1
Q
What is the function of the GI tract?
A
Convey food along GIT, allowing it to be broken down into small molecules which can be absorbed into the circulation
2
Q
Name 6 activities of the GIT.
A
- Ingestion
- Secretion (glandular activity for chem breakdown)
- Motility (propulsion & physical breakdown)
- Digestion
- Absorb (transfer to blood circulation)
- Defecation
3
Q
Provide the values for the digestive and absorptive capacity for the following… (GIT)
Carbohydrates: __%
Fats: __%
Proteins __%
A
99
95
92
4
Q
Propulsive, secretory and absorptive activities are highly coordinated by _____ and ____ mechanisms.
A
Neural
Hormonal
5
Q
True or false?
The lumen is considered intracellular environment.
A
False!
Extracellular
6
Q
The length of the GIT is approximately ___ in a living adult.
A
4.5m
7
Q
The total internal surface area of the GIT is ___x larger that the external surface area
A
600
8
Q
True or false?
The external surface area is 600x larger than the total internal surface area.
A
False!
The INTERNAL is 600x larger than EXTERNAL.
9
Q
What are the 4 main layers of the GIT wall?
A
Mucosa
Submucosa
Muscularis externa
Serosa
10
Q
The muscularis externa layer of the GIT is composed of which type(s) of fiber(s)?
A
Longitudinal fibers
Circular fibers
11
Q
______ (layer of GIT wall): thin, tough layer of connective tissue and is continuous in places with the abdominal mesentery
A
Serosa
12
Q
Muscular externa (GIT wall layer) is striated muscle found in the …..
A
Oral cavity
Pharynx
Upper 1/3 of esophagus
External anal sphincter
(Note: the rest of the GIT is smooth muscle)
13
Q
The outer layer of the muscular externa of GIT is composed of _____ fibers.
When contracted, they _____.
A
Longitudinal
Shorten GIT
14
Q
The inner layer of muscular externa (GIT wall layer) is composed of _____ fibers.
When contracted…
A
Circular
GIT narrows
15
Q
______ (GIT wall layer): loose connective tissue which contains a neuronal network, lymphatics and blood vessels.
A
Submucosa
16
Q
The mucosa layer of the GIT is composed of _____.
A
Muscularis mucosae (smooth muscle)
17
Q
The epithelial layer of the mucosa layer of GIT contains…
A
Secretory (exocrine and endocrine) + absorptive cells
18
Q
The lamina propria layer of the mucosa layer of the GIT contains…
A
Loose connective tissue
19
Q
True or false?
The neurons of the ENS reside within the wall of the GIT
A
True
20
Q
The ENS …. (4) activities of muscular, secretory & absorptive elements of the GIT.
A
Initiates
Programs
Regulates
Coordinates
21
Q
Sensory neurons in the GIT are found where?
A
Mucosa
Muscle
22
Q
_____ neurons activate the secretory and muscle cells.
A
Motor/effector
23
Q
Many _______ expand the responses to stimuli in the GIT, allowing for integration over long distances.
A
Interneurons
24
Q
What are the 2 GIT plexuses?
A
Submucosal
Myenteric (between longitudinal and circular muscle layers)
25
True or false?
The myenteric and submucosal plexuses behave as one functional unit
True!
(Even if they are anatomically distinct)
26
What elements are required for reflex arcs (3)?
Sensory neurons
Motor/effector neurons
Interneurons
27
The ENS consists of ____ cells and their processes which synapse with **smooth muscle** cells, **endocrine** and **exocrine** cells and other ____ cells.
Ganglion
Ganglion
28
Enteric **sensory fibers** have cell bodies in ____ and get information from gut ____ and ____ (receptors).
Plexuses
Chemoreceptors
Mechanoreceptors
29
**parasympathetic** neurons reach the wall of the GIT as ______ fibers, synapsing via ____ receptors with enteric neurons (both excitatory and inhibitory), exerting an _____ effect.
