Wandisford - Regulation Of GI Functions

Question 1

Good dermatome mnemonics

Answer 1

T4 - at the teat pore
T10 - At the belly butTEN
L1 - is IL (inguinal ligament)
L4 - Down on all 4s
S234 - keeps the penis off the floor

Question 2

Preganglionic neurons excrete what into the synaptic cleft?

Answer 2

Ach always regardless whether it is sympathetic or parasympathetic

Question 3

Postganglionic neurons secrete what into the synaptic cleft?

Answer 3

Sympathetic - NE, E (and acetylcholine to sweat glands)

Parasympathetic - Ach

Question 4

WHat hormone is responsible for causing the GI tract to get going? Which one makes it stop?

Answer 4

Acetylcholine from the PSNS. It contracts smooth muscle but relaxes the internal sphincter
Norepinephrine - released from Sympathetics. It relaxes smooth muscle and contracts the internal sphincter

Question 5

Vasoactive Intestinal Polypeptide (VIP)

Answer 5

Relaxes smooth muscle (would stop you from popping), BUT it increases salivary, gastric, and pancreatic secretions (which increase pooping).

Question 6

Substance P

Answer 6

Co secreted with Ach and helps it do the exact same thing. It contracts the smooth muscle and increases salivary gland secretions

Question 7

Enkephalins (opiates)

Answer 7

Contracts smooth muscle (which would make you poop) , BUT it reduced glandular secretions.
- Overall constipation

Question 8

Neuropeptide Y

Answer 8

relaxes smooth muscle (which would make you not poop) and reduces glandular secretions (which also make you not poop)

Question 9

Gastrin-releasing Peptide (GRP) (aka Bombesin)

Answer 9

Increases gastrin secretin

Question 10

Gastrin

Answer 10

Increase gastric H+ secretion.

• causes H+ secretion in during cephalic phase, gastric phase, and intestinal phase (even after it has passed the stomach)
• also grows gastric mucosa and increases gastric motility
• secreted from G cells
• in response to dietary peptides.

Question 11

Mechanism of Gastrin secretion

Answer 11

Vagus nerve comes down and either directly or Indirectly activates G cells (through GRP or Ach). Gastrin is then released into the blood stream and it stimulates the parietal cells to via the CCKb receptor to release H+. This is done either directly or indirectly through histamine. Eventually we have negative feedback through the H+ stimulating D cells to excrete somatostatin, which turns off the G cells.
- the indirect pathway is more powerful.

Question 12

CCK

Answer 12

Secreted from I cells in the duodenum and jejunum in response to fat. Binds to CCKa. Causes contraction of the gallbladder and relaxation of sphincter of Oddi, stimulates enzymes from the exocrine pancreas.

Question 13

Secretin

Answer 13

Comes from S cells In the duodenum and jejunum. Secretin responds mostly to stomach acids and some fatty acids. Secretin promotes HCO3 secretions from pancreas and bile in order to neutralize acid.

Question 14

Incretins

Answer 14

Incretins augments insulin release due to any sort of nutrient load. Therefore when people were on the Atkins diet, they would get hypoglycemic because Incretins were secreted to lower blood sugar even though there was no glucose around.
- Main Incretins are: GIP and GLP-1

Question 15

What are the two treatments for too much stomach acid Being produced? How do they work?

Answer 15

H2 blocker - Blocks histamine from activating the parietal cells to secrete H+. More powerful but takes longer
PPI - blocked the H+/K+ pump. Blocks all acid production but is not as powerful but acts quicker.

Question 16

What are the 2 extrinsic reflexes of the GI tract?

Answer 16

Gastrocolic - when you eat you have to poop. This is normal. Gastric distension causes evacuation of the colon.
Enterogastric - when the duodenum is distended it sends signals to inhibit the stomach. Makes sense because it can’t handle more nutrients than it already has.

Question 17

GI reflexes that involve cognitive awareness?

Answer 17

Vomiting reflex
Pain reflex that causes general inhibition of the entire GI tract
Defacation reflexes that travel from the colon and rectum to the spinal cord and back again. Essentially control over external sphincter.

Question 18

Positive hypothalamic input

Answer 18

Appetizing sight/smell/taste of food

Ghrelin

Question 19

Negative hypothalamic input

Answer 19

Afferents from stomach relaying fullness
Insulin, CCK
Leptin

Question 20

Innervation of the GI system

Answer 20

There is an enteric nervous system that can fuel GI mobility on its own.

• We also have ANS acting on the GI system.
• • Parasympathetics come from the cranial and sacral levels of the spinal cord to synapse on the enteric nervous system.
• • Sympathetics from the thoracolumbar region of the spinal cord synapse at various ganglia and then their postganglionics travel to the GI tract.