Cells responsible for contraction in Stomach/intestine?

[stronghold]

Cajal cells or stomach stretch receptors?

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[stronghold]

???????

 

[Transposony]

Please correct me if I am wrong but I think Cajal cells ARE the stretch receptors in GIT.

 

[StIGMA]

Smooth muscle cells. Where the hell do you go to school?

 

[Anastomoses]

cajal cells are specialized to work with smooth muscle to cause the slow waves of electrical activity; these waves do not cause contraction except in the stomach sometimes. So it's a complex. Most contraction is due to the myenteric plexus acting on smooth muscle cells, I think.

 

[Transposony]

Specialised cells known as interstitial cells of Cajal (ICCs), distributed in specific locations within the tunica muscularis of the gastrointestinal tract, serve as electrical pacemakers and mediators of enteric neurotransmission.

Neurotransmitter released from enteric motor neurones binds primarily to receptors expressed by interstitial cells of Cajal (ICCs). Activation (depolarisation or hyperpolarisation) of neighbouring smooth muscle cells occurs by conduction of excitatory or inhibitory junction potentials via gap junctions between ICCs and smooth muscle cells. Thus terminals of enteric motorneurones, interstitial cells of circular and longitudinal muscle (IC-IM), and smooth muscle cells form functional units that release transmitter and mediate and transduce neural inputs into mechanical responses. IC-IM appear to be a critical component in these functional units. The physically close association between varicose nerve terminals and ICCs suggests specialised neuro-ICC junctions may be the primary sites of innervation.

In the gastrointestinal tract, phasic contractions are caused by electrical activity termed slow waves. Slow waves are generated and actively propagated by interstitial cells of Cajal (ICC). The initiation of pacemaker activity in the ICC is caused by release of Ca2+ from inositol 1,4,5-trisphosphate (IP3) receptor-operated stores, uptake of Ca2+ into mitochondria, and the development of unitary currents. Summation of unitary currents causes depolarization and activation of a dihydropyridine-resistant Ca2+ conductance that entrains pacemaker activity in a network of ICC, resulting in the active propagation of slow waves. Slow wave frequency is regulated by a variety of physiological agonists and conditions, and shifts in pacemaker dominance can occur in response to both neural and nonneural inputs. Loss of ICC in many human motility disorders suggests exciting new hypotheses for the etiology of these disorders.

 

[CaliAtenza]

i'd never heard of Cajal cells before....

 

[stronghold]

Thanks guys. So if you get a question like that, without having muscles choice, which one will you pick? The point that makes me confused, BRS and UW frankly differentiate between slow waves (induced by Cajal cells?) and actual contraction

 

[Anastomoses]

Thanks guys. So if you get a question like that, without having muscles choice, which one will you pick? The point that makes me confused, BRS and UW frankly differentiate between slow waves (induced by Cajal cells?) and actual contraction

Well, stretch definitely leads to contraction. By vagus and myenteric reflexes. When I learned about Cajal cells via Guyton, the distinction was also made pretty clear that Cajal cells don't in and of themselves lead to contraction. They are mainly responsible for the slow wave (baseline) voltage.

But I do recall that stomach was a place that sometimes the slow waves could lead to contractions, not to make things more confusing. In short, if all 3 of these very reputable sources are making the distinction that interstitial Cajal cells aren't responsible for contraction - take heed.