Term
| Major differences among myosin isoenzymes |
|
Definition
| intrinsic ATPase activity |
|
|
Term
| What is the myosin tail responsible for? |
|
Definition
| The assembly of myosin molecules into thick flaments |
|
|
Term
| How do thick filaments assemble? |
|
Definition
| tail-to-tail in the center, and head-to-tail from then on. thus no heads project from the center. they are then staggered within the bundle and arranged as a helix. |
|
|
Term
| How many actins can a single myosin filament interact with? |
|
Definition
|
|
Term
| What is meant by actin-activated myosin ATPase activity? |
|
Definition
| when actin and myosin binding occures, the atpase activity of myosin increases dramatically. |
|
|
Term
| How are the thick filaments linked together in the center of the A band? |
|
Definition
| the M line protein, myomesin |
|
|
Term
| How is the thick filament tehered to the Z line? |
|
Definition
| the elastic protein, titin (acts as a spring) |
|
|
Term
| How do the thin filaments insert into the Z line? |
|
Definition
|
|
Term
| What is the working distance of a crossbridge? |
|
Definition
| 100 angstroms, thus repeated cycling is necessary to account for all shortening |
|
|
Term
What is the motion of a crossbridge? |
|
Definition
|
|
Term
| What does the sliding filament mechanism of contraction predict? |
|
Definition
| the degree of actin and myosin filament overlap will determine the force developed upon stimulation |
|
|
Term
|
Definition
| The optimum length for force production |
|
|
Term
| What is the long, rod-shaped molecule that lies in the goove formed by the helix of the actin filament? |
|
Definition
|
|
Term
| What are the three subunits of troponin? |
|
Definition
TnT: site of attachment of troponin to tropomyosin TnI: inhibits actin activation of myosin ATPase TnC: calcium binding site |
|
|
Term
| How does calcium initiate contraction in skeletal muscle? |
|
Definition
| reverses the inhibitory effect of the troponin-tropomyosin complex |
|
|
Term
| What is the function of T-tubules? |
|
Definition
| extension of the sarcolemma, provides a pathway for the conduction of electrical signals deep into the muscle fiber to the sarcoplasmic reticulm. the t-tubules encircle each myofibril |
|
|
Term
| What is the terminal cisternae? |
|
Definition
part of the SR which store and release calcium |
|
|
Term
What are longitudinal tubules? |
|
Definition
| part of the SR, the membranes of which contain a Ca++ ATPase for the reuptake of calcium from the cytoplasm into the SR. |
|
|
Term
| Where is the SR in relation to myofibrils and T-tubules? |
|
Definition
| The SR encircles each myofibril. the T-tubules which are continuous with the sarcolemma, surround each SR-shrouded myofibril. |
|
|
Term
| What is the triad in skeletal muscle? |
|
Definition
| the anatomic site of coupling of excitation at the t-tubule with the release of calcium from the SR in skeletal muscle. consists of the T-tubule and its two neighboring terminal cisternae. |
|
|
Term
| What does functional interaction between the t-tubules and the SR involve? |
|
Definition
| dihydropyridine receptors in the T-tubules and the ryanodine receptors in the terminal cisternae of the SR. |
|
|
Term
What is the dihydropyridine receptor? |
|
Definition
| a voltage-sensor protein in the t-tubule membrane that controls the permeability of Ca++ release channels (ryanodine receptors in the SR) |
|
|
Term
| Why isn't the force response of skeletal muscle after a single stimulus not maximal? |
|
Definition
| the free calcium and clacium bound to troponin begins to decrease much beore peak force is reached |
|
|
Term
| What causes the slow rise in force and sub-maximal force output? |
|
Definition
| the troponin-tropmyosin complex undergoes conformation change before crossbridges can attach to actin, crossbridges attach to actin and then undergo the conformational change to a force generating state, series elastic elements need to yield, calcium actively pumped back into the SR. |
|
|
Term
| How can force production by skeletal mucles be graded? |
|
Definition
| varying the frequency of stimulation, the number of motor units simultaneously activated, and the size of motor units simultaneously activated |
|
|
Term
|
Definition
the mechanical response to a single stimulus consisting of a period of force development and relaxation |
|
|
Term
| What is summation of force? |
|
Definition
| occurs if a muscle is stimulated repetitively so that the second stimulus is applied before the muscle has relaxed |
|
|
Term
|
Definition
| the maximum force the muscle can produce, fully activated. |
|
|
Term
| What percentage of tetanus force is a twitch in general? |
|
Definition
|
|
Term
| The maximum frequency at which a membrane can be excited is set by what? |
|
Definition
| the duration of its refractory period |
|
|
Term
| Why can't cardiac muscles be tetanized? |
|
Definition
| electrical and mechanical events follow similar, overlapping time courses (unlike skeltal and smooth where they are are temporally separate); so the refractory period of the sarcolemma persists until the muscle has nearly completely relaxed. |
|
|
Term
|
Definition
| the increase in the number of motor neurons firing and activating multiple motor units. |
|
|
Term
| How are the t-tubules arranged in cardiac muscle? |
|
Definition
| diads- one cistern and a t-tubule) |
|
|
Term
| In a cardiac ventricular fiber, when does calcium enter? |
|
Definition
| during the plateau phase of an action potential |
