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VMP814 Physiology/Microanatomy 1 > Lecture 38 11/15/23 > Flashcards

Lecture 38 11/15/23 Flashcards

1
Q

What movements fall into GI tract motility?

A

-propulsive
-retentive
-mixing

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2
Q

What is transit time?

A

time it takes for ingesta to travel from one portion of GI tract to another

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3
Q

What are the functions of GI movements?

A

-propel ingesta from one location to the next
-retain ingesta at a given site for digestion, absorption, or storage
-break up food material and mix it with digestive secretions
-circulate ingesta so it comes in contact with digestive/absorptive surfaces

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4
Q

What are the characteristics of slow waves?

A

-slow, rhythmic movements
-slow changes in resting membrane potential
-NOT action potentials/do not cause contraction
-frequency varies by location
-determine maximum rate of muscle contractions

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5
Q

What are the characteristics of the interstitial cells of Cajal?

A

-pacemaker cells
-generate slow waves
-form network between smooth muscle layers
-connected by tight junctions

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6
Q

What happens when excitatory peptides, like acetylcholine, are released into an area of GI tract?

A

increase in cell membrane potential and contraction

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7
Q

What happens when inhibitory peptides, like norepinephrine, are released into an area of GI tract?

A

decreased cell membrane potential and no contraction

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8
Q

What is the overarching function of propulsive movements?

A

move food forward through the GI tract

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9
Q

What are the characteristics of contraction during peristalsis?

A

-contractile ring behind bolus
-relaxation of muscle in front of bolus

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10
Q

What are the potential stimuli for peristalsis?

A

-distension of gut
-physical or chemical irritation of gut lining
-strong parasympathetic NS signals

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11
Q

What are the functions of mixing movements?

A

-grinding/mixing food material with digestive enzymes
-allowing food to come in contact with gut mucosa for absorption

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12
Q

What are the characteristics of prehension?

A

-process of getting food into the mouth
-involves coordination of small, voluntary muscles of the face/lips/tongue

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13
Q

What are the characteristics of chewing/mastication?

A

-first act of digestion
-breaks food down small enough to pass through esophagus
-moisten and lubricate food by mixing with saliva

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14
Q

What are the four phases of swallowing/deglutition?

A

-oral preparatory phase
-oral propulsive phase
-pharyngeal phase
-esophoageal phase

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15
Q

What are the characteristics of the oral preparatory phase of swallowing?

A

-voluntary
-food enters oral cavity
-chewing
-bolus formation

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16
Q

What are the characteristics of the oral propulsive phase of swallowing?

A

-voluntary
-tongue elevates and propels bolus to pharynx

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17
Q

What are the characteristics of the pharyngeal phase of swallowing?

A

-involuntary
-bolus in caudal pharynx stimulates mechanoreceptors
-soft palate elevates to seal nasopharynx
-epiglottis covers trachea and stops respiration
-pharyngeal wave occurs as upper esophageal sphincter relaxes/opens

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18
Q

What are the characteristics of the esophageal phase of swallowing?

A

-involuntary
-bolus passes into esophagus
-esophagus contracts sequentially
-lower esophageal sphincter relaxes
-bolus enters stomach

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19
Q

What are the three segments of the esophagus?

A

-upper esophageal sphincter
-body
-lower esophageal sphincter

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20
Q

What is primary peristalsis of the esophagus?

A

-peristaltic wave from pharynx to stomach
-initiated by swallowing

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21
Q

What is secondary peristalsis of the esophagus?

A

secondary wave that occurs if food does not reach stomach following first wave

22
Q

Why is the lower esophageal sphincter typically tightly closed?

A

prevent gastric reflux

23
Q

What are the characteristics of lower esophageal sphincter relaxation?

A

-mediated by vasoactive intestinal peptide
-occurs when food bolus distends area just orad to sphincter muscle

24
Q

Why does the stomach have an additional inner oblique layer of muscle?

A

to help the stomach have more powerful contractions for grinding/mixing food

25
Q

What are the motor functions of the stomach?

