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BIOM1052 > The GIT > Flashcards

The GIT Flashcards

1
Q

The gastrointestinal tract is approximately …meters in an adult

A

4.5

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2
Q

What are the 4 key processes of the GIT?

A

Motility
* Digestion
* Secretion
* Absorption

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3
Q

What are the 6 steps on the GIT in order?

A
  • Ingestion
  • Motility
  • Digestion
  • Secretion
  • Absorption
  • Defecation
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4
Q

Pair the parts of the GIT with their function:

  1. Oral cavity, pharynx,
    oesophagus, anal canal
  2. Stomach
  3. Small intestine
  4. Large intestine

A. Absorptive
B. Protective
C. Absorptive/protective
D. Secretory

A

1B, 2D, 3A & 4c

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5
Q

Which of the following is NOT composed of simple squamous epithelium?

  1. Oral cavity, pharynx,
    oesophagus, anal canal
  2. Stomach
  3. Small intestine
  4. Large intestine
A

1 is composed of stratified squamous epithelium

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6
Q

In which parts of the GIT does food get propelled forward?

A

Esophagus
Stomach
Small & Large intestines

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7
Q

In peristalsis which of the following comes first?

A. Contraction of circulatory muscles
B. Contraction of longitudinal muscles

A

A.

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8
Q

In peristalsis circulatory muscles contract ahead/behind the food bolus whilst longitudinal muscles contract ahead/behind the food bolus

A

behind
ahead

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9
Q

Segmentations occurs in which parts of the GIT?

A

The small and large intestine

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10
Q

T or F
Segmentation is slow

A

T

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11
Q

T or F
Segmentation is not mechanical digestion

A

F

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12
Q

There are 9-12 contractions per minute in the small/large intestine and 3-12 contractions per minute in the small/large intestine

A

small
large

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13
Q

Which function of the GIT am I?
- Mixes chyme with digestive secretions
- Increases exposure to
epithelium for absorption

A

Segmentation

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14
Q

Involuntary control of the GIT can be caused by…

A

External stimuli
Long reflexes

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15
Q

Examples of voluntary control of the GIT are…

A

Ingestion & swallowing
Defecation (some)

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16
Q

Internal stimulation of the GIT tract activates what 3 types of receptors?

A

Chemoreceptors,
osmoreceptors,
mechanoreceptors

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17
Q

What are the effectors of the GIT tract?

A

Smooth muscle
or glands

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18
Q

What in the saliva can break down carbohydrates?

A

salivary amylase

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19
Q

What in the saliva can break down lipids?

A

lingual lipase

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20
Q

The oral cavity performs what four things for the GIT?

A
  • Ingestion and sensory analysis (pressure, temp and taste) before swallowing
  • Mastication (mechanical digestion) – teeth, tongue, and palatal surfaces
  • Lubrication – mixing with mucus and salivary secretions (mucins)
  • Limited digestion of carbohydrates &
    lipids (immediate chemical digestion)
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21
Q

What is the pH of lingual lipase?

A

pH 3.0 – 6.0

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22
Q

Match the oral cavity glands with their functions:

  1. Parotid gland
  2. Submandibular gland
  3. Sublingual gland:

A. Salivary amylase → starch breakdown
B. Mucus → buffering & lubrication
C. Buffers, glycoproteins (mucin) + salivary amylase

A

1A, 2C and 3B

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23
Q

Saliva is …% water

A

99.4

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24
Q

Other than water, what is saliva composed of?

A

Electrolytes, antibodies, buffers (pH 7.0),
mucins, enzymes, immunoglobulins, lysozomes

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25
Q

What can activate the salivary centre in the medulla?

A

The cerebral cortex (upon seeing, smelling or thinking about food)
Pressure receptors and chemoreceptors in the mouth

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26
Q

What events take place when the salivary centre in the medulla is activated?

A

The medulla activates autonomic nerves which activate salivary glands which increases salivary secretion

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27
Q

What nerves innervate the taste buds?

A

Trigeminal (CN V), Facial (CN VII) & Glossopharyangeal (CN
IX)

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28
Q

T or F
There aren’t chemoreceptors on taste buds

A

F

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28
Q

During the buccal phase of digestion afferent signals are sent to the swallowing centre via
… and … nerves

A

Trigeminal & Glossopharyngeal

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29
Q

Is the pharyngoesophageal sphincter closed or open when swallowing?

