Term
| What are the 6 sphincters of the digestive tube? |
|
Definition
| -upper esophageal sphincter, lower esophageal sphincter, pyloric, ileal orifice (variable), internal anal sphincter, and external anal sphincter |
|
|
Term
| What are the 4 major divisions of the digestive tube? |
|
Definition
-headgut: oral cavity + pharynx
-foregut: esophagus + stomach
-midgut (longest): SI (duodenum+ jejunum + ileum)
-hindgut: cecum + colon + + rectum + anus |
|
|
Term
|
Definition
| -cecum + colon + rectum + anus |
|
|
Term
| Definition: Large intestine |
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
| -transverse + descending (straight) colon |
|
|
Term
| Definition: Proximal colon |
|
Definition
|
|
Term
|
Definition
|
|
Term
What is the specific name for the ileal orifice (sphincter) in the following species:
a) dog
b) cat
c) equids
d) pigs
e) ruminants |
|
Definition
a) ileocolic sphincter
b) ileocolic
c) ileocecal
d) ileocecocolonic
e) ileocecocolonic |
|
|
Term
| What are the 3 types of colon? Their portions? |
|
Definition
1) simple: ascending + transverse + descending (doc, cat, human)
2) intermediate: ascending and descending spiral+transverse+ straight colon: ruminants, pigs
3) Complex: right/left ventral colon+ left/right dorsal colon+ transverse colon+ straight colon
3) |
|
|
Term
| What structures does the embryonic midgut give rise to? |
|
Definition
| -ileum, jejunum, distal duodenum, and cecum |
|
|
Term
| What structures does the embryonic hindgut give rise to? |
|
Definition
|
|
Term
| Compare/contrast foregut and hindgut fermenters |
|
Definition
-foregut: rely on microbial digestion in compartments cranial to and connected with the true stomach
0hindgut: microbial digestion in cecum and colon |
|
|
Term
| _____ and ______ and _____ are derived from ectoderm whereas the digestive tube b/n mouth and anus are derived from _____. |
|
Definition
-oral
-nasal cavity
-anus
-endoderm |
|
|
Term
| What are the 5 major steps of resistance to flow of digesta in the equine hindgut? |
|
Definition
-ileocecal sphincter
-sternal flexure
-pelvic flexure
-diaphragmatic flexure
-transverse colon |
|
|
Term
| What is the significance of the length of the SI? |
|
Definition
-longest part of intestine (80%)
-small diameter and inc length enhance SA |
|
|
Term
| What portion of the digestive system has largest volume? Why? |
|
Definition
-stomach (67%)
-TRUE IN ALL EXCEPT PIG AND HORSE (LI b/c hindgut fermenters)
-to hold food so that can be let through in controlled small amounts |
|
|
Term
| What is special about the sizes of stuff in digestive tract of horse? |
|
Definition
| -stomach is proportionally small (9%) and colon is proportionally large (45%) |
|
|
Term
| Definition: Ailimentary canal/ digestive tube/ gut |
|
Definition
| -a tubular structure beginning at the mouth and ending at the anus; consists of smooth muscle that surrounds a mucous membrane |
|
|
Term
| Definition: embryonic gut |
|
Definition
| -foregut (mouth to duodenal papilla), mindgut, and hindgut |
|
|
Term
| Definition: Gastrointestinal tract |
|
Definition
| -stomach + SI and LI (cecum and colon) |
|
|
Term
| How does the length and volume of digestive tube relate to the size of the animal? |
|
Definition
|
|
Term
| The SI accounts for __% of the total length of the intestins and about __% of the gross V of the GI tract. |
|
Definition
|
|
Term
| The SI has impressive ___________ due to its length, mucosal folding, villi, and microvilli. |
|
Definition
|
|
Term
| The stomach V approximates __% of the total V of the GI tract in man and domestic animals except pigs and horses. |
|
Definition
|
|
Term
| True or False: The LI of the horse is relatively small, thus it dictates that the horse eats frequent small-sized meals. |
|
Definition
| -FALSE, stomach is small and LI is large |
|
|
Term
| Why is the LI large in the pig and horse instead of the stomach? |
|
Definition
| -b/c they are hindgut fermenters |
|
|
Term
