Chapter 11 Part 4

Chapter 11 Part 4 - More muscle contraction. 11/5 What are...

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More muscle contraction. 11/5 What are membrane potentials? How does the action potential reach a myofiber? Why does a depolarized myofiber contract? What limits depolarization and contraction? What is fatigue? How are myofiber functions specialized? How does conditioning and exercise effect myofibers? Review of smooth muscle and cardiac muscle physiology.
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We make a muscle cell contract by depolarizing it, causing calcium release. How do we polarize a membrane creating membrane voltage and what is depolarization? What are the relative Na+, K+ and Ca++ concentrations on the inside/outside of the plasma membrane? Pumps maintain this difference at ATP cost! Why does this create a voltage (membrane potential)? Ways to depolarize the membrane: 1) Ligand-gated channels: Acetylcholine 2) Voltage-gated channels: Na+ or Ca++ 3) Gap junctions: cardiac and some SMC 4) Stretch-gated channels or damage Arrival of an action potential at a motor end plate is critical for skeletal myofiber coupling of depolarization and contraction!
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The arrival of an action potential at a neuromuscular junction is the critical event for muscle depolarization/ contraction by a somatic motor neuron. 1) Arrival of AP depolarizes end of axon (synaptic knob). 2) Depolarization of knob causes voltage gated calcium channels to open on knob. 3) Ca++ enters and causes vesicular exocytosis acetylcholine (ACH) released into synaptic cleft.
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This note was uploaded on 04/17/2008 for the course BIOL 211 taught by Professor Wilson during the Fall '07 term at Winona.

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Chapter 11 Part 4 - More muscle contraction. 11/5 What are...

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