Physiology: nervous system and muscles

Question 1

What cell type enables the spontaneous contraction of the GIT?

Answer 1

Interstitial cells of Cajal

Question 2

Interstitial cells of Cajal:
- What cell type are they? Thus, are they technically part of the myenteric plexus?
- What is the name of the electrical activity they generate?

Answer 2

Non contractile SMC - not neurons, so technically they aren’t part of the myenteric plexus.
Slow waves

Question 3

Interstitial cells of Cajal:
- Do they have intrinsic activity?
- Can their activity be modulated by neuronal/hormonal factors?
- Do they always reach threshold?

Answer 3

Yes
Yes
No
They are connected to SMCs by gap junctions. APs spread

Question 4

Interstitial cells of Cajal
- How does their APs lead to SMC contraction?
- Can APs be additive and make contraction larger?

Answer 4

Interstitial cells of Cajal and SMCs are electrically coupled by gap junctions.
AP spreads from ICC to SMC.
Causes calcium to be released from intracellular stores - leading to contraction.

Yes

Question 5

What are the 4 divisions of nervous system in the GIT?

Answer 5

Question 6

What are the 2 enteric NS plexuses?

Answer 6

Submucosal plexus and myenteric plexus

Question 7

Submucosal and myenteric plexus

Answer 7

Question 8

In the enteric NS:
- How many NTs are involved?
- Can neurons contain multiple NTs?
- 3 peptides that are excitatory (result in contraction?)
- 3 peptides that are inhibitory (result in relaxation?)

Answer 8

> 20
Yes
Histamine, Ach, substance P
NO, vasoactive intestinal polypeptide (VIP), dopamine

Question 9

Does the circuitry of the ENS follow the ANS pattern?

Answer 9

No

Question 10

Role of the somatic NS?

Answer 10

Controls skeletal muscle sphincters: upper oesophageal and external anal sphincters