| Name the layers of a X-section of the intestines (4) and their divisions |
|
Definition
1) Tunica mucosa: epi+lamina propria+lamina muscularis
2)submucosa
3)Tunica muscularis: longitudinal m+ circular m
4)Tunica serosa |
|
|
Term
| What are the major components of a X-section of an intestine from lumen to serosal surface? (10) |
|
Definition
1)mucosa
2)mucosal gland
3)muscularis mucosae
4)submucosa
5)submucosal plexus (Meissner's): enteric NS
6)submucosal gland
7)circular m
8)Myenteric plexus (Auerbach's) enteric NS in b/n circular and longitudinal mm
9)Longitudinal m
10)Serosa |
|
|
Term
| What are the 5 types of intramural glands of the gut? |
|
Definition
1)Epithelial goblet cells: esophagus, stomach, and intestines: inc motility and protect against acid
2)Mucosal crypt cells: pdc mucous and contain epi progenitor cells
3)Mucosal gastric glands: pdc hydrochloric acid
4)Submucosal Brunner's glands: in proximal duodenum: pdc mucous and HCO3- to neutralize stomach acid
5) Submucosal mucin-secreting cells in esophgus |
|
|
Term
| What are the 3 types of extramural glands of the but? |
|
Definition
1)Salivary acinar and ductal cells
2)Pancreatic acinar (exocrine) and ductal cells
3)Hepatic parenchymal cells (hepatocytes) and ductal cholangeocytes |
|
|
Term
| Compare/contrast the primary function of the Submucosal and myenteric ganglions. |
|
Definition
-Myenteric is primarily in control of smooth muscle contraction
-Submucosal ganglion is primarily in control of secretion |
|
|
Term
| The sympathetic NS uses ____ as its neurotransmitter. In contrast, the parasympathetic NS uses ___. |
|
Definition
|
|
Term
| What is the largest endocrine organ in the body? |
|
Definition
|
|
Term
| What is the difference between the digestive tube and the gastrointestinal tract? |
|
Definition
-digestive tube: oral space, pharynx, esophagus, stomach, SI, cecum, colon, rectum, and sphincters
-GI tract: mucous membrane and associated muscle wall that runs from the mouth to the anus |
|
|
Term
| The _______ nervous system is comprised of aggregations of nerve cell-bodies located in the myenteric plexus (______) and the submucosal plexus (______). |
|
Definition
-enteric
-Auerbach's
-Meissner's |
|
|
Term
| True or False: The ENS can control many of the important functions of the GI tract independent of the CNS but is not completely autonomous. |
|
Definition
|
|
Term
| What are the 7 roles in the ENS in gut function? |
|
Definition
1) control of gut motility
2) control of transmucosal fluid exchange
3) digestion and absorption of food stuff
4) control gastric acid secretion
5) regulate local blood flow
6) interact with immune (mast cells, gut lymphoid tissue) and endocrine cells of the gut
7) maintain functional epithelial barrier b'n body tissues and gut lumen |
|
|
Term
| Which nucleus is responsible for projecting vagal fibers throughout most of the digestive tube? |
|
Definition
| -dorsal motor nucleus of Vagus |
|
|
Term
| Is the parasympathetic NS mostly inh or exc towards the GI tract? |
|
Definition
|
|
Term
| What are the prevertebral sympathetic ganglia for the GI tract? |
|
Definition
-celiac
-superior mesenteric
-inferior mesenteric |
|
|
Term
| True or False: The sympathetic NS is not usually the dominant player in the GI tract without exception. |
|
Definition
| FALSE, this true except in the sphincters |
|
|
Term
| What are the functions of the motor fibers of the ENS? |
|
Definition
|
|
Term
| Are sensory fibers of the ENS intrinsic or extrinsic? Afferent or efferent? |
|
Definition
|
|
Term
| What are the 4 types of sensory neurons of the GI tract? |
|
Definition
1) Vagal sensory neurons
2) Spinal sensory neurons
3) Intestinofugal neurons
4) Intrinsic neurons |
|
|
Term
| What nucles is responsible for vagal sensory neurons of the GI tract? |
|
Definition
| -nucleus tractus solitaries (NTS) |
|
|
Term
| Where are the cell bodies of the vagal sensory neurons of the GI tract? |
|
Definition
|
|
Term
