Gut motility

Question 1

Which cells cause the spontaneous generation of electrical waves in the GI?

Answer 1

Interstitial Cells of Cajal (ICC’s)

Question 2

Function of interstitial Cells of Cajal?

Answer 2

1. Spontaneous generation of electrical slow waves

2. Conduction of slow waves to smooth muscle

Question 3

Name the 3 cells types for the intrinsic control of GI movement

Answer 3

1. Interstitial Cells of Cajal (ICC)
2. Smooth Muscle Cells
3. Enteric Neurons

Question 4

How are smooth muscle cells arranged in the gut? What is the function of this?

Answer 4

Muscle arranged as a functional syncytium-

allows wave to spread over many cm’s (gap junctions)

Question 5

When ICC’s generate a wave where does it propagate from? Where is the frequency highest?

Answer 5

Propogates in the syncytia from the dominant pace maker cell the body of the stomach.

Greater curvature

Question 6

What is the main function of the Myenteric plexus and the Submucosal plexus?

Answer 6

Primary motility controller

Primary fluid exchange controller

Question 7

Where will you find sensory and motor nerve endings in the gut?

Answer 7

The mucosa

Question 8

Describe the Vago-Vagal reflexes

Answer 8

Efferent nerve- Vagal sensory nerves enter the CNS and transmit to the nucleus tractus solitarius.

The nucleus tractus solitarius. communicates with the paraventricular nucleus and the Dorsal Motor Nucleus before before sensing and afferent neurone to the stomach to induce an effect

Question 9

What is the purpose of GABA in the Vago-Vagal Reflexes?

Answer 9

It helps control the firing rate of the Dorsal Motor Nucleus

Question 10

What are the control systems for the oesophagus, stomach, small intestines, colon and rectum?

Answer 10

Oesophagus- CNS (vagus)
Stomach- Myogenic, ENS and CNS (vagus)
Small intestines- ENS 
Large intestines- ENS and myogenic 
Rectum- ENS and CNS

Question 11

Describe what the Migrating Motor Complex is

Answer 11

Waves of gut contractions which sweep through the stomach or small intestines between meals. It is a house keeping mechanism to clear out the system and move matter towards the colon. It happens in 3 phases ever 90-120mins

Question 12

List the main functions of the Migrating Motor Complex

Answer 12

• Clear undigested material
• Prevent bacteria overgrowth
• Hunger sensations?

Question 13

What is the difference Migrating Motor Complex in the stomach and in the small intestines?

Answer 13

Stomach- vagus dependant

Small intestines- Vagus independent

Question 14

Describe the cephalic,gastric and intestinal phase of digestion

Answer 14

Cephalic-
Thought, Sight, Smell, Taste
Prepares GI tract (secretions begin)
MMCs abolished.

Gastric- Satiation, Early Digestion, Gastric emptying

Intestinal- Feedback & Satiation
Triggered mainly by chemoreceptor activation in small bowel

Question 15

Describe the peristalsis in esophagus

Answer 15

-Primary peristaltic wave occurs on swallowing, when bolus enters esophagus
(striated muscle; vagus)

-Stretch receptors stimulated & local reflex causes a secondary peristaltic wave forcing bolus into the stomach (smooth muscle; ‘back-up’)

Question 16

How does the body prevent reflux?

Answer 16

Closure of LES & tightening of crural fibres

Question 17

What is the function of the proximal stomach? What is the mechanism behind this?

Answer 17

Receptive relaxation - vago-vagal reflex releases CCK

Adaptive relaxation- enteric reflex releases NO from the ENS

Question 18

What causes the formation of pressure in the stomach? How do you relive it?

Answer 18

Formation- formation of gas bubbles resulting in swallowing air while eating/ drinking

Relieving- Relaxation of lower oesophageal sphincter allow gas to escape
- belching/ burbing

This lowers the pressure inside the stomach

Question 19

What is the function of the distal stomach?

Answer 19

1. Propulsion, grinding and mixing

2. Powerful contractions in closed pyloris

Question 20

What is the size of particles emptied into the duodenum?

Answer 20

1-2 mm