Physiology I: Enteric Nervous system and Disorders of motility

Parts of the alimentary system from beginning to end: … (6)

Mouth, esophagus, stomach, small intestine, large intestine, anus

Stretching of the gut wall, such as occurs with a large amount of food, stimulates contraction … to the stretched wall

2-3 cm proximal

Stimuli of peristaltic movement: … (4)

stretching, parasympathetic signals, physical irritation (ep), chemical irritation (ep)

The smooth muscle of the gut is a …, thus, stimulation at 1 point spreads to adjacent areas, creating a peristaltic spread

syncytium

Peristalsis also occurs in the … (3)

bile ducts, glandular ducts, ureter

…: primarily controls peristalsis an interconnected chain of neurons between the longitudinal and circular layers of muscle that extends the entire length of the GI tract

Myenteric plexus

…: mainly controls GI secretion and local blood flow

submucosal plexus

2 types of movement in the GI tract: …

Propulsive movement, mixing movements

Stimulation of the myenteric plexus causes: … (4)

Increased tonic contractions, increased intensity of contractions, slight increase in rhythm of contractions, increased velocity of excitatory waves along the gut wall

…: the directional movement of food in the GI tract

Peristaltic reflex

Electrical activity in GI smooth muscle is excited by fairly constant, slow electrical activity that consists of 2 types of electrical activity: …

slow waves, spikes

The … can be adjusted (by myenteric plexus, autonomic nervous system, and hormones), this is important, as spikes occur once a threshold resting membrane potential is reached

resting membrane potential

…: undulating changes in the resting membrane potential caused by the entry of Na+

Slow waves

The … of slow waves sets the rhythm of contraction

frequency

The slow waves don’t usually cause the contractions, they …, causing spikes to occur

drive the membrane to threshold

…: APs, caused by the influx of primarily Ca2+ and some Na+, they cause contraction

Spikes

Spikes occur once the resting membrane potential …

depolarizes to ~40 mV

The … depolarized the resting membrane potential becomes during the slow waves, the greater the frequency of spikes

more

The … that enters the muscle during the spike causes the contraction

Ca2+

Factors that depolarize the resting membrane permeability and increase the excitability are: … (3)

stretching, parasympathetic stimulation (acetylcholine), GI hormones

When the resting membrane potential … it becomes less excitable by sympathetic stimulation

hyperpolarizes

…: continous instead of rhythmical and last several minutes-to-hours

tonic contractions

Tonic contractions are caused by: … (3)

repetitive spikes, continuous depolarization, continuous entry of Ca2+

Longitudinal muscles … contract, the circular muscle layer relaxes, and segment receives the aborally moving intestinal contents

ahead

Circular muscles … contract, longitudinal muscle simultaneously relax

behind bolus

…: modified contraction propelling the contents of the large bowel forward en masse

Propulsive mass movements

Propulsive mass movements occur by peristaltic contraction pushing the contents through 20cm or more of colon in which the …

haustrations are relaxed

Transmission series for regulation of peristalsis excitation: … (5)

sensory neurons, cholinergic interneuron, excitatory motor neuron, Substance P/Acetyl choline, contraction

Transmission series for regulation of peristalsis inhibition: … (5)

Sensory neurons, cholinergic interneuron, inhibitory motor neuron, Vasoactive intestinal peptide/Nitric oxide, relaxation

Myogenic origin and control of GI motor function: … (4)

Myogenic, neurogenic, endocrine, paracrine

Myogenic origin and control of GI motor function: … (2)

smooth muscle, interstitial cells of Cajal (sm pacemaker cells)

Neurogenic origin and control of GI motor function: … (2)

intrinsic (enteric NS), Extrinsic

In diarrhea toy have … (2)

increased circulating 5-HT+, increased number of EC cells in Postinfectious IBS

In constipation you have …

decreased number of EC cells