1. In excitation-contraction coupling in skeletal muscle cells, the Na+ that ent
ID: 3476860 • Letter: 1
Question
1. In excitation-contraction coupling in skeletal muscle cells, the Na+ that enters the skeletal muscle cell at the T-SR junction enters the cell through:
a. nicotinic acetylcholine receptors
b. voltage-gated Na+ channels
c. DHP receptors
d. ryanodine receptors.
e. All of the above.
2. Tropomyosin binds to:
a. thin filaments.
b. thick filaments.
c. z-lines.
d. Ca2+
e. a and d are correct.
3. At the junction between the T-tubule and the sarcoplasmic reticulum in skeletal muscle, Ca2+ enters the cytoplasm of the muscle cell from the _____ through ________.
a. T-tubule, ryanodine receptors.
b. sarcoplasmic reticulum, DHP receptors
c. sarcoplasmic reticulum, ryanodine receptors
d. extracellular space, ryanodine receptors.
e. a and d are correct.
4. For skeletal muscle, the movement of the myosin head occurs when:
a. the myosin head binds ATP.
b. the myosin head binds actin
c. ADP and inorganic phosphate ion leave the myosin head.
d. the myosin head cleaves ATP to ADP and inorganic phosphate ion.
e. the myosin head forms ADP and inorganic phosphate ion.
Explanation / Answer
1) In excitation contraction coupling, the sodium ions enters the skeletal muscle cell at the T-SR junction through voltage gated sodium channels (option b). This causes decrease in the resting membrane potential of the cell and results in depolarisation.
DHP receptors and ryanodine receptors transmit calcium ions. Nicotinic acetylcholine receptors respond to acetylcholine.
Please post other questions separately.
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