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Biological Systems > GI Block > Flashcards

GI Block Flashcards

1
Q

What are the storage sites for proton/potassium pumps in the parietal cells?

A

tubulovesicular membranes - fuse to the apical membrane for proton secretion **this is caused by gastrin, histamine, and acetylcholine binding to respective receptors **there are 2 types of second messengers involved in this process (calcium and cAMP), which allows for potentiation

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2
Q

What stimulates the secretion of somatostatin from D cells?

A

likely acetylcholine actually inhibits somatostatin secretion acid

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3
Q

Which drug blocks the M3 receptors?

A

atropine

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4
Q

Describe the local control mechanisms for the GI system

A
  • the GI system is controlled locally by the enteric nervous system (ENS) - comprised of the submucosal plexus and the myenteric plexus - it is located close to the effector systems (which makes sense because it is local control)
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5
Q

What are the primary characteristics of Absorption?

A
  • nutrients, electrolytes, and water are absorbed - active transport, diffusion, and osmosis
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6
Q

What is the role of colipase?

A
  1. lipase absorbs to the surface of fat droplets 2. lipase is displaced by the binding of amphipathic bile acids 3. colipase binds to bile acids and lipase, which brings lipase in proximity to its substrates
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7
Q

What are the regulatory factors of CCK, and how do they regulate?

A
  1. Increased by proteins/aa 2. increased by fatty acids 3. increased by neural stimulation 4. increased by peptide releasing factors
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8
Q

What are the layers of neural control of the GI system?

A
  • Local - ENS - Systemic - CNS - Global - CNS
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9
Q

Interstitial Cells of Cajal

A
  • mediate between efferent neurons and smooth muscle cells - responsible for slow waves - “pacemaker cells” - amplify neuronal input - they are central to GI motility regulation - keep pacemaker function by randomly depolarizing at specific intervals - loss of ICC causes motility disorders
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10
Q

What are the relative frequencies of the BERS in the different sections of the GI tract?

A

Rate small intestine>colon>stomach

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11
Q

What is primarily responsible for gastric motility in the stomach?

A

smooth muscle - pacemaker region in the antrum

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12
Q

Functions of the myenteric plexus

A
  • muscle control (between the 2 muscle layers of the GI tract) - increases intensity of rhythm of contraction, tone, rhythm rate, and velocity of conduction - ICC - interstitial cells of cajal are located here
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13
Q

What types of motility occur in the mouth and esophagus?

A

chewing swallowing peristalsis

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14
Q

What types of motility happen in the large intestine?

A

haustral shuttling mass movements defecation

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15
Q

Which systems exert control over salivary secretions?

A

parasympathetic is the dominant system of control. it is possible that the sympathetic nervous system affects the sublingual gland (cotton mouth feeling)

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16
Q

What do chief cells secrete?

A

pepsinogen and gastric lipase

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17
Q

What is the response to the smell/sight/thought/taste of food?

A
  • preganglionic vagus nerves stimulate postganglionic nerves that are part of the enteric system of the stomach - postganglionic nerves stimulate secretion from parietal and chief cells - gastrin secretion by endocrine cells is also stimulated - the gastrin moves through circulation and returns to the stomach where it continues to stimulate secretion from parietal and chief cells (feed forward!)
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18
Q

How are short peptides absorbed in the intestine?

A

coupled with proton transport using protons that are transported in through sodium/hydrogen exchangers… the H+ gradient created drives the transport of the short peptide sequences *they are then digested by intracellular/cytosolic peptidases and the resulting amino acids are transported out of the basolateral side of the cell through basolateral aa transporters

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19
Q

Describe the 2-stage model of salivary secretions

A
  1. The acinar cells secrete the primary secretion, which includes amylase and isotonic ion solution 2. While traveling through the duct, the ductal cells engage in ion exchange, primarily reabsorbing sodium in exchange for potassium and chloride in exchange for bicarbonate
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20
Q

What are the primary characteristics of Secretion?

A
  • water, electrolytes, acid, and enzyme movement - aids in digestion and absorption
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21
Q

Which part of the brain responds to special signals during the cephalic phase of digestion?

A

medulla oblongata, which causes parasympathetic action potentials to travel via the vagus nerves to the stomach

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22
Q

What are the key requirements for acid generation/release by parietal cells?

