Flashcards in Week 1 Deck (100)
Digestion is the chemical breakdown by enzymatic hydrolysis of complex foodstuffs to smaller, absorbable units.
Absorption is the transfer of products of digestion from the digestive tract to the blood or the lymph
What are the four layers of the digestive tract wall
Mucosa (inner layer)
Serosa (outer layer)
What effect does circular muscle and longitudinal muscle contraction have?
Contraction of circular muscle causes the lumen to become narrower and longer
Contraction of longitudinal muscle causes the intestine to become shorter and fatter.
How are smooth muscle cells in the GI tract arranged?
The cells are arranged in sheets and coupled by gap junctions
Explain the synchronous wave in smooth muscle
- Spontaneous activity is triggered by pacememaker cells (modulated by nerves and hormones)
- This activity causes slow waves which cause hundreds of cells contract at the same time
What is meant by slow waves?
Rythmic membrane depolarisation and depolarisation that spreads from cell to cell via gap junctions
What is the function of ICCs and where are they located?
These are the pacemaker cells which trigger electrical activity.
They are spread between the smooth muscle cells
(located between the longitudinal and circular muscle layers in the submucosa)
In a smooth muscle cell action potential, what is the upstroke and downstroke mediated by?
The upstroke is mediated by voltage-activated calcium channels
The downstroke is mediated by voltage activated potassium channels
What 3 stimuli affect whether slow wave amplitude reaches threshold?
In terms of basic electrical rhythm, what is the frequency of slow waves in the; stomach, small intestine and large intestine?
Stomach - 3 per min
Duodenum - 12 per min
Ileum - 8 per min
proximal colon - 8 per min
distal colon - 16 per min
In the ENS system, what is the purpose of the myenteric plexus and the submucosa plexus
Myenteric plexus - Regulates motility and sphincters
Submucous plexus - Modulates epithelia and blood vessels
Which is more important in terms of innervation of the G.I tract; parasympathetic or sympathetic?
What effects do parasympathetic have on the G.I tract?
Increase blood flow
Increase smooth muscle contraction
Relax sphincters and the stomach
What effects do sympathetics have on the G.I tract?
Increase sphincter tone
Decrease blood flow
Where do parasympathetic and sympathetic fibres synapse?
PARASYMPATHETIC - Ganglion cells
SYMPATHETIC - Prevertebral ganglia
What is peristalsis?
A wave of relaxation followed by contraction that proceeds along the gut in aboral direction
What do circular and longitudinal muscles do in peristalsis?
Circular muscles contract
Longitudinal muscles relax
What is segmentation?
The churning and mixing which is caused by contractions of the circular muscle layer
How many sphincters are there in the G.I tract?
Name the 6 sphincters in the G.I tract
Which two sphincters have skeletal muscle and are therefore usually under voluntary control?
Upper oesophageal sphincter
External anal sphincter
What are the 3 major phases in swallowing?
What diseases can obesity contribute to?
NAFLD (fatty liver disease)
What part of the brain is responsible for neural control of factors influencing energy intake and body weight?
What is CCK and when is it secreted?
- Secreted in the duodenum and jejunum in proportion to meals
What is Ghrelin and when is it produced?
Grehlin is a hunger signal
Its level increase before eating and decrease after eating
What are the two hormones which inform the hypothalamus to alter energy balance?
LEPTIN and INSULIN
Outline the present drug therapy/management for obesity
- Inhibits pancreatic lipase
- Reduces fat absorption in the S.I
- Gastric by-pass surgery
- Restricts calorie intake
- Substantial weight loss
- Can resolve T2DM