Cardiovascular Physiology 2- Smooth muscle: Exam III Flashcards
1
Q
The main populations of smooth muscle surround: (category + specifics)
A
hollow organs- blood vessels, airways, GI tract, uterus, fallopian tubes, ureters, and bladder
2
Q
In addition to surrounding hollow organs, smooth muscle is also important in _____ & _____
A
ocular function and piloerection
3
Q
Contraction of smooth muscle may cause ____ or ____
A
propulsion or resistance
4
Q
Contracting the smooth muscle around a hollow organ will ____ which may result in ____.
A
Narrow the lumen; forcing contents through
5
Q
A stimulus for contraction of smooth muscle may be ____ or _____.
A
Extrinsic or intrinsic
6
Q
The contraction of smooth muscle can be described as :
A
involuntary
7
Q
Involuntary smooth muscle contraction is regulated by: (3)
A
- autonomic neurons
- hormones
- autocrine/paracrine signals
8
Q
Smooth muscle is comprised of ____ cells with a ____ nucleus.
A
smaller; single central nucleas
9
Q
Describe the contractions of smooth muscle
A
slow, steady, forceful and long
10
Q
How does smooth muscle generate ATP?
A
primarily oxidative metabolism
11
Q
The cellular shape of smooth muscle cells is:
A
elongated and tapered- (pointed at each end)
12
Q
Describes the striation of smooth muscle and why:
A
Not striated because the sarcomere is NOT the functional unit
13
Q
Smooth muscle lacks _____ and only has a _____ SR.
A
T-tubules; rudimentary
14
Q
Compare the twitch duration of smooth muscle to skeletal and cardiac:
A
by far the slowest twitch duration
15
Q
What are the two types of smooth muscle?
A
- multi unit
- single-unit
16
Q
What can single unit smooth muscle also be referred to as?
A
unitary or visceral
17
Q
A type of smooth muscle with no gap junctions resulting in an independent response per each cell:
A
Multi-unit
18
Q
What type of smooth muscle behaves as multiple units?
A
mutli- unit
19
Q
The type of smooth muscles which is controlled by mainly nerve signals:
A
multi-unit
20
Q
Type of smooth muscle where cells function independently:
A
Multi unit
21
Q
Describe the tone in multiunit smooth muscle:
A
No tone
22
Q
Type of smooth muscle in which the cells are extensively connected via gap junctions allowing them to behave as a functional syncytium
A
Single-unit
23
Q
Single unit smooth muscle is controlled by:
A
variety of stimuli
24
Q
What type of smooth muscle may be controlled by pacemaker cells?
A
Single-unit
25
The type of smooth muscle in which cells may be organized into sheets or bundles, often around a lumen of a hollow organ:
Single unit
26
Unlike multi unit, single unit smooth muscle can exhibit:
tone
27
Determine whether the following smooth muscle is single or multi-unit:
1. piloerector muscle
2. gut
3. bladder
4. iris
5. uterus
6. ciliary muscles
7. blood vessels
1. MU
2. SU
3. SU
4. MU
5. SU
6. MU
7. B
28
The gap junctions in single unit smooth muscle permit:
coordinated contraction
29
The electrical isolation of cells in multi-unit smooth muscle allow for:
finer motor control
30
An example of smooth muscle that spends most of its time in a relaxed state and when stimulated will briefly contract and then relax again (similar to skeletal and cardiac muscle)
smooth muscle of the esophagus and urinary bladder
31
An example of smooth muscle that is completely contracted in its resting state, and when stimulated it relaxes briefly and then returns to contracted state:
Sphinctors
32
Sphinctors are an example of a muscle with _____, because its contracting in its resting state
tone
33
Example of smooth muscle that is partially contracted in the resting state, but neither completely contracted nor relaxed and will fluctuate dependent on its needs:
blood vessels and airways
34
Example of smooth muscle that is phasically active meaning that it will go through states of contraction and relaxation:
Stomach and intestines
35
Smooth muscle myocytes contain:
actin and myosin
36
The actin and myosin in smooth muscle myocytes is not organized into:
sarcomeres
37
Describe the actin in smooth muscle compared to cardiac and skeletal muscle: (4)
1. higher levels
2. longer
3. attached to dense bodies
4. arranged diagonally to long axis of cell
38
What is responsible for attaching actin to dense bodies?
alpha actinin
39
The dense bodies of smooth muscle myocytes may be located:
intracellular and membrane bound
40
Describe the myosin in smooth muscle myocytes compared to skeletal/cardiac myocytes:
Fewer myosin fibers
41
The myosin filaments of smooth muscle are interspersed with:
actin
42
Smooth myocytes lack ____.
troponin
43
Rather than calcium binding to troponin (as it does in skeletal and cardiac muscle), in smooth muscle, calcium binds to :
calmodulin
44
What are the two actin binding proteins?
Calponin & Caldesmon
45
What can calponin and caldesmon be described as?
Inhibitory proteins
46
Both calponin and caldesmon are assoicated with:
actin
47
What needs to be removed from actin in order for the smooth muscle to be able to contract?
Calponin & Caldesmon
48
_____ inhibits the myosin ATPase
Calponin
49
_____ inhibits myosin/actin bond
Caldesmon
50
What removes the calponin & caldesmon from actin?
Calcium-calmodulin complex
51
Contraction of smooth muscle results in ____ of the cell
rounding up
52
Smooth muscle contracts efficiently over:
Wide range of resting lengths
53
What is the teleological explanation for why smooth muscle can contract over a wide range of resting lengths?
