Control of the digestive system

Question 1

What is found within the gut walls that is part of the intrinsic control systems?

Answer 1

enteric nervous system and gut hormones

Question 2

what is part of the extrinsic control systems?

Answer 2

outside of the gut:
vagus and pelvic nerve (parasympathetic)
splanchnic nerves (sympathetic)
Aldosterone

Question 3

what are the two plexuses of the enteric nervous system?

Answer 3

submucosal plexus
myenteric plexus

Question 4

fight or flight –>

Answer 4

digestive system inhibited

Question 5

what are vagal nerve fibres responsible for?

Answer 5

innervating the abdominal viscera (stomach)
carrying signals from the taste buds (to determine what animal eats)
projecting from the CNS to parasympathetic ganglia near organs and to the pharynx (the afferents and efferents)

Question 6

what does the splanchnic nerve do?

Answer 6

carries signals to the CNS regarding presence of pathologies

Question 7

result of painful stimuli?

Answer 7

evokes sympathetic repsonses in GI tract results in inhibition of gut motility and increased glandular secretions

Question 8

what is aldosterone?

Answer 8

it is a steroid hormones

Question 9

where is aldosterone secreted from? and when?

Answer 9

secreted by adrenal cortex following stimulation by:
low sodium
angiotensin
andrenocorticotrophic hormone
high potassium

Question 10

what does aldosterone do?

Answer 10

it stimulates sodium and water reabsorption from gut and salivary glands

Question 11

what is vomiting?

Answer 11

an active reflex

Question 12

what is invovled in vomiting?

Answer 12

chemoreceptors trigger zone, vafal afferent system, vestibular system and CNS

Question 13

What happens to ensure airway protection from vomiting?

Answer 13

epiglottis closes off laryngeal opening
soft palate elevates to seal off nasopharynx

Question 14

what does the mecahnisms allow?

Answer 14

portect the airway from aspiration odf stomach contents in the animal

Question 15

what else happens ot ensure the path from oesophagus to mouth is ready?

Answer 15

the larynx elevates and straightens out oesophagus

Question 16

what is vomiting controlled by?

Answer 16

by the vomit centre in thje brainstem

Question 17

what are the four ways that vomitting can be induced by naturally?

Answer 17

intiated at GI level
initiated outside GI tract
Initiated by irritation of the gastric epithelium e.g. pain and anxiety
or by partially digested food

Question 18

what kind of process is regurgitation?

Answer 18

passive process

Question 19

ileus?

Answer 19

no movement, no contraction of the stomach

Question 20

what type of organ is the gut?w

Answer 20

an immune organ

Question 21

why is the gut an immune organ?

Answer 21

the intestinal mucosa is exposed to microorganisms (e.g. contaminated food/toxins) and antigens

Question 22

what type of cells reside in the gut mucosa?

Answer 22

immune cells

Question 23

Describe the first way that defence occurs by the gut?

Answer 23

Cells respond to antigenic stimulation by synthesising antibodies and recruiting killer cells

Question 24

Describe the second way that the gut defends itself?

Answer 24

Cells secrete inflammatory mediators (eg PG, cytokines, histamine) which interact directly with the ENS and GI endocrine/paracrine cell

Question 25

what are the anatomical causes of regurgitation?

Answer 25

megaoesophagus, hiatal hernia

Question 26

what are the functional causes of regurgitation?

Answer 26

ileus (no movement) gastric reflux

Question 27

apart from anatomical and functional causes, what else causes regurgitation?

Answer 27

foreign bodies in upper GI tract

Question 28

what happens during regurgitation?

Answer 28

undigested content moves back up the oesophagus

Question 29

what is regurgitation?

Answer 29

the incapacity of oesophagus to empty content into stomach

Question 30

When vomiting is initiated at GI level, how does this happen?

Answer 30

sensory cells (mechanoreceptors) with nerve endings in the pharynx tension receptors and chemoreceptors in the gastric/duodenal mucosa

Question 31

when vomiting is initiated outside GI tract, what happens?