| What are the 3 possible destinations of a spinal sensory neuron in the GI tract? |
|
Definition
| -spinal cord, myenteric plexus, or submucosal plexus |
|
|
Term
| To what do vagal mechanosensitive afferent nn sensitive? |
|
Definition
| -they are low threshold tension detectors |
|
|
Term
| What are some examples of what vagal chemosensitive afferent fibers are concerned with? |
|
Definition
| -luminal pH, osmolality and nutrient concentration, primarily glucose, FAs and AAs and noxious agents |
|
|
Term
| True or False: chemosesitive receptors sample lumen composition to report concentrations. |
|
Definition
| FALSE, respond to local release of serotonin from gun enterochromaffin cells (EC)or gut hormones released across the basilateral membrane of open-type gut endocrine cells that express chemoresponsive receptor proteins in their apical membrane |
|
|
Term
| Describe a vago-vagal reflex |
|
Definition
| -integration of the sensory info=> activation of vagal preganglionic efferent fibers that exit the dorsal motor nucleus=> relay appropriate adjustment to influence motility or secretion |
|
|
Term
| Where are the cell bodies of the spinal sensory neurons? |
|
Definition
| -spinal dorsal root ganglia |
|
|
Term
| True or False: Splanchnic nn are mixed nn htat contain both sympathetic efferent and visceral sensory afferent fibers. |
|
Definition
|
|
Term
| What is the function of the visceral afferent fibers of spinal sensory neurons? |
|
Definition
| -transmit information from the GI tract and gallbladder to the CNS for processing |
|
|
Term
| What is the function of intestinofugal neurons? |
|
Definition
-relay mechanosensory information directly to sympathetic prevertebral ganglion neurons
-respond to circular muscle stretch rather than tension |
|
|
Term
| Which neurotransmitters do sympathetic postganglionic fibers use? |
|
Definition
|
|
Term
| Which neurotransmitters do parasympathetic preganglionic fibers use? |
|
Definition
|
|
Term
| Luminal contents activate which four major affectrs? |
|
Definition
1) enteroendocrine system
2) nervous system
3) gut immune system (GALT)
4) nonimmune defense system of the gut |
|
|
Term
| _________ cells in the mucosal epi of the digestive tract sense luminal chemicals and release hormones that act locally on nerve endings, on enteric neurons, on the epi, and on cells of the immune system. |
|
Definition
| -Enteroendocrine cells (EEC) |
|
|
Term
| True or False: The ENS receives input from the sympathetic AND parasympathetic systems. |
|
Definition
|
|
Term
| (Extrinsic/intrinsic) sensory fibers include vagal sensory neurons, spinal sensory neurons, and intestinofugal neurons. |
|
Definition
|
|
Term
| Parasympathetic, preganglionic excitatory and inhibitory motor fibers of the vagus terminate on intramural glands and cell bodies of ganglionic nerve cell in the myenteric/Auerbach and submucosal/Meissner plexuses. Excitatory fibers of the vagus secrete ___ or ___ whereas inhibitory fibers of the vagus secrete ___ or ___. |
|
Definition
-ACh or Substance P
-NO or VIP |
|
|
Term
| What effects do vagal excitatory fibers have on motility and secretions? |
|
Definition
|
|
Term
| What types of glands doe vagal excitatory fibers affect? |
|
Definition
-mucosal gastric glands
-mucosal crypt enterocytes
-submucosal Brunner's glands of the duodenum
-submucosal mucin-secreting glands of the esophagus |
|
|
Term
| Vagal inhibitory fibers are considered inhibitory because they secrete neurotransmitters that induce lowering of cytosolic _________ in smooth muscle and thus they promote ___________. |
|
Definition
|
|
Term
| Where are the cell bodies of sympathetic, postganglionic efferent fibers? |
|
Definition
-myenteric and submucosal plexuses
-blood vessels and some sphincters |
|
|
Term
| Sympathetic input to the GI tract (dec/inc) blood flow, thus (dec/inc) from the splanchnic to the systemic circulation during excerise and stressful environmental changes. |
|
Definition
|
|
Term
