Lecture 37 11/15/23

Question 1

What are the functions of the GI system?

Answer 1

-ingestion, digestion, and absorption of food/nutrients
-ecological niche for commensals
-prevent pathogens from penetrating epithelial barrier
-eliminate waste

Question 2

Which species have a simple stomach?

Answer 2

-humans
-dogs
-cats
-pigs

Question 3

What are the characteristics of foregut fermenters?

Answer 3

-multi-chambered stomachs which allow for fermentation
-4 compartments in ruminants
-3 compartments in pseudoruminants

Question 4

Which species are foregut fermenters?

Answer 4

even-toed ungulates

Question 5

What are the characteristics of hindgut fermenters?

Answer 5

-monogastric stomach
-extensive cecum and colon

Question 6

Which species are hindgut fermenters?

Answer 6

-odd-toed ungulates
-rabbits
-guinea pigs

Question 7

Which section of the brain serves as the control center for appetite regulation?

Answer 7

hypothalumus

Question 8

What are the two centers of the hypothalamus?

Answer 8

-appetite center: increases hunger
-satiety center: decreases hunger

Question 9

What are the short term signals for appetite regulation?

Answer 9

-neuronal signals
-blood levels of nutrients
-GI hormones

Question 10

What are orexigenic neurons?

Answer 10

neurons that send signals that increase hunger

Question 11

What are anorexigenic neurons?

Answer 11

neurons that send signals that decrease hunger

Question 12

How does the oral cavity play into appetite regulation when eating?

Answer 12

-taste receptors distinguish between acceptable and unacceptable foods
-acceptable foods encourage intake

Question 13

How does the stomach play into appetite regulation when eating?

Answer 13

-stretch-sensitive mechanoreceptors detect distension
-neuronal input relays info. to hypothalamus via vagus nerve

Question 14

How do the intestines and colon play into appetite regulation when eating?

Answer 14

-chyme triggers release of hormones
-CCK, peptide YY, and insulin have important roles

Question 15

What is the short-term regulator of appetite when fasting?

Answer 15

Ghrelin, an orexigenic hormone that stimulates appetite/food intake

Question 16

What is the long-term regulator of appetite?

Answer 16

Leptin, an appetite suppressant produced by adipose tissue

Question 17

What are the five categories of taste?

Answer 17

-sour (H+ ions)
-salty (sodium)
-sweet (organic comp.)
-bitter (organic comp./alkaloids)
-umami (L-glutamate)

Question 18

What are the types of GI function regulation?

Answer 18

-intrinsic: within GI system walls
-extrinsic: outside GI system walls

Question 19

What is the role of the enteric/intrinsic nervous system?

Answer 19

controls localized GI functions

Question 20

Which ganglionated plexuses make up the enteric nervous system?

Answer 20

-myenteric plexus
-submucosal plexus

Question 21

What are the characteristics of the myenteric plexus?

Answer 21

-between muscle layers of GI system
-controls GI movements

Question 22

What are the characteristics of the submucosal plexus?

Answer 22

-under submucosal layer of GI tract
-controls local secretion, absorption, and blood flow

Question 23

What is the function of enteric neuron varicosities?

Answer 23

allow the neurons to activate a wider area

Question 24

What are the sources of input for enteric sensory neurons?

Answer 24

-mechanoreceptors (sensing stretch)
-chemoreceptors (sensing chemical conditions)

Question 25

What are the characteristics of enteric motor neurons?

Answer 25

-supply gut muscle, vascular muscle, and glands -may be inhibitory or stimulatory -secrete various neuropeptides

Question 26

What are the characteristics of enteroendocrine cells?

Answer 26

-"taste buds" of gut -scattered throughout mucosal layer -largest endocrine organ -senses components of chyme to determine secretions

Question 27

How can GI peptides act, hormonally?

Answer 27

-endocrine (released in circulation) -paracrine (diffuse short distances) -autocrine (act on same cell) -neurocrine (released from nerve endings)

Question 28

What are the characteristics of parasympathetic innervation of the GI system?

Answer 28

-stimulatory -mediated by acetylcholine -innervation through vagus and pelvic nerves

Question 29

What are the characteristics of sympathetic innervation of the GI system?

Answer 29

-inhibitory -mediated by norepinephrine -innervation through splanchnic nerves

Question 30

What are the characteristics of aldosterone?

Answer 30

-mineralocorticoid hormone -produced by adrenal glands -functions in H2O and Na reabsorption and K excretion

Question 31

Which organs are involved in splanchnic circulation?

Answer 31

-GI tract -pancreas -liver -spleen

Question 32

How does blood flow through splanchnic circulation?

Answer 32

-blood from GI tract/pancreas/spleen dumps into portal vein -portal vein carries blood to liver -blood passes through liver sinusoids -blood leaves through hepatic veins which dump into caudal vena cava

Question 33

What is the role of reticuloendothelial cells in the liver sinusoids?

Answer 33

remove bacteria and potentially harmful substances from the blood

Question 34

How does blood flow change within the GI system?

Answer 34

-blood flow increases for a few hours following a meal -sympathetic NS can reduce blood flow for short periods

Question 35

What are the characteristics of the microvasculature of intestinal villi?

Answer 35

-counter-current system -arterioles and venules diffuse oxygen to each other -80% of oxygen and nutrients bypass the tips of the villi