A

closed

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30
Q

Efferent signals via … and … nerves mediate peristaltic contractions in
esophagus muscles

A

Vagus & Glossopharyngeal

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31
Q

The Body of the stomach is also known as the…

A

oxyntic mucosa

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32
Q

Which part of the stomach has the most gastric glands?

A

the body/oxyntic mucosa

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33
Q

Temporary storage of the stomach ranges from …mL to …L

A

50
1.5

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34
Q

What does the stomach secrete?

A

HCl, pepsinogen, intrinsic factor, gastric lipase

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35
Q

What does the stomach secrete to break down proteins?

A

HCl and pepsin

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36
Q

What does the stomach secrete to break down fats?

A

gastric lipase

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37
Q

Chyme is composed of…

A

bolus + gastric secretions

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38
Q

What does the stomach absorb?

A

Some absorption – water, ions, alcohol (lipid soluble), aspirin (weak acid,
lipid soluble)

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39
Q

How does gastic mixing occur?

A

When the pyloric sphincter closes abruptly chyme is disrupted and slushes backwards

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40
Q

What three exocrine cells aid in chemical digestion?

A

Mucous cells
* Parietal cells
* Chief cells

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41
Q

Match the cell to its secretion:

A. Mucous cells
B. Parietal cells
C. Chief cells

  1. HCl, intrinsic factor
  2. pepsinogen, gastric lipase
  3. mucous
A

A3, B1, C2

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42
Q

Exocrine cells are stimulated by…

A
  • Vagus & intrinsic nerves
  • pH of lumen
  • Distension from presence of bolus
  • Chemical contents (proteins)
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43
Q

Enterochromaffin-like (ECL) cells secrete
… and are stimulated by what two things?

A

histamine

  • Triggered by gastrin
  • Increases Chief & Parietal cell activity
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44
Q

G Cells secrete … (acts via bloodstream) and are stimulated by what two things?

A

gastrin

  • Mediated by Vagus nerve & presence of proteins
  • Increases Chief & Parietal cell activity
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45
Q

D Cells secrete … and are stimulated by what two things?

A

somatostatin

  • Stimulated by acid accumulation in duodenum
  • Decreases Chief, Parietal & ECL cell activity
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46
Q

List the three Regenerative (stem) cells/Entero-endocrine cells (regulation) of the GIT

A

D cells
G cells
ECL cells

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47
Q

… acid maintains stomach lumen and provides non-specific disease resistance by destroying most ingested pathogens

A

Hydrochloric

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48
Q

H+ and Cl ions are
released as …
and combined in …
as HCl

A

ions
lumen

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49
Q

T or F
HCl is critical for enzyme activation

A

T

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50
Q

… converts pepsinogen (secretes by chief cells) to pepsin (active enzyme)

A

HCl

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51
Q

Pepsin is a … enzyme –
digests proteins

A

proteolytic

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52
Q

The mucous in the gut provides protection from what?

A

Protection from acidic
environment and pepsin

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53
Q

Stomach activity involves three phases – …, … and …
Mediated by …, … and … factors

A

Cephalic, Gastric & Intestinal

Neural, hormonal and local

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54
Q

Acetylcholine (Ach) is released by …. in the stomach, under control of …. & …

A

intrinsic nerve plexuses
short local reflexes
vagus nerve

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55
Q

Gastrin (G cells) require …. for release, stimulates … and … cell activity

A

vagal stimulation
chief and parietal

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56
Q

Histamine (ECL cells) – released in response to …, secondary stimulant of … and … cells

A

gastrin
chief and parietal

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57
Q

Somatostatin (D cells) – released in response to … accumulation in the …
… affect on …, … and … cells

A

acid
duodenum
duodenum
inhibitory
parietal, G & ECL

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58
Q

… receptors are responsible for distension and emptying of stomach and duodenum

A

Stretch

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59
Q

Stretch receptors are located in the ….

A

small intestine

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60
Q

Enterogastrones (CCK, secretin) – presence of … in duodenum, … affect on …. and ….