|
|
Term
| How is cacium induced contraction different in cardiac muscle compared to skeletal? |
|
Definition
| in cardiac there is trigger calcium that enters during the action potential and activator calcium which is derived from the SR. in skeletal mucle contraction depends entirely on Ca++ released from the SR |
|
|
Term
| How does calcium enter the myoplasm? |
|
Definition
| through L-type channels in the sarcolemma and T-tubules. dihydropyridine receptors associated with them mediate a small influx of Ca++ |
|
|
Term
| What is Calcium-induced-Calcium-Relase? |
|
Definition
| the calcium that entered during the action potential binds to the SR calcium release channels (RyRy2) triggering their opening, allowing the release of a much larger amount of caclium into the myoplasm which is sufficient to activate contraction. |
|
|
Term
| How do changes in the duration of the action potential affect cardiac muscle? |
|
Definition
| affect the strength of the subsequent beat. |
|
|
Term
| How is calcium removed from cardiac muscles? |
|
Definition
| primarily by the SR Ca++ATPase on the longitudinal tubules of the SR; also the Na+/Ca++ exchanger and the Ca++ ATPase on the sarcolemma |
|
|
Term
|
Definition
| an integral SR membrane phosphopreotein, phosphorylation of it stimulates Ca++ transport. acts on the SR-Ca-ATPase pump |
|
|
Term
| What are two factors that can modulate the contractile state of the heart on a beat-to-beat basis? |
|
Definition
| length changes that increase the force of contraction at a given calcium concentration, mechanisms by which calcium increases or decreases the magnitude and rate of force production at a given muscle length. |
|
|
Term
| What can increase calcium sensitivity in cardiac muscle? |
|
Definition
| Increasing muscle lengths from lengths < Lo, brings it closer to the ideal conformation for force production |
|
|
Term
| What are two determinants of contractility in cardiac muscle? |
|
Definition
| the availability of calcium to the myofilaments, the regulatory processes that control actin-myosin interaction |
|
|
Term
| What are three factors that affect the availability of calcium to the myofilaments? |
|
Definition
| time course of the action potential, extracellular [Ca], frequency of stimulation |
|
|
Term
| What does thyroid hormone do to muscles? |
|
Definition
| Alters the kinetics of the crossbridge cycle, resulting in a positive inotropic action |
|
|
Term
| How is intracellular calcium modulated in cardiac muscle? |
|
Definition
| cyclic AMP typically following Beta1 receptor activation |
|
|
Term
| What are the sites of phosphorylation resulting from beta 1 adrenergic stimulation? |
|
Definition
| voltage dependent ca channels increasing their open time, RyR2 receptors increasing open time, phospholamban causing an increase in teh rate of reuptake of calcium, troponin I leading to a decreased sensitivity to Ca++ and an increased rate of dissociation (increased relaxation) |
|
|
Term
| What are the functional consequences of stimulation of autonomic sympathetic nerves to the heart? |
|
Definition
| increased rate and magnitude of force production, and increased rate of relaxation |
|
|
Term
| How does parasympathetic stimulation on the heart work? |
|
Definition
| can block sympathetic effects by limiting production of cAMP and activation of protein kinase A |
|
|
Term
|
Definition
slack length, or the muscle length at which passive force is just detectable. maximum length that a resting muscle will assume
|
|
|
Term
| What is the foce observed on stretching a resting muscle due to? |
|
Definition
| passive elastic elements (no crossbridges attached) |
|
|
Term
| What is an important source of passive tension? |
|
Definition
| titin, will resist stretch when muscle is extended. there are a larger porportion of stiff components in cardiac titin so it is more resistant to stretch. |
|
|
Term
| At long muscle lengths, what is the force due to? |
|
Definition
| passive and active, but active force actually decreases because filament overlap decreases. |
|
|
Term
|
Definition
| the maximum active force produced at Lo |
|
|
Term
| What is the range as a percent of Lo that skeletal muscle can produce force? |
|
Definition
|
|
Term
| What function does the high passive force have in cardiac muscle? |
|
Definition
| it prevents over-distention during filling, the muscle performs on the ascending line of its active-force curve |
|
|
Term
|
Definition
| a state where no atp, adp or pi is bound to myosin |
|
|
Term
| What is the most important ATP recovery reaction? |
|
Definition
| phospocreatine + adp -> atp + creatine |
|
|
Term
| What is the myokinase recovery reaction? |
|
Definition
|
|
Term
| What reaction is catalyzed by adenylate deaminase? |
|
Definition
|
|
Term
| How long does it take for glycolysis to be turned on? Oxidative phosphorylation? |
|
Definition
|
|
Term
| What is the fatigue associated with high intensity exercise usually due to? |
|
Definition
| a large build up of lactate and an associated fall in pH |
|
|
Term
|
Definition
| force times velocity= work/time |
|
|
Term
| When is power output maximum? |
|
Definition
|
|
Term
| What is energy used for during crossbridge cycling? |
|
Definition
| 70% in cycle, 30% in calcium pump |
|
|
Term
| What force can a muscle resist? |
|
Definition
|
|
Term
| What are the characteristics of a slow twitch muscle? |
|
Definition
| type I, very high oxidative enzyme content (red), good for continuous activities |
|
|
Term