A

Carbonic anhydrase catalyzes the reaction between carbon dioxide and water to form carbonic acid - bicarbonate is exchanged with chloride and moves into circulation and the dissociated proton can be released through primary active transport mechanism

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23
Q

What do D cells secrete?

A

somatostatin

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24
Q

What are the four processes in the GI system?

A
  1. Motility 2. Secretion 3. Digestion 4. Absorption
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25
Q

What are the regulatory factors of Gastrin, and how do they regulate?

A
  1. increased by proteins/amino acids 2. decreased by acid 3. increased by neural stimulation and stretch ** the inhibition of SST is most likely a primary driving force for the release of Gastrin
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26
Q

Where and how does the water ABSORPTION in the small intestine occur?

A

at the villi of epithelial and following sodium being cotransported into the cell along with nutrients

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27
Q

What are the primary characteristics of Digestion?

A
  • enzyme secretion and activation - food is broken down into absorbable molecules
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28
Q

Functions of the submucosal plexus

A
  • regulates GI blood flow - controls epithelial function
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29
Q

What is the function of the gallbladder?

A
  1. Absorptive: sodium, chloride, and water - concentrates bile 2. Secretory: H+, Mucin - acidification of bile and protection of epithelial layer 3. Motor: Relaxation, Contraction - storage of bile and delivery of bile
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30
Q

Which ion is involved in the movement of water into the intestinal lumen and how is it transported out?

A

chloride - through CFTR proteins

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31
Q

What do G cells (enteroendocrine) secrete?

A

Gastrin

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32
Q

in which parts of the intestine is protein absorbed

A

throughout the entire small intestine

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33
Q

name the 3 primary pairs of glands responsible for salivary secretions and what quality of fluid they secrete

A
  1. Parotid glands - serous (watery) fluid 2. sublingual glands - mucous 3. submaxillary glands (aka submandibular) - mixture of the 2 **90% of salivary secretions
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34
Q

Describe the neural pathways of the GI system

A
  • they are activated by special senses (smell, taste, sight, etc) and by sensory nerve endings - regulated primarily through feedback loops (both positive and negative)
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35
Q

Which contractile parameters do pacemaker potentials in the stomach determine?

A
  1. Maximum frequency 2. Propagation velocity 3. Propagation direction **note: the pacemaker region in the mid corpus is the first place where you start to see ICC cells
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36
Q

How does slow wave frequency change as you move from the duodenum to the ileum?

A

decreases in a step-wise motion

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37
Q

which transporter transports glucose?

A

SGLT-1 co-transported with sodium (also galactose)

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38
Q

Which hormone is released from the duodenum, travels to the DVC, and ultimately causes relaxation?

A

CCK - this is a big way that the timing of gastric emptying is controlled

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39
Q

What are the regulatory factors of GIP, and how do they regulate?

A
  1. increased by fatty acids 2. increased by glucose
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40
Q

which transporter transports fructose?

A

GLUT5

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41
Q

What queue from the duodenum also triggers relaxation in the fundus?

A

distension in the duodenum

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42
Q

What can stimulate the secretion of chief and parietal cells?

A
  1. direct stimulation by gastrin 2. acetylcholine from vagal/ENS nerves 3. histamine from ECL cells, which are stimulated by gastrin
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43
Q

Name the H2 blocker examples

A

zantac, pepcid, axid

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44
Q

Name the additional salivary glands (not primary)

A

Von ebner’s gland (provides most of the lingual lipase in the mouth) and the glands in the mucous membrane of the lips, palate, and cheeks also secrete mucous **remaining 10% of salivary secretions

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45
Q

Describe primary peristalsis

A

distension in the esophagus triggers peristalsis locally and through vago-vagal reflex the action of swallowing causes the upper esophageal sphincter to relax and then to have increased pressure (to prevent backflow. the lower esophageal sphincter relaxes and primes receptive relaxation in the stomach. Peristaltic waves in the esophagus immediately following a food bolus are primary

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46
Q

Name the proton pump inhibitors

A

Prilosec, prevacid, nexium

47
Q

What types of motility happen in the small intestine?

