Question

sul cause the intestinal phase to switch from excitatory to inhibitory Describe the neural response to the intestinal phase stimul 1. What is the name of this inhibitory neural reflex? Describe the endocrine response to the intestinal phase stimuli 1. What is the name of the group of hormones that target the stomach to inhibit gastric secretion (and motility? What is the goal of this inhibitory period of the intestinal phase of gastric section? vi. How is gastric motility (and thus emptying) regulated? 1. How much can the stomach hold before distention causes a significant rise in pressure? a. Which region of the stomach produces the strongest contractions? b. How is force of contraction regulated? c. What are the interstitial cells of Cajal' and what is their function? i. What causes their sub threshold depolarizations to reach threshold and produce contractions? 1. What allows these cells to spread their APs to the rest of the muscularis externa? 2. What is the BER? 2. What is the function of the pyloric sphincter? a. hat determines the rate of gastric emptying? b. How is gastric emptying regulated? vil. What is emesis? 1. Describe the events involved in emesis (.e., what contracts and what relaxes?) a. Which acid/base imbalance can be caused by emesis?

Answer 1

Answer :

vi)

The rate of gastric emptying is regulated by humoral and neural factors. When glucose, fat or aminoacids come in contact with duodenal mucosa inhibitory mechanisms decreases fundic pressure there by slowing gastric emptying of nutrients. Stimulation of gastric emptying is seen with motilin and somatostatin. Also vasoactive intestinal peptides and secretin delay gastric emptying. Actually gastric motility is regulated by gastric myoelectric activity.

1)

As an adult on an average stomach can hold 2.5 ounces of food when empty and relaxed. It can expand to hold 1 quart of food before pressure rises significantly. In other words 4 litres of food or fluid.

a)

The lower portion of stomach with lower body and antrum develops strongest peristaltic contractions.

b)

Gastric muscles are innervated by inhibitory and excitatory nerves. Control by enteric neurons enables complex motor patterns, such as peristaltic reflex, segmentation, regulation of tonic contractions and control of sphincters.

c)

Intestinal cells of Cajal are mesenchymal cells called intestinal pacemakers. They play critical role in small intestinal contractile activity. Located within muscle layers of alimentary tract that mediate communication between autonomic nervous system and smooth muscle.

i)

Sub threshold depolarizations reach threshold by summation.

1)

The action potential is transmitted to other cells via gap junctions creating a peristaltic wave.

2)

BER is basic electrical rhythm.

Its the spontaneous depolarization and repolarization of pacemaker cells in smooth muscles of stomach, small intestine and large intestine.

2)

Pyloric sphincter is a band of smooth muscle cells. It acts as a valve to control flow of food from stomach to duodenum. Prevent entry of food from duodenum to stomach.

a)

Rate of gastric emptying is affected by osmolality, excercise intensity, meal volume, meal temperature, fat and protein in the ingestate, particle size and dietary fiber.

b)

Cholecystokinin, secretin and gastrin inhibit gastric emptying. GLP1 also inhibit gastric emptying via GIVMC. In the interdigestive period motilin and grehlin fasten gastric emptying via GEVMC

vi)

Emesis is forcefully expelling gastric content through mouth. Its also called vomiting.

1)

The noxious stimulation of vomiting center causes contraction of pyloric sphincter. Oesophageal sphincter relaxes. Then reverse peristalsis occurs and gastric content reaches mouth.

a)

Compensated alkalosis occurs by vomiting.