General Principles Of Gastrointestinal Function

Front 1

what determines the amount of food we eat? what determines what type of food we eat?

Back 1

hunger; appetite

Front 2

what centers in the CNS control the regulation of food? (5)

Back 2

hypothalamus, nucleus tractus solitarius (brainstem), amygdala, the cortex prefrontalis, and the area postrema

Front 3

what two hormones in the endocrine system control the regulation of food?

Back 3

insulin and leptin

Front 4

what are the three hormones of the GI system that regulate food intake?

Back 4

cholecystokinin, ghrelin, peptide YY

Front 5

what is the key region in the CNS that is involved in feedback control of appetite and food intake?

Back 5

hypothalamus

Front 6

where is the feeding or hunger center? what is it involved in?

Back 6

lateral hypothalamic area; involved in stimulation of food intake and storage of calories

Front 7

where is the satiety center? what is it involved in?

Back 7

ventromedial nuclei; involved in the limitation of food intake or satiety.

Front 8

what are the two hypothalamic pathways that exist to regulate food intake? what purposes do they serve?

Back 8

melanocortin pathway: increase metabolism and inhibit food intake; neuropeptide Y: stimulate food intake and decrease metabolism.

Front 9

what is the purpose of NTS?

Back 9

to serve as a gateway for neural signals from the GI tract to the hypothalamic feeding centers

Front 10

what is the source, site of action and clinical effect of insulin?

Back 10

source: pancrease
Site of action: hypothalamus
clinical effect: decreased appetite and increase metabolism

Front 11

what is the source, site of action and clinical effect of Leptin?

Back 11

source: fat cell
site of action: hypothalamus
clinical effect: decreased appetite and increased metabolism

Front 12

what is the source, site of action and clinical effect of CCK?

Back 12

source: duodenum
site of action: vagal afferents
clinical effect: decreased appetite and decreased gastric emptying

Front 13

what is the source, site of action and clinical effect of PYY?

Back 13

source: ileum and colon
site of action: hypothalamus
clinical effect: decreased appetite and increased metabolism

Front 14

what is the source, site of action and clinical effect of Ghrelin?

Back 14

source: stomach
site of action: hypothalamus
clinical effect: increased appetite and decreased metabolism.

Front 15

what are the four functions of the digestive system?

Back 15

motility, secretion, digestion and absorption

Front 16

what is the function of the oral cavity? what does it prevent?

Back 16

food intake, mixing and size reduction; food propulsion; taste. Prevents pulmonary aspiration.

Front 17

what is the function of the esophagus? what does it prevent?

Back 17

food bolus propulsion into the stomach. Prevents gastric reflux.

Front 18

what is the function of stomach?

Back 18

nutrient storage; mixing; homogenization and propulsion; secretion.

Front 19

what is the function of small intestine?

Back 19

major site of nutrient digestion and absorption, mixing and propulsion of chyme; secretion

Front 20

what is the function of large intestine?

Back 20

mixing and propulsion; final water and electrolytes absorption

Front 21

what is the function of the rectum?

Back 21

storage of fecal material

Front 22

what is the function of the anus?

Back 22

control of defecation

Front 23

The functional structure of the GI wall contains 7 layers, name them in order.

Back 23

serosa, longitudinal muscle layer (smooth), myenteric plexus of enteric NS, circular muscle layer (smooth muscle cells), submucosal plexus of the enteric NS, submucosa, mucosal muscle cellls and mucosa.

Front 24

what are the voluntary muscles of the upper tract? lower tract?

Back 24

upper: mouth, pharynx, and first 1/3 of esophagus.
lower: external anal sphincter.

Front 25

what action does the longitudinal muscle perform?

Back 25

peristalsis, food propulsion

Front 26

what does the action of the circular muscle produce?

Back 26

segmentation, mixing

Front 27

what does the action of mucosal muscle produce?

Back 27

surface area and lymph flow

Front 28

what are the five hormones that regulate GI functions?

Back 28

Gastrin, CCK, secretin, gastric inhibitory peptide, motilin

Front 29

what are the two paracrines released for regulation of the GI functions?

Back 29

somatostatin and histamine

Front 30

what are the four neurocrines released for regulation of the GI functions?