Preganglionic
Nicotinic acetylcholine (ACh)
Excitatory
30
**Sympathetic** neurons reach the wall of the GIT as _______ fibers, synapsing via ______ receptors with enteric neurons (both excitatory and inhibitory), exerting an _____ effect.
Postganglionic
Noradrenaline (norepinephrine)
Inhibitory
31
**sympathetic** neurons also innervate **smooth muscle** in blood vessels of GIT, causing ________.
Vasoconstriction
32
______ neurons allow for ‘’long reflexes’’ (GIT).
Sensory
33
Acetylcholine in GIT is blocked by _____.
Atropine
34
The ANS can only influence the GIT via the ____
ENS
35
Parasympathetic input to GIT results in ____ of blood vessels
dilation
36
Sympathetic input to GIT results in ____ of blood vessels
constriction
37
True or false?
The ENS must operate with input from CNS
False!
Can operate without
38
The **ENS** regulates GIT via _____ (short/long) , _____ (intramural/extrinsic) **reflexes**.
short
intramural
39
The **ANS** regulates GIT via ____ (short/long), _____ (intramural/extrinsic) **reflexes**.
long
extrinsic
40
the ANS has synaptic connections with ____ neurons
ENS
41
What causes activation of the **ANS**?
sensory afferent fibers from GIT --> CNS
42
True or false?
**Efferent autonomic neurons** cannot act directly on muscle/gland
True!
They affect neurons of ENS (which then act on muscle/gand)
43
**Non-GIT hormones** may influence....
growth and development of GIT
44
**GIT hormones** may influence....
activities outside the GIT
45
**GIT hormones** regulate....
activities **inside** the GIT
46
**Diffuse endocrine system** is composed of **endocrine cells** scattered in the GIT ____ (layer)
mucosa
47
What is the largest, most diverse endocrine system in the body?
Diffuse endocrine system
48
What are the 5 most important GI hormones?
Gastrin
CCK
Secretin
Somatostatin
GIP/VIP
49
GIT regulatory hormones are mostly _____.
peptides
50
GIT regulatory hormones are released from ____ (GIT layer) into _____ (blood) **-->** _____ (organ) **-->** ____ (organ) **-->** _____ (circulation) **-->** _______ (final destination)
mucosa
portal blood (hepatic portal vein)
liver
heart
systemic circulation
target cells
51
True or false?
GIT regulatory hormones have a single target
False!
They have multiple targets (excitatory and inhibitory)
52
True or false?
GIT regulatory hormones interact with other hormones and neurotransmitters in a synergistical manner only.
False!
They interact both in **synergistical**(potentiate one another) and **antagonistic** ways.
53
True or false?
Normally, flow in the GIT is fast, aboral, and meets little/no resistance.
False!
Flow is generally **slow** (the rest is true)
54
Propulsion (flow) in the GIT is dependent on what 2 factors regarding **gradients of pressure**?
**Peristalsis** (pushing contents forward)
**Segmentation** (effective for mixing)
55
List the phases of deglutition in order and whether they are voluntary or involuntary.
1. **Oral** (voluntary)
2. **Pharyngeal** (involuntary)
3. **Esophageal** (involuntary)
4. **Gastric** (involuntary)
56
''Voluntary'' steps in swallowing occurs at the ______.
Cortex
57
''Involuntary'' steps in swallowing occurs at the ____.
Medulla (deglutition center)
58
The transport of bolus (masticated, insalivated, mass of food) from anterior to posterior portion of mouth involves a series of reflexes coordinated in the ______.
**deglutition center** in the **medulla oblongata**
59
''Stretch'' of **pharyngeal receptors** leads to...
activation of the deglutition reflex
60
Where do the respiratory and digestive tracks cross?
Pharynx
61
True or false?
Respiration is briefly inhibited during the pharyngeal phase.
True
62
In the absence of a meal, what happens to the **upper esophageal sphincter**?
