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21 Cards in this Set
- Front
- Back
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What is afterload?
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Load that the muscle contracts against
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What is passive tension?
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Tension develped by the muscle as it is stretched to different lengths.
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What is total tension?
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Tension developed by the muscle when it contracts at different lengths
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What is active tension?
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The difference between total tension and passive tension
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What is active tension proportional to?
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The number of cross bridges
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When is tension maximum?
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When there is maximum overlap of thick and thin filaments permitting the most cross bridges to form.
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What happens to the velocity of shortening ina muscle as the afterload increases?
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Decreases
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What are the components of smooth muscle?
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Thick filaments
thin filaments |
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Are there sarcomeres in smooth muscle?
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No.
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Is there troponin in smooth muscle?
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No.
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What is the consequence of this?
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Smooth muscle does not have striations
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What are the types of smooth muscle?
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Muliunit
Single unit Vascular |
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Which type is most common?
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Single unit
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Which type has a high degree of electrical coupling between cells?
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Single unit
This type also has spontaneous activity(pacemaker) |
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What type is densely innervated?
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Multiunit
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Do multiunit smooth muscle units coordinate?
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No, they behave separately.
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What properties does vascular smooth muscle exhibit?
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Mix of multiunit and single unit properties
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What regulates excitation-contraction coupling in smooth muscle?
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Ca+2(ther is no troponin)
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What are the mechanisms by which intracellular ca+ can be increased in smooth muscle?
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1. Depolarization of the cell membrane opens voltage gated Ca+2 channels
2. SR may release additional Ca+2 with depolarization 3. SR can be stimulated by hormones and neurotransmitters to release Ca+2 via IP3 gated Ca=2 channels |
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Describe excitation-contraction coupling in smooth muscle.
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1. Intracellular Ca+2 increases
2. Ca+2 binds to calmodulin activating myosin light chain kinase 3. Myosin is phosphorylated and binds to actin 4. Shortening occurs |
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What causes relaxation in smooth muscle?
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Dephosphorylation of myosin
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