Back 30

substance P, VIP, gastrin-releasing peptide, enkephalins

Front 31

what is the primary action of gastrin?

Back 31

increased HCL secretion and increased pepsinogen secretion

Front 32

what is the primary action of secretin?

Back 32

increased water and bicarb secretion by pancreatic ductal cells and biliary tract

Front 33

what is the primary action of the CCK?

Back 33

increased enzyme secretion by pancreatic acinar cells, increased contraction of the gallbladder

Front 34

what is the primary action of the Gastric inhibitory peptide?

Back 34

inhibit gastric secretion, motility, and emptying

Front 35

what is the primary action of Motilin?

Back 35

increased motility and initiate the migrating motor complex MMC

Front 36

what is the main example of intrinsic control of neural control of GI functions?

Back 36

enteric NS

Front 37

what is the 2 main examples of extrinsic control of neural control of GI functions?

Back 37

autonomic NS and CNS

Front 38

Parasympathetic pathways generally have an _________ influence on the functions of the GI tract.

Back 38

Excitatory

Front 39

what time of receptors do the afferent fibers come from?

Back 39

chemo- or mechano receptors

Front 40

where do the preganglionic fibers synpase in parasympathetic pathways in the GI?

Back 40

cells of the enteric plexuses

Front 41

what effect does the parasympathetic pathway have on GI smooth muscle, mucosal secretory and/or endocrine, and vascular smooth muscle cells?

Back 41

GI smooth muscle: increased GI motility, decreased tone of GI smooth muscle sphincters
Mucosal secretory and/or endocrine cells: increased secretion
Vascular smooth muscle cells: vasodilation and increased blood flow.

Front 42

Sympathetic stimulation generally has an _____________ influence on the functions of the GI tract.

Back 42

inhibitory

Front 43

what receptors do the afferent fibers come from? where do they connect to?

Back 43

mucosal and smooth muscle receptors directly to the prevertebral ganglia and/ or to spinal cord.

Front 44

where do the efferent preganglionic fibers synapse? postganglionic fibers?

Back 44

outside of the GI tract with prevertebral ganglia; neurons located with the enteric nerve plexi

Front 45

Most efferent sympathetic pathways are what type of ganglionic fiber?

Back 45

postganglionic

Front 46

what are the effects sympathetic nerves on vascular smooth muscle cells, GI smooth muscle, and mucosal secretory and/or endocrine cells.

Back 46

Vascular smooth muscle: Vasoconstriction, decreased blood flow
GI smooth muscle: decreased GI motility, increased tone of GI smooth muscle sphincters.
Mucosal secretory and/or endocrine cells: decreased secretion activity

Front 47

what are the two examples of reflexes regulated by the CNS?

Back 47

Long reflexes: pain, defecation

Front 48

where is the enteric nervous system located?

Back 48

entirely within the GI tract : from esophagus to anus

Front 49

what are the two plexi contained under the enteric nervous system umbrella?

Back 49

myenteric plexus (auerbach's plexus) and submucosal plexus (Meissner's plexus)

Front 50

T/F
The enteric Nervous system can function autonomously.

Back 50

TRUE

Front 51

what does the submucosal plexus innervate?

Back 51

glandular epithelium, intestinal endocrine cells and submucosal blood vessels.

Front 52

what is the primary control of the submucosal plexus?

Back 52

primarily controls GI secretion and local blood flow

Front 53

what does the submucosal plexus regulate?

Back 53

contraction of the muscularis mucosae.

Front 54

what does the myenteric plexus primarily control? what does it regulate?

Back 54

GI movements. the local and inter-regional motility activity through regulation of contraction/ relaxation of circular and longitudinal smooth muscle layers.

Front 55

what are the major neurotransmitters of the enteric NS? are they inhibitory or excitatory?

Back 55

ACH: excitatory; NE: inhibitory

Front 56

what are the 8 non-peptide neurotransmitters of the enteric nervous system?

Back 56

ATP, NO (Both inhibitory), adenosine, serotonin, GABA, histamine, glycine, dopamine

Front 57

what are the 2 peptide neurotransmitters of the enteric nervous system?

