Smooth muscle Intro and GI Flashcards
(116 cards)
1
Q
How is smooth muscle different from cardiac or skeletal?
A
Does not have true sarcomere
2
Q
Dense bodies contain
A
Alpha-actinin for thin filament attachment
3
Q
Thin, actin filaments attach to dense bodies located at the
A
cell membrane and within the cytosol
4
Q
Dense bodies are also sites where
A
intermediate filaments can bind
5
Q
Smooth muscle is specialized for
A
Slow, steady contraction
6
Q
Smooth muscle is under the influence of
A
ANS and hormones
7
Q
Smooth muscle produces a wave of contraction in the GI tract termed
A
peristalsis
8
Q
Smooth muscle cells are connected via
A
Gap junctions
9
Q
Smooth muscle cells have a rudimentary sarcoplasmic reticulum but lack
A
T- tubules
10
Q
Thin filaments of smooth muscle will have tropomyosin, but lack
A
troponin
11
Q
What consumes more ATP- smooth muscle ctx or striated muscle?
A
Striated
12
Q
Describe multi unit smooth muscle
A
- Few gap junctions, most cells in bundle are innervated
- Ex: Ciliary muscle, erector pili
13
Q
Describe single unit smooth muscle
A
- Many gap junctions
- 1-2 cells in bundle are innervated
- Variscosities are present for syncytium
- Ex: GI, uterine, tunica media of BVs, urinary bladder
14
Q
Intracellular Ca can be increased by what 3 pathways?
A
- VGCCs
- Receptor activated channels
- Receptor activated release of Ca from sarcoplasmic reticulum (IP3)
15
Q
Ca that is released from SR must be pumped back into SR by what?
A
Ca ATPase pump
16
Q
In order to lower intracellular calcium levels, the SUVSM must:
A
- Inhibit VGCC
- Pump Ca into SR by SERCA pumps
- Use exchangers, H/Ca or Na/Ca
17
Q
Mitochondria can also act as
A
a store for Ca in order to prevent apoptosis
18
Q
Once Ca enters cytosol of smooth muscle, it binds to what?
A
Calmodulin
19
Q
Calcium-calmodulin activated
A
myosin light chain kinase (MLCK)
20
Q
MLCK phosphorylated
A
myosin light chains and this will icnrease myosin ATPase activity
21
Q
Myosin light chain phosphatase is responsible for
A
the relaxation of smooth muscle
22
Q
Myosin light chain phosphatase (MLCP) will remove phosphate groups from myosin light chains to
A
cause relazation or prohibit continued contraction
23
Q
Nitric oxide can induce relazation of smooth muscle through
A
increased cGMP production
24
Q
Rho kinase can inhibit MLCP and this can
A
increase smooth muscle contraction
25
What are the main functions of GI system
- Provide environemnt for physical and chemical breakdown of food
- Provides environment for absorption of products of digestion
- Way to eliminate wastes
- Helps develop immune system
- Provides a symbiotic relationships for commensal bacteria
26
GI contains intrinsic innervation from
enteric nervous system (submucosal and myenteric plexuses)
27
Myenteric plexus is aka
Auerbach plexus
28
Submucosal plexus is aka
Meissner plexus
29
Serosal layer of GI faces the
blood
30
Musocal layer of GI faces the
lumen
31
Mucosal layer of GI will contain
Epithelial cells, lamina propria and muscularis mucosae
32
Submucosa of GI contains
Collagen, elastin, glands and more blood vessels
33
Circular muscle of muscularis is
thick and densly innervated
34
Longitudinal muscle of muscularis is
thin and contains few nerve fibers
35
Neurons do not make true synapses on GI smooth muscle and instead release neurotransmitters from
Varicosities along the length of the axon
36
GI involves 4 seperate, but interdependent control systems which include
- Enteric nervous system or neurocrines
- Endocrine secretions
- paracrine secretions
- Unitary visceral smooth muscle (gap junctions)
37
Postganglionic autonomic neurons will run along
the membranes of smooth muscle cells
38
Single, unitary visceral smooth muscle is dependent on
gap junctions and work as syncytium
39
Interstitial cells of Cajal (ICC) are found in the GI and serve as
Pacemaler cells
40
ICCs generate the slow waves and are abundant in
Myenteric plexus to stimulate peristalsis
41
What has the lowest rate of slow waves?
Stomach
42
What has the highest rate of slow waves?
Duodenum
43
What is the importance of the slow wave?
Sets frequncy of smooth muscle contraction
44
Are slow waves influenced by nerves or hormonal input?
No
45
Spike potentials are mediated by what?
The opening of non-selective cation channels (slow Ca/Na channels). APs occur on top of slow waves
46
Amount of force by muscle CTX is correlated with the appearance of
spike potentials
47
What are inhibitory signals
Opening of K channels causing membrane hyperpolarization
48
What are phasic contractions?
Rhythmic contractions followed by relaxation
49
Where are phasic contractions found?
In esophagus, distal stomach and S/L intestines
50
Phasic contractions are invovled in
mixing and propulsion
51
Phasic contractions require
pacemaker, APs to initiate Ca influx
52
What do tonic contractions do?