A

segmental contractions peristalsis

48
Q

What are the primary characteristics of Motility?

A
  • neural regulation of smooth muscle - works to propel food from the mouth to the rectum - mixes and grinds food to increase its surface area (to allow for better digestion by digestive enzymes)
49
Q

What is another name for “slow waves” and what are their characteristics?

A

BER - basal electric rhythm - controlled by ICC cells, and set the rate of contraction - only produce a contraction when a threshold is reached - contractile stimulus is needed - determine maximal rhythm of phasic contraction - parasympathetic input (ach) increases the force of contractions - sympathetic inputs (epi) stops contractions

50
Q

What is secreted in the antrum?

A
  • mucus, pepsinogen, gastrin
51
Q

What do mucous cells secrete?

A

mucous bicarbonate trefoil peptides

52
Q

What does peptide YY do?

A

inhibits meal-stimulated GI functions

53
Q

What do parietal cells secrete?

A

HCl intrinsic factor

54
Q

What are MMCs and how are they controlled?

A

MMC - migrating motor complex - controlled by an increase in motilin concentration during fasting - concentration of motilin decreases immediately after eating

55
Q

How are triglycerides treated in the stomach?

A

Gastric lipase and acid break ONE fatty acid from the triglyceride. The rest travels to the duodenum where they trigger CCK release

56
Q

What is secreted in the body/fundus?

A
  • HCl, mucus, pepsinogen
57
Q

Name the 5 true GI hormones

A
  1. CCK 2. Gastrin 3. Secretin 4. GIP 5. Motilin
58
Q

What are the basic steps in swallowing?

A
  1. Receptors in the pharynx are stimulated by food/drink and brought to the rear of the mouth (primarily mechanoreceptors) 2. Impulses are sent via afferent parasympathetic to medulla oblongata in the brain stem (swallowing center) 3. Efferent impulses are sent back to the muscles of the pharynx and esophagus to coordinate the swallowing reflex
59
Q

Describe secondary peristalsis

A

the primary wave immediately after swallowing may be followed by a secondary wave, but only in the smooth muscle. the secondary wave serves the function of continuing to clear the bolus as well as preventing gastric reflux acid can trigger secondary peristalsis

60
Q

What are the functions of the fundus

A
  • primary role is reservoir function. - relaxes to accommodate additional food
61
Q

What are the primary biliary solutes?

A

secretory: bile acid (micelle-forming), phospholipids, and sIgA excretory: cholesterol is the most important

62
Q

What are the 3 phases of the MMC cycle?

A
  1. Quiescence - basically nothing going on 2. intermittent, non-propulsive contractions - enough said 3. intense, propulsive contractions - these start to look more like the contractions seen during peristalsis after feeding
63
Q

Describe the musculature of the esophagus and which neural circuits control them

A

The upper 1/3 of the esophagus is made of striated squamous skeletal muscle, which is under somatic control There is a middle 1/3 section of mixed muscle (autonomic control) The bottom 1/3 is made of columnar smooth muscle cells that are under autonomic control **regulation comes from the swallowing center of the brain

64
Q

What are the phases of digestion?

A
  1. cephalic - Sugar and fat digestion begins, primarily to enhance the taste sense. - Salivary secretions begin - Acid secretion starts - Peristalsis Starts 2. gastric - Protein digestion begins - Acid secretion - Pancreatic and biliary secretions begin - Mixing and churning - Some drug absorption (acidic drugs) 3. early intestinal and late intestinal - Digestion - Pancreatic and biliary secretions - Mixing and peristalsis - Nutrient and drug absorption
65
Q

What stimulates the secretion of Gastrin from G cells?

A
  1. Vagus/ENS release GRP which stimulates gastrin release 2. presence of peptides/aa in stomach
66
Q

What stimulates GIP release and what are its effects?

A

Glucose in the duodenum stimulates release from GIP cells; it stimulates the islets of lagerhans in the pancreas to secrete insulin

67
Q

What do ECL cells secrete?

A

histamine

68
Q

What happens to salivary amylase while food is digested?

