Lab 6 - Digestion Flashcards
What substances taste salty?
Neutral salts of strong acids and bases
Histamine acts on which receptors?
H2 receptors
What effect has verapamil?
Ca2+ channel inhibitor
Effects of acetylcholine is mediated by which type of receptors?
Muscarine Ach receptors
Which effect has acetylcholine on gastric SM?
Stimulating
Which gastric juice producing cells are influenced by Acetycholine?
Parietal Cells
What enzyme initiates SM contraction?
MLCK = Myosin Light Chain Kinase
What pathway does muscarinic Ach receptors activate?
G-protein phosphlipase C pathway
ED50?
Active ingredient concentration needed for half maximal muscle contraction
Examples of bitter taste?
Several alkaloids: strychnine, quinine, several glycosides, ethers, some Mg2+ and Ca2+ salts, ammonium compound and sulphates
Examples of sour taste?
Hydrogen ion dissociating molecules – buffers of saliva alters sensation
What dissociates the actomyosin complex?
Myosin phosphatase (MP) enzyme
How to measure the basal HCl consentration?
By titratin 0.01 M NaOH, after adding phenophtalein
Where can you find the food eaten last?
in the cardia
Which cells does gastrin have effect on?
Parietal cells
In which way does verapamil inhibit muscle contraction?
Ca2+ channel inhibition
What substance act on pariental cells?
Acetylcholine, Histamine and Gastrin
Where in gastrointestinal tract does ptyalin act?
In the stomach
Mixture of stomach content is called?
Chymus
The mixture of food structure resembles what?
onion
The taste pathway?
fascial (VII), glossopharyngeal (IX) and vagus (X) are involved
Feed taken up first is at ?
At the curvature major
What does the next part of the feed thats not in contact with the gastric wall do?
Allowis the ptyalin enzyme from the saliva to function further.
What finally mixes the different layers?
Gastric peristalsis, and the saliva enzymes are inactivated.
Gastric juice is secreted by?
The chief (peptic) and parietal cells in the fundus region of the gastric mucosa.
What does Parietal cells produce?
HCl, while chief cells produce pepsinogen.
What does cheif cells produce?
Pepsinogen.
HCl secretion of the parietal cells is regulated by ?
Neuronal and endocrine mechanisms.
What activates the Parietal cells?
Acetylcholine (neurotransmitter), histamine (paracrin mediator), and gastrin (hormone)
What does the The central nervous system have an effect on?
The central nervous system has an effect on gastric juice secretion through the vagus nerve
What does Acetylcholine released from cholinergic postganglionic do?
Directly stimulates the parietal and ECL (enterochromaffin-like) cells.
What does Acetylcholine indirectly do?
indirectly stimulates the G cells as well.
Histamine is produced by?
ECL (enterochromaffin-like) cells
What does Histamine do?
It diffuses to the parietal cells and acts on H2 receptors.
What is Histamine production primarily regulated by?
Gastrin and the vagus nerve.
What is Gastrin secreted by?
Gastrin is secreted by G cells in the antrum region
What is the effect of gastrin secretion?
It increases HCl secretion by stimulating the parietal cells and the H cells as well.
What regulates the function of a G cell?
Vagus nerve and gastric pH.
Where do you find the stomach?
In the left side of the body, covered by the guts and the liver.
Pharmacological effect and Effect on smooth muscles in the GI tract of Acetylcholine?
parasympathicomymetic
stimulation
Pharmacological effect and Effect on smooth muscles in the GI tract of atropine?
parasympathicolytic
inhibition
Pharmacological effect and Effect on smooth muscles in the GI tract of norepinephrine?
sympathicomymetic
sphincter: constriction, elsewhere: relaxation
Pharmacological effect and Effect on smooth muscles in the GI tract of Verapamil?
Ca2+ channel inhibition
inhibition
What kind of contraction are the contractions of the GI tract?
Rhythmic.
What are the “slow waves”?
The frequency is determined by the so-called slow waves:
the continuous change in the membrane potential of smooth muscle cells
When will spike potentials appare?
When the slow waves reach the threshold potential due to membrane depolarizing effects
What is spike potentials?
Action potentials in the smooth muscle cells caused by a calcium influx that elicits muscle contraction.
What initiates the muscle contractions?
MLCK (myosin light chain kinase) enzyme after intracellular Ca2+ has reached a certain level.
What dissociates the actomyosin complex?
Phosphatase (MP) enzyme.
In smooth muscles, what is the efect of acetylcholine (parasympathetic neurotransmitter)?
Mediated by type M(3) muscarinic Ach receptors.
What does the M(3) muscarinic Ach receptors do?
Activate the G-protein – phospholipase C pathway,
What is caused by the activation of the G protein?
Increase in the intracellular calcium level thus activating the MLCK (myosin light chain
What is the overall effect of the acetylcholine?
An increase in the contraction rate and spontaneous activity of GI smooth muscles.
What can inhibit the effect of different transmitters?
With specific receptor antagonistic drugs.
What happens in case of competitive antagonism?
The transmitter (agonist) and the antagonist compete for the same binding sites.
What happens in case of reversible competitive antagonism?
The binding of the antagonist can be eliminated by increasing the concentration of the agonist.
What inhibits the muscarinic Ach receptors?
Atropine
What is the competitive antagonist of acetylcholine?
Atropine
Is it posible to block non-spesific block the smooth muscle function in another way than by using drugs acting on different receptors?
Yes, by administering calcium channel blockers.
What blocks calcium channels thus the activation of MLCK enzyme?
Verapamil
What happens when verapamil blocks the calcium chanels?
Muscle contraction is hindered.
What is the substance that compleetly blocks the effect of ED50 acetylcholine on the smooth muscle sample?
Varapamil
Where is the location of taste sensation?
On the surface of the tounge
Name some of the multiple physiological roles of the sensation of taste.
Food checking,
inducing saliva and gastric juice production
(cephalic phase), etc
What is the receptor cells of taste sensation are organized into?
Taste buds
What does the taste sensation pathway include, and what does they do?
Facial (VII), glossopharingeal (IX), and vagus (X) nerves and projects sensation to the solitary tract
What are the 4 basic tastes?
- Sweet (sugars e.g.: saccharine, saccharose)
- Salty (neutral salts of strong acids and bases)
- Sour (hydrogen ion dissociating molecules – buffers of saliva alters sensation)
- Bitter (several alkaloids e.g.: strychnine, quinine, several glycosides, ether, some Mg2+ and Ca2+ salts, ammonium compounds, sulphates)