Maintain constant level of contraction without regular periods of relaxation
53
Tonix contractions are found where?
Upper stomach, lower esophagus, ileocecal and internal/external sphincters
54
Tonic contractions do not require what?
Pacemaker, or APs to intiate Ca influx
55
Excitatory junctional potentials (EJPs) can be summated to
Induce action potentials in smooth muscle
56
Inhibitory junctional potentials (IJPs) will
hyperpolarize the smooth muscle making it more difficult to generate an AP
57
Enteric nervous system (ENS) can function in
the absence of extrinsic innervation; however, information can be sent to autonomic nervous system (ANS).
58
Intrinsic innervation is located within the
submucosal and myenteric plexus
59
Intrinsic innervation receive stimuli from what?
Mechanoreceptors and chemoreceptors within the mucosa
60
Hirschsprungs disease is congenital absence of
myenteric plexus
61
Hirschsprungs disease elads to
functional obstruction of colon
62
What nerve innervates upper GI?
Vagus enrve
63
What nerve innervates lower GI?
Pelvic nerve
64
Postganglionic fibers of parasym are classified as
Cholinergic or peptidergic
65
Pregnaglionic fibers of sympathetic release
Ach or Norepi
66
Co-release and co-transmission of neurotransmitters can function as
neuromodulators
67
What is co-transmission
When 2 neuroTs are packaged in different vesicles and can have different sensitivities to intracellular calcium
68
Example of Co-release
Packaging of ATP with norepi in sympathetic neuronsE
69
Example of co-transmission
Ach and VIP
70
Neuromodulation can
enhance or decrease the sensitivity to the primary neurotransmitter
71
Local GI reflexes are
integrated entirely within the ENS
72
Local GI reflexes will control
GI secretion, peristalsis, mixing contractions, local inhibitor effects
73
Reglional reflexes fo to the
sympathetic ganglia and back to GI tract
74
Regional reflexes include
gastrocolic reflex, enterogastric reflex and colonoileal reflex
75
Systemic reflexes are processed in the
spinal cord or brainstem and will control overall activity of the Gi
76
What are the 4 GI hormones?
- Gastrin
- CCK
- Secretin
- Glucode dependent insulinotropic peptide (GIP)
77
CCK, secretin, GIP are released from
duodenum (SI)
78
When is G34 (big gastrin) secreted?
Between meals
79
When is G17 (little gastrin) secreted?
During the meal
80
Both types of gastrin require
C-terminal tetrapeptide in order to have activity
81
What are the most potent stimuli for gastrin secretion?
Phenylalanine and tryptophan
82
Gastrin releasing peptide aka bombesin will stimulate
gastrin release from G cell
83
How is gastrin inhibited?
decreased pH of gastric acid or somatostatin
84
Sollinger ellison syndrome is caused by
tumors that secrete gastrin and inactivate pancreatic enzymes in the duodenum
85
CCK coordinates the release of bile acids to
aid in digestion and absorption of nutrients
86
CCK(A) receptors are selective for
CCK
87
CCK(B) receptors can bind
gastrin and CCK
88
CCK does not get released due to the presence of
TAGs
89
CCK -acts on gallbladder and causes
contraction
90
CCK acts on pancreas and
stimulates acinar secretion
91
CCK acts on stomach and stimulated
reduced emptying
92
CCK- acts on sphincter of Oddi and causes
relaxation
93
Secretin induces the release of bicarbonate from
pancreas and bile ducts
94
Secretin is a member of what family?
glucagon
95
If vomiting occurs or there is a loss of H+ from the stomach, then secretin will
not get released and HCO3- can buildup in the blood (metabolic alkalosis)
96
GIP promotes the release of
insulin from pancreatic beta cells
97
GIP is a member of what family?
Glucagon
98
GLP-1 is part of what family
Incretins
99
GIP is secreted from what?
K cells of duodenum and jejunum
100
GIP inhibits
gastric H secretion and delays gastric emptying
101
DPP4 can degrade
incretins, so incretins have short half life
102
Histamine si secreted by what?
EC cells found in stomach and mast cells within GI
103
Histamine stimulates
H+ secretion
104
What are used to treat peptic ulcer?
H2R antagonists
105
Somatostatin is secreted by
D cells in the GI and hypothalamus and delta cells of pancrease
106
Somatostatin inhibits
secretion of other GI hormones, including gastrin
107
Somatostatin inhibits
H+ secretion
108
What is octreatide?
Somatostatin drug analog
109
Serotonin is secreted by
EC cells due to gastric distension
110
Serotonin works through what system?
ENS (neurocrine)
111
Drugs that block 5-HTR3 are utilized in the treatment of
nausea and vomiting in CINV patients
112
Ghrelin actions
Increase food intake, increase growth hormone secretion from hypothalamus
113
Motilin actions
Increase GI motility
114
PP actions
Decrease pancreatic secretion of HCO3- and enzymes
115
Enteroglucagon actions
Increase liver glycogenolysis and gluconeogenesis
116
GLP-1 actions
Increase insulin secretion from beta cell in pancreas
-Decrease glucagon secretion, gastric emptying and appetite
