Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives.
A) endocytosis
B) apoptosis
C) exocytosis
D) hydrolysis
E) sodium
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Question 2) Which of the following statements about excitation-contraction coupling is incorrect?
A) Calcium ions travel through the transverse tubule.
B) Calcium ion is released from the sarcoplasmic reticulum.
C) Tropomyosin moves to expose myosin binding sites on actin.
D) Troponin binds calcium ion and signals tropomyosin to move.
E) Relaxation requires uptake of calcium ion by the sarcoplasmic reticulum.
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Question 3) At what point during excitation contraction coupling does exocytosis play a role?
A) during calcium ion reuptake into the sarcoplasmic reticulum
B) when sodium channels open up on the motor end plate
C) during acetylcholine release from the synaptic terminal
D) when the action potential surges through the T-tubules
E) when ATP splits into ADP and P on the free myosin head
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Question 4) The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter
A) epinephrine.
B) norepinephrine.
C) acetylcholine.
D) antidiuretic hormone.
E) adrenaline.
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Question 5) When acetylcholine binds to receptors at the motor end plate, the sarcolemma becomes
A) more permeable to sodium ions.
B) less permeable to sodium ions.
C) more permeable to calcium ions.
D) less permeable to potassium ions.
E) less permeable to potassium and sodium ions.
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Question 6) How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle?
A) It would make the muscles less excitable.
B) It would produce muscle weakness.
C) It would cause muscles to stay contracted.
D) It would cause muscles to stay relaxed.
E) It would have little effect on skeletal muscles.
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Question 7) The following is a list of the events that occur during a muscle contraction. What is the correct sequence of these events? 1. Myosin cross-bridges bind to the actin. 2. The free myosin head splits ATP. 3. Calcium ion is released from the sarcoplasmic reticulum. 4. The myosin head pivots toward the center of the sarcomere. 5. Calcium ion binds to troponin. 6. The myosin head binds an ATP molecule and detaches from the actin.
A) 1, 3, 5, 4, 6, 2
B) 5, 1, 4, 6, 2, 3
C) 3, 5, 1, 2, 4, 6
D) 3, 5, 1, 4, 6, 2
E) 1, 4, 6, 2, 3, 5
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Question 8) Triggering of the muscle action potential occurs after
A) acetylcholine binds to chemically-gated channels in the motor end plate.
B) acetylcholinesterase is released from synaptic vesicles into the synaptic cleft.
C) calcium ion binds to channels on the motor end plate.
D) the action potential jumps across the neuromuscular junction.
E) Any of these can produce an action potential in the muscle cell.
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Question 9) In a sarcomere, cross-bridge attachment occurs specifically in the
A) zone of overlap.
B) A band.
C) I band.
D) M line.
E) H band.
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Question 10) In rigor mortis
A) the myosin heads are attached to actin.
B) ATP is depleted.
C) calcium ions keep binding to troponin.
D) sustained contractions occur.
E) All of the answers are correct.
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