Flashcards in Physiology and Pharmacology of Salivary and Gastric Secretion and Gastric Motility Deck (91):
What are the three pairs of salivary glands?
Where is the parotid gland located?
Below ear and over the masseter
Where is the submandibular gland located?
Under lower edge of mandible
Where is the sublingual gland located?
In floor of mouth under tongue
What makes the saliva anti-bacterial?
Lysozymes, lactoferrin and immunoglobulisn
What - in the saliva - digests complex carbohydrates?
How does the saliva neutralise acid?
In the formation of saliva, what does primary secretion?
In the formation of saliva, what does secondary secretion?
What does the formation of saliva require?
What cells produce a primary secretion with Na+, K+, Cl- and HCO3- content similar to plasma, plus mucus and amylase?
What cells modify secretion by removing Na+ and Cl- and to a lesser extent adding K+ and HCO3- no movement of H2O - hence diluting?
How much saliva a minute do we actively produce when salivating?
What two things reflex regulate (neuronal control) the rate of formation of saliva?
1. Simple unconditioned reflex (citrus fruits)
2. Conditioned (acquired) reflex
In the simple (unconditioned) control of salivary secretion, what can activate pressure receptors in the mouth?
In the simple (unconditioned) control of salivary secretion, what happens after pressure receptors are activated by food?
Impulses are send via afferent nerves
Where is the salivary centre?
In the medulla
In the aquired (conditioned) control of salivary secretion, where does the signal go before reaching the salivary centre in the medulla?
What occurs as a result of the salivary centre in the medulla, sending impulses via extrnisic autonomic nerves - both paraysmpathetic and sympathetic stimulation?
Salivary glands increase production
What stimulation is the dominant role in normal saliva production?
What nerves does the parasympathetic stimulation control?
Glossopharyngeal and facial nerves
In parasympathetic stimulation of saliva secretion, what receptors are mediated to produce large volumes of watery saliva?
M3 muscarinic acetylcholine receptors
At what times is sympathetic stimulation dominant at?
Stressful times - dry mouth when nervous!
In the sympathetic stimulation of saliva secretion, what do postganglionic fibres from superior cervical ganglia cause?
Small volume, thick, mucus rich saliva, mediated by B1-adrenoceptors
How much capacity does the stomach have?
50 > 1000ml
What nerve causes relaxation of the stomach to accomodate food from the oesophagus?
What two acids are secreted in the stomach, for the start of protein digestion?
Pepsin and hydrochloric acid
Where does the stomach secrete gastric juice from?
Gastric pits in the gastric mucosa
What wave strength determines the escape of chyme through the pyloric sphincter?
What do gastric factors and duodenal factors govern?
What does distention of the stomach increase?
Motility, due to stretch of smooth muscles
When smooth muscles of the stomach are stretched, what is stimulated, increased and released?
Intrinisc nerve plexuses, increased vagus nerve activity and gastrin release
What reflex can delay empyting of the stomach?
What does the enterogastric reflex do by signals from the intrinisc nerve plexus and autonomic nervous sytem?
Decrease antral peristalic activity
Name two enterogastrones?
Secretin and cholecystokinin (CKK)
What do release of enterogastrones from the duodenum inhibit?
What food substance has an imporant role in delaying gastric emptying required for digestion and absorption in small intestine?
What does acid in the duodenum do to stomach contractions?
Slows it to allow time for neutralisation by bicarbonate from pancreas
What are two main areas of the stomach, important in secretions?
Pyloric gland area (PGA)
Oxyntic mucosa (OM)
What do D cells secrete?
What do G cells secrete?
Where are D cells and G cells located?
In the pyloric gland area
What do chief cells secrete?
What do Enterochromaffin cells release?
What do parietal cells secrete?
Hydrochloric acid and intrinsic factor
Where are parietal cells, enterochromaffin like cells and chief cells found?
In the oxyntic mucosa (OM)
What does gastrin stimulate?
What does somatostatin inhibit?
What are three functions of HCl released from parietal cells?
1. Activates pepsinogen to pepsin
2. Denatures protein
3. Kills micro-organisms ingested with food
What does pepsinogen released from chief cells do?
