5.3 Digestion Flashcards
What does digestion involve? (2) - Not the process
- Enzymatic breakdown of foods (3)<div>2. Bacterial fermentation (2)<br></br></div>
Enzymatic breakdown of foods (3)
<ul> <li>Proteins > Amino Acids</li> <li>Sugar & Starch > Simple Sugars (Glucose & Fructose)</li> <li>Lipids > Fatty Acids and Glycerol</li></ul>
Bacterial fermentation (2): overview and importance
<ul> <li>Bacterial fermentation (by gut microbiota) breaks down cellulose into short chain fatty acids (SCFAs) and sugars</li> <li>SCFAs (acetate, propionate, butyrate) are important for: (a) Energy metabolism in mucosa of human colons, and (b) are important signalling molecules</li></ul>
Why do animals with active lifestyles (primates) depends on food high in simple sugars and proteins? (1)
They are relatively easy to digest and we can harness a large amount of energy from them
Networks involved in digestion? (2)
Somatic NS<br></br>Visceral NS<br></br>
What happens when we see/smell food? (2)
“Initiate <span>cephalic phase</span> of digestion (aka Pavlov classical conditioning).<div><br></br></div><div>We don’t need to have ingested food to initiate this response, but food in the mouth initiates this response</div>”
What are some things, or some factors, that affect this cephalic phase? (3)
<ul> <li>Salivation, gastric relaxation and gastric acid secretion occur via parasympathetic NS innervation from the vagus nerve</li></ul>
<ul> <li>The more palatable the food, the greater the response (requires memory of previous meals)</li></ul>
<ul> <li>Depends on hunger and appetite, which is partly determined by the nature of previously consumed foods</li></ul>
Digestion: Specific Mouth (2)
<ul> <li>Chewing and Swallowing: Motor pattern generator in the brainstem, voluntary processes (hence, cortical involvement)</li> <li>Tongue: Set of voluntary muscles controlled by motor cortex (think about homunculus representations)</li></ul>
Stomach: Neural Features (2) Part one
Major peripheral control network under substantial central regulation from the parasympathetic NS via the vagus nerve (lesser role for sympathetic NS)<div><br></br></div><div>Vagus axons do not directly innervate muscles of the stomach, but its efferent contact some enteric neurons, activating motor patterns in the stomach. (Note: Vagus still controls a variety of secretory processes)</div>
Stomach: Neural Features (1) Part two
ENS is less studied than the vagal control system, and may act like parasympathetic ganglion, being controlled by the PSNS, with some autonomy
StomachNon-Neural (1)
Non-neural pacemaker cells in the antrum (interstitial cells of Cajal; ICC) generate a rhythmic depolarization of the muscle, causing 3-6 contractions per minute, which powerfully mixes the stomach contents
Intestines: Where does digestion occur?
Digestion occurs in the duodenum and jejunum
Intestines: Where does absorptions of nutrietns and water occur? (2)
<ul> <li>Absorption of nutrients occurs in the duodenum and jejunum</li> <li>Absorption of water occurs in the ileum and colon</li></ul>
Intestines: Where does propulsion occur? (1)
<ul> <li>Occurs along the whole length of the small and large intestines</li></ul>
Neurons of the ENS (1)
All types of neurons are required for the complex behaviours performed by the ENS (e.g., mixing and propulsion). They are present and mixed at every ganglia (unlike spinal cord).
