Term
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Definition
| in internal organs, blood vessels, iris |
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Term
| Smooth muscle is under voluntary or involuntary conrtrol by which nervous system |
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Definition
| Involuntary control by autonomic nervous system |
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Term
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Definition
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Term
| Number of nuclei in smooth muscle |
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Definition
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Term
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Definition
| Small, 1/10 size of skeletal muscle |
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Term
| Do they have thick or thin filaments? How is smooth muscle arranged? |
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Definition
Have both thick and thin filaments, arranged diagonally
**NO Sarcomeres
No striations
Appears smooth |
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Term
| Thin filaments in smooth muscle: |
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Definition
have tropomyosin, but NO troponin
Attach to dense bodies (much like they attach to Z disks in skeletal muscle) |
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Term
| ATPase speed in smooth muscle |
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Definition
| slow, 10-100 times slower than skeletal muscle meaning a slow contraction time |
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Term
| How much SR is in Smooth? |
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Definition
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Term
| The diagnoal organization of actin and myosin allows the muscles |
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Definition
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Term
| actin and myosin are --- in smooth than skeletal |
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Definition
| longer- so they slide over greater area |
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Term
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Definition
| the whole length of thick filaments= longer range of contraction |
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Term
| what triggers contraction |
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Definition
| Calcium binds to cytoplasmic protein called calmodulin bc there is no troponin. |
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Term
| Where does calcium come from |
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Definition
extracellular fluid, large concentration gradient (High conc. Ca in ECF than ICF)
Smooth don't have much SR so little calcium is stored there |
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Term
| Excitation-Contraction Coupling |
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Definition
1. Opening of Ca channels in plasma membrane (voltage, ligand/chemical, mechanically gated)
2. Calcium influx into cell
3. Calcium binds to calmodulin
4. Ca-calmodulin complex activates myosin kinase enzyme
5. Myosin kinase phosporylates myosin (adds a phosphate) myosin heads can now bind to actin on thin filaments
6. cross bridge cycling |
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Term
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Definition
Phospatase removes phosphate from myosin
Ca is removed from cytoplasm by-
Ca ATPase pump and Ca-Na counter transport (Ca leaves Na comes in cell) |
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Term
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Definition
| Can be excitatory or inhibitatory by parasympathetic and sympathetic autonomic nervous system |
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Term
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Definition
Intercellar Ca determines tension and is influenced by
1. Hormones
2. Paracrines (chemicals produced by other cell types near smooth muscles) |
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Term
| Classification of Smooth Muscle |
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Definition
1. Single-unit smooth muscle
2. multi-unit |
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Term
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Definition
most common
located in intestinal tract, blood vessels, respiratory tract.
Connected by gap junctions and contract as a single unit at the same time |
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Term
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Definition
Gap junctions
pacemaker cells with spontaneous depolarizations
innervation to few cells
tone= level of contraction w/out stimulation
Contract for long periods |
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Term
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Definition
Single unit
Pacemaker potentials- spontaneous depolarizations to threshold, leads to opening of voltage gated Ca channels
Contractions |
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Term
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Definition
located in large airways, eye
few, if any gap junctions
each fiber acts individually, receives own innervations, no tone |
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