It is tonically closed
63
How is muscle contraction of the UES sustained during absence of a meal?
impulses originate in the **CNS**, mediated by the **vagal somatic nerve**, tonically releasing **ACh** onto the striated muscle, causing sustained muscle contraction
64
During deglutition, what happens to the **upper esophageal sphincter**
it **relaxes/opens** due to cessation of impulses (which leads to muscle relaxation)
65
Body of esophagus lies within the ____ cavity.
thoracic
66
True or false?
The pressure in the thoracic cavity is 5-10 mm Hg
False!
**-5** - **-10** mm Hg!! (negative)
67
What are the 2 main esophageal forces?
Gravity (small effect for liquids so less important)
Peristalsis (esophageal contents carried towards stomach)
68
Each time we swallow, a single _____ wave is generated
**primary** peristaltic
69
Primary peristalsis is a _____ reflex
deglutition
70
_______: time between the onset of stimulation and the response
latency
71
True or false?
There is decreased latency of activation in distal esophagus
False!
increased latency
72
True or false?
The proximal esophagus has the enteric circuitry necessary for the propagation of the peristaltic wave
False
**distal** esophagus ''...''
73
______: essential for initiating peristalsis in the **proximal esophagus**.
Vagus nerve
74
_____: essential for **continuing** and **propagating** peristalsis in the **distal esophagus**.
Intact ENS
75
Secondary peristalsis is initiated by...
local distension
76
Secondary peristaltic waves are mediated by...
**enteric reflexes** (Short, local reflexes)
**long reflexes** (vagal-vagal reflexes)
77
The closure of the lower esophageal sphincter is _____
myogenic (contracted at rest)
78
Relaxation of the lower esophageal sphincter is _____
neurogenic
79
True or false?
Increases in intraabdominal pressure increases pressure equally on the stomach and the intraabdominal segment of the LES
true
80
What does progesterone do to resistance of LES?
lowers it
81
What are the 3 motor functions of the stomach?
1. Temporary storage: 1-2L
2. Physical disruption and mixing of contents
3. Propulsion into duodenum (regulated propulsion)
82
bolus --> semi-liquid consistency = ____
CHYME
83
The proximal stomach is ____-walled
thin
84
the distal stomach is ____-walled
thick
85
What is the extra layer of muscularis externa in the stomach called?
oblique muscle (smooth muscle)
86
How does the stomach accommodate a meal?
receptive relaxation (restricted to proximal stomach)
87
If the vagi to the proximal stomach are cut...
receptive relaxation is limited, causing a great **increase** in intragastric pressure
88
True or false?
Receptive relaxation is restricted to the distal part of the stomach
False!
Restricted to the **proximal** part
89
Receptive relaxation starts with a _____ reflex, initiated by swallowing, causing an _____ of stomach muscle tone, and an ____ in intragastric volume.
This is a ____ reflex.
Vagally-mediated
Inhibition
Increase
Deglutition
90
**Local distension** created by the entering meal activates ______ neurons and _____ reflexes which **increase** and **sustain receptive relaxation**.
Local enteric sensory
Long (vago-vagal)
91
**Peristalsis** is the main form of contractile activity in the ____ stomach (does NOT occur in ____ stomach).
Distal
Proximal
92
True or false?
The upper stomach has rhythmic waves of partial depolarization.
False!
The upper stomach has a steady resting potential (-55mV).
The **lower** stomach has rhythmic waves of partial depolarization
93
There are _ waves of partial depolarization per minute in the stomach
3
94
True or false?
The basic electrical rhythm of the distal stomach occurs synchronously throughout the entire distal stomach.
False!
Only along the circumference of the stomach.
As we go more distally, there is a delay
95
Does the **basic electrical rhythm** of the distal stomach cause muscle contraction?
Not alone
96
The **second electrical signal** causes _____.
Muscle contraction
97
What is the **second electrical signal** in regards to basic electrical rhythm (of distal stomach) depolarization?
The ‘’spikes’’ / peaks of BER depolarization
98
The ______ of the stimulus determines the number of spikes on top of them **basic electrical rhythm** of distal stomach.