A

-food storage
-mechanical breakdown of food/mixing
-release of chyme at a controlled rate

26
Q

What type of motility is seen in the proximal region of the stomach (cardia, fundus, first 1/3 of body)?

A

sustained tonic contractions that allow for storage

27
Q

What type of motility is seen in the distal region of the stomach (distal 2/3 of body, antrum)?

A

phasic propagating contractions that allow for grinding of food

28
Q

What are the characteristics of the vago-vagal reflex?

A

-response to presence of food in stomach
-leads to gastric hormone release

29
Q

What is the post-prandial period?

A

digestive period after food intake

30
Q

What occurs directly after food intake?

A

weak peristaltic waves in the stomach that move the food towards the antrum

31
Q

What happens once food reaches the antrum of the stomach?

A

-more powerful contractions
-shearing/grinding of food particles

32
Q

What happens once food reaches the pylorus?

A

-pylorus tightens
-only small food particles can enter duodenum

33
Q

What factors impact the rate of gastric emptying?

A

-water content
-nutrient composition
-nutrient acidity
-nutrient osmolality
-temperature
-intestinal feedback

34
Q

What are the characteristics of the migrating motility complex?

A

-fasted motility
-clears gut of undigested residue
-NOT present in cats and rabbits
-cycles every 90 minutes
-mediated by GI hormone Motilin

35
Q

What are the phases of the migrating motility complex?

A

-phase 1/slow waves
-phase 2/intermittent contractions
-phase 3/intense propulsive motility

36
Q

What are the four components of the vomiting/emetic reflex?

A

-visceral receptors
-vagal and sympathetic afferent neurons
-chemoreceptor trigger zone
-emetic center

37
Q

Which components of the body provide input to the emetic center?

A

-vagal and sympathetic afferent neurons
-chemoreceptor trigger zone
-vestibular apparatus
-cerebral cortex

38
Q

What are the physical steps of the emetic reflex?

A

-relaxation of stomach muscles, closing of pylorus, and relaxation of lower esophageal sphincter
-contraction of abdominal muscles
-expansion of thoracic cavity while glottis remains closed
-opening of lower esophageal sphincter

39
Q

Which species are unable to vomit?

A

-horses
-rabbits
-rodents

40
Q

Which movements occur in the small intestine during the post-prandial period?

A

-non-propulsive movement/mixing
-propulsive movement

41
Q

What type of fasted motility is seen in the small intestine?

A

migrating motility complex

42
Q

What are the characteristics of the ileocolic sphincter?

A

-prevents colonic contents from moving into ileum
-ring of circular muscle that is typically closed
-peristaltic activity forces sphincter to open and allow ingesta through

43
Q

What are the characteristics of colonic anatomy?

A

-varies by species/amount of fermentation occurring
-some species have haustra/sacculations

44
Q

What are the functions of the colon?

A

-water and electrolyte absorption
-fecal matter storage
-fermentation
-evacuation of fecal matter

45
Q

What are the characteristics of mixing activity in the colon?

A

-important for absorption and fermentation
-achieved by segmental and longitudinal contraction
-can include retropulsion

46
Q

What are the characteristics of mass movements in the colon?

A

-move feces down the colon
-cause urge to defecate
-initiation can occur after meals

47
Q

What are the reflexes that initiate mass movements of the colon?

A

-gastrocolic reflex/distension of stomach
-duodenocolic reflex/distension of duodenum

48
Q

What are the characteristics of the internal anal sphincter?

A

-smooth muscle
-normally contracted
-responsible for fecal continence
-parasympathetic NS relaxes
-sympathetic NS contracts

49
Q

What are the characteristics of the external anal sphincter?

A

-voluntary striated muscle
-innervated by pudendal nerve

50
Q

What must occur for defecation to take place?

A

-relaxation of internal anal sphincter
-peristaltic contractions of rectum

VMP814 Physiology/Microanatomy 1 (46 decks)

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