Regulation of Gut Function Flashcards
What is the intrinsic nervous system of the gut called?
The enteric nervous system
What two divisions can the autonomic nervous system be split into?
Sympathetic and parasympathetic
Where do sympathetic pre-ganglionic neurones arise from?
From thoracic and lumbar spinal cord
Where do sympathetic pre-ganglionic neurones that innervate the stomach arise from?
T6-9
Where do sympathetic pre-ganglionic neurones that innervate the colon arise from?
L2-5
Which ganglia do postganglionic neruones innervating the stomach arise from?
Coeliac ganglion
Which ganglia do postganglionic neruones innervating the small intestine arise from?
Superior mesenteric ganglion
Which ganglia do postganglionic neruones innervating the colon arise from?
inferior mesenteric and pelvic ganglion
which neurotransmitter is involved in the sympathetic nervous system of the GI system?
Norepinephrine
What effect does the sympathetic nervous system have on the activities of the GI tract?
Activation of sympathetic nervous system inhibit activities of gastrointestinal tract
Which nerves supplies parasympathetic innervation to stomach, small intestine and proximal colon?
The vagus nerve
Where do parasympathetic preganglionic neurons originate from?
the dorsal vagal complex within brainstem from sacral spinal cord.
What neurotransmitter is used for parasympathetic nervous control?
ACh
What effect does activation of the parasympathetic nervous system have on the activities of the GI tract?
stimulates the GI Tract
Are post-ganglionic neruones myelinated?
No
Where is the sympathetic ganglia located?
Nerve the spinal cord in a row
Where is the parasympathetic ganglia located?
near the target organ
What does the enteric nervous system allow?
The orchestration of gut function independently from the brain due to the presence of many microcircuits
Which layers of the gut wall contain nervous plexuses?
Submucosa and Muscularis
What nervous plexus is found in the muscularis propria?
Auerbach’s (Myenteric) Plexus
What is the role of the myenteric plexus?
Controls gut motor function by regulating the tone, velocity and intensity of contractions
Which nervous plexus is found in the submucosal layer of the gut wall?
Meissner’s plexus
What does Meissner’s plexus do?
- senses the local environment (gut lumen)
- controls secretion, blood flow, epithelial and endocrine cell function
Describe the local reflex which the enteric nervous system displays?
- Food enters gut lumen and stretches the intestinal smooth muscles
- Distension of the gut causes stimulation of the sensory neurons in the myenteric plexus
- Chemicals in food stimulates sensory neurons in submucosal plexus
- Sequential contraction/relaxation of circular and longitudinal muscle by inhibitory/excitatory neurotransmitter cause peristalsis, which allows food to move along the GI tract
Describe how circular and longitudinal muscles interact to allow peristalsis?
- Circular muscle contracts behind the bolus of food
- Longitudinal muscle contracts and relaxes ahead of the bolus, allowing t to receive the bolus
What do the stimuli of pain, nausea and fullnes stimulate?
The enteric nervous system
What are the actions of the sympathetic nervous system on the GI Tract?
reduces peristalsis
reduces absorption
reduces secretion
reduces blood flow (via enteric nervous system and also directly)
What are the actions of the parasympathetic nervous system on the GI Tract?
increases peristalsis
increases absorption
increases secretion
increases blood flow
What is the consequence of Hirschsprung’s Disease?
Intestinal distension proximal to aganglionic segment of bowel
Why does Hirschsprungs disease lead to an enlarged distal bowel?
Congenital absence of ganglion of myenteric and submucosal
Tonal contraction without reciprocal relaxation
What are the gut endocrine hormones which are secreted by enteroendocrine cells into the blood stream?
gastrin, cholecystokinin, secretin, glucose-dependent insulinotropic peptide (GIP), motilin
Which gut hormones have endocrine and paracrine mechanisms?
glucagon-like peptide-1 (GLP-1), pancreatic polypeptide, and peptide YY