| What are the characteristics of slow twitch muscles? |
|
Definition
| Type IIx, high glycolytic enzyme content (white), large cross section, rapid fatique, spurt activities. |
|
|
Term
| What is muscle hypertrophy? |
|
Definition
| an increase in the amount of contractile material, a result of an increase in size and subsequent splitting of myofibrils. this results in an increase int he overall diameter of the mucle fiber, but maintains the close spatial relationship between the Sr and the contractile proteins. |
|
|
Term
| What muscles selectively hypertrophy? |
|
Definition
|
|
Term
| What happens if a muscle is denervated? |
|
Definition
| Ach receptors spread over the entire muscle membrane and the muscle tries to catch another motor nerve and form a new neuromuscular junction |
|
|
Term
| What do actin filaments of smooth muscle insert into? |
|
Definition
| dense bodies which are connected by intermediate filaments |
|
|
Term
| What does smooth muscle have instead of T-tubules? |
|
Definition
| surface couplings which link the plasma membrane to adjacent elements of the SR |
|
|
Term
| What is tonic contractile activity? |
|
Definition
| sustained contractile responses, characteristic of multi-unit smooth muscles. |
|
|
Term
| what is phasic contractile activity? |
|
Definition
| twitch-like contractions which are ideal for propulsion. characteristic of single-unit smooth muscles. |
|
|
Term
| What happens upon depolarization n single-unit smooth muscle? |
|
Definition
| opens voltage operated Ca2+ channels to trigger contraction (also CICR from RyR receptors in the SR) |
|
|
Term
| How do multi-unit smooth muscles behave in response to autonomic nerve stimulation? |
|
Definition
| show graded depolarization, binding of neurotransmitter to a cell membrane receptor results in the opening of receptor-operated channels, resulting in ion fluxes, depolarization and CICR |
|
|
Term
| What happens with pharmacomechanical coupling? |
|
Definition
agonists iteract with plasma membrane receptors leading to the production of the second messentger inositol triphosphate which causes the release of calcium from the SR |
|
|
Term
|
Definition
| calcium activated K+ channel, which causes repolarization following excitation via VOCC |
|
|
Term
|
Definition
| store operated calcium channels, respond to decreased calcium in the SR to allow ion entry |
|
|
Term
| What determines the amplitude of depolarization in smooth muscle? |
|
Definition
| the quantity of transmitter interacting with the receptors whihc is determined by the number of nerves activated as well as their firing frequency |
|
|
Term
| How does electrical activity spread in single-unit smooth muscle? |
|
Definition
|
|
Term
| What two types of electrical activity occur in single unit smooth muslces? |
|
Definition
| slow waves and action potentials. |
|
|
Term
| Where do slow waves initiate? |
|
Definition
| Interstitial cells of cajal |
|
|
Term
| How can a slow wave lead to a muscle contration? |
|
Definition
| if the peak amplitude of the slow wave occurring in the muscle reaches the excitation threshold, actions potentials are generated and the muscel contracts, magnitude is dependent on the frequency of action potentials. |
|
|
Term
| What type of cell produces an active contractile response after a large stretch? |
|
Definition
| phasic, single-unit smooth muscle |
|
|
Term
| What does the gastric slow wave consist of? |
|
Definition
| an initial spike like depolarization phase based on Na/Ca conductances followed by a plateau phase based on Ca and K conductances. |
|
|
Term
| What triggers contraction in a gastric slow wave? |
|
Definition
| inward Ca conducatance, graded depolarization, not an action potential |
|
|
Term
| What happens in the distal stomach to give rise to contractons? |
|
Definition
| action potentials are superimposed upon slow waves so both include calcium currents that give rise to contractions. |
|
|
Term
| Why is the force production of smooth muscle about equal to that of skeletal muscle even though the myosin content is much smaller? |
|
Definition
| myosin filaments of smooth muscles are longer putting more crossbridges in parallel, the crossbridge cycle is slower so they are attached for a longer period of time. |
|
|
Term
| How much can smooth muscles shorten? |
|
Definition
|
|
Term
| How is smooth muscle myosin activated? |
|
Definition
| phosphoylation at myosin regulatory light chain |
|
|
Term
| How does calcium lead to myosin activation? |
|
Definition
| 4 ca bind calmodulin. this associates with the tail region of myosin light chain kinase which phosphorylates the regulatory light chain of myosin. |
|
|
Term
| what deactivates the myosin? |
|
Definition
| myosin phosphatase dephosphoylates the light chain |
|
|
Term
| What reduces phosphatase activity? |
|
Definition
| phosphorylation of mypt1 and an inhibitory protein cpi-17; additionally inhibited in response to actiationof protein kinase C and RhoA-activated kinase. |
|
|
Term
| What can mediate smooth muscle relaxation? How? |
|
Definition
| elevation of cAMP or cGMP dependent kinases. both target Ca signal pathway and reduce cellular ca concentration |
|
|
Term
| How does epinephrine affect smooth muscle? |
|
Definition
| Binds beta adrenergic receptor and mediates activation of adenylyl cyclase which forms cAMP, which activates cAMP dependent kinase |
|
|
Term
| How do Ach and NO affect smooth muscle? |
|
Definition
| activates guanylyl cyclase and prodcues cGMP |
|
|
Term
