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(1) Neuromuscular (Nervous Transmission (Role of ATP (1) Actin-Myosin
At…
(1) Neuromuscular
Nervous Transmission
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B) Action Potential
1) Both voltage gated Na+ & K+ closed
Leaky K+ opened
2) Wave of depolarization
Voltage gated Na+ channels opened
Voltage gated K+ channels slowly open
Overall depolarization
3)Threshold is reached
AP generated
4) Na+ channels close
5) K+ channels close slower
6) Resting membrane potential (Na+/K+pump)
Refractory Period
- Absolute: Voltage gated Na+ wouldn't open
- Relative: Membrane potential is slightly below resting membrane potential
Saltatory conduction
- Increases speed of transmission
- No leak of electric currents
- Conserves energy
- Restoration of ionic concentration only at ranvier
C) Synaptic Transmission
- Electrical
- Cells connected by gap junctions
- Chemical
- Cells not connected
- Synaptic cleft
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Spatial summation
- Axon Hilock
Temporal Summation
- Axon Hilock
Excitation-Contraction Coupling; Ca2+ / Ach impt
- AP Calcium ion channel opens
- Ach Presynaptic into synpase
- Ach Postsynaptic
- Opens Na+ channel
- AP continues
- Ach broken down / diffuse away
- Calcium from sarcoplasmic reticulum
- Calcium on troponin
- Troponin complex change shape
- Tropomyosin moves away
- Actin and Myosin binds
- Powerstroke
- Calcium back into sarcoplasmia reticulum (Pump)
Tetanus/isation: Many successive contractions fuse, appear smooth and continuous (Saturated with Ca2+)
Role of ATP
1) Actin-Myosin
- At rest, ATP is split into ADP and Pi left on myosin head
- Energy is stored in myosin head
- Myosin bind to actin
- Power stroke:
- Pi released
- Energy stored from previous hydrolysis is released
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Types of muscle
Smooth
Extracellular Ca: Yes
- Slow cycling of myosin cross bridges
- No troponin
- Electrically linked by gap junction
- No t-tubules
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Cardiac
Extracellular Ca: Yes
- Electrically linked by gap junction
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