| True or False: Sympathetic input stimulates blood flow, secretion and motility of the gut. |
|
Definition
| FALSE, suppresses blood flow |
|
|
Term
| Sympathetic postganglionic neurons secrete ___ that acts directly on _________ receptors located in the sarcolemma of smooth muscle in sphincteric mm to maintain contractile tone and keep the sphincter closed. |
|
Definition
|
|
Term
| Sphincters are inhibited (relaxed or opened) when inhibitory chemicals such as ___ and ___ are secreted by active inhibitory motor fibers of the ENS that innervate the sphincter muscle. |
|
Definition
-VIP: vasoactive intestinal polypeptide
-NO: nitrous oxide |
|
|
Term
| Sustained sympathetic input to the gut produces a state of _________ (absence of gut contractions) with reduced blood flow and closed sphincters. This state is called _______ when it occurs ttransiently and ________ when it persists for several days or more, as is commonly observe after abdominal surgery and other surgeries. |
|
Definition
-intestinal paralysis
-physiological ileus
-paralytic ileus |
|
|
Term
| Where is visceral smooth muscle found? |
|
Definition
| -gut, ureters, bile duct, uterus, and blood vessels |
|
|
Term
| VSM is known as single- or multi-unit smooth muscle? What is another name for this? |
|
Definition
-single-unit
-aka unitary-type |
|
|
Term
| Within each VSM bundle, the individual fibers are electronically connected with one another via ________. What is the purpose of this? |
|
Definition
-gap junctions
-allow APs to flow freely from one cell to the next thus allowing multiple bundles of muscle fibers to contract together as one unity |
|
|
Term
| What are the two ways in which gut smooth muscle can contract? |
|
Definition
-sustained tone (tonic contration)
-variable phasic tone |
|
|
Term
| Rhythmicgut SM contractions are driven by cycles of membrane depolarization and repolarization called ________. |
|
Definition
|
|
Term
| True or False: Slow waves of electrical ativity are absent in vascular smooth muscle. |
|
Definition
|
|
Term
| What is the function of the interstitial cells of Cajal (ICC)? |
|
Definition
| -act as pacemaker cells of electrical activity of smooth muscle syncytia |
|
|
Term
| Where in the gut does slow, intrinsic electrical activity usually occur? Where are slow waves absent? |
|
Definition
-present: distal stomach, SI, and colon
-absent: proximal stomach, sphincters, and gallbladder |
|
|
Term
| What are the unique characteristics of inherent slow electrical activity? |
|
Definition
1) slow waves
b) spikes (APs)
3) variable resting membrane voltage |
|
|
Term
| How does VSM contraction differ from that in skeletal muscle? |
|
Definition
-skeletal mm contract and relax rapidly whereas most smooth muscle contraction is prolonged
-VSM has slower onset of contraction and relaxation than skeletal
-VSM uses much less energy (ATP) is required to sustain the same degree of tension of contraction of SM than skeletal m |
|
|
Term
| True or False: Smooth muscle cell membrane has abundant voltage-gated L-type calcium channels and few voltage-gated sodium channels, which is similar to the situation in skeletal muscle. |
|
Definition
| -FALSE; this is true for smooth muscle, but is the opposite in skeletal muscle |
|
|
Term
| Is it the flow of calcium or sodium into the interior of the smooth muscle fiber that is primarily responsible for the AP? |
|
Definition
|
|
Term
| What is calmodulin? What is its significance in smooth muscle contraction? |
|
Definition
-a regulatory pprotein that behaves similarly as troponin-C is skeletal muscle contraction
-forms a Ca-calmodulin complex that activates MLCK |
|
|
Term
| Outline skeletal muscle contraction. |
|
Definition
| -inc in intracellular [Ca]=> activation of crossbridge cycling =>calcium binds to troponin C=>induces rotation of troponin complex=> troponin leaves myosin=>myosin binds to actin=>ATPase activity activated=>contraction begins |
|
|
Term
| Outline smooth muscle contraction. |
|