Answer 31

chemoreceptors trigger zone (closed to 3rd ventricle) afferent input to vomit centre: drugs, toxins inflammatory mediators in blood Constant stimulatioh of the semicircular canals afferent input to vomit

Question 32

what is vomiting controlled by?

Answer 32

the brainstem

Question 33

contraction of which muscles does vomiting involved?

Answer 33

contraction of striated muscles and other structures outside the GI tract

Question 34

What 5 things have to happen in order for vomiting to take place?

Answer 34

Relaxation of muscles and closing of pylorus Contraction of abdominal muscles Expansion of chest while glottis closed Opening of upper oesophageal sphincter Antiperistaltic motility in duodenum

Question 35

What muscles need to relax in order for vomiting to take place?

Answer 35

stomach and lower oesophageal sphincter

Question 36

why do abdominal muscles need to contract to allow vomiting to take place?

Answer 36

to increase the pressure in the abdominal cavity

Question 37

why does the chest need to expand while the glottis is closed in order for vomiting to occur?

Answer 37

need to lower intrathoracic pressure on oesophagus

Question 38

Vomiting requires high/low intraabdominal pressure?

Answer 38

high

Question 39

how is high intraabdominal pressure achieved?

Answer 39

diaphragm squeezes the stomach, raising pressure inside simultaneous contraction of abdominal oblique muscles further squeezes stomach

Question 40

high abdominal pressure plus what two other things results in vomiting?

Answer 40

high abdominal pressure as well as low thoracic pressure and open oesophagus

Question 41

How is low intrathoracic pressure achieved to allow vomiting?

Answer 41

the diaphragm sharply and strongly contracts and moves caudally this lowers the pressure in the thorax low thoracic pressure opens the lower oesophageal sphincter

Question 42

What does distension of the stomach lead to? (in terms of regulating muscle contractions)

Answer 42

There is an increase in activity of stretch-sensitive sensory cells leading to both an increase in gastrin and an increase in contraction of smooth muscle cells which results in an increase in empyting the stomach

Question 43

what does peptides in the stomach result in? (to do with regulating muscle contractions)

Answer 43

peptides in stomach results in an increase of gastrin which results in an increase in contraction of smooth muscle cells which results in an increase in emptying the stomach

Question 44

give an example of when and how the splanchnic nerve would carry signals to the CNS regarding presence of pathologies:

Answer 44

overdistension of gut wall > inflammation > presence of noxious substances in lumen

Question 45

what does the presence of noxious substances in the lumen present as?

Answer 45

presents as colic or pain

Question 46

what is involved in extrinsic control (outside of the gut)?

Answer 46

the vagus and splanchnic nerves aldosterone (hormonal control) zona glomerulosa of adrenal cortex (adrenal gl.) sodium conservation (kidney, salivary gl, colon)

Question 47

what are the five gut hormones?

Answer 47

gastrin, secretin, CCK, GIP, motilin

Question 48

what does CCK stand for?

Answer 48

cholecystokinn

Question 49

what GIP stand for?

Answer 49

gastric inhibitory polypeptide

Question 50

where is gastrin produced?

Answer 50

the distal stomach

Question 51

where is secretin produced?

Answer 51

mainly duodenum

Question 52

where is CCK produced?

Answer 52

mainly duodenum

Question 53

where is GIP produced?

Answer 53

proximal small intestine

Question 54

where is motilin produced?

Answer 54

duodenum

Question 55

what is the release stimuli for gastrin?

Answer 55

protein

Question 56

what is the release stimuli for secretin?

Answer 56

H+ in the small intestine

Question 57

what is the release stimuli for CCK?

Answer 57

fat and protein

Question 58

what is the release stimuli for GIP?

Answer 58

fat and glucose

Question 59

what is the release stimuli for motilin?

Answer 59

ACh

Question 60

what are the major effects of gastrin?

Answer 60

stimulates acid (HCl) secretion stimulates growth of mucosa

Question 61

what are the major effects of secretin?

