Chapter 62 - Guyton Flashcards Preview

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Flashcards in Chapter 62 - Guyton Deck (23):
1

Layers of intestinal wall from outer to inner layer.

serosa-->longitudinal muscle layer-->circular muscle layer-->submucosa-->mucosa

2

syncytium

when an action potential is elicited anywhere within the muscle mass, it generally travels in all directions in the muscle

3

Most GI contractions occur rhythmically, as a result of which types of waves?

slow waves (these waves will initiate spike potentials which are the true action potentials that cause smooth muscle contraction)

4

The slowness of opening and closing of the __________ channels accounts for the long duration of the action potentials.

calcium-sodium

5

Factors that depolarize the membrane (make it more excitable).

stretching of the muscle, Ach, stimulation parasympathetic nerves that secrete Ach
at their endings, and stimulation by several specific gastrointestinal hormones

6

Important factors that make the membrane potential hyperpolarized (less excitable).

effect of NE or EPI on the fiber membrane and stimulation of the sympathetic nerves that secrete mainly NE at their endings

7

During which type of waves does a significant amount of calcium enter the fibers and cause contraction?

spike potentials

8

Two plexuses of the enteric nervous system.

myenteric - GI movements; submucosal - GI secretion and blood flow

9

Why might the myenteric plexus inhibit some muscles?

it inhibits the pyloric sphincter and ileocecal valve to allow emptying

10

_____________ most often excites gastrointestinal
activity.

Acetylcholine

11

_____________ almost always inhibits gastrointestinal activity.

Norepinephrine

12

Stimulation of parasympathetic nerves causes general ________ in activity of the entire enteric nervous system.

increase

13

The sympathetic fibers to the gastrointestinal tract originate in the spinal cord between segments?

T5-L2

14

The parasympathetic fibers to the gastrointestinal tract originate?

cranial (mainly vagus) and sacral (S2-S4) nerves

15

Strong sympathetic stimulation of the gut results in?

little to no movement of food through the GI tract

16

Primarily stimulates gastric acid secretion.

gastrin

17

At the same time that this hormone causes emptying of the gallbladder, it also slows the emptying of food from the stomach to give adequate time for digestion of the fats in the upper intestinal tract.

CCK

18

In response to gastric juice emptying into the duodenum from the stomach, this hormone has a mild effect on motility of the gastrointestinal tract and acts to promote pancreatic secretion of bicarbonate which in turn helps to neutralize the acid in the small intestine.

secretin

19

Functional types of movement in the digestive tract.

propulsive (peristalsis) and mixed movements

20

Effectual peristalsis requires an active ________ plexus.

myenteric

21

Splanchnic Circulation

blood flow through the gut itself plus blood flows through the spleen, pancreas, and liver

22

Fats absorbed from the intestinal tract are not carried in the portal blood to the liver, as with the other nutrients. What occurs with fat?

absorbed by intestinal lymphatics and then conducted to the systemic circulating blood by way of the thoracic duct, bypassing the liver

23

What is a major value of sympathetic vasoconstriction of the gut and splanchnic blood supply?

to provide muscles and the heart with blood during exercise, or to send blood to other tissues where it is needed during circulatory or hemorrhagic shock