Definition
| -increase in [Ca]=>Ca binds to calmodulin=>activates Myosin Light Chain Kinase (MLCK)=> MLCK-calmodulin cplx phosphorylates Regulatory Light Chain (MLC20) of myosin head=> inc in ATPase activity=> hydrosization of ATP, returning of myosin head to cocked state |
|
|
Term
| PHOSPHORYALTION OF MLC20 BY MLCK IS ESSENTIAL FOR MYOSIN BINDIN TO ACTIN AND MYOSIN-ATPASE ACTIVITY |
|
Definition
|
|
Term
| What are the two requirements of smooth muscle contration? |
|
Definition
-return to low cytosolic concentrations of [Ca]
-dephosphorylation of the regulatory myosin light chain of the head |
|
|
Term
| What enzyme desphsphorytes the myosin head group in SM to allow relaxation? |
|
Definition
| -myosin light chain phosphatase (MLCP) |
|
|
Term
| THE DEPHOSPHORYLATED FORM OF MYSOIN CANNOT BIND TO AND INTERACT WITH ACTIN TO UNDERGO CROSS-BRIDGE CYCLING. |
|
Definition
|
|
Term
| The degree of contraction and relaxation in VSM at any time is closely related to the relative activities of __________ and __________. |
|
Definition
|
|
Term
| What are the three general mechanisms that stimulate GI smooth muscle? |
|
Definition
1) electromechanical cpling with VOCC
2) pharmacomechanical cpling with ROCC
3) mechanomechanical cplg with SACC |
|
|
Term
| What causes electromechanical coupling? Describe how it occurs. |
|
Definition
-caused by membrane depolarization
-opens voltage-operated calcium channels (VOCC) in the plasma membrane: slow waves of electrical activity depolarize the cell membrane and activate voltage-dependent L-type calcium channels |
|
|
Term
| What causes pharmacomechanical soupling? |
|
Definition
| -agonists such as neurotransmitter chemicals and local chemical signals (hormones, immunokines) released from a myriad of cell types within the gut wall |
|
|
Term
| How does pharmacomechanical coupling occur? |
|
Definition
| -agonists bind to their G-cpled receptors in the cell membrane leads to the opening of voltage-independent calcium channels (VICC) and generation of IP3=> binds to receptor on SER=> allows Ca to flow into cytosol |
|
|
Term
| True or False: Pharmacomechanical coupling begins without the need for intial depolarization of the cell membrane. |
|
Definition
|
|
Term
| What is pharmacomechinal cpling mediated by? |
|
Definition
| -ROCC: receptor-operated calcium channels |
|
|
Term
| What causes mechanomechanical coupling? |
|
Definition
| -distention of the hollow tube induces change in the contractile state of the VSM contained in the wall of the tube |
|
|
Term
| How does mechanomechanical coupling occur? |
|
Definition
| -stretch=>opening of stretch-activated calcium channels in cell membrane (SACC)=>induction of membrane depolarization=> thus rise in Ca entry via VOCC |
|
|
Term
| What are the three types of voltage INDEPENDENT calcium channels and how are they activated? |
|
Definition
1) Receptor-operated calcium channels (ROCC): activated by agonist-receptor interaction
2) Store-operated calcium channels (SOCC): activated by the emptying of Ca stored in the SER
3) Mechanosensitive/stretch-activated channels (SACC): activated by membrane stretch |
|
|
Term
| What type of channel s Purine-2 channel? (P2X)What is its ligand? |
|
Definition
-it is a ligand-gated receptor-operated calcium channel
-ligand= ATP |
|
|
Term
| True or False: G-protein cpld receptors are responsible for the majority of ROCCC pathways that participate in pharmacomechanical coupling. |
|
Definition
|
|
Term
| True or False: SER-derived Ca is the major source of calcium in cardiomyocytes wheras extracellular and SER sources of calcium are both important for contraction in cardiomyocytes. |
|
Definition
|
|
Term
| What are the basal levels of intracellular calcium concentrations? Stimulatory levels? |
|
Definition
|
|
Term
| What are the 4 mechanisms by which intracellular [Ca] increases? |
|
Definition
1) Across cells mem via Voltage-operated Ca Channels (VOCC)
2)Receptor-operated Calcium Channels (ROCC)