| By what 3 pathways do cAK and cGK block both Ca influx and release? |
|
Definition
1 activate BKca that induces hyperpholarization and inhibits VOC (outward channel) 2 phos phospholamban which activates SR Ca ATPase 3 phos IRAG wich inhibits IP3R and blocks Ca release from SR |
|
|
Term
| What do inhibitors of phosphodiesterase do? |
|
Definition
| increase cellular cyclic nucleotide level and induce smooth muscle relaxation |
|
|
Term
| What are the neurotransmitters primarily responsible for the ascending contraction in the gut? |
|
Definition
Ach, substance P (tachykinin) also serotonin |
|
|
Term
| What neurotransmitters are primarily responsible for the descending relaxation in the gut? |
|
Definition
|
|
Term
| Which part of the gut exhibits tonic or sustained contraction? |
|
Definition
| sphincters, the proximal stomach, and the gall bladder |
|
|
Term
| What is the normal contractive pattern of the alimentary tract? |
|
Definition
| propagated contractions or peristalsis |
|
|
Term
| What is the normal motility pattern of the small intestine and colon? |
|
Definition
| segmental contractions (localized for mixing contents), peristalsis also seen |
|
|
Term
| What is the submucosal enteric nerve plexus? |
|
Definition
|
|
Term
| What eneric nerve plexus is located between the circular and longitudinal muscular layers in the gut? |
|
Definition
|
|
Term
| Why does each smooth muscle not need to be innervated in the gut? |
|
Definition
| axons have varicosities with neurotransmitter-containing vesicles (no specialized neuromuscular junctions), gap junctions in between |
|
|
Term
| What inhibits gastric slow waves from reaching the threshold for depolarization? |
|
Definition
|
|
Term
| What physical feature are slow waves believed to be generated by? What is the evidence for this? |
|
Definition
an oscillating electrogenic sodium pump inhibited by ouabain |
|
|
Term
What is the speed of slow waves in the stomach? the duodenum? the illeum? the colon? |
|
Definition
3/min 11/min 8/min 3-6/min |
|
|
Term
| What would happen if there were no neural input to the gut? |
|
Definition
| each myogenic slow wave would activate muscle contraction |
|
|
Term
| What is the difference between primary and secondary peristalsis in the esophagus? |
|
Definition
| primary is peristalsis induced by a swallow, secondaryis initiated by esophageal distension in the absence of a swallow and is important in clearing the esophagus of material refluxed up from the stomach |
|
|
Term
| What is the main function of the lower esophageal sphinctor? |
|
Definition
| to prevent the reflux of gastric contents into the esophagus, must relax during swallowing to allow the passage of ingested material from the esophagus into the stomach |
|
|
Term
| What are common factors changing lower esophageal pressure? |
|
Definition
high protein meals increase high fat meals, alcohol, chocolate, and peppermint decrease high progesterone (as during pregnancy or with birth control) decreases |
|
|
Term
| What is the effect of parasympathetic and sympathetic stimulation to the lower esophageal sphintor? |
|
Definition
parasympathetic- both excitatory and inhibitory sympathetic- increase LES pressure |
|
|
Term
|
Definition
| sensation of food getting stuck, a symptom of esophageal disfunction |
|
|
Term
|
Definition
| incomplete LES relaxation with swallows and aperistalsis of the esophageal body. lead to the impairment of esophageal emptying. primarily due to the loss of intrinsic inhibitory innervation of the LES |
|
|
Term
| What is diffuse esophageal spasm? |
|
Definition
| contractions in the esophageal body that are simultaneous rather than peristaltic, can cause dysphagia or chest pain |
|
|
Term
| What is scleroderma esophagus? |
|
Definition
| a dramatic decrease in the resting LES tone, lack of propulsive force in the smooth muscle portion of the esophagus |
|
|
Term
| In what part of the stomach does the majority of mixing occur? |
|
Definition
|
|
Term
| What is the migrating myoelectric complex (MMC)? |
|
Definition
| in the fasting state, the antrum is quiescent for 1-2 hours followed by a short period of intense electrical and mechanical activity tht lasts for 10-20 minutes. this activity is characterized by strong contractions of the antrum with a relaxed pylorus. serves a housekeeping function. this pattern of cyclical contractile acticity is knows as MMC. |
|
|
Term
| Where is the pacemaker region of the stomach? |
|
Definition
| on the greater curvature near the middle of the body |
|
|
Term
| What stimulates gastic contractility? How? |
|
Definition
Ach and gastrin increase the amplitude and duration of the plateau phase of the gastric slow wave. |
|
|
Term
| What decreases the frequency of the gastric slow wave? |
|
Definition
| secretin, norepinephrine and neurotensin |
|
|
Term
| What are four factors that cause slowing of gastric emptying? |
|
Definition
| duodenal acidification, presence of fatty acids in the duodenum and jejunum, hypertonicity of duodenal contents, presence of peptides and amino aids in the duodenum |
|
|
Term
| What is released in response to the presence of acid in the duodenum? What does it do? |
|
Definition
secretin diminishes the gastric emptying rate by inhibiting antral contractions, stimulating contraction of the pyloric sphincter, and stimulating the output of the bicrabonate-rich secretions of the panreas and liver. |
|
|
Term
| What hormones cause contraction of the pyloric sphinctor? |
|
Definition
| CCK, gastrin, GIP, and secretin |
