Monogastric pt 3

Question 1

What are the GI pacemaker cells?

Answer 1

Modified muscle cells between smooth muscle layers called ICC

Question 2

The resting membrane of ICC cells fluctuate as a function of what?

Answer 2

Ca

Question 3

What sets basic electrical rhythm?

Answer 3

Partial depolarization

Question 4

Smooth muscle slow wave frequency, amplitude and kinetics differ btw..

Answer 4

Species and vary depending on the segment of GI tract

Question 5

What gives rise to smooth muscle contraction?

Answer 5

Action potentials that travel through gap junctions

Question 6

When do action potential occurs?

Answer 6

Threshold potential is more positive than -40mV due to parasympathetic input

Question 7

What happens when there is no parasympathetic input?

Answer 7

Only get slow myogenic waves which is rarely enough to reach action potential and you do not get contraction or change in muscle tension

Question 8

What effect does excitatory neurohormonal substances have on action potentials?

Answer 8

Depolarize the resting membrane potential to increase likelihood for contraction and increase contraction/motility

Question 9

Sympathetic input has what effect on action potentials?

Answer 9

Inhibitory neurohormonal substances hyperpolarize the resting membrane potential and decrease the likelihood for contraction and decrease contraction/motility

Question 10

Triggering local sensory nerve endings from food bolus at the back of the pharynx does what?

Answer 10

Trigger the involuntary phase of swallowing reflex

Question 11

What muscle must relax in order for the epiglottis to close and esophagus open enough for food?

Answer 11

Cricopharyngeal muscle

Question 12

What type of muscles are in the esophagus?

Answer 12

• Striated: Somatic control (vagus)

- Smooth muscle: IX and X maybe myenteric plexus

Question 13

Are the sphincters of the esophagus normally open or closed?

Answer 13

Closed

Question 14

Describe food through the esophagus?

Answer 14

Upper esophageal sphincter relaxes and food is prepulsed through peristaltic down to stomach, lower esophageal sphincter opens and it goes into stomach

Question 15

What is the storage region of the stomach?

Answer 15

The proximal part, fundus

Question 16

What activates the fundus to accommodate ingesta?

Answer 16

Adaptive relaxation through PS not through Ach but through vasoactive intestinal peptide

Question 17

What part of the stomach grinds ingesta?

Answer 17

Antrum

Question 18

What increases muscular activity of the antrum?

Answer 18

PS (Ach)

Question 19

Describe the grinding of ingesta in the antrum?

Answer 19

Peristaltic waves at the proximal part moves towards the pylorus causing the pylorus to constrict. ingesta gets crushed in the peristaltic ring and propelled backwards. as the wave reaches the pylorus finely ground material sieve into the duodenum and the rest moves back to the antrum

Question 20

Describe the stomach during the cephalic phase of digestion.

Answer 20

Anticipation of food causes the vagus to prime the stomach. once food is in the stomach you get a positive sensory feedback further priming stomach and increases motility

Question 21

What hormones stimulate gastric motility?

Answer 21

• Gastrin

- Motilin

Question 22

What hormones inhibit gastric motility?

Answer 22

• CCK
• Secretin
• GIP

Question 23

What wipes the stomach of indigestible material?

Answer 23

Interdigestive migrating motility complex does this 1x/hr or constantly in herbivores