GI 7

Question 1

Defecation

Answer 1

Two reflexes initiated by distension of the rectum
Short and long reflex

Question 2

Short reflex of defecation

Answer 2

Local peristaltic waves

Question 3

Long reflex of defecation

Answer 3

Relaxation of internal sphincter (smooth muscle)
Contraction of external (skeletal)
More forceful peristaltic contractions form parasympathetic input

Question 4

What is the defecation reflex completed by

Answer 4

Voluntary relaxation of external sphincter (skeletal) and aided by increased abdominal pressure

Question 5

Diarrhea

Answer 5

An increase in frequency, volume, and fluid content of feces due to increased secretion, reduced absorption or increased motility

Question 6

What is diarrhea induced by

Answer 6

Osmotic, secretory, inflammatory or motility

Question 7

Osmotic diarrhea

Answer 7

Excess solute stays within lumen of GI which prevents normal amt of H20 absorption
Water stays and leaves

Question 8

Inflammatory diarrhea

Answer 8

Due to infection
Breaks barrier and causes damage to int preventing proper absorption

Question 9

What can secretory be caused by

Answer 9

Immune cells (flush out GI)
Bacteria

Question 10

How does cholera cause secretory diarrhea

Answer 10

Cholera toxin causes persistent opening of Cl leak channels
Cl draws Na, water into lumen
Creates watery secretion

Question 11

Use of penicillin based antibiotics can alter

Answer 11

Normal bacterial flora
Remaining bacteria have reduced competition for space and nutrients

Question 12

What does reduced competition of bacteria leave you prone to

Answer 12

Infection by C.difficile

Question 13

What does c. Difficile cause

Answer 13

Colitis: watery diarrhea, fever, nausea, abdominal pain

Question 14

What is cure for C. difficile infection

Answer 14

Fecal transplant from healthy individual
Rapid addition of good bacteria

Question 15

Vomiting

Answer 15

Contents of stomach and occasionally small int are forcefully expelled through mouth
- associated with nausea

Question 16

Vomiting center is where

Answer 16

Medulla

Question 17

Vomiting center in medulla causes 3 responses

Answer 17

1. Retrograde contractions in small int and stomach (towards stomach +lower esophageal)
2. Contraction of abdominal inspiratory muscles (diaphragm) increases gastric pressure
3. Relaxation of esophageal sphincters

Question 18

What is outside BBB and communicated with vomiting center

Answer 18

Chemoreceptor trigger zone

Question 19

Causes of vomiting

Answer 19

Abnormal vestibular input (motion sickness, spinning)
Input from sensory receptors in stomach and intestines
Direct input from drugs, toxins in chemoreceptor trigger zone

Question 20

Where is immune function in GI tract

Answer 20

Gut -Associated lymphoid tissue (GALT)
80% of lymphocytes located in gut

Question 21

What cells play big role in immune responses

Answer 21

M cells

Question 22

How do M cells work in immune responses

Answer 22

Receptor mediated endocytosis
- transport antigens to macrophages, lymphocytes, and dendritic cells
- release cytokines to attract more immune cells

Question 23

What do cytokines do in gut

Answer 23

• attract more immune cells to attack invaders
• trigger increased Cl secretion (diarrhea) to flush out pathogens

Question 24

What do we rely on to regulate intake

Answer 24

Behavioural mechanisms
Appetite and satiety

Question 25

During feeding state and 3-6 hours following what state is body in

Answer 25

Anabolism Body will store nutrients

Question 26

During fasting state body is in

Answer 26

Catabolism High levels of breakdown

Question 27

What is the hunger center

Answer 27

LH- Lateral hypothalamus

Question 28

Communication between 2 areas for satiety

Answer 28

ARC - Arcuate nucleus PVN- paraventricular nucleus

Question 29

What in medulla plays role in appetite and satiety

Answer 29

NTS- nucleus tractus solitarii

Question 30

What maintains body weight at a relatively stable value

Answer 30

Behavioural mechanisms

Question 31

Theories of long term regulation of feeding behaviour

Answer 31

1. Glucostatic theory 2. Lipostatic theory

Question 32

Glucostatic theory

Answer 32

Glucose metabolism in the hypothalamus regulates food intake (proved to be short term)

Question 33

Lipostatic theory

Answer 33

Signals from the bodies fat stores regulate food intake (long term regulator)

Question 34

If weight is lost during starvation

Answer 34

Weight is rapidly gained when food is freely available

Question 35

What is ob/ob gene

Answer 35

Encodes a protein that tell brain fat reserves are normal

Question 36

What was ob/ob mouse

Answer 36

Obese

Question 37

Leptin

Answer 37

Released from adipocytes and regulates body mass by acting on neurons of hypothalamus that decrease appetite and increase energy expenditure

Question 38

In most obese individuals what does leptin do

Answer 38

Brain doesnt respond to it

Question 39

Elevated leptin

Answer 39

Decrease energy intake Increase energy output

Question 40

What does leptin act on

Answer 40

Arcuate nucleus

Question 41

Response to elevated leptin

Answer 41

1. Inhibition of lateral feeding center 2. Activation of paraventricular nucleus (PVN)

Question 42

What are 2 responses of activation of PVN from increased leptin

Answer 42

Humoral response Visceromotor response

Question 43

Humoral response

Answer 43

Increase TSH, ACTH from pituitary - increased metabolic rate throughout body

Question 44

Visceromotor response

Answer 44

Increased sympathetic output - increase body temp to increase metabolism

Question 45

What do anorectic peptide do when increased leptin

Answer 45

Reduce food intake

Question 46

Response to decreased leptin

Answer 46

1. Reduced activation of a-MSH and CART neurons 2. Activation of NPY and AgRP containing neurons

Question 47

Reduced activation of a-MSH and CART neurons

Answer 47

Reduced activation of PVN (decreased TSH and ACTH) - Decreased metabolic rate Activation of parasympathetic output

Question 48

Activation of NPY and AgRP containing neurons

Answer 48

-stimulation of feeding center - further inhibition PVN

Question 49

Orexigenic peptides

Answer 49

From NPY/AgRP neurons of Arcuate nucleus - facilitate eating

Question 50

When is aMSH/CART neuron activity high

Answer 50

High leptin level

Question 51

Why did leptin supplementation fail to treat obesity

Answer 51

Have to have OB/OB mutation (rare)