Flashcards in Principles of Neuroscience Lecture 11, The Enteric Nervous System Deck (27)
Describe how bacteria are important in digestion
Bacteria are important in many different animals
They break down molecules that we can't to provide us with energy (short chain fatty acids)
In humans, gut bacteria in the mucosa in the ascending colon provide a large portion of our energy by breaking down cellulose.
Bacteria can influence the brain
Which two major divisions of the nervous system are involved in the neural coordination of digestion?
Somatic nervous system
Visceral nervous system
Which process are under voluntary control ?
Which processes are under involuntary control?
Gastric acid secretion
Everything from oesophagus -> anus
What happens when we smell and see food?
How is this mechanism neurally controlled?
The Cephalic phase
This is salivation, gastric acid secretion and gastric relaxation
The Cephalic response is controlled by the parasympathetic nervous system, and the vagus nerve in particular
Which nerve from the CNS is most important for digestion?
What factors influence the magnitude of the response in the Cephalic phase?
Memory of the food that we are smelling/seeing
The palatability of the food.
Describe the processes that occur when food is in the mouth, and how these are controlled neurally
These are all under voluntary control via the cortex of the brain
Motor cortex involved in the motor patterns of tongue and swallowing
However, salivation is involuntary, Parasympathetic division of the autonomic nervous system
Describe the processes when food passes through the oesophagus, and how this is controlled neurally
Primary peristalsis is controlled by the vagus nerve
Secondary peristalsis is the enteric nervous system
Sphincter operation is autonomic, via vagus nerve
What diseases involve problems with the oesophagus?
Achalasia: sphincters don't work and increase muscle tone of the oesophagus lead to difficulty ingesting food
What processes occur when food enters the stomach? How are these neurally controlled?
Stomach responses are controlled by the vagus nerve (parasympathetic)
Pacemaker cells in the Antrum coordinate muscle contraction and bile release via Interstitial Cells of Cajal
What is the lower section of the stomach called?
What is important about the cells of this region?
The wall of the Antrum has pacemaker cells
What do the interstitial cells of cajal do?
Where are the ICCs located?
These are located along the gastrointestinal tract
Coordinate bile release and muscle contraction
What are the three main processes that occur in the intestines?
Why are the intestines described as a chemical refinery?
They break up (digest) food
Prepare waste for excretion
What is the major control of the intestines?
What is special about this?
The enteric nervous system
The enteric nervous system is intrinsic to the digestive system and functions basically in isolation from the brain
What are the three functional and locational divisions in the small intestine?
1. Duodenum: digestion and absorption (nutrients)
2. Jejunum: digestion and absorption (nutrients)
3. Ileum: absorption of water (colon also does this)
Where is the enteric nervous system?
It spans the whole length of the gut
What is the brain's function in the enteric nervous system?
It moderates the function of the E.N.S.
Describe the 'in vitro' segment of guinea pig intestine experiment
A segment of the gut from a guinea pig, when isolated but with fatty acids present inside, will undergo mixing contractions and peristalsis
Describe the five different types of neurons in the enteric nervous system
1. Intrinsic sensory neurons
2. Excitatory neurons
3. Inhibitory neurons
5. Secretomotor neurons
What is meant by the 'recurrent sensory network'?
This describes the phenomenon in the enteric nervous system of sensory neurons, as well as being activated by movement in the gut and chemical stimuli, also being activated by other sensory neurons.
One would think this would cause a positive feedback loop leading to spasms
Which major nerve is important, and to which division of the nervous system does it belong?
The vagus nerve.
It belongs to the visceral nervous system
For which processes is motor pattern generation important?
Chewing and swallowing
What generates the motor patterns?
The spinal cord
Which processes have cortical involvement, motor cortex?