PrepGenie

All aspects of the GI processes are controlled by neural, hormonal and paracrine controls, specific control systems include

 Long & Short Reflexes 

GI peptide reflexes 

The autonomous function of the enteric nervous system (ENS) 

Long Reflexes 

Integrated within in the CNS 

May originate in or outside of the GI tract 

Feedforward & emotional reflexes are initiated and integrated entirely outside the GI tract 

Called cephalic reflexes 

Short Reflexes 

Integrated in the enteric nervous system

Initiated by changes in pH, distension, osmolarity, products of digestion 

Submucosal plexus contains the sensory neurons 

Afferent information to ganglia 

Efferent information to submucosal and myenteric plexuses for control of secretion, motility and growth 

GI Peptide Reflexes 

Peptides released by the GI tract may act: 

as hormones 

Secreted into the blood 

Act on accessory organs, other parts of the GI tract or the brain 

As paracrine signals 

Secreted into the lumen or extracellular fluid 

Lumenal signals bind to apical epithelial receptors 

ECF signals act in the immediate vicinity of secretion 

Effect:

Peptides alter secretion and motility 

Alter behaviour related to eating 

Enteric Nervous System 

Allows for the autonomous behaviour of the digestive system 

CNS control is not required for digestive functioning 

Commonalities between ENS and CNS:

 Intrinsic neurons – similar to interneurons of CNS 

Extrinsic neurons – composed of autonomic neurons 

Neurotransmitters and neuropeptides 

Nonadrenergic and noncholinergic receptors - same as adrenergic and cholinergic in CNS 

Glial support cells – similar to astrocytes in CNS 

Diffusion barrier – cells around capillaries in the ganglia are tight, just as the capillaries in the brain, forming the BBB 

ENS acts as its own integrating centre, just as the CNS does 

Cephalic phase

Stimulus-CNS-Vagus nerve-ANSSalivary glands-salivary amylase & lingual lipase 

Enteric Nervous system-increased gastric secretions and motility 

Gastric phase  

Stores food; digests into chyme 

Protects (mucus and HCl)

Intestinal phase

Digestion of proteins, formation of chime in ileum 

Controlled entry of chyme into ileum