Magnitude
99
The **number** of spikes on top of the basic electrical rhythm determines the _____ of muscle contraction.
Amplitude
100
What is the origin of **basic electrical rhythm** of the distal stomach?
Non-neuronal, not ENS pacemakers!
They are **interstitial cells of Cajal** (ICC)
101
_______ function as the **pacemakers** for the spontaneous Basic Electrical Rhythm of the gastrointestinal tract.
Interstitial Cells of Cajal (ICC)
102
Where are **interstitial cells of Cajal** (ICC) located?
Between the smooth muscle layers and the enteric plexuses
103
**Frequency** of contractile activity of the stomach is determined by…
Basic electrical rhythm of distal stomach
104
Amplitude of the contractile activity of the stomach is determined by…
Magnitude of stimulus **stretch**, **ACh**
105
The band of contraction becomes ______ and the contractions _____ as it approaches the **pyloric sphincter**
Wider
Stronger
106
The entire terminal portion of the stomach — the antrum and the pyloric sphincter — contract synchronously to _____ the pyloric sphincter
Close
107
Pyloric sphincter is ___ at rest.
Open
108
The pyloric sphincter is closed by ____.
Antral peristalsis
109
Mixing is achieved by the **strong** ______ and the early **closure** of the _______.
Antral systole
Pyloric sphincter
110
Gastric emptying of **liquids** occurs due to…
**Pressure** difference between **proximal stomach** and **duodenum**
111
If vagus nerves to proximal stomach are cut (vagotomy).. what happens to change in pressure?
Increases (Therefore fluid will rush through)
112
How does vagotomy to distal stomach affect liquid emptying?
Not much effect
113
Meal is stored in the _____ of stomach.
Fundic reservoir (in proximal stomach)
114
What are 3 factors controlling Antral peristalsis?
1) stretch of muscle
2) local ENS reflex
3) vago-vagal reflex
115
Factors in the duodenum _____ the rate of gastric emptying/antral peristalsis.
Slow
116
Vomiting results from...
an increase in intraabdominal pressure due to the action of the diaphragm and abdominal muscles
117
Vomiting is controlled by the vomiting center in the ______.
midbrain
118
**imbalance** between parasympathetic and sympathetic activities _____ and ____ vomiting.
precedes
accompanies
119
Agents in the bloodstream can act on the ______ in the **medulla** (vomiting)
chemoreceptor trigger zone
120
**Chemoreceptor trigger zone** sits _____ (in relation to) the blood-brain barrier
outside
121
True or false?
The vomiting center is required for vomiting
true
122
List the 3 stages to vomiting in order
1. **Nausea** (psychic experience)
2. **Retching** (abrupt uncoordinated respiratory movements w/ glottis closed)
3. **Emesis** (actual expulsion of contents of upper GIT)
123
Most digestion and ALL absorption of nutrients occurs in the ________.
small intestine
124
What are the functions of the **upper** small intestine?
1. Neutralization (of chyme)
2. Osmotic equilibration
3. Digestion
4. Absorption
125
True or false?
intrinsic frequency of BER increases systematically from proximal to distal
False!
decreases
126
The frequency of intestinal contractions is governed by ___
BER
127
spikes in the intestinal contractions are phase-locked to ____
BER
128
spikes in the intestinal contractions are initiated by ___ or ____.
stretch
ACh
129
amplitude of contraction for intestinal contractions is related to...
number of spikes/burst
130
Net aboral movement in the small intestine is _____ (speed).
slow
131
in the small intestine, peristalsis is...
infrequent, irregular
weak, shallow
travels for short distances only (few centimeters)
132
intestinal peristalsis is mediated by...
a series of local reflexes
133
True or false?
The colon's contractile activity is slower than the small intestine
true
134
some H2O and ions are absorbed in the ____.
colon
135
What are functions of the colon (3)?
1. Mixing (promotes absorption of water and ions)
2. Propulsion (slow)
3. Storage
136
segmentation and peristalsis of colon is governed by an ____ BER
irregular
137
PHGY 210
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