Please answer for 48-50. The contractile proteins in skeletal muscle are: a. Act

Question

Please answer for 48-50.

The contractile proteins in skeletal muscle are: a. Actin and myosin b. Keratin and collagen c. Titin and myosin d. Troponin and actin e. Troponin and tropomyosin Which of the following is true of transverse tubules? a. They are invaginations of the plasma membrane that extend into the muscle cell b. They are specialized smooth endoplasmic reticulum c. They contain myofilaments d. They store acetylcholine e. They store calcium ions required for muscle contraction Smooth muscle: a. Has intercalated disks b. Has striations c. Is regulated by the autonomic division of the nervous system d. Is typically attached to bones in the body e. Is under voluntary control Which of the following is true when the muscle cell is contracted and shortened? a. Acetylcholine is stored inside the vesicles b. Calcium is located inside the terminal cisterns c. Myosin heads are detached d. The I-band is shorter e. The thick filaments are shorter Place the events at the neuromuscular junction in the order in which they occur: 1. Release of acetylcholine from an axon end bulb 2. Binding of acetylcholine to its receptors on motor endplate 3. Arrival of an action potential at the synaptic end bulb 4. Diffusion of acetylcholine across the synaptic cleft 5. Opening of sodium channels in the motor endplate 6. Production of muscle fiber action potential a. 1, 4, 5, 3, 2, 6 b. 3, 1, 4, 2, 5, 6 c. 3, 1, 5, 6, 3, 4 d. 4, 1, 2, 5, 6, 3 e. 4, 1, 5, 2, 3, 6 Wave summation in a muscle fiber: a. Is the muscle's response to a single stimulus b. Is the switching of stimulus between muscle fibers c. Occurs when additional stimuli arrive before the fiber has relaxed after the initial stimulus d. Usually results in subsequent contractions that are weaker than the first e. When applied continuously helps to maintains muscle tone

Explanation / Answer

1. When the muscle cell is contracted and shortened then the I-band get reduced because the red line attached to the actin filament are pulled inwards causing the shortening of the sarcomere. Therefore due to this the length of the I-bands is reduced. Therefore Option D is correct.
2.The events at the neuromuscular junction are in the order as follows :

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