GI Physiology: apptite, saliva, swallowing, vomiting

Question 1

What regulates appetite?

Answer 1

2 regions in hypothalamus=> feeding and satiety centers

Question 2

How do the 2 regions controlling appetite interact?

Answer 2

feeding center is active but transiently inhibited by satiety center

Question 3

What is the location, stimulation and destruction of the feeding center in the hypothalamus?

Answer 3

location=> lateral hypothalamic area
stimulation=> feeding
destruction=> anorexia

Question 4

What is the location, stimulation and destruction of the satiety center in the hypothalamus?

Answer 4

location=> ventromedial nucleus of hypothalamus
stimulation=> cessation of feeding
destruction=> hypothalamic obesity syndrome

Question 5

What are 2 hormones that may affect appetite?

Answer 5

cholecystokinin (CCK);

calcitonin

Question 6

What releases cholecystokinin?

Answer 6

released from I cells in mucosa of small intestine

Question 7

where is cholecystokinin found?

Answer 7

CCK-A=> periphery
CCK-B=>brain

both reduce appetite when stimulated

Question 8

When is calcitonin released and what is its function?

Answer 8

released mainly from thyroid gland=>decreases appetite

Question 9

how does mechanical distention lead to alterations in appetite?

Answer 9

distention of alimentary tract inhibits appetite => empty stomach stimulates it

satiety derived from mastication and swallowing alone

Question 10

What are the salivary glands?

Answer 10

submandibular;
parotid;
sublingual

Question 11

What are the functions of the salivary glands?

Answer 11

presence of food in mouth, taste, smell, sight, thought of food or stimulation of vagal afferents at distal end of esophagus increase production of saliva

Question 12

functions of saliva

Answer 12

lingual lipase (initial triglyceride digestion);
alpha-amylase (initial starch digestion);
lubrication

Question 13

what are the ions of saliva?

Answer 13

HCO3; K+; Na+; Cl-

Question 14

enzymes of saliva

Answer 14

alpha-amylase;

lingual lipase

Question 15

what kind of solution is saliva?

Answer 15

hypotonic

Question 16

pH of saliva

Answer 16

7-8

Question 17

How does saliva provide immunological help?

Answer 17

lysozyme; lactoferrin;
defensins;
IgA

Question 18

What is the PANS regulation of saliva?

Answer 18

increase synthesis and secretion of WATERY saliva via MUSCARINIC receptor stimulation =>
anti-cholinergics=dry mouth

Question 19

SANS regulation of saliva

Answer 19

increase synthesis and secretion of VISCOUS saliva via BETA-ADRENERGIC receptor stimulation

Question 20

Where is the swallowing center?

Answer 20

medulla

Question 21

what carries the reflex action for swallowing?

Answer 21

afferents carried by CN-IX (glossopharyngeal);

CN-X (vagus nerves)

Question 22

How is food moved from the mouth to the esophagus?

Answer 22

movement of tongue (CN-XII => hypoglossal);
CN-IX => palatal muscles
CN-x => pharyngeal muscles

Question 23

What are the 6 steps of swallowing?

Answer 23

1) initiation of swallowing
2) involuntary contraction of pharynx
3) closure of glottis
4) upper esophageal sphincter
5) peristaltic contraction of esophagus and lower esophageal sphincter
6) relaxation of LES

Question 24

Describe the first step of swallowing

Answer 24

initiation of swallowing occurs voluntarily when mouth is closed on bolus of food and tongue propels it from oral cavity to pharynx

Question 25

describe 2nd step of swallowing

Answer 25

advances bolus into esophagus (involuntary contraction of pharynx)

Question 26

describe 3rd step of swallowing

Answer 26

automatic CLOSURE OF GLOTTIS during swallowing => inhibits BREATHING and prevents aspiration

Question 27

describe 4th step of swallowing

Answer 27

relaxation of UES allows food to enter esophagus

Question 28

describe the 5th step of swallowing

Answer 28

peristaltic contraction of esophagus propels food toward LES

Question 29

What is the lower esophageal sphincter (LES)?

Answer 29

muscle at GE junction

Question 30

describe 6th step of swallowing

Answer 30

LES is tonically contracted, relaxing on swallowing => relaxation of LES mediated via vagus nerve => VIP (vasoactive inhibitory peptide) major neurotransmitter causing LES relaxation

Question 31

What is achalasia?

Answer 31

pathologic inability of LES to relax during swallowing => food accumulates in esophagus causing MEGAESOPHAGUS

Question 32

How does gastric reflux occur?

Answer 32

LES TONE is low=> allows acid reflux into esophagus => may cause GERD

Question 33

3 phases of vomiting

Answer 33

nausea, retching, vomiting

Question 34

How does nausea occur?

Answer 34

hypersalivation, decreased gastric tone, increased duodenal and proximal jejunal tone => reflux of contents into stomach

Question 35

How does retching occur?

Answer 35

gastric contents travel to esophagus => occurs if upper esophageal sphincter remains closed

Question 36

How does vomiting occur?

Answer 36

if pressure increases enough to open UES=> vomiting occurs

Question 37

What can trigger vomiting?

Answer 37

oropharyngeal stimulation, gastric overdistention and gastroparesis, vestibular stimulation or input from CHEMORECTOR TRIGGER ZONE

Question 38

Where is chemoreceptor trigger zone? what does it stimulate?

Answer 38

located in area postrema in floor of 4th ventricle => stimulates the medullary vomiting center