Inactive precursor of the peptidase, pepsin
What does intrinsic factor released from parietal cells do?
Binds vitamin B12, allowing absorption in the terminal ileum
What 4 receptors does the parietal cell have?
1. Muscarinic ACH receptor 3
2. Gastrin (CCK2) receptor
3. Histamine receptor
4. Prostaglandin receptor
Where does cholinergic nerve (postganglionic parasympathetic) meet, and what does this cause?
Meets M3 receptor on parietal cell, causing HCl release
What happens once gastrin has landed on an enterochromaffin like cell?
Cell releases histamine which acts on H2 receptors on parietal cell to release HCl
What two receptors are present on an enterochromaffin cell?
Gastrin CCK2 receptor
M1 ACh receptor
What does enterochromaffin cell release to cause HCl secretion?
What inhibits gastrin between meals?
What does activation of the PGE receptor on parietal cells do?
Inhibits all stimulating signals, and prevents HCl secretion
During the resting state of the parietal cell, what can be said about the H+/K+ATPase?
It is largely within the cytoplasmic tubulovesicles
What occurs to the H+/k+ATPase when the parietal cell is stimulated?
Traffics to the apical membrane taking residence in extended microvilli
What phase of gastric secretion occurs before food reaches stomach?
What phase of gastric secretion occurs when food is in the stomach?
What phase of gastric secretion occurs when food has left the stomach?
What nerve is activated when smell and taste of food occurs?
The vagal activation stimulates an enteric neurone to do what?
What does ACh do to a D cell, and what does it do to ECL cell?
Inhibits D cell
Stimulates ECL cell
Other than ACh what else does enteric neurone increase?
Increases GRP (gastrin releasing peptide)
What does the GRP from enteric neurone, during eating stimulate?
G cells to secrete gastrin etc
What two factors in the gastric phase. cause increased secretion, and what do they act on to achieve this?
Distension - enteric neurone
Protein digestion products - G-cell
What does a low pH in the stomach, drive secretion of?
What class of drugs block competitevly and an example of one is pirenzepine?
Muscarinic receptor antagonists
What class of drugs (ranitidine) block competitively the H2 receptor on parietal cells?
H2 receptor antagonistst
What drugs block cyclo-oxygenase (which stimulates prostaglandin receptor on parietal cells), and so increase acid secretion?
NSAIDs block irreversibly
What drugs (omeprazole) block by covalent modification at the H+K+ATPase?
What three effects does locally produced prostaglandins (PGE and PGI) have in relation to protection of the mucosa from attack by HCl and pepsin?
1. Reduce acid secretion
2. Increase mucus and bicarbonate secretion
3. Increase mucosal blood flow
What term is given to ulcers in an area where the mucosa is exposed to hydrochloric acid and pepsin (stomach/duodenum)?
What reduces prostaglandin formation (COX 1 inhibition)?
What can gastric damage due to long-term NSAID treatment be prevented with?
PGE analogue (misoprostol)
Name a drug that inhibits basal and food stimulated gastric acid formation and maintains secretion and mucus and bicarbonate?
Misoprostol (stable PGE analogue)
What, protected in teh mucus gel, secretes agents causing a persistent inflammation that weakens the mucosal barrier?
Name a syndome that involves a rare, gastrin producing tumour?
What condition causes heightened vagal tone, leading to acid hypersecretion?
What drugs inhibit the membrane inserted (micro villi) H+/K+dependent ATPase (proton pump)?
What sort of proton pumps are not inhibited by PPIs?
Ones in the tubulovesicles
What kind of drugs are PPIs, because they are inactive at neutral pH (proton pump hidden in tubulovesicles)?
Where are absorbed PPIs delivered to?
The secretory canaliculi of the stomach
When PPIs are in the secretory canalicula of the stomach, what are they activated to?
Sulfenamide (then block lumenal sulphydrl groups of membrane inserted proton pump)
What is a complex of aluminium hydroxide and sulphated sucrose?
Name two mucosal strengtheners?
What does sucralfate release to acquire a strong negative charge?