|
|
Term
| What is the intestinointestinal reflex? |
|
Definition
| overextension of one region relaxes the rest |
|
|
Term
| What is the ileogastric reflex? |
|
Definition
| inhibition of gastric emptying by nutrients in ileum |
|
|
Term
| What is the gastroileal reflex? |
|
Definition
| increased gastric secretory and motor activity increases ileal empyting through the ileocecal valve |
|
|
Term
| What are the three phases of the MMC? |
|
Definition
I- the quiescent phase is characterized by slow waves with very few action potentials and very few contractions II- characterized by irregular action potentials and contractions and gradually increase in intensity and frequency III- a period of intense electrical and contractile activity lasting 3-6 minutes (sweeps small intestine clean and empties its contents into the cecum, inhibits migration of colonic bacteria into the distal illeum) |
|
|
Term
| How can hyperthyroidism cause diarrhea? |
|
Definition
| the slow wave frequency is increased causing rapid transit |
|
|
Term
| What is chronic idiopathic intestinal pseudo-obstruction? |
|
Definition
| a rare disorder of GI tract motility characterized by symptoms of severe intestinal obstruction and grossly dilated loops of intesting in the absence of mechanical obstruction |
|
|
Term
| What are the three contraction patterns of the colon? |
|
Definition
| mixing, haustral, mass movements |
|
|
Term
| What is the colonocolonic reflex? |
|
Definition
| When distension of one part of the colon elicits reflex relaxation of other parts of the colon |
|
|
Term
| What is the gastrocolic reflex? |
|
Definition
| when the motility of proximal and distal colon and the frequency of mass movements increase after the entry of food in the stomach |
|
|
Term
| What reflex occurs upon filling of the rectum? |
|
Definition
| relaxation of the internal anal sphictor and contraction of the external anal sphintor; produces the urge to defecate and protects continence |
|
|
Term
| What is Hirshprung's disease? |
|
Definition
| congenital absence of enteric neurons and tonic contraction of the colonic circular muscle that lead to obstruction of the colon |
|
|
Term
|
Definition
| stimulates gastric acid secretion, stomach emptying and increases mucosal growth. it is stimulated by feeding, gastric distension, and digested protein. |
|
|
Term
| What does cholecystokinin (CCK) do? |
|
Definition
| stimulates pancreatic enzyme secretion and synergizes with secretin to enhance HCO3- secrection. it is stimulated by digested proteins and fats, and also decreases stomach emptying and gallbladder contraction |
|
|
Term
|
Definition
| stimulates pancreatic H2O and HCO3- secretion from the pancreas and liver and can potentiate CCK activity, stimulated by digested fats and low pH. also decreases acid secretion and emptying of the stomach |
|
|
Term
| What is saliva made up of? |
|
Definition
| lysozyme, lactoferrin, secretory IgA, alpha-amylase, lingual lipase, mucins |
|
|
Term
| What regulates salivary gland secretion? |
|
Definition
| parasympathetic nervous stimulation releasing Ach |
|
|
Term
|
Definition
| epithelial invaginations composed of several secretory cell types that can accommodate increased secretory requirements. |
|
|
Term
| How do the striated and exretory ducts modify the composition of the primary saliva secretion? |
|
Definition
| Na and Cl removed, K and HCO3 levels increase; becomes more hypotonic and basic relative to the plasma |
|
|
Term
| What is the funciton of HCl in the stomach? |
|
Definition
| activates pepsinogen to pepsin and is bacericidal |
|
|
Term
| What is the function of pepsin in the stomach? |
|
Definition
| protease that functions optimally at pH 3 and initiates digestion of proteins. can degrade the mucous gel that coats the surface of the stomach |
|
|
Term
|
Definition
| mucous tetrames (monomers crosslinked by disulfide bonds) which protect the stomach lining from mechanical and chemical damage. |
|
|
Term
| What is intrinsic factor? |
|
Definition
| binding protein that is absolutely required for absorption of vitamin B12 by ileal mucosa. |
|
|
Term
| What is the oxyntic glandular region of the stomach? |
|
Definition
| comprises the upper 80% of the stomach and is the site of acid secretion. |
|
|
Term
| What is the pyloric glandular region of the stomach? |
|
Definition
| in the antrum, although predominantly made up of mucous cells, it is the location of the G cells that secrete gastrin |
|
|
Term
| What is necessary for acid production? |
|
Definition
| H+K+ ATPase and carbonic anhydrase in the tubulovesicular membrane of the parietal cell |
|
|
Term
| What stimulates pareital cells to secrete acid? What happens after stimulation? |
|
Definition
gastrin, Ach, histamine the tubulovesicles fuse with the intracellular canaliculus which greatly expands the apical membrane surface of the cell. also causes the release of intrinsic factor |
|
|
Term
| What reaction produces the H+ in parietal cells? |
|
Definition
CO2+H2O -> H2CO3 -> H+ + HCO3- mediated by carbonic anhydrase |
|
|
Term
|
Definition
irreversible inhibitor of the H+ K+ATPase, thus blocking H+ ion transport. |
|
|
Term
| What is histomine released from? How can it be blocked? |
|
Definition
enterochromaffin cells H2 antagonists like cimetidine |
|
|
Term
| What blocks Ach release in the stomach? |
|
Definition
| muscarinic antagonist like atropine |
|
|
Term
| What blocks gastrin release? |
|
Definition
| somatostatin and increased concentrations of H+ |