A

chyme
inhibitory
gastric secretions and motility

61
Q

The … phase of gastric secretion is short (minutes) whilst the … and … phases are long (hours)

A

cephalic
gastric and intestinal

62
Q

Which mechanisms does the body use in order to prepare the stomach for the arrival of food?

A

The CNS uses the vagus nerve to stimulate the submucosal plexus, which then stimulates the mucous, chief, parietal and g cells to secrete their respective products (gastric juices). (Enteric neural stimulation of gastric cells)

63
Q

(referring to the mechanics of the gastric phase of digestion)

Distension is detected by … receptors and alerts the … plexus
An elevated pH detected by …receptors and alerts the … plexus
Partially digested peptides promote … cells to secrete more …

A

stretch
myenteric
chemo
submucosal
G
gastrin

64
Q

During the gastric phase of digestion the presence of partially digested peptides promote G cells to secrete more gastrin. What effects does gastrin then have on the stomach?

A

It encourages chief and parietal cells to secrete more pepsinogen and HCL and enhances gastric motility

65
Q

During the gastric phase of digestion distention and an elevated pH are detected by stretch and chemoreceptors. What effects does this then have on the stomach?

A

The stretch and chemoreceptors send messengers to the submucosal and myenteric plexuses which then increase stomach contractions and promote gastric secretions from chief, parietal, mucous and G cells

66
Q

During the intestinal phase of digestion … and … trigger the enterogastric reflex

A

distension
low pH

67
Q

During the intestinal phase of digestion a low pH triggers … cells to release …

A

D
somatostatin

68
Q

The presence of lipids and carbohydrates in the stomach triggers the release of … and … which then inhibit the activity of … and … cells and peristalsis

A

CCK and GIP
chief and parietal

69
Q

A decreased pH in the stomach triggers the release of …, … and ….which then inhibit the activity of … and … cells and peristalsis

A

secretin
CCK and GIP
chief and parietal

70
Q

What are the 3 actions of the intestinal phase of digestion?

A
  • ↓ gastric contractility & gastrin secretion
  • Stimulation of accessory organs
71
Q

… and … stimulate accessory organ
functions

A

CCK
Secretin

72
Q

What effects does secretin have on the liver?

A

Increase bile, HCO3
production

73
Q

Presence of …, … and …
stimulate release of enterogastrones

A

lipids, proteins & carbs

74
Q

T or F
Choleocystokinin (CCK) and secretin stimulate accessory organ functions

A

T

75
Q

What are the 6 steps of the accessory organs?

A

1- Chyme enters duodenum
2- CCK & secretin
released
3- CCK causes pancreas to secrete digestive enzymes.
Secretin causes pancreas to secrete HCO3 & mucous
4- Secretin causes liver to increase bile and HCO3 production
5- CCK causes gallbladder to contract and relax sphincter so bile enters duodenum
6- Secretion of digestive
enzymes, buffers & bile for
chemical digestion in SI

76
Q

What effect does secretin have on the liver?

A

Increase bile, HCO3
production

77
Q

What effect does CCK have on the gallbladder?

A

Contract gallbladder
Relax sphincter
Bile enters duodenum

78
Q

What effect does CCK have on the pancreas?

A

Causes the pancreas to secrete digestive enzymes

79
Q

What effect does secretin have on the pancreas?

A

Causes the pancreas to secrete HCO3 & mucous

80
Q

What is the endocrine proportion of the pancreas called?

A

The islets of Langerhans

81
Q

T or F
Endocrine glands have local effects
Exocrine glands have systemic effects

A

F
vice versa

82
Q

What two cells compose the exocrine portion of the pancreas?

A

Duct and acinar cells

83
Q

What do duct cells secrete?

A

Water, ions, HCO3

84
Q

What do acinar cells secrete?

A

Digestive enzymes

85
Q

What are the 2 endocrine hormones of the pancreas?

A

insulin and glucagon

86
Q

What function do the products secreted by duct cells perform?

A

Neutralise acid in the duodenal lumen

87
Q

What function do the products secreted by acinar cells perform?

