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M- Line
- Stabilizes thick filament lattice
- Thicker in Type I vs. Type II
- 3 Components
- -Creatine Kinase (CK) ~2% Enzyme catalyzes rxn of PCr + ADP → ATP
- -CK mostly soluble and associated c H-band
- -M protein
- -Myomesin
- -Myosin
- -Titin
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Smooth Muscle Organization
- 1. Whole muscle (epimysium) belly
- 2. Muscle Fascicle (perimysium) Bundle of muscle fibers
- 3. Muscle Fiber (endomysium/ sarcolemma)Muscle cell
- 4. MyofibrilSarcomeres in series
- 5. SarcomereZ-disc to Z-disc
- 6. MyofilamentsSuch as actin, myosin, titin etc.
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Action Potential generated at Axon Hillock
- 1.Gradual depolarization to threshold
- 2.Rapid rising phase
- 3.Overshoot
- 4.Repolarization
- -Followed by a brief afterhyperpolarization.
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Action Propagation / Myelin
- 1)Action potential propagation is unidirectional.
- 2)All or none.
- 3)No decrement in AP magnitude.
- 4)Conduction velocity depends on axon diameter and the presence/absence of myelin.
- 5)Myelin is an insulator.
- 6)Myelin is produced by:
- -CNS: Oligodendrocytes
- -PNS: Schwann Cells
- 7)Action potential propagation is saltatory
- 8) At nodes of Ranvier
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Activated Nerve Terminal
- 1) Nerve Impulse
- 2)Voltage gated Ca+ channel opens Ca+->
- 3) Neurotransmitter released
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Ligand-gated ion channel
- ~70 vesicles fuse with presynaptic membrane
- ~6,000 – 10,000 ACh molecules are released/quantal packet (one vesicle)
- ~250,000 AChRʼs are opened per AP
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Excitation-Contraction (EC) coupling
- -AP;s travel in T-tubule @ 7cm/s
- -Superficial myofibrils contract first.
- -Conversion of electrochemical energy into mechanical energy.
- -AP -- ACh -- AP -- Ca -- Actin/Myosin interaction++
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