|
|
Term
| What stimulates pepsinogen secretion by chief cells? |
|
Definition
| vagal activation and the release of Ach. acid activates the enteric nervous system reflexes |
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Term
| What are the 3 phases of gastric secretion? |
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Definition
| cephalic, gastric, intestinal |
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Term
| What happens during the cephalic phase of gastric secretion. |
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Definition
| vagal nerves stimulated by sensory perception of food. releases ach which can stimulate parietal and gastrin releasing peptide |
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Term
| What happens during the gastric phase of gastic secretion? |
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Definition
| when most acid secretion occurs, when food frst enters the stomach it neutralizes the stomach acid, allows gastrin release by different effectors. induced by presence of food in the stomach |
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Term
| What happens during the intestinal phase of gastric secretion? |
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Definition
| acid secretion stimulated by the presence of protein digests in duodenum, a region rich in gastrin-producing G cells. |
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Term
| What are the proteases in pancreatic juice and what are they activated by? |
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Definition
trypsinogen - enterokinase or trypsin chymotrypsin- trypsin procarboxypeptidase - trypsin |
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Term
| What does trypsin inhibitor do? |
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Definition
| prevents activation of trypsinogen within the pancreas |
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Term
| How is HCO3- moved into the lumen from the pancreas? |
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Definition
| exchanged for Cl-, Na+ moved in as a counter ion, this creates an osmotic gradient moving water in as well |
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Term
| What does the ion composition of pancreatic juice depend on? |
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Definition
secretion rate: active pancreas -> Na+/HCO3- predominate resting pancreas -> NaCl predominates |
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Term
| What inhbits HCO3 secretion? What stimulates it? |
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Definition
inhibit -> somatostatin, glucagon, pancreatic peptide stimulate: secretin |
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Term
| What is critical micellar concentration? |
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Definition
| the concentration when the molecules aggregate, the hydrophobic regions interacting with each other and the hydrophilic regions interacting with water |
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Term
|
Definition
bile acids phospholipids (lecithins) cholesterol bile pigments inorganic ions (Na, K Ca, Cl, HCO3) |
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Term
| What regulates bile secretion? |
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Definition
|
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Term
| How is bile released from the gall bladder? |
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Definition
| igested food stimulates CCK secretion, CCK casuses gall bladder contraction and the opening of the sphincter of oddi which allows the contents of the gall bladder to be emptied into the duodenum |
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Term
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Definition
| usually due to cholesterol present in bile in greater quantities than can be solubilized in the bile acid-phospholipid mixed micelles. bile pigment stones are formed from the calcium slat of unconjugated bilirubin. |
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Term
| How are bile acids recycled? |
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Definition
| absorbed in the distal ileum and travel in portal blood to the liver and taken up by hepatocytes |
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Term
| Where are calcium and iron preferentially absorbed? |
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Definition
| duodenum and proximal jejunum |
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Term
| How are glucose and galactose absorbed into the epithelial cell? How does it leave? |
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Definition
a sodium dependent cotransport system (SGLT1) leaves through GLUT2 |
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Term
| How is fructose transported into the epithelial cell? |
|
Definition
| facilitated diffusion via the GLUT5 carrier protein |
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Term
| Which amino acids do not depend on sodium for uptake? |
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Definition
| hydrophobic neutral and basic |
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|
Term
| How are phospholipids hydrolyzed? What is the product of this? |
|
Definition
phopholipase A2 lysophosphatides |
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Term
| Where are folic acid and B12 absorbed? |