3) Store-operated calcium channels (SOCC)
4) Stretch-activated calcium channels (SACC) |
|
|
Term
| How do Voltage-operated Ca channels work? What kind of coupling is this? |
|
Definition
-in plasma membrane
-they are primarily L-type calcium channels
-respond to depolarization of plasmalemma caused by slow waves of electrical activity emanating from interstitial cells of Cajal (ICC)
-called electromechanical coupling |
|
|
Term
| How do receptor-operated calcium channels (ROCC) work? What kind of coupling is this? |
|
Definition
-agonists bind to G-protein coupled receptors thereby initiating signal transduction mechanisms that activate voltage-independent nonselective, calcium permeable channels in the plasmalemma and/or activate IP3-receptor-calcium channels in the SR
-pharmacomechanical coupling |
|
|
Term
| How do Store-operated calcium channels (SOCC) work? |
|
Definition
-Ca depletion of SR per se and not the calcium released from the sotres activate Ca-permeable, voltage-independent channels referred to as SOCC that are located in the plasmalemma
=>can be initiated by VOCC or ROCC |
|
|
Term
| How do Stretch-activated calcium channels (SACC) work? |
|
Definition
| -smooth muscle cells are continuously exposed to mechanical stimulation such as compression, shear stress, and stretch |
|
|
Term
| SACC on the cell membrane are referred to as _______ since they convert physical forces into biological signals and cell response. |
|
Definition
|
|
Term
| True or False: Contraction and relaxation of skeletal muscle is regulated solely by electrical depolarization of the plasma membrane and activation of voltage-operated calcium channels. |
|
Definition
|
|
Term
| True or False: Smooth muscle in the proximal stomach, sphincters and gallbladder typically display sustained tonic contraction in the absence of slow waves of partial depolarization, and absence of action potentials. |
|
Definition
|
|
Term
| Tro or False: Smooth muscle in the distal stomach, SI, and colon typically display sustained tonic contraction in the absence of slow waves of partial depolarization an dabsence of action potentials. |
|
Definition
| -FALSE; typically displays continual slow, intrinsic electrical activity and its therefore analogus to cardiac muscle. |
|
|
Term
| What are the 3 important characteristics of continual slow, intrinsic electrical actibity in smooth muscle? |
|
Definition
1) slow waves
2) action potentials
3) variable resting membrane potential |
|
|
Term
| True or False: Slow waves reflect partial depolarization of the cell membrane. Slow waves are not action potentials and they do not cause contraction. |
|
Definition
|
|
Term
|
Definition
| -rhythmical changes in the flow of cations (Na, Ca) through adjoining smooth muscle cells via gap junctions. |
|
|
Term
| What determines the slow wave frequency of VSM? |
|
Definition
| -interstitial cells of Cajal (ICC) |
|
|
Term
| The transmembrane votage has to attain an electrical threshold value of about ___mV in order for a true action potential to occur in visceral smooth muscle. |
|
Definition
|
|
Term
| The greater the difference in voltage b/n the peak of the slow wave and the electrical threshold for depolarization of about -40mV then the (greater/lesser) is the frequency of the spike potentials and frequency of contractions which can vary from 1 to 10 per second. |
|
Definition
|
|
Term
| Spike potentials are caused by __influx via voltage-gated calcium channels in the cell membrane. |
|
Definition
|
|
Term
| The resting membrane potential (RMP) in resting smooth muscle fibers approximates __-__ mV. |
|
Definition
| -negative 50 to negative 60mV |
|
|
Term
The RMP can be reduced and thus more excitable by:
a)
b)
c) |
|
Definition
a) stretching of the muscle
b) acetylcholine stimulation from parasympathetic nerve endings
c) stimulation by several gastrointestinal hormones or lymphokines |
|
|
Term
