You discover a mutant mouse whose skeletal muscles do not work properly.  You remove a piece of muscle tissue in an attempt to discover the problem.  The only abnormal thing you can find is that the acetylcholinesterase gene seems to be OVER-expressed, resulting in excess amount of this enzyme in and around the NMJ. How does this affect contraction?

Can you modify this experiment so that the mass lifted by the muscle contraction continues to increase for every trial? If yes, explain how it should be modified. If no, explain why.

You are studying a Drosophila protein called FROZN that you think is a vesicle snare that plays a role in exocytosis of synaptic vesicles containing acetylcholine at the neuro-muscular junction. Because this protein has been isolated from neuromuscular junctions, you hypothesize that this snare is a Ca+2 sensor that mediates the final merging of vesicles with the membrane. To test this hypothesis you perform 2 experiments: 1. You make a mutant Drosophila that lacks FROZN and find that synaptic vesicle release at the neuromuscular junction is blocked. 2. You block Ca+2 entry into the presynaptic neuron terminal in a normal (wild type) fly and find that synaptic vesicle release is blocked. Do these experiments support your hypothesis that FROZN is a vesicle snare and is the Ca+2 sensor? Is there another possible explanation for the function of FROZN? Explain your answer.

The sliding filament model depicts how myosin motors attached to actin lead to muscle contraction. This process proceeds in a precise series of events. Indicate which of the following shows the correct order of steps in the sliding filament model. Group of answer choices Myosin binds ATP; myosin tightly binds actin; power stroke; myosin releases actin Myosin binds GTP; myosin releases actin; power stroke; myosin tightly binds actin Actin binds ATP; power stroke; myosin tightly binds actin; actin releases ADP Actin binds ADP; myosin releases actin; power stroke; actin releases ADP

Describe the position where wrist and finger are in full extension.  What sensation will be felt in this position? What explains this sensation that you felt when the wrist and fingers were positioned in extension? *NOTE: Apply any of the following concepts to the explanation as deemed appropriate and connected to the situation above: Mucle Contraction, Concentric Contraction, Isometric Contraction, Eccentric Contraction, Force Velocity Curve, Stretch Reflex, Reciprocal Inhibition, Autogenic Inhibition, Length-Tension Relationship

An ion that is essential for muscle contraction is Ca2+.  Which of the following statements about the calcium ion and muscle contractions is TRUE? Select one: a. Muscle contractions can occur whether Ca2+ concentrations are high or low.  b. Ca2+ binds to the tropin-tropomyosin protein complex shifting it out of the way and allows the myosin to bind to the actin so contraction can occur. c. When Ca2+ concentrations are high, tropomyosin inhibits myosin binding and the muscle is relaxed. d. Ca2+ ions are stored in the sacroplasmic reticulum during the muscle contractions. I do not know which one is

Put these events that occur in skeletal muscle in the correct chronological sequence: 1. Opening of mechanically-gated ryanodine receptors (RyR) on the sarcoplasmic reticulum 2. Ca²+ binding to troponin to initiate contraction 3. Activation of voltage-gated dihydropyridine (DHP) receptor in the T-tubule 4. Na+ influx through ligand-gated ion channels on the motor end plate 4, 3, 2, 1 2, 1, 4, 3 3, 1, 2, 4 4, 3, 1, 2 3, 1, 4, 2

In a skeletal muscle if calcium levels in the cytosol increase, as calcium is released from the sarcoplasmic reticulum (SR,) how would this affect the position of the actin and myosin filaments?  Group of answer choices Calcium released from the SR binds to calmodulin. Calmodulin activates myosin light chain kinase, causing cross bridge formation. Calcium released from the SR binds to troponin, moving tropomyosin and allowing for cross bridge formation. Calcium released from the SR binds to troponin, moving tropomyosin and inhibiting cross bridge formation. Calcium released from the SR binds to troponin, causing actin to detach from myosin. pick one answer

96. An investigator is studying the contraction and relaxation of vascular smooth muscle in an experimental animal model. Which of the following describes the most likely order of events during this process? 0000000 200602 H) Myosin Light Chain Phosphorylation 1 2 2 3 3 4 4 Binding of Calcium to Calmodulin 3 1 4 2 4 2 3 Myosin Light Chain Dephosphorylation 2 3 4 3 4 2 1 2 Calcium Entry Into the Cell 4 2 3 1 1 1 3 1

An ion that is essential for muscle contraction is Ca2+.  Which of the following statements about the calcium ion and muscle contractions is TRUE? Select one: a. Muscle contractions can occur whether Ca2+ concentrations are high or low.  b. Ca2+ binds to the tropin-tropomyosin protein complex shifting it out of the way and allows the myosin to bind to the actin so contraction can occur. c. When Ca2+ concentrations are high, tropomyosin inhibits myosin binding and the muscle is relaxed. d. Ca2+ ions are stored in the sacroplasmic reticulum during the muscle contractions. i do not knwo which one is the answer