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Definition
folic acid -> active in the duodenum and jejunum B12 -> complexed with intrinsic factor is taken up in the brush border of the ileum |
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Term
| What is the number of sodium channels in the large intestine regulated by? |
|
Definition
| aldosterone (increases during sodium deprivation) |
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|
Term
| What form of free iron is most readily absorbed? What assists this absorption? |
|
Definition
|
|
Term
| How is Fe++ transported into the cell from the brush border? |
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Definition
| binds to mobilferrin which moves the iron to the basolateral membrane where it is transferred to the protein transferrin. then it is released to the extracellular fluid |
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|
Term
| How is heme iron taken up? |
|
Definition
| enters the epithelial cell via facilitated diffusion and heme oxygenase removes the iron. then binds mobilferrin |
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|
Term
|
Definition
| prevents excess absorption of iron. iron bound to ferritin is not available for transport into the basolateral space. eventually is lost in the lumen and then the feces |
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|
Term
| How is calcium absorbed? What assists its absorption? |
|
Definition
moves down its electrochemical gradient through calcium channels into the cell. then bound to calbindin or CaBP. extruded into the basolateral space by a ca-dependent atpase and the na/ca exchanger. some transported through the cell in vesicles which fuse with the basolateral membrane and relesa the calcium into the basolateral space. vitamin D stimulates ca absorption by intestinal epithelial cells |
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|
Term
| What cells secrete solute and water into the intestine/ |
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Definition
|
|
Term
| What is secretory diarrhea? |
|
Definition
| toxin binds to the secreting cells in the small intestine and increase the permeability of the luminal wall to chloride. water osmotically drawn into intestine |
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|
Term
| What is osmotic diarrhea? |
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Definition
| occurs when there is some substance in the intestine which is not absorbed and which exerts an osmotic force to keep fluid in the intestine. can also result from ingestion of a large quantity of poorly absorbed salts such as mgso4 (epsom salts) |
|
|
Term
| What are nicotinic receptors? |
|
Definition
| ligand gated ion channels located on the membrane of the postganglionic neurons for both the PNS and SNS |
|
|
Term
| What are adrenergic receptors? |
|
Definition
| located on the membrane of cells/organs innervated by postganglionic sympathetic neruons. activated by epinephrine |
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|
Term
| What are muscarinic receptors? |
|
Definition
| located on the membrane of cells/organs innervated by postganglionic parasympathetic nerons and in the sweat glands, which are innervated by the pregangionic sympathetic neurons. respond to Ach |
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|
Term
| What is the effect of epinephrine on blood vessels? |
|
Definition
| epinephrine has a higher affinity for the beta 2 receptors but there are more alpha receptors. thus at low concentration epinephrine activates the beta receptors and causes dilation while at high concentration it binds more alpha receptors and the net effect is constriction |
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Term
|
Definition
| located at the neuromuscular junction, its activation generates the end plate current and is responsble for skeletal muscle contraction |
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Term
|
Definition
| located on the membrane of the postganglionic neurons, its activation generates the postsynaptic current and action potentials in the postganglionic neuron |
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Term
|
Definition
| found in autonomic ganglia. its activation produces slow espss which can modulate the fast EPSPs generated by the N2-R |
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Term
|
Definition
| found in the heart. activates K channels through the G protein betagamma subunits. primary functions are reduction of heart rate, reduction of action potential duration, decreased conduction velocity and reduced contraction |
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|
Term
|
Definition
| found in smooth muscle and secretory glands, its activation causes smooth muscle contraction and increases secretion of secretory glands |
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Term
|
Definition
| found primarily on the membrane of the target organs. its activation results in contraction of vascular smooth muscle, and relaxation of intestinal smooth muscle. |
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|
Term
|
Definition
| found on the membrane of the presynaptic neurons. its activation by NE serves as a negative feedback mechanism to reduce transmitter release though the inhibition of voltage gated Ca channels |
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|
Term
|
Definition
| found primarily in the heart. its activation increases the heart rate, conduction velocity and contraction |
