5.7.2. Overview of the Small Intestines - Intestinal Motility

Question 1

What are the 2 types if Intestinal Motility?

Answer 1

1. Segmentation

2. Peristalsis

Question 2

What is Segmentation, in relation to the Intestinal Motility?

Answer 2

Alternating contraction and relaxation of adjacent parts of the Small Intestine

Question 3

How does Segmentation affect the contents?

Answer 3

The Contents move, upon contraction of one part, to the adjacent relaxed parts

Question 4

What is the purpose of Segmentation?

Answer 4

1. The thorough mixing of contents with Digestive Enzymes

2. Encouraging the contact of Chyme with the Absorbing Surface

Question 5

What causes the contraction in Segmentation?

Answer 5

The Intestinal Basic Electrical Rhythm (BER)

Question 6

What initiates the Intestinal Basic Electrical Rhythm (BER), with regards to Segmentation?

Answer 6

The depolarization of the “Pacemaker Cells”

Question 7

Where are the “Pacemaker Cells” located, with regards to Segmentation?

Answer 7

In the Longitudinal Muscle of the Muscularis Externa

Question 8

What do the “Pacemaker Cells” produce, with regards to Segmentation?

Answer 8

Oscillations in the Membrane Potential

Question 9

What do Oscillations in the Membrane Potential result in, with regards to Segmentation?

Answer 9

1. The Threshold being reached
2. Action Potentials being Fired
3. Contraction of the Muscle Occuring

Question 10

What determines the Strength of Contraction, with regards to Segmentation?

Answer 10

1. Parasympathetic innervation increases the Strength of Contraction
2. Sympathetic innervation decreases the Strength of Contraction

Question 11

Is the Basic Electrical Rhythm (BER) effected by the Autonomic Nervous System, with regards to Segmentation?

Answer 11

No, just the Strength of Contraction is

Question 12

What is determined by the Basic Electrical Rhythm, with regards to Segmentation?

Answer 12

The Frequency of Segmentation

Question 13

How does Segmentation change, as you move more Distally down the Intestinal Tract?

Answer 13

It Decreases

Question 14

When does Peristalsis (the second type of Intestinal Motility) occur?

Answer 14

Following the Absorption of Nutrients

Question 15

What is the Migrating Motility Complex (MMC)?

Answer 15

A Pattern of Peristaltic Activity

Question 16

Where does the Migrating Motility Complex (MMC) travel from / to?

Answer 16

From - The Gastric Antrum

To - The Terminal Ileum

Question 17

When does the Migrating Motility Complex (MMC) cease?

Answer 17

When food enters into the Stomach

Question 18

What is the function of Migrating Motility Complex (MMC)?

Answer 18

1. To move undigested material into the Large Intestine

2. To Limit the Bacterial Colonization in the Small Intestine

Question 19

By what “Laws” does Peristalsis act?

Answer 19

“The Law of the Intestine”

Question 20

What is Peristalsis mediated by?

Answer 20

The Myenteric Nervous Plexus

Question 21

When is Peristalsis activated?

Answer 21

1. The Bolus / Chyme distends the Distal Smooth Muscle (in front of it)
2. The Proximal Smooth Muscle to the Bolus / Chyme contracts
3. The Distal Smooth Muscle the the Bolus / Chyme relaxes

Question 22

What is the Gastroileal Reflex?

Answer 22

Gastric Emptying causes an increase in Segmentation in the Ileum

Question 23

What occurs in the Gastroileal Reflex?

Answer 23

1. Opening of the Ileoceacal Valve (Sphincter)
2. Entry of the Chyme into the Large Intestine (Colon)
3. Distension of the Colon
4. Reflex Contraction of the Ileocaecal Sphincter to prevent Backflow