Physiology

Question 1

Which systems control the gut?

Answer 1

Autonomic

Enteric

Hormones and paracrine substances

Question 2

How does the ANS control the gut?

Answer 2

Cell bodies in CNS

Pre (ACh)/postganglionic (ACh)

Preganglionic fibres synapse with ganglia outside the CNS – postganglionic fibres synapse on peripheral organs

Question 3

What is the sympathetic NS role in the gut?

Answer 3

Reduces blood flow to gut inhibiting GI function

Form:
greater (T5-9),
lesser (T10-11)
least (T12) splanchnic nerves

Question 4

Outline the parasympathetic supply to the GI tract

Answer 4

Craniosacral output

Vagus N (cranial N)

Pelvic splanchnic Ns (S2-4)

Fibres release ACh, gastrin releasing peptide, vaso inhib peptide

Question 5

What are the 2 major plexuses in the enteric NS?

Answer 5

Submucosal = submucosa, secretions, blood flow

Myenteric = between circular and longitudinal muscle, motility

Question 6

What is the enteric NS?

Answer 6

Governs the function of the GI tract

Controls motor functions, local blood flow, mucosal transport and secretions, and modulates immune and endocrine functions

Can operate independently

Question 7

Describe the role of hormones/peptides which affect the motility/secretions in the gut

Answer 7

Somatostatin = inhib gastrin and secretin

Gastrin releasing peptide (GRP) = increase release of gastrin from G cells

Question 8

What are the 2 broad categories of GI hormones?

Answer 8

Gastrin family = gastrin, cholecystokinin

Secretin family = secretin, gastric inhib polypeptide (GIP)

Question 9

What is the role of gastrin?

Answer 9

Increases gastric acid secretion

Question 10

What is the role of cholecystokinin?

Answer 10

Increase pancreatic/gallbladder secretions

Question 11

Outline the role of secretin

Answer 11

Increases HCO3, decreases gastric acid secretion

Question 12

Discuss the role of gastric inhib polypeptide

Answer 12

Increases insulin, decreases gastric acid secretion

Question 13

What is an appendicitis?

Answer 13

Normally follows illness

Lymphoid ring enlarges = blocks

Initial pain = visceral peritoneum = vague and midline

Later pain = grows, coming in contact with parietal peritoneum = somatic, radiates to R iliac fossa

Question 14

Relate visceral referred pain to the embryological development of the gut

Answer 14

Viscera gets distended

Visceral peritoneum doesn’t have its own nerve supply

Viscera have afferent Ns that trace greater (T5-9), lesser (T10-11), least (T12) Ns = signal goes back to that level = makes assumption pain is coming from that dermatome

Question 15

Where do certain zones of the gut present their visceral pain?

Answer 15

Foregut = epigastric

Midgut = periumbilical

Hindgut = suprapubic/hypogastric

Question 16

What are the common types of movements are present in the GI tract?

Answer 16

Peristalsis = propels gut contents, one direction

Segmentation = mixes gut contents

Mass movement = rapid movement of contents into the rectum

Question 17

What is a paralytic ileus?

Answer 17

Movement temporally impaired

Typically after GI surgery

Question 18

List the general secretions of the GI

Answer 18

Water = for reactions

Acid = stomach

Alkali = to combat acid

Enzymes = to break things down

Mucus = lubricant for materials that must pass over membranes

Waste products = bilirubin, cholesterol

Emulsifiers = bile salt dealing with fat

Intrinsic factor = to absorb vitamins

Question 19

Where do GI secretions come from?

Answer 19

Salvia, gastric, intestinal (liver, pancreas)

Question 20

Classify the major types of gastrointestinal secretions and discuss their function

Answer 20

Stomach acid = barrier to infect, prepare proteins for digestion, activate enzymes

HCO3 = neutralise acid

Waste products = mainly from liver

Emulsifiers = bile salts increase area of lipids to aid digestion by lipases

Mucus = hold bicarb, lubricates, catches bacteria, antibacterial

Enzymes = break down protein, fat, carb

Question 21

What are the principles of absorption in the gut?

Answer 21

Movement across enterocytes, cytosol, basolateral mem, then into the capillary

Paracellular (tight junctions) movement in the SI

Have to be small enough

Question 22

What gets absorbed in the gut?

Answer 22

Carb, proteins, lipids, fat sol vits, water sol vits, vit B12, bile salts, Ca, Fe, electrolytes, water

Question 23

Explain why it is necessary for water to move in both directions across the gut lumen

Answer 23

Water passively follows the movement of electrolytes/nutrients

Stool needs to be desiccated

Too little water and stool wont pass