| Norepinephrine (enhances/inhibits) contractility of non-sphincter smooth muscle primarily by (hyper/hypopolarization) of the emembrane. |
|
Definition
-inhibits
-hyperpolarization |
|
|
Term
Describe the muscle contractile activity of:
a) sphincters
b) blood vessels/airways
c) stomach/intestines
d) esophagus/urinary bladder |
|
Definition
a) normally contracted: constant innervation and [Ca]
b) Normally partially contracted (tone)=> tonically contract thus no massive change
c) Phasically active=> contract then relax then contract due to slow wave electrical activity
d) Normally relaxed: contracts when afferent stretch receptors are activated |
|
|
Term
| What are the 4 mechanisms for increasing cytosolic [Ca]? |
|
Definition
1) electromechanical coupling via voltage-operated Ca channels
2) Pharmacomechanical coupling via receptor-operated calcium channels
3) Mechanomechanical coupling via stretch-activated calcium-permeable cation channels
4) Store-operated calcium channels |
|
|
Term
| Definition: Mechanotransducers |
|
Definition
| -conduct ionic currents by responding to mechanical deformation (stretch/tension) of the lipid bilayer |
|
|
Term
| How do store-operated calcium channels work? |
|
Definition
| -depletion of calcium stored I the sarcoplasmic reticulum in the activation of Ca-permeable, voltage-independent calcium channels in the sarcolemma |
|
|
Term
| What is Myosin Light Chain Kinase? What does it do? |
|
Definition
-enzyme that phosphorylates Myosin
-allows for ATPase activity
-only myosin head group can bind actin |
|
|
Term
| What is Myosin Phosphatase? |
|
Definition
-dephosphorylates Ca-calmodulin-MLCK complex
-this makes myosin unable to undergo cross-bridge cycling |
|
|
Term
| True or False: There is no troponin in SM. |
|
Definition
|
|
Term
Contraction or Relaxation:
a) deplorazitaion
b) hyperpolarization
c) alpha-1-adrenergic agonists
d) beta-adrenergic agonists
e) ACH using Muscarinic 3 Receptor
f) Nitric Oxide
g) Substance P
h) Vasoactive intestinal Peptide
i) thromboxane A2
j) prostacyclin (PGI2)
k) Endothelium |
|
Definition
a) contraction
b) relaxation
c) contraction
d) relaxation
e) contraction
f) relaxation
g) contraction
h) relaxation
i) contraction
j) relaxation
k) contraction |
|
|
Term
| Contraction of smooth muscle initiated by passive stretching of the muscle (myogenic response) is elicited by ___________ coupling mechanisms of muscle contraction. |
|
Definition
|
|
Term
| How does electrical depolarization of the VSM cell membrane elicit contraction? |
|
Definition
| -opens voltage dependent calcium channels |
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Term
| Pharmacomechanical coupling indicates that the contraction of smooth muscle can be stimulated by several chemical agents, hormones, and cytokines. Give some examples. |
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Definition
-Acetylcholine (ACh)
-Substance P
-Angiotensin II
-Endothelin-1
-Thromboxane A2 |
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Term
| Name a few examples of chemical agents that stimulate relaxation. |
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Definition
-Norepinepherine: beta-adrenergic agonists
-Vasoactive intestinal polypeptide
-nitric oxide
-prostacyclin (PGI2) |
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Term
| What is the key regulatory component in smooth muscle contraction? |
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Definition
| -the amount of active (phosphorylated) myosin light-chain kinase (MLCK) enzyme |
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Term
| There are 5 subtypes of Muscarinc Receptors. What are the subtypes in which they can be further categorized? |
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Definition
-M1, M2, M4 are Gi-coupled receptors
-M3 and M5 are Gq-coupled receptors |
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Term
| What are the two types of receptors that ACh can bind to? |
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Definition
