Physio - Git

Front 1

What are short reflexes in git?

Back 1

reflexes controlled by ganglia outside the GI tract eg, celiac ganglion

Front 2

When does swallowing occur?

Back 2

when a food bolus comes in contact with pressure receptors in the pharynx

Front 3

Where is swallowing center?
It's efferents?

Back 3

-Medulla
- Efferents are vagus and glossopharyngeal nerves

Front 4

Stages of esophageal phase of swallowing?

Back 4

-Respiration is inhibited
- Bolus is moved into oral pharynx
- larynx is raised and glottis closes
- esophageal sphincter is relaxed and bolus enters the upper esophagus
-peristalsis initiates and leads to downward movements
-larynx descends, glottis opens, respiration restarts

Front 5

Function and importance of upper esophageal sphincter?

Back 5

- contracted at rest, by the action of continuously firing motoneurons
- prevents the entry of air which would otherwise follow the -ve intrathoracal pressure
- relaxes prior to swallowing due to inhibition of discharge of somatic nerves (cns mediated)

Front 6

What is receptive relaxation in stomach?

Back 6

Stomach relaxes after receival of food, increasing its volume
- involves a long reflex (vagovagal) and a local reflex in myenteric plexus.
- mediated by atp or vip.
-continues until swallowing ceases

Front 7

What controls the basic electrical rythm of stomach?
Where is this pacemaker located?

Back 7

A pacemaker located in the proximal region of greater curvature, in longitudinal muscle
-frequency of basic electrical rythm is about 3 per minute

Front 8

what does basic electrical rythm initiate?

Back 8

low amplitude contraction waves

Front 9

how are high amplitude contraction waves created?

Back 9

acetylcholine(or gastrin, substance P) further depolarize smooth muscle cells creating high amplitude contractions, bursts of action potentials.

Front 10

Which factors influence gastric emtpying?

Back 10

-fat
-protein
-acid
- hyper/hypo-osmotic solutions
-----> slow gastric emptying

Front 11

What is gastrin? How is it produced?
what are the effects of gastrin?

Back 11

-A hormone produced by G cells in the stomach antrum
- is produced after stomach distension
- causes secretion of highly acidic gastric juice
- stimulates stomach wall contraction
-enhances activity of pyloric pump

Front 12

How do fats/protein delay stomach emptying?

Back 12

upon entering the duodenum proteins/fats stimulate release of cholecystokinin. cck blocks the actions of gastrin on antral muscle

Front 13

How do acids influence gastric emptying?

Back 13

acid in duodenum releases secretin,which acts directly on smooth muscle and relaxes it

Front 14

how does sympathetic system affect gastric emptying?

Back 14

it blocks the response of myenteric neurons to acetylcholine

Front 15

What is the migrating myoelectric complex? (stomach& small intestine)

Back 15

-A series action potentials triggering powerful contractions that clears any undigested food or chyme in stomach/intestine.

Front 16

What is segmentation in small intestine?

Back 16

Standing waves produced by the pacemakers, creating randomly standing waves of contractions along the small intestine.
- these ensure chyme contact against the epithelium

Front 17

Describe stages in peristalsis

Back 17

1. Distention of ileum activates met-enkephalin neurons with ascending axons, that mediate contraction above the distended portion.
2. Distention also stimulates VIP neurons that trigger relaxation in the area ahead of distention
3. other sets of neurons, serotonin, substance p, stimulate later contraction in the relaxed area.
4.chyme is pushed forward,distends the region there and the whole process repeats

Front 18

What reflexes control peristalsis? (long,short, local?)

Back 18

Local reflexes in myenteric plexus.

Front 19

When does the ileocecal valve open allowing its contents into cecum?

Back 19

When pressure in ileum rises 15-20mmHg above colon.

Front 20

Which hormone is linked to generation of migrating myoelectric complex?

Back 20

motilin produced by the epithelium of the upper intestine

Front 21

3 motility 'stages' of small intestine

Back 21

- migrating myoelectric complex during interdigestive phase
-segmentation
-peristalsis

Front 22

term for motility in colon?

Back 22

haustral shuttling

Front 23

gastrocolic reflex

Back 23

the incease of colon motility during or shortly after a meal.

Front 24

which cells secrete which compounds in the stomach?

Back 24

-mucus cells
-parietal cells : HCL and intrinsic factor
- chief cells: pepsinogen
-g-cells : gastrin and somatostatin

Front 25

how is HCL secreted by parietal cells?

Back 25

co2 + h2o -> h2co3 (under enzymatic activity of carbonic anhydraze)
-h2co3 -> hydrogen ions and hydrogen carbonate
-hydrogen ions are exchanged with K from lumen
-bicarbonate ions are exchanged with Cl and enter venous blood.
-Cl follows the hydrogen pumped into lumen

Front 26

stages of stimulation of gastric secretion

Back 26

-cephalic phase (imagining, smelling etc)
- gastric phase :
*long reflexes
*local reflexes
*humoral factors (gastrin)
-intestinal phase : secretion of chyme into intestine affects gastric secretion

Front 27

stages of inhibition of gastric secretion.

Back 27

cephalic phase : symp. stimulation increases somatostatin release (inhibits parietal and G cells)
gastric phase: -ve feedback of acidic milieu in antrum, inhibits release of gastrin
-intestinal phase: acids in duodenum stimulate release of secretin (inhibits parietal cells and gastric motility)

Front 28

What are the secretions of pancreas ? (acinar and epothelial cells)

Back 28

Acinar cells secrete:
-nucleases,peptidases,amylases,lipases
Ductal cells secrete:
-water, bicarcarbonate and Na ions.

Front 29

what are the saliva components?

Back 29

-sodium,potassium,calcium,bicarbonate
- IgA, lysozyme, lactoferrin
- alpha-amylase(ptyalin)
-mucoproteins for lubrication

Front 30

how is sodium bicarbonate formed in pancreas? (NaHCO3)

Back 30

1. co2+ h2o -> h2co3 (carbonic anhydrase)
2. h2co3 -> H + HCO3
3. hco3 transported (with Na) out of cell into lumen
4. hydrogen ion is exchanged for sodium ions at the basal site of cell.

Front 31

what factors stimulate panreatic secretion?

Back 31

-smell, taste of food, hypoglycemia (cephalic phase)
- distention of stomach : gastropancreatic reflex
-factors stimulating the release of gastrin eg.proteins,amino acids, calcium cause a low-volume high-enzyme secretion from pancreas

Intestinal phase:
-entry of chyme(proteins/fats) in duodenum stimulates CCK-> secretion of high protein low volume juice
-secretin ->rich in bicarbonate secretion

Front 32

What are the stimulants and effects of CCK? (cholecystokinin)

Back 32

chyme with fats/proteins entering duodenum stimulates cck formation.
- inhibits gastric emptying
- Pancreas: it binds to specific receptors on the acinar cells, mobilizes Ca and cGMP causing a secretion high in protein and low-volume
-contracts the bladder

Front 33

Stimulants and effects of secretin

Back 33

stimulated by acid entering duodenum
- inhibits gastrin activity in stomach
-inhibits gastric motility
- in pancreas: via cAMP stimulates secretion of juice rich in bicarbonate

Front 34

activation and protection from pancreatic proteases

Back 34

- trypsinogen, chymotrypsinogen, procarboxypolypeptidase
-trypsinogen is secreted along with trypsin inhibitor in pancreas
- in duodenum it is converted to trypsin by enterokinase or by already activated trypsin (aytocatalysis)
-trypsin activates the other 2 enzymes