Control of the Digestive System

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Smooth
Involuntary muscle found in most regions of the digestive system
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Skeletal
Voluntary striated muscle found in the pharynx, top third of the oesophagus and in the external anal sphincter
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Gut wall
Muscles here are arranged as such: (outer) serosa, longitudinal muscle, circular muscle, submucosa, mucosal muscle, mucosa, epithelial layer (inner)
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Phasic
The rapid contraction and relaxation of smooth muscle, e.g. peristalsis
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Tonic
Sustained contractions and relaxation of muscle, e.g. sphincters
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Interstitial cells of cajal
Pace-maker type cells which are electrically coupled to smooth muscle cells via gap junctions. The help induce motility by depolarising the membrane when acted on by the parasympathetic nervous system, causing contraction
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Mechanism of contraction
Ca2+ binds to calmodulin which allows myosin light chain kinase to phosphorylate myosin. Myosin-P interacts with actin, causing the breakdown of ATP to release energy needed for a contraction
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Myenteric plexus
Stimulation causes increase in tonic contraction, intensity of contractions, rate of contractions and velocity of conduction
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Submucosal plexus
Has sensory functions - it increases secretory activity and modulates intestinal absorption
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Gastro-colic
An excitatory reflex where the innervation of the stomach whilst eating causes a reflex reaction in the colon to stimulate activity, i.e. evacuation of bowels
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Ileo-gastric
An inhibitory reflex where distension of the ileum causes the stomach to stop contracting; this stops propelling matter towards the ileum
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Propulsion
First phase of gastric mixing. The movement of luminal contents down towards the antrum of the stomach and towards the pylorus - small particles sediment at the bottom whilst large ones remain at the top
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Grinding
Second phase of gastric mixing. Material is trapped within the antrum and grinding occurs which breaks down larger particles into small particles. The small ones (
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Retropulsion
Third phase of gastric mixing. Material from the antrum moves to the main body of the stomach (the corpus) where they are pulverised and sheared
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Segmentation
Rings of circular muscle which are contracting and relaxing; allows for production of bolus but the main function is mixing. Occurs in absorptive/fed state
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Peristalsis
Contraction of circular AND longitudinal muscle which illicits propulsion. Occurs in absorptive/fed state
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Migrating motor complex
synchronised, rhythmic changes in electrical and motor activity; usually starts in stomach and progresses down the gut, decreasing in intensity. Occurs every 2 hours. Electrical complex drops off as soon as you eat, and reverts back to segmentation
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Large intestine
It consists of longitudinal muscle layers that are thickened to form 3 muscular bands which run through the length of the colon - taeniae coli
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Colonic rhythmic phase contractions
Colon generates short-duration (no propogation) and long-duration RPCs (propogate over short distances - allows change from semi-solid to solid contents more effectively)
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Giant migrating contractions
Large-amplitude lumen-occluding contractions that propagate very rapidly (about 1 cm/sec) in the distal direction over appreciable distances to produce mass movements. Occurs in both fed and fasting state
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Other cards in this set

Card 2

Front

Voluntary striated muscle found in the pharynx, top third of the oesophagus and in the external anal sphincter

Back

Skeletal

Card 3

Front

Muscles here are arranged as such: (outer) serosa, longitudinal muscle, circular muscle, submucosa, mucosal muscle, mucosa, epithelial layer (inner)

Back

Preview of the back of card 3

Card 4

Front

The rapid contraction and relaxation of smooth muscle, e.g. peristalsis

Back

Preview of the back of card 4

Card 5

Front

Sustained contractions and relaxation of muscle, e.g. sphincters

Back

Preview of the back of card 5
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