Answer 61

stimulates secretion of HCO3- in pancreas

Question 62

what are the major effects of CCK?

Answer 62

stimulates production and secretion of pancreatic enzymes causes gall bladder contractions

Question 63

what are the major effects of GIP?

Answer 63

stimulates insulin production inhibits HCl production and gastric emptying

Question 64

what are the major effects of motilin?

Answer 64

regulation of MMC (migrating motor complex) during fasting

Question 65

what are the five characteristics of gut hormones?

Answer 65

they: must be secreted by one cell in the gut and affect another cell must be transported in the blood (endocrine) release must be stimulated by food secretion does not have to be controlled by neurones A synthetic version of it must be able to mimic the natural hormone

Question 66

meaning of endocrine?

Answer 66

hormones secreted near blood vessels

Question 67

meaning of paracrine?

Answer 67

substances secreted in interstitial space (locally by diffusion)

Question 68

meaning of enterochromaffin?

Answer 68

serotonin (muscle excitatory) & chemoreceptors

Question 69

what are the hormones of the intrinsic system secreted by?

Answer 69

specialised epithelial cells: endocrine, paracrine and enterochromaffin

Question 70

what type of function does the hormonal control of the intrinsic system have?

Answer 70

regulatory function not digestive

Question 71

what is involved in the hormonal control of intrinsic system?

Answer 71

gut peptides and gut hormines

Question 72

what nerve fibre does a signal go down which leads to the inhibition of digestive action when a fight or flight response is stimulated in an animal?

Answer 72

the preganglionic and postganglionic sympathetic nerve fibre

Question 73

the majority of the reflexes coordinated by the secretion and muscle contraction involved in gut neuronal regulation exert what?

Answer 73

they exert a stimulatory influence using acetylcholine as a transmitter

Question 74

certain reflex arcs release what other kind of neurotransmitters? And why is this important?

Answer 74

they release inhibitory neurotransmitters - this is important for relaxation of sphincters (facilitating emptying of that portion of the tract

Question 75

what are the sensory neurones involved in gut neuronal regulation affected by?

Answer 75

affected by changes in content (via chemoreceptors within gut mucosa) and by changes in distension of wall (via mechanoreceptors within gut muscular layers)

Question 76

what are the two types of motor neurones involved in gut neuronal regulation?

Answer 76

they can either be inhibitory or stimulatory

Question 77

Which three neurones are involved in the gut neuronal regulation?

Answer 77

sensory neurons motor neurons interneurons

Question 78

which neuron in the gut neuronal regulation is afferent?

Answer 78

sensory neurons

Question 79

which neuron in the gut neuronal regulation is efferent?

Answer 79

motor neurons

Question 80

what are the motor neurons in the gut neuronal regulation connected to?

Answer 80

either: smooth muscle cells or epithelial (secretory) cells that produce digestive juices or hormones

Question 81

how do plexuses communicate with each other?

Answer 81

via interneurons

Question 82

what are interneurons?

Answer 82

shorter neurones

Question 83

how do plexuses communicate with the CNS?

Answer 83

via vagal and splanchnic nerves

Question 84

What do the neurons within each plexus form synapses with?

Answer 84

each other smooth muscle cells or glandular cells for contractions/secretions neurons in the other plexus

Question 85

what nervous system does the intrinsic control use?

Answer 85

the enteric nervous system

Question 86

how many plexuses make up the enteric nervous system?

Answer 86

two

Question 87

what are the two plexuses that the enteric nervous system contains?

Answer 87

the submucosal plexus and the myenteric plexus

Question 88

what do the guts 'own'?????????????????

Answer 88

the CNS WHAT DOES THIS EVEN MEAN

Question 89

what are the two types of control of the gut?

Answer 89

neural and hormonal

Question 90

what are the gastrointestinal tract motor and secretory functions controlled by?

Answer 90

the gastrointestinal nervous system and the gastrointestinal endocrine system

Question 91

what is the the gastrointestinal nervous system and the gastrointestinal endocrine system controlled by?

Answer 91

the CNS