A

While it is most active in the higher pH of the mouth, amylase continues to have activity throughout digestion

69
Q

Describe the regulation of pepsinogen release

A

after the initial release of pepsinogen in the stomach from chief cells (caused by vagal response) - gastrin, histamine, acetylcholine and inhibition of somatostatin S cells in duodenum detect H+, which stimulates them to release secretin, which further stimulates chief cells and inhibits parietal cells - this occurs so that more pepsinogen is released to digest the food - once the food is almost completely digested, it can no longer buffer the acid in the stomach and the pH drops, stimulating the release of somatostatin from the D cells (this inhibits gastrin release and stops the rest of the cycle)

70
Q

What are the 3 phases of the 3 sub-phases of intestinal digestion?

A
  1. luminal - proteins, CHO, and fat - chyme is mixed with enzymes 2. brush border - proteins and CHO - enzymes on the luminal surface of enterocytes 3. cytosolic/intracellular - only proteins - intracellular digestion in enterocytes (only di and tai-peptides)
71
Q

where does digestion of carbohydrates occur?

A

in the intestinal lumen and at the brush border - only monosaccharide are absorbed - glucose is completely absorbed along the small intestine

72
Q

What are the regulatory factors of Secretin, and how do they regulate?

A
  1. increased by fatty acids 2. increased by acid
73
Q

Why is iron the only ion that is absorbed in the duodenum?

A

it requires an acidic environment to be absorbed

74
Q

What types of motility happen in the stomach?

A

filling churning peristalsis emptying

75
Q

What neurotransmitters trigger relaxation?

A

NO and VIP (vasoactive intestinal polypeptide)

76
Q

What are the regulatory factors of Motilin, and how do they regulate?

A
  1. reduced by feeding (so decreased by all of the macromolecules 2. increased by neural stimulation
77
Q

What regulates movement through sections of the GI tract?

A

sphincters

78
Q

Where and how does water SECRETION in the small intestine occur?

A

in the crypt epithelial cells and following chloride and bicarbonate being secreted

79
Q

What are the 2 phases of receptive relaxation?

A
  1. true receptive relaxation (caused by swallowing) 2. accommodation (mechanoreceptors)
80
Q

What are the characteristics of the cardia?

A
  • includes the esophagus and the area where the esophagus comes in contact with the lower esophageal sphincter - squamous epithelial cells transition into columnar epithelial cells (now a single layer)
81
Q

What are the 2 divisions of the autonomic nerves?

A

1. Sympathetic - cell bodies originate in the thoracolumbar region

2. Parasympathetic - cell bodies originate in the craniosacral region

82
Q

What are the primary neurotransmitters of the autonomic nervous system?

A

Ach - acetylcholine

NE - norepinephrine

83
Q

Name the cholinergic receptors

A

Nicotinic

always excitatory

ion channel/depolarization mechanism

Muscarinic

can be both excitatory and inhibitory

G-protein mechanism

*Both receptors respond to acetylcholine, but the specific response is dictated by which receptor is present in target organ/cell type

84
Q

Name the adrenergic receptors

A

alpha1, alpha2, beta

*beta2 also exists, but only has affinity for epinephrine

85
Q

Summarize the characteristics of autonomic nerves

A
  • innervates all organs except skeletal muscle
  • synapses are located in ganglions outside cerebrospinal axis
  • extensive peripheral plexuses
  • postganglionic nerves are not axonated
  • some level of spontaneous activity without intact innervation
86
Q

Summarize the characteristics of somatic nerves

A
  • innervates only skeletal muscle
  • synapses within CNS
  • myelinated
  • deenervation results in paralysis and atrophy
87
Q

List the functions of the parasympathetic nervous system

A
  1. conservation of energy
  2. bradycardia
  3. vasodilator predominance
  4. blood pressure reduced
  5. renal blood flow increased
  6. urine output increased
  7. salivation increased
  8. respiration reduced
  9. GI motility and secretions increased
88
Q

List the functions of the sympathetic nervous system

A
  1. expenditure of energy
  2. tachycardia
  3. vasoconstrictor predominance
  4. blood pressure increased
  5. renal blood flow decreased
  6. urine output decreased
  7. salivation reduced
  8. respiration increased
  9. GI motility and secretions reduced
89
Q

How does the sympathetic nervous system act on the eye?

A

mydriasis by innervating the iris dilator muscle

90
Q

How does the sympathetic nervous system act on the eye?

