Term
| Functions of GI movements (4) |
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Definition
Propel ingesta
Retain ingesta
Break up material
Circulate material |
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Term
| What is electric coupling? |
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Definition
| smooth muscle cells are linked via gap junctions, so that depolarizations can be transmitted from cell to cell |
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Term
| What are interstitial cells of Cajal? |
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Definition
| pacemaker cells of the GIT |
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Term
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Definition
| intrinsically rhythmic depolarization/repolarization of cells of cajal |
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Term
True or False
As slow waves are propagated through GI smooth muscle, APs do not fire, and there is no contraction that occcurs |
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Definition
True!
they operate at 'subthreshold' depolarization levels |
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Term
| What is required for contraction of smooth muscle to take place? |
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Definition
-slow wave determines pattern of contraction
-neurotransmitter is required (ACh) for an action potential to be generated & contraction to occur |
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Term
| How doe NE, NO, VIP and ATP make AP's less likely? |
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Definition
| they hyperpolarize the membrane, so an even larger change in membrane potential is required for generation of an action potential |
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Term
| Where are interstitial cell of cajal found? |
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Definition
smooth muscle of:
stomach
duodenum
colon |
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Term
| How does the peristaltic reflex work? |
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Definition
-food bolus creates a stretch in the smooth muscle
-proximal to the bolus, the stretch will stimulate motor neurons promoting contraction of circular muscle (longitudinal is relaxed)
-distal to bolus, stretch will promote relaxation of circular muscle and contraction of longitudinal
-pushes food bolus aborally (forward) |
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Term
| The main nerve involved with prehension... |
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Definition
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Term
| What are the phases of deglutition? |
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Definition
(deglutition = swallowing)
1. Voluntary - tongue forms bolus, food pushed into oropharynx by tongue
2. Involuntary - swallowing reflex moves food into pharynx
3. Cricopharyngeal - opening of upper esophageal sphincter, food enters esophagus, sphincter contracs, tracheal entrance opens |
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Term
True or False
With segmental contractions, there is no net forward movement of the bolus |
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Definition
true
(splits in half, one portion goes 'upstream' and one goes 'downstream' |
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Term
| Inhibition/promotion of gut motility is modulated by the _____ nervous system |
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Definition
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Term
| Individual patterns of contraction are regulated by the ___ nervous system |
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Definition
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Term
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Definition
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Term
| What antibacterial enzyme is found in saliva |
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Definition
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Term
True or False
Thermoregulation is a role of saliva |
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Definition
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Term
|
Definition
sublingual
mandibular
parotid
zygomatic (carnivores only) |
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Term
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Definition
mucus
enzymes
water
electrolytes (Na, Cl) |
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Term
| What phenomenon is resonsible for saliva being hypotonic, relatively neutral pH despite the fact that Na and Cl are secreted in saliva? |
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Definition
| collecting duct cells absorb the Na and Cl (return them to the bloodstream), and secrete K+ and HCO3- |
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Term
| How does ydration status affect saliva composition |
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Definition
| aldosterone is released when dehydrated, will promote reabsorption of Na+ from salivary glands |
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Term
| Most salivary glands secrete a primarily (serous/mucus) product |
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Definition
mucous, or mixed
(except for parotid which is more serous) |
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Term
| What salivary gland is especially important in ruminants, and why? |
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Definition
Parotid gland
-secretes lots!
-secretion is more alkaline
-buffers rumen contents (counters the acidity of VFAs produced during fermentation) |
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Term
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Definition
| ingesta once it's been broken down by the stomach and enters the duodenum |
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Term
| What are the two functional parts of the stomach? What does each do? |
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Definition
1. Proximal part (fundus, body)
-mostly for storage, salivary enzymes will partially digest here, some fermentation (for horses, pigs)
2. Distal Part (antrum, plylorus)
-mixing, grinding, liquifying
-chyme pushed out of pylorus in small amounts |
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Term
| How is emptying of the stomach regulated? |
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Definition
Promotion of emptying: gastric factors
-gastrin secreted in response to stretching, food composition
Inhibition of emptying: duodenal factors
-low pH, high osmolality, fat contents
-CCK & somatostatin inhibit emptying
-important bc duodenum is sensitive to acidity, if too much chyme is released at once, damage will occur |
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Term
| What is the Interdigestive Motility Complex? How often does this occur? |
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Definition
-clearing indigestible material from stomach
-pylorus relaxes while a strong peristaltic wave moves across the antrum
-forces a mass movement of material into the duodenum
-roughly once an hour, when there is no digestible material in stomach |
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Term
| What triggers the interdigestive motility complex? |
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Definition
| motilin released from proximal SI |
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Term
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Definition
| chemoreceptor trigger zone in brainstem |
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Term
| Explain the phrase "vomiting is a non-specific sign of disease" |
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Definition
| -can be triggered by stimulating the inner ear, mechanoreceptors in pharynx, receptors in gastric & duodenal mucosa, stimulation of CTZ etc |
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Term
| What happens during vomiting? |
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Definition
-salivation increases
-cardiac sphincter & stomach muscles relax
-pylorus closes
-glottis closes
-upper esophageal sphincter opens
-abdominal muscles contract
-retrograde peristalsis in duodenum prevents movements of contents into SI |
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Term
| Compare vomiting to regurgitation |
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Definition
Vomiting
-active
-contains semi digested food, bile, blood (from lower stomach)
-pH <5
Regurgitation
-passive
-undigesed food (from upper stomach)
-pH >7 |
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