Physiology Exam 3 - Dr. Sullivant

The GI Tract provides ______, _______, ______, and ________ to the rest of the body for normal function and repair

water, electrolytes, vitamins, and nutrients

What type of muscle is in the GI tract?

Smooth muscle

What direction is the outer layer of smooth muscle in the GI tract?

longitudinal

What direction is the inner layer of smooth muscle in the GI tract?

circular

How are the smooth muscle fiber bundles conntected?

low-resistance gap junctions

What is the resting membrane potential of GI smooth muscle?

-50 to -60 mV

What is uncoordinated or a lack of movement of the GI tract?

Dysmotility

What are the three depolarization triggers?

muscle stretching, Ach release, and GI hormones

What waves have no action potential and acts like “radio static”?

slow waves

What waves allow for a bigger contraction?

spike waves

What excites spike waves?

slow waves

How fast are waves in the stomach?

3 waves per min

How fast are waves in the duodenum?

12 waves per min

How fast are waves in the ileum?

8 or 9 waves per min

What interstitial cells control slow waves?

cells of Cajal

What action potential do spike waves occur?

-40 mV

What is the normal range for spike potentials?

-50 to -60 mV

What controls spike potentials?

slow calcium-sodium channels

What is more negative and slows or stops gut motility?

hyperpolarization

What is stronger: sympathetic or parasympathetic?

sympathetic

What controls GI motility/secretions, is contained in the gut wall, and has two plexuses to communicate?

enteric nervous system

What are the two plexuses of the enteric nervous system?

myenteric and submucosal

T/F Plexuses are also innervated by sympathetic and parasympathetic nerves

TRUE

What plexus provides control of motility throughout the gut, is excitatory to muscles and inhibitory to sphincters?

myenteric

What plexus controls local GI secretions and absorption and blood flow locally?

submucosal

What is a chemical substance that is released at the end of a nerve fiber?

neurotransmitter

Through what nerves are cranial parasympathetic transmitted through?

vagus nerve

What organs goes the vagus nerve control motility in?

esophagus, stomach, pancreas, small intestine, and half of large intestines

What is the main neurotransmitter released by the parasympathetic nervous sytstem?

acetylcholine

What is suppressed in fight or flight response?

acetylcholine

What inhibits acetylcholine?

anticholinergics

What nerves house the sacral parasympathetic nerves?

S2, S3, S4

What nerves pass through the pelvic nerve to the distal half of the large intestine and is well innervated for defecation reflexes?

S2, S3, S4

What are outlying ganglia that pass through sympathetic chains lateral to the cord?

celiac ganglia

What is the main neurotransmitter released by the sympathetic nervous system?

norepinephrine (and epinephrine)

What nerves may prompt excitatory (borborygmus/diarrhea) or inhibitory (ileus) responses?

afferent sensory nerves

What are some examples of the reflexes within the enteric nervous system?

GI secretions, peristalsis, mixing contrations, and local inhibitory effects

What are the three reflexes from the gut to the pre-vertebral sympathetic ganglia and then back to the GI tract?

gastrocolic, enterogastric, and colonileal

What are the reflexes from the gut to the spinal cord or brain?

pain and defecation

What does gastrin stimulate?

secretion

What does cholcysokinin stimulate?

primary secretion and motility

What does secretin stimulate?

primary secretion and motility

What does glucose-dependent insulinotropic peptide stimulate?

primary secretion and motility

What does motilin stimulate?

motility

What is the source of gastrin?

G cells of stomach antrum

What triggers the release of gastrin?

gastric distention, proteins, and gastrin releasing peptide

What does gastin do?

secrete gastric acid and stimulate mucosal growth in stomach

What can an overstimulation of gastrin cause?

ulcers

What is the sources of cholecystokinin?

I cells of duodenum and jejunum mucosa

What is cholecystokinin triggered by?

fats and proteins

What does cholecystokinin do?

contracts gallbladder, inhibit stomach motility, increase appetite

What is the source of secretin?

S cells of the duodenum

What triggers the release of secretin?

gastric acid in duodenum

What does secretin do?

pancreatic secretions of HCO3

What dose the secretion of HCO3 cause?

neutralization and increased watery portion of digestive juices

What is the sources of glucose insulinotropic peptide (GID)?

small intestine mucosa

What triggers the release of GIP?

presence of food in the small intestine

What does GIP do?

increase insulin release and slows stomach emptying

What is the source of motilin?

stomach and duodenum

What triggers the release of motilin?

cyclical relase

What does motilin do?

interdigestive myoelectric complexes making the intestine move

What has something to do with the law of the gut?

propulsion/peristalsis

What has a constrictive, chopping, churning effect on the ingesta?

mixing movement

What has a contractile ring moves ingesta along the gut and is stimulated by distention or irritation?

propulsion/peristalsis

What moves blood from the GI, spleen, and pancreas flows to the liver via the portal vein?

portal circulation

Where are fats absorbed?

intestinal lacteals/lymphatics

What increases GI blood flow?

GI activity and decreases oxygen supply

What are the two vasodilator substances that increase blood supply?

kallidin and bradykinin

What increase glandular activity and local blood flow?

parasympathetic stimulation

What causes intense GI vasoconstriction?

sympathetic stimulation

What type of blood flow is going on in villi?

countercurrent

What percent of blood oxygen diffuses directly from arterioles to venules before reaching the villus tips?

80%

What does countercurrent blood flow leave villus tips susceptible to?

hypoxia, ischemia, sloughing, and blunting

What is the term for too little motility?

ileus

What does a lack of motility cause?

vomiting, regurgitating, nausea, and bloating

What does too much motility cause?

poor absorption, cramping, and diarrhea

What never modulates chewing?

cranial nerve 5 (trigeminal nerve)

What action increases the surface area for digestive enzymes to act upon the ingesta?

chewing

What neuro things control swallowing?

medulla and pons (swallowing center)

What nerves control swallowing?

5,9,10,12

What phase of swallowing initiates the swallowing process, voluntary, and pushes the food bolus to the pharynx?

oral phase

What phase of swallowing moves food from the pharynx to the esophagus and is involuntary?

Pharynegeal phase

What closes during the pharyngeal phase?

vocal folds and epiglottis

What moves up over the caudal nares during the pharyngeal phase of swallowing?

soft palate

What movement forces food into the esophagus in the pharyngeal phase of swallowing?

peristaltic waves

What relaxes to allow for the pharyngeal phase of swallowing to occur?

upper esophageal sphincter

What phase of swallowing consists of primary and secondary peristalsis, and is involuntary?

esophageal phase

What are the three phases swallowing?

oral, pharyngeal, esophageal

What phase of swallowing is voluntary?

oral phase

What type of muscle is the canine esophagus?

skeletal muscle

What type of muscle is the feline esophagus?

smooth and skeletal

Which sphincter is important for esophageal health/function, has high resting tone, and relaxes when esophageal peristalsis occurs?

Lower esophageal sphincter

What is the failure of the lower esophageal sphincter relaxation?

achalasia

What are the three motor functions of the stomach?

storage, mixing to make chyme, and emptying into duodenum

What is a gastric capacity of the dog?

90 ml/kg

What is the gastric capacity of the cat?

60 ml/kg

What reflex allows the stomach to stretch significantly?

vasovagal reflex

What is a circular smooth muscle that controls the opening of the distal part of the stomach, is slightly contracted, and only lets small solids and fluids leave the stomach?

pyloric sphincter

When food is present, how often are mixing contractions in the stomach?

every 15-20 seconds or 3-4x a/minute

What are mixing contractions in the stomach mediated by?

slow waves