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24 Cards in this Set
- Front
- Back
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Why does the smooth muscle cytosol look as if it has a hairy, fuzzy look?
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Actin, intermediate filaments
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Dense bodies
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-On the membrane or cytosol
-connected together by IF (made of desmin) |
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Gap junctions found in what type of muscle?
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Cardiac & smooth
NOT skeletal |
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Caveloi
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-Not true T-tubules
-sac-like invaginations of the PM |
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Filamentous structures
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-Actin & myosin
-No sarcomeres -No troponin |
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What are the force-coupling proteins
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1. Found in dense bodies instead of Z disk
2. Intermediate filaments made of desmin |
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What is the length-force relationship in smooth muscle?
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(inc. length, inc. in force)
Smooth muscle has a wider range of operating lengths |
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What is the force-velocity relationship in smooth muscle?
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Much slower than skeletal
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What NS controls smooth muscle
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Autonomic NS, both sympathetic & parasympathetic
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Varicosities or boutons
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Swellings on the autonomic nerves
Release neurotransmitters (NE or Ach) |
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What is the arrangment for neurohormonal control of smooth m?
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1. Nerve only signals to one smooth muscle cell and the others get the signal via gap junction
2. Each smooth muscle is innervated |
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Which type of muscle has a motor end plate?
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Skeletal only
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In which muscle can contraction occur w/o depolarization?
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Cardiac & smooth
Spontaneous activity |
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What are the 3 ways to increase intracellular [Ca]?
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1. Leak channels
2. Voltage-gated channels 3. Ligand gated channels: Ligands open w/o change in membrane voltage |
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How does cross bridge formation occur in smooth?
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Ca binds to calmodulin-->phosphorylation of myosin-->contraction
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Which type of muscle is "myosin-regulated?"
"actin-regulated" |
smooth muscle
Cardiac/skeletal m |
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What are the ways Ca can enter the cytoplasm?
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1. leak, voltage-gated, ligand-gated
2. Ca induced Ca release 3. IP3 pathway |
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What happens when NE binds?
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NE-->alpha-adrenergic receptor-->Gq-->Phospholipase C-->IP3 released-->binds to receptor on SR-->Ca released
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How does Ca excit the cytoplasm?
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1. PM Ca/ATPase
2. SR membrane Ca/ATPase 3. PM Na/Ca exchanger |
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Cross bridge regulation in smooth muscle?
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Ca enters cytoplasm-->binds to Calmodulin-->binds to Myosin light chain kinase-->active MLCK phosphorylates Myosin-->cycling
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How does smooth m relaxation occur?
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Epi-->B-adrenergic receptors-->inc. cAMP-->Protein Kinase-->MLCK-P-->dec. MLC-P-->relaxation
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What does the Rho-Kinase pathway do?
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Stops dephosphorylation so promotes contraction
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tone
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smooth muscle of some organs exhibit sustained contraction
low use of ATP, low rate of cross bridge cycling Ex: sphincters |
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Hollow organs that need to adapt to the volume of their contents
Stomach |
Viscoelastic behaviour
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