Peristaltic reflex
The peristaltic reflex is the reflex contraction and relaxation of certain muscles of the intestine, which are used to transport the intestinal contents. In principle, this reflex is responsible for the propulsive peristalsis of the intestine.
The reflex is triggered by intrinsic, primarily afferent neurons (IPAN) in the intestinal wall. These are sensitive to stretching, such as that caused by the intestinal contents (bolus) . This neuron projects via cholinergic excitatory (i.e. excitatory) synapses onto several interneurons, which in turn activate orally and aborally located motor neurons via the same type of synapses. Orally located motor neurons form excitatory cholinergic synapses with circular muscles located orally from the bolus, and aborally located motor neurons form inhibitory synapses with circular muscles located aborally from the bolus with the neurotransmitters nitric oxide and vasointestinal peptide . In addition, the first interneuron activates motor neurons that project excitatory onto the longitudinal muscles. Ultimately, the tone of the oral circular muscles increases, as well as the longitudinal muscles and the tone of the aboral circular muscles decreases. This will advance the bolus.
The autonomic nervous system can intervene in this system: Postganglionic sympathetic and preganglionic parasympathetic neurons project onto the motor neurons. Parasympathetic fibers excite the motor neurons for the circular and longitudinal muscles and inhibit the motor neurons of the sphincter, while sympathetic fibers do exactly the opposite.
Individual evidence
- ↑ a b Jan C. Behrends et al .: Dual series: Physiology . 3. Edition. Thieme, Stuttgart 2016, ISBN 978-3-13-138413-3 , p. 565 .