A

They digest fat, protein and carb products in
duodenal lumen

88
Q

T or F
The vagus nerve stimulates acinar cells during the cephalic phase of gastric function

A

T

89
Q

Pancreatic nucleases break down … into …

A

nucleic acids (DNA/RNA)
nucleotides

89
Q

Pancreatic lipase breaks down … into …

A

Lipids (triglycerides) → fatty acids, monoglycerides

90
Q

Pancreatic amylase breaks down … into …

A

Starch, glycogen (carbs) → tri/disacchirides

91
Q

What proteolytic enzymes in the pancreas break down proteins into di/tripeptides?

A
  • Trypsinogen (inactive form)
  • Chymotrypsinogen
  • Pro-carboxypeptidase
92
Q

What comprises the biliary system?

A

Liver & gallbladder & ducts

93
Q

What comprises the hepatic blood supply?

A

The hepatic artery and hepatic portal vein

94
Q

T or F
The liver is composed of 3 lobes

A

F
2 (left and right)

95
Q

What are sinusoids?

A

“Leaky capillaries”
Highly permeable
endothelium – rapid and
rich blood supply to
hepatocytes
Waste removal – Kupffer
cells engulf & destroy old
RBCs, bacteria
Drain into central vein

96
Q

What are the functions of the liver?

A
  • Carbohydrate, lipid and protein metabolism
  • Store vitamins (A, D, K) and minerals (iron, zinc, magnesium)
  • Phagocytosis of RBC, WBC and bacteria
  • Processing of hormones and drugs
  • Bile salt and bile production (increased upon secretin stimulation)
97
Q

What are bile canaliculi?

A

Collection of bile
secreted by
hepatocytes

98
Q

What sphincter connects the bile duct and the pancreatic duct to the duodenum?

A

Hepatopancreatic
sphincter
(sphincter of Oddi)

99
Q

What sphincter appears on the bile duct just before the hepatopancreatic sphincter?

A

Sphincter of common
bile duct
(sphincter of Boyden)

100
Q

What is bile composed of?

A
  • Water & ions – to dilute & buffer acids in chyme
  • Bilirubin – from haemoglobin
  • Cholesterol
  • Bile salts – made from cholesterol
101
Q

What drains into gallbladder via cystic duct?

A
  • Storage of bile – capacity for 40-70mL
  • Concentrates bile – osmotic efflux of water
  • Releases bile upon digestive need – neural &
    hormonal stimulation
102
Q

Bile is produced in the …, stored in the …

A

liver
gallbladder

103
Q

Bile secretion triggered during … phase of gastric function

A

Intestinal

104
Q

T or F
The liver creates bile continuously

A

T

105
Q

T or F
Bile becomes more concentrated the longer it stays in the gallbladder

A

T

106
Q

When chyme is present in the duodenum, CCK is released. What effects does this have on the gallbladder?

A

CCK triggers dilation of the hepatopancreatic sphincter and contraction of the gallbladder. This ejects bile into the duodenum through the duodenal ampulla

107
Q

In the lumen of the digestive tract, bile salts break down lipid droplets by …

A

emulsification

108
Q

…% of bile salts are re-absorbed at the terminal ileum

A

95

109
Q

What accessory organ of the GIT is the major site of chemical digestion and 90% of all nutrient absorption?

A

The small intestine

110
Q

The small intestine extends from the … to the …

A

pyloric sphincter (stomach-SI junction)
ileocecal sphincter (SI-LI junction)

111
Q

What are the 3 segments of the small intestine and their respective lengths?

A
  • Duodenum – first 25 cm, site of accessory organ
    secretions
  • Jejunum – 2.5 m, site of most chemical digestion &
    nutrient absorption!
  • Ileum – 3.5 m, longest and final portion before large intestine
112
Q

What are the secretory cells of the mucosal layer of the small intestine?

A
  • Brush border cells – enzymes for chemical digestion
  • Goblet cells – mucins to buffer acidic content
  • Paneth cells – antimicrobial peptides,
    immunomodulating proteins to regulate the gut microbiome (gut immunity)
  • Submucosal glands – mucous, HCO3
113
Q

T or F
Stem cells aren’t present in the mucosal layer of the small intestine

A

F

114
Q

T or F
Digestion begins prior to the small intestine

A

T

115
Q

T or F
Solely chemical digestion facilitates the breakdown of chyme contents into simplest units

A

F
Chemical AND mechanical digestion facilitates breakdown of
chyme contents into simplest units

116
Q

Nutrients have to cross what TWO membranes to be absorbed?