-muscarinic receptors (G-protein coupled receptors)
-Nicotinic receptors |
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Term
| True or False: ACh can bind as an agonist to either muscarinic subtype 3 receptors or muscarinic subtype 2 receptors in smooth muscle. |
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Definition
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Term
| What kind of receptors are muscarinic receptors? |
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Definition
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Term
| M3 receptors are Gq receptors that activate membrane calcium channels and also stimulate the membrane-associated enzyme __________. |
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Definition
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Term
| What does Phospholipase C do? |
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Definition
| -phospholipase C produces DAG and IP3=> IP3 binds to its receptor in SR membrane=> receptor is a saclium associated channel thus releases Calcium from SR=. this may lead to activation of coltage-operated calcium channels |
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Term
| Type 2 muscarinic receptors are G__-coupled receptors. ACh binding to MR receptors leads to (inhibition/exhitation) of the membrane-bound enzyme _________ and thus a reduction in the production of cAMP. |
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Definition
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Term
| Increase in cytosolic levels of cAMP and PKA promotes (contraction/rlaxation) of VSM b/c PKA phosphorylates MLCK and the phosphorylated form of MLCK is (able/unable) to interact with Ca-calmodulin complexes. |
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Definition
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Term
| When does Myosin light-chain kinase become activated? |
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Definition
| -when it combines with calcium-calmodulin |
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Term
| True or False: The ATPase activity of the myosin head group will only function if the regulatory light chains are dephosphorylated by MLCK. |
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Definition
| -FALSE; must be phosphorylated |
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Term
| What does myosin light-chain phosphatase (MLCP) do? |
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Definition
| -removes phosphate from the regulatory light chain of myosin, thus the dephosphorylated myosin head group is unable to participate in crossbridge cycling |
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Term
| True or False: Relaxation occurs if the activity of the MLCP exceeds that of the MLCK. |
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Definition
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Term
| Via what 6 mechanisms do PKA and PKG induce VSM relaxation? |
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Definition
1) inhibit VOCC via phosphorylation of VOCCs (closes them)
2) activation/opening of subsets of leak potassium channels leads to hyperpolarization
3) stimulate SERCA pumping of Ca back into SR (for storage compled to calreticulin and calsequestrin): does this by counteracting inhibitory phospholamban
4) phosphorylation and of IP#-receptors rendering them unable to bind IP3 agonist
5) stimulate efflux of cytosolic calcium by timulating NCX (3Na/1Ca XC) and PMCA (plasma mem calcium ATPase)
6) These kinases decrease the amount of active MLCK and increase the amount of MLCP |
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Term
| What is phospholambin? How can it be inhibited? |
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Definition
-regulatory protein that closes SERCA
-can be inh when PKA phosphorylates it, thus activating SERCA |
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