A

Miosis by innervating the iris sphincter muscle

91
Q

What are the 5 key steps in neurotransmission?

A
  1. synthesis
  2. storage
  3. release
  4. recognition
  5. metabolism
92
Q

List the effects of activating muscarinic receptors

A

SLUDE

bradycardia

vasodilation

bronchospasm

miosis

increased urination

increased GI motility

increased salivation

increased tears

increased sweating

93
Q

List the effects of activating the beta1 receptor

A

increased contractile force

increased heart rate

increased renin release

94
Q

List the effects of activating the beta2 receptor

A

vasodilation

decreased TPR

95
Q

List the effects of activating the alpha receptors

A

vasoconstriction

increased TPR

96
Q

List the effects of activating adrenergic receptors

A

tachycardia (beta1)

vasodilation (beta1) vasoconstriction (alpha1 or 2)

bronchorelaxation (beta2)

mydriasis (alpha1)
accommodation (beta2)
decreased urination (beta2)

decreased GI motility (beta2)

relaxation of the uterus (beta2)

97
Q

What are the exceptions to dual innervation?

A

blood vessels (only sympathetic)

bronchiolar smooth muscle (only parasympathetic)

98
Q

What are the exceptions to the fact that the predominant tone of the autonomic nervous system is parasympathetic?

A

sweat glands (sympathetic cholinergic)

blood vessels (sympathetic adrenergic)

99
Q

What are the potential adverse effects of overstimulating muscarinic receptors

A

diarrhea, diaphoresis

urination

miosis

bradycardia, bronchosecretions

emesis

lacrimation

salivation

100
Q

How does botox work?

A

acts by inhibiting the release of ACh from cholinergic nerve terminals

treatment for ailments involvement overactive skeletal muscle

101
Q

fusobacterium

A

helps form scaffold for other bacterial species in oral biofilm

102
Q

What are the key roles for gut microbiota?

A
  1. Metabolism/fermentation of unused energy substrates
  2. Training of the immune system
  3. Production of Vitamins, like vitamin K
  4. Competitive inhibition of harmful species
103
Q

What are the protective functions of good gut flora?

A
  1. Pathogen displacement
  2. Nutrient competition
  3. Receptor competition
  4. Production of anti-microbial factors
104
Q

Structural functions of of good gut flora

A
  1. Barrier fortification
  2. Induction of IgA
  3. Apical tightening of tight junctions
  4. Immune system development
105
Q

Metabolic functions of good gut flora

A
  1. control of IEC differentiation and proliferation
  2. metabolize dietary carcinogens
  3. synthesize vitamins
  4. ferment non-digestible dietary residue and endogenous epithelial-derived mucus
  5. ion absorption
  6. salvage of energy
106
Q

What are the different types of organisms existing in the bicrobiota?

A

bacteriophage, archaea, protozoa, ameboa, flagellates, algae, fungi

107
Q

What is a major role for colonic flora?

A

major source of short-chain fatty acids, which are primary source of fuel for the epithelium of the colonic epithelial cells

108
Q

Which species of bacteria alters placental blood vessels?

A

fusobacterium nucleatum

109
Q

What are the metabolic effects of enteric bacteria?

A
  • endogenous substrates produced by the body are modified by microbiota
  • SCFA are produced and are actively reabsorbed by epithelial cells
110
Q

Name some of the primary diseases associated with dysbiosis of the microbial communities

A

Adipose Tissue: Obesity/insulin resistance

Liver: NAFDL/NASH (cause of liver disease)

Pancreas: Type 2 Diabetes

Cardiovascular System: Stroke, atherosclerosis, thrombosis

Brain: autism spectrum disorder, stress response, metabolic disease

Lung: allergic response

111
Q

What are M cells?

A

specialized epithelial cells that sample the environment of the lumen and travel through the lamina propria into area with immune cells

112
Q

What are the beneficial functions of bacterial metabolites in the GI system?

A
  • metabolites are an energy source for colonocytes
  • stimulate naive T cells to differentiate into Treg, which prevents autoimmunity
  • increase barrier integrity for neutrophil function
113
Q

What is the name of the voluntary defecation reflex?

A

Valsalva Maneuver

Biological Systems (3 decks)

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