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|
Term
|
Definition
| found in smooth muscle. its activation causes relaxation |
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|
Term
|
Definition
| found in adipose tissue. its activation is responsible for regulation of metabolism such as glycogenolysis |
|
|
Term
| What are four types of cholinergic synapses? |
|
Definition
postganglionic nerves and sweat glands sympathetic and parasympathetic gaglion cells autonomic preganglionic nerves and adrenal medulla motor end plates on skeletal muscles |
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|
Term
| Name four sites where nicotinic receptors occur |
|
Definition
adrenal medulla neuromuscular junction central nervous system autonomic ganglia |
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|
Term
| What is the most important mechanism for terminating the activity of norepinephrine released from the presynaptic nerve terminal? |
|
Definition
| reuptake into the nerve terminal |
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|
Term
What are the major ions in the ECF? The ICF? |
|
Definition
ECF -> Na, Cl, HCO3 ICF -> K, Mg (balanced with proteins and inorganic phosphates) |
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|
Term
| What markers can you use to determine total body water? |
|
Definition
| D2O, tritiated water, antipyrine |
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|
Term
| What markers can you use to measure extracellular fluid? |
|
Definition
| sulfate, mannnitol, innulin |
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|
Term
| What marker can you use to measure the plasma fluid? |
|
Definition
| Radioiodinated serum albumin, Evan's blue |
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|
Term
What percent of ECF is plasma? interstitial fluid? |
|
Definition
plasma 20% interstitial fluid 75% rest is transcellular |
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|
Term
| In an average male, what percent of body weight is total body water? |
|
Definition
|
|
Term
What percentage of total body water is ICF? ECF? |
|
Definition
|
|
Term
| What does adding isotonic saline to the body do? |
|
Definition
| expands the ECF without affecting the ICF |
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|
Term
| What will infusing hypertonic NaCL do? |
|
Definition
| net movement of water from ICF to ECF |
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|
Term
| What happens to osmolarity and volume during secretory diarrhea? |
|
Definition
| osmolarity the same, ECF volume decreases |
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|
Term
| What happens to osmolarity and volume during water deprivation? |
|
Definition
| ICF and ECF osmolarity increase equally, both lose water volume |
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|
Term
| What is regulatory volume increase? |
|
Definition
| response to shrinkage, increase in intracellular osmole that draws water into the cell to restore cell volume toward normal |
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|
Term
|
Definition
|
|
Term
| What is malignant hyperthermia? |
|
Definition
| patients have a mutation in the RyR1 such that the opening of the Ca release channel is hypersensitive to certain stimuli, these stimuli include potent inhalation anaesthetics such as halothane and the muslce relaxant succinlycholine, potentially lethal pharmacogenetic disorder |
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|
Term
| How can you save people with malignant hyperthermia? |
|
Definition
| dantrolene binds to RyR1 and stabilize the ca channel in the closed state. supresses channel dysfunction |
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|
Term
| What are signs of malignant hyperthermia? |
|
Definition
strong: muscle rigidity, increased co2, rhabdomyolysis, temp elevation, dark urine non-specific: tachycardia, tachypnea, acidosis, hyperkalemia |
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|
Term
| Summation of force in skeletal muscle is a process that involves what? |
|
Definition
| the response of the muscle to increased frequency of stimulation |
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|
Term
| If muscle glycogenolysis is impaired, how would that affect long duration, high intensity exercise? |
|
Definition
| it would be very difficult |
|
|
Term
| Potentiation of gastric acid secretion is caused by what? |
|
Definition
|
|
Term
| What effect does somatostatin have on the exocrine pancreas? |
|
Definition
| causes it to produce much less NaHCO3 |
|
|
Term
| What does bile concentration in the gallbladder depend upon? |
|
Definition
| the active pumping of ions out of the gallblader and the removal of water down the osmotic gradient |
|
|
Term
| How do drugs and toxins that increase the cAMP content of intestinal mucosa cause diarrhea? |
|
Definition
| increase Cl- secretion into the intestinal lumen |
|
|
Term
| Where is water permeability of the paracellular pathway highest? |
|
Definition
|
|
Term
| Why is fecal fluid Na+ concentration less in osmotic than in secretory diarrhea? |
|
Definition
| the excess fluid in secretory diarrhea results from water movement associated with active salt secretion |
|
|
Term
| How does potassium ion absorption from the intestine occur? |
|
Definition
| mostly through diffusion down its electrochemical gradient from the lumen to the plasma |
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