Back 57

VIP (inhibitory) and substance P (excitatory)

Front 58

what are the 4 signals for sensory neurons?

Back 58

mechanical, thermal, osmotic and chemical

Front 59

what are the effector cells for motor neurons?

Back 59

smooth muscle, secretory cells and I endocrine cells

Front 60

what are the interneurons mainly responsible?

Back 60

for integrating information (from sensory to motor)

Front 61

what controls the short reflexes of the gut? what are the short reflexes responsible for?

Back 61

Enteric NS. Controls secretion, peristalsis, mixing contraction

Front 62

what controls the long reflexes of the gut? where do they travel?

Back 62

CNS and ENS.
reflexes are from the gut to the prevertebral sympathetic ganglia and then back to the GI tract (gastrocolic, enterogastric, and colonoileal reflexes); from the stomach and duodenum to the CNS;

Front 63

what is controlled by the long reflexes?

Back 63

controls gastric motor and secretory activity, pain reflexes (general inhibition of entire GI), and defecation reflexes

Front 64

how are smooth muscle cells electrically connected?

Back 64

gap junctions

Front 65

what are the interstitial cells of Cajal connected to?

Back 65

one another, smooth muscle cells and nerve endings

Front 66

where are ICC's pace-maker cells?

Back 66

caudad stomach and intestine

Front 67

T/F
Initiation of GI smooth muscle contraction is dependent of neural or hormonal input.

Back 67

FALSE:

its independent

Front 68

what is the spontaneous cycles of depolarization and repolarization of GI smooth muscle known as?

Back 68

electrical slow waves or Basic electrical Rhythm (BER)

Front 69

T/F
the frequency of the BER is the same throughout the entire digestive system.

Back 69

FALSE.

It varies by region. (ie 3/in in stomach and 12/min in duodenum

Front 70

what causes muscle contractions?

Back 70

action potentials "spikes"

Front 71

what generates the BER or electrical smooth waves?

Back 71

ICC: interstitial cells of Cajal

Front 72

what is the range of the spontaneous rhythmic fluctuation of the "resting" membrane potential of smooth muscle?

Back 72

-65- (-45) mV

Front 73

what is the depolarization phase of smooth muscle due to? Repolarization phase?

Back 73

Na influx; K+ efflux

Front 74

where are these slow wave potentials generated in the GI tract?

Back 74

from mid stomach to rectum

Front 75

where are their no slow waves?

Back 75

esophagus and proximal portion of stomach

Front 76

T/F
slow waves initiate contraction in the intestine?

Back 76

FALSE.

They may (rarely) cause muscle contraction in stomach, but not intestine

Front 77

T/F
slow waves are influenced by body temperature and metabolic activity.

Back 77

True!

Front 78

the spike is formed by both depolarization and repolarization, what is influxing in depolarization and what is effluxing in repolarization?

Back 78

Ca2+ and K+

Front 79

What is the force of the contraction directly related to? what about the duration?

Back 79

force is directly related to frequency of APs. Duration of contraction is releated to number of AP.

Front 80

what are two depolarizing factors that stimulate GI smooth muscle contraction?

Back 80

stretching of the muscle and stimulation by parasympathetic nerves (ach)

Front 81

what are two hyperpolarizing factors that will inhibit GI smooth muscle contraction?

Back 81

stimulation by sympathetic nerves (norepi) and epi

Front 82

____ increase the number of spikes and increases _______ of the smooth muscle

Back 82

Ach; tension

Front 83

what is another name for tonic contraction of GI smooth muscle?

Back 83

basal myogenic tone

Front 84

T/F
Tonic contraction of the GI is characterized by very high ATP consumption.

Back 84

FALSE
very low --> latch mechanism

Front 85

what increases the intensity of the tonic contraction? (3)

Back 85

an increased number of action potentials, factors that cause partial depolarization of SM membrane and factors that increase Ca influx.

Front 86

what is the function of the orad stomach?

Back 86

tonic contraction of proximal stomach

Front 87

what is the function of the sphincter of oddi?

Back 87

separates pancreatobiliary ducts from duodenum

Front 88

what is the function of internal anal sphincter?

Back 88

control defecation