferent axons of A-delta and class C dorsal root fibers in DRG, dendrites synapse in dorsal horn of SC w/interneuron synapses w/alpha motor neuron in ventral horn and efferently innervates a flexor muscle to withdraw from painful stimulus
The Flexor withdrawal reflex falls under what classification of reflex?
Somatosomatic reflex
Describe the crossed extensor reflex?
Activated by noxious stimuli on the skin, excites A-delta and class C dorsal root fibers enter dorsal horn and activate multiple interneurons in grey matter through polysynaptic pathways linked w/extensor muscles on both sides of cord so while flexor withdrawal is facilitated by contraction on same side of stimulus the extensors are contracted on the opposite limb providing support of body during withdrawal as a righting reflex
Describe the Stretch/Deep tendon/Myotatic reflex
Striked muscle tendon causes spindles to stretch sending an impulse along an afferent neuron which synapses w/alpha motor neuron of stimulated muscle which contracts and also synapses with Renshaw cell (lamina IX) which synapses with same alpha motor neuron and glycine is released from the Renshaw cell to cause antagonists to relax and this can be further modified from the brain
Characteristics of an upper motor neuron lesion:
spastic paralysis, hyperreflexia, babinski sign, no atrophy, no fasciculations