Flashcards in Pharmacology Deck (85):
What are the hollow organs separated by?
What do sphincters do?
Control the movement of food
What occurs in the mouth and oropharynx?
Chopping of food, lubrication, beginning of carbohydrate and fat digestion and propel food to oesophagus
What is the function of the oesophagus?
To deliver food to the stomach
What the the main function of the stomach
Temporary storage of food
What else does the stomach do?
Continues digestion of carbs and fat and initiates the digestion of proteins
What is the main function of the small intestine?
Principal site of digestion and absorption of nutrients
What 3 structures does the small intestine consist of?
Duodenum, jejunum and ileum
What is the main function of the large intestine?
The reabsorption of fluids and electrolytes back into the body. It also stores fecal matter before regulated expulsion
What 7 structures is the large intestine made up of
Cecum, Ascending colon, Transverse colon, Descending Colon, Sigmoid Colon, Rectum, Anus
How many accessory structures are there?
Name the accessory structures
Salivary glands, liver and gall bladder and the pancreas
What is the function of the salivary glands
What is the function of the liver and gall bladder?
Storage and secretion of bile which aids in fat digestion
Where is the location of the pancreas?
Inferior to the stomach
Gastrointestinal motility is due to what?
The activity of smooth muscle
What happens to the lumen when circular muscle contracts?
Becomes long and narrow
What happens to the intestine when the longitudinal muscle contracts?
It becomes short and fat
What happens when the muscularis mucosae contract
There is a change in absorptive area and the secretory area of mucosa
What is motility?
A mechanical activity mostly involving smooth muscle
Name the 3 movements of motility
Propulsive, Mixing and Tonic
Give an example of propulsive
An example of mixing
elecrtolytes and digestive enzymes
Give an example of tonic movement
Where can secretion occur?
In the GI tract itself
The biochemical breakdown of chemically complex foodstuff into smaller, absorbable units
What are carbohydrates broken down to? and name an enzyme for this process
Monosaccharides and amylases
What are proteins broken down to? Name an enzyme for this process
AMino acids, dipeptides and tripeptides. Proteases or dipeptidases
What are fats mostly broken down to? What is the enzyme mediating this?
Monoglycerides and free fatty acids. Lipases
The transfer of absorbable products of digestion from digestive tract to the blood or lymph.
Does the structure of the digestive wall vary at all?
No - It is roughly the same throughout
Name the layers of the digestive wall from innermost to outermost
Mucosa, Submucosa, Muscularis externa, Serosa
How do skeletal muscles cells function with other skeletal muscle cells
Independently of eachother
How do smooth muscle cells function with other smooth muscle cell?
Coupled by gap junctions
What do gap junctions in smooth muscle allow for?
Spread of electrical current from cell to cell forming a functional synctium in which 100s of cells are depolarised and so contract at the same time.
What happens if one smooth muscle cell depolarises?
Its current will be spread to neighbouring cells so the whole sheet of muscle will contract simultaneously
What is the spontaneous activity of smooth muscle modulated by?
Intrinsic and extrinsic nerves and also numerous hormones
How does spontaneous activity of smooth muscle occur?
Slow waves in the stomach, small intestine and large intestine.
What does slow wave electrical activity determine?
The maximum frequency, velocity and direction of rhythmic contractions which occur in smooth muscle sheets
What drives slow wave electrical activity? And what are they?
Interstitial Cell of Cajal. Pacemaker cells
When will contraction not occur in terms of slow waves?
When the amplitude is insufficient to trigger action potentials
What is the force in slow waves related to?
The number of action potentials discharged
Where are ICCs located
Between the circular and longitudinal muscle layers and in the submucosa
What are slow waves representative of?
Rhythmic patterns of depolarisation, followed by repolarisation
The upstroke of the slow wave is regulated by what?
voltage activated Ca++ channels
The downstroke of the slow wave is regulated by what?
voltage activated K+ channels
What do slow waves determine?
The basic electrical rhythm (BER)
What 3 things does the threshold being met depend on?
Neuronal stimuli, hormonal stimuli and mechanical stimuli
When is BER at its lowest and where?
During the fed stage in the stomach
What is the average number of waves per minute in the stomach?
What is the average number of waves per minute in the duodenum?
What is the average number of waves per minute in the terminal ileum?
What is the average number of waves per minute in the proximal colon?
What is the average number of waves per minute in the distal colon
What is the importance of the distal colon having double the number of waves of the proximal colon?
It favours backwards movement and retention
What would happen if the body did not have different slow waves in different places?
The body would lose substances as loose stool
What is the most important factor in terms of autonomic innervation?
What is the main role of the parasympathetic system?
To increase blood flow, secretions and contractions
What inhibitory factors are exerted by the parasympathetic system?
Relaxation of sphincter and stomach
Inhibitory actions of the sympathetic system exert what?
Decrease motility, blood flow and secretions
What are the 3 broad types of neurones in the Enteric Nervous system
Sensory neurone, interneurone and effector neurone
Peristalsis is an example of what type of reflex?
Give an example of a short reflex
Interstino-interstinal inhibitory reflex
The gastroileal reflex is an example of what type of reflex?
Name 3 components that make up sensory neurones
Chemoreceptors, Thermoreceptors and mechanoreceptors
What is the role of the interneurones in the ENS
To coordinate reflexes and initiate simple functions such as peristalsis
What 5 things do the effector neurones supply?
The longitudinal and circular muscle layers, secretory epithelium, endocrine cells and blood vessels
A wave of contraction that normally preceeds along the gut wall
What route does peristalsis take?
Where is the propulsive segment
Behind the bolus
Where is the receiving segment?
Infront of the bolus
In terms of relaxation and contraction, what occurs in the propulsive segment?
Relaxation of the longitudinal muscle and contraction of the circular muscle
In terms of relaxation and contraction, what occurs in the receiving segment?
Relaxation of the circular muscle and contraction of the longitudinal muscle
How is contraction accomplished?
The release of a transmitter by excitatory neurones.
What neurotransmitters are found during contraction?
ACh and substance P (peptide substance) are the neurotransmitters
How is relaxation accomplished?
The release of VIP and Nitric Oxide from inhibitory motoneurone
What does segmentation cause?
Rhythmic contractions of circular muscle
Where does segmentation occur?
In the small intestine
Where are tonic contractions found?
How many sphincters are there?
Name the first 3 sphincters
Upper oesophageal, Lower oesophageal and pyloric
Name the last 3 sphincters
Ileocecal, Internal and External sphincters
What is the function of the uvula
It helps seal off the nasal passage
What is the function of the tongue
To guide food towards to oesophagus