Because we still want smooth muscle to contract efficiently even if it is being stretched (such as a full stomach, or bladder)
54
All three types of muscle need an increase in _____ in order for contraction
intracellular calcium
55
_____ binds to calmodulin for contraction
calcium
56
When calcium binds to calmodulin, it then removes ___ & _____ from ____.
caldesmon;calponin; actin
57
In addition to calcium, ____ is needed for smooth muscle contraction and this comes from _____.
ATP; myosin head ATPase
58
In addition to calcium and ATP, what is the 3rd requirement for smooth muscle contraction?
myosin light chain phosphorylation
59
What specifically is the myosin light chain phosphorylation require for?
Required for myosin to be able to interact iwth actin
60
What are the 3 requirements for smooth muscle contraction?
1. Intracellular calcium
2. ATP
3. Myosin light chain phosphorylation
61
What is responsible for the phosphorylation of the myosin head?
Myosin light chain kinase (enzyme)
62
What removes the phosphate from the myosin head to stop contraction?
Myosin light chain phosphatase
63
Smooth muscle contraction can be stimulated by:
1. stretch
2. ligands
3. Intrinsic activity
64
The ligands that can stimulate smooth muscle contraction may include:
1. neurotransmitters
2. hormones
3. paracrines
4. autocrines
65
The intrinsic activity that can stimulate smooth muscle contraction includes:
pacemaker cells
66
What are not necessarily required for increases in contractile cell force (AKA contraction)
Action potentials (depolarization)
67
When the concentration of calcium is high, the activity of the myosin-light chain is _____ than the activity of the myosin light chain phosphatase so there will be a ___ in contraction
greater than; increase
68
When the calcium concentration in the cytosol is low, the activity of the myosin light chain kinase is is ____ than the activity of the the myosin light chain phosphatase so there will be a ____ in contraction
less than; decrease
69
What are the 3 sources of cytosolic calcium?
1. VG calcium channel in cell membrane
2. Ligand binding Gq GPCR
3. Calcium coming in from outside stimulating SR
70
What occurs when a ligand binds Gq GPCR?
The Gq GPCR will generate IP2 which will lead to calcium release from SR
71
What is unique about increasing cytosolic calcium through a Gq GPCR?
No action potential is required (depolarization)
72
For a smooth muscle to relax, ___ has to be removed
calcium
73
What are the two ways for calcium to be removed in order for smooth muscle to be relaxed?
1. calcium ATPase (to SR or ECF)
2. Na+ Ca++ exchanger (to ECF)
74
Both mechanisms to remove calcium in order for smooth muscle to relax are _____ processes
active transport
75
The muscle twitch tension in smooth muscle is:
graded
76
What is the mechanistic explanation to why the muscle twitch tension in smooth muscle is graded?
The force of contraction is dependent on how much calcium is released inside the cell
77
What is the teleological explanation to why the muscle twitch tension is graded in smooth muscle?
we need to be able to vary the force at which out smooth muscles contract
78
Smooth muscle will continue to contract as long as:
myosin head stays phosphorylated
79
the phosphorylated cross-bridges continue to cycle because:
The myosin ATPase is active
80
In smooth muscle, we probably never get complete relaxation unless we:
remove calcium
81
When myosin is dephosphorylated, myosin and actin may form:
latch bridges
82
Allow tension to be maintained within the smooth muscle even though the concentration of calcium within the cell may be going down and the and the ATP usage to maintain those contractions go way down:
Latch state
83
In the Latch state, tension is ____ although calcium levels in cytosol ___ and ATP usage ____.
maintained; decrease; decrease
84
sustained contraction at low cost
latch state
85
Dephosphorylation of the myosin by the myosin light chain phosphatase can result in what two things?
1. Relaxation
2. Sustained contraction due to latch bridge
86
Only smooth muscle cells can be ____ or _____.
stimulated or inhibited
87
Input to smooth muscle can be either ____ or ____.
In put to skeletal muscle and cardiac muscle are always _____.
Inhibitory or excitatory
excitatory
88
Inputs to smooth muscle contractile activity include: (5)
1. Action potential (pacemaker cells)
2. NTs via autonomic neurons
3. Hormones
4. Locally induced changes via ECF
5. Stretch
89
Give examples of locally induced changes of the ECF that act as an input to smooth muscle contractility: (5)
1. paracrine factors
2. acidity
3. oxygen
4. osmolarity
5. ion concentrations
90
Smooth muscle activation via autonomic neurons:
1. Do not form _____
2. Axons have _____
3. NT released into _____
4. Distribute to receptors on smooth muscle cell surface via _____
5. Each smooth muscle cell may be influence by _____.
6. _____ or _____ contraction
1. synapses
2. varicosities
3. interstitial fluid
4. simple diffusion
5. more than one varicosity
6. stimulate or inhibit
91
In the case that the smooth muscle cell is being acted on by more than one varicosity, which one would yield the result?
The stronger stimulus
92
Smooth muscle activation: hormonal control:
Dependent on the receptor, there may or may not:
Induce a VM change
93
Smooth muscle activation: hormonal control:
Dependent on the receptor, contraction can be:
activated or inhibited
94
In multi-unit smooth muscle, cells are activated _____.
Independently of other cells
95
In single unit smooth muscle, you can activate some of the cells and due to the gap junctions ____ occur
propagation of signal