A
  • From the lumen across gut epithelium
  • Across basolateral membrane into capillaries/lacteal
117
Q

Fructose is absorbed across the gut lumen via facilitated diffusion by …

A

GLUT5

118
Q

Glucose is absorbed across the gut lumen via what two methods?

A

Sodium-linked cotransport & secondary active
transport

119
Q

Glucose, galactose and glucose are transported into blood capillaries by …

A

GLUT2

120
Q

What is enterokinase?

A

A protease of the intestinal brush border that specifically cleaves the acidic propeptide from trypsinogen to yield active trypsin.

121
Q

Which brush border enzymes convert small peptides → amino acids?

A

Aminopeptidase and dipeptidase

122
Q

Which intracellular enzymes convert small peptides → amino acids?

A

intracellular peptidase

123
Q

Which proteolytic enzyme converts large → small polypeptides?

A

Chymotrypsin

124
Q

Which proteolytic enzyme converts small polypeptides → amino acids?

A

Carboxypeptidase

125
Q

Which proteolytic enzyme activates other peptidases?

A

Trypsinogen (in its active form trypsin)

126
Q

What modes of transport help amino acids cross the gut epithelium?

A

Sodium-linked cotransport & secondary active transport

127
Q

What facilitates the transportation of sodium peptides across the gut epithelium?

A

Sodium-linked tertiary active transport
Na+
-H+ counter-transport: Na+ into cell down
conc gradient; H+ out of cell against conc
gradient
* Peptides co-transported with H+ down conc
gradient into cell

128
Q

Bile salts used to package simple fats into …

A

micelles

129
Q

Bile salts bind to & break apart large fat …

A

globules

130
Q

T or F
Lipids passively diffuse across the gut epithelium

A

T

131
Q

Lipids coagulate with lipoproteins to become…

A

Chylomicrons

132
Q

How to chylomicrons leave the epithelial cells of the villus and enter the central lacteal ducts via what process?

A

exocytosis

133
Q

What are the 3 main functions of the large intestine?

A

Absorption
Storage of waste
Defecation

134
Q

… cells of the intestinal
glands have local reflexes in response to friction from the passing faecal matter

A

Goblet

135
Q

What is the outer longitudinal muscle of the externa muscalaris called?

A

Taeniae coli

136
Q

T or F
The Taeniae coli is organised as 4 individual “bands” along length
of colon

A

F
3

137
Q

What part of the large intestine is formed by tonic contraction of inner,
circular muscle layer?

A

Haustra

138
Q

T or F
Haustra are segmented pouches separated by
haustral folds

A

T

139
Q

What is meant by the words ‘Haustral “shuffle”’

A

The haustral shuffle is how motility works along the large intestine wherein phasic contraction of circular muscle at adjacent sections churns contents. Slow progression (shuffle) along colon length, ~ every 30 mins

140
Q

What is the gastro colon -colic reflex?

A

Progressive, powerful, sweeping (mass) contractions at colon sections

141
Q

How many gastro colon -colic reflex does a human have each day?

A

3-4

142
Q

Feces are stored in the …. until defecation

A

distal portion (sigmoid
colon)

143
Q

How are stretch receptors in the rectum stimulated and what nerve is innovated?

A

When feces move into and distend the rectum, stimulating stretch receptors that send signals via afferent fibers to spinal cord neurons.

144
Q

During defecation a spinal reflex is initiated in which
… motor (efferent)
fibers stimulate contraction of the
… and …., and
relaxation of the ….

A

parasympathetic
rectum and sigmoid colon
internal anal sphincter

145
Q

If it is convenient to defecate, voluntary … neurons are …, allowing external anal sphincter to relax so feces may pass

A

motor
inhibited

146
Q

T or F
Messages from the motor
nerve to the external
anal sphincter are voluntarily controlled

A

T

147
Q

T or F
When it comes to defecation neural stimulation is voluntarily controlled whilst neural inhibition is involuntarily controlled

A

F
Vice versa

148
Q

T or F
Messages through the motor nerve to the internal anal sphincter sent via the parasympathetic nervous system are voluntary

A

F
Involuntary

BIOM1052 (9 decks)

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