Neuronal & hormonal regulation of GIT

Question 1

2 levels of control?

Answer 1

Intrinsic (enteric)

Extrinsic

Question 2

Intrinsic properties?

Answer 2

GIT has own NS - self regulatory
Intrinsic nervous & endocrine components
As many neurons as spinal cord
Some info from ANS but mostly independent

Question 3

Extrinsic properties?

Answer 3

ANS

Endocrine

Question 4

What is a plexus?

Answer 4

nerve network

Question 5

2 major plexuses & characteristics?

Answer 5

Submucosal plexus - regulates gut blood flow & ion/water transport
Myenteric plexus - regulates gut motility & enzyme secretion

Question 6

Plexus contains what?

Answer 6

Sensory neurons (chemo-, mechanoreceptors)
Interneurons
Motor neurons

Question 7

3 main influences of Extrinsic NS on GIT motility & secretion?

Answer 7

1. Modifies ongoing activity in intrinsic plexus
2. Alters levels of GIT hormone secretion
3. Acts on SM & muscle cells

Question 8

4 types of hormones?

Answer 8

1. Endocrine - via blood
2. Paracrine - to neighbouring cells
3. Autocrine - out then back onto itself
4. Neurocrine - via enteric NS to nearby muscles & glands

Question 9

Endocrine peptides…?

Answer 9

Gastrin
Secretin
CCK
GIP
Motilin

Question 10

Neurocrine peptides…?

Answer 10

Vasoactive intestinal peptide (VIP)
Gastrin-releasing peptide (GRP)
Enkephalins

Question 11

Paracrine peptides…?

Answer 11

Somatostatin

Histamine

Question 12

3 digestion regulation phases?

Answer 12

1. Cephalic - rapid, feed forward
2. Gastric - slower than ceph, food in stomach
3. Intestinal - slowest, in response to factors in duodenum

Question 13

Regulation of appetite occurs where?

Answer 13

At the satiety & appetite centre within the hypothalamus

Question 14

3 main hormones that control long-tern appetite?

Answer 14

Leptin - long term hunger suppression 
Ghrelin - appetite stimulant
Peptide YY (PYY) - reduces appetite

Question 15

Short-term regulation of feed intake?

Answer 15

Balances hunger vs satiety

Question 16

Short-term satiety factors?

Answer 16

Insulin
CCK
Neural input from mechano-, chemoreceptors in GIT wall

Question 17

Immune sys & GIT protection…?

Answer 17

Immune cells line gut mucosa (PP’s, mesenteric lymph nodes)

Monitors antigenic environment

Question 18

What monitors chemical & physical environment in the GI?

Answer 18

Enteric NS & GI endo/paracrine sys

Question 19

2 key immune cell functions in GIT?

Answer 19

Antigenic memory (synthesise antibodies)
Inflam mediators (PGEs, histamine, cytokines)

Question 20

Cascade of events following exposure to antigen?

Answer 20

Antigen ingested -> lymphocytes -> cytokines-> Inflammatory response + intrinsic NS & endocrine systems