21) The enzyme acetylcholinesterase causes acetylcholine to
A) break down.
B) synthesize.
C) : 1200497.
21) The enzyme acetylcholinesterase causes acetylcholine to
A) break down.
B) synthesize.
C) bond to actin.
D) be secreted.
E) form cross-bridges.
22) The ________ contains vesicles filled with acetylcholine.
A) axon terminal
B) motor end plate
C) neuromuscular junction
D) synaptic cleft
E) transverse tubule
23) The specialized sarcolemma that contains acetylcholine receptors is the
A) synaptic knob.
B) motor end plate.
C) motor unit.
D) synaptic cleft.
E) I band.
24) During active-site exposure, calcium ions bind to which of the following?
A) actin
B) the sarcolemma
C) troponin
D) the sarcoplasmic reticulum
E) myosin
25) Neurotransmitters that cause skeletal muscle contraction are normally stored in
A) myofibrils.
B) motor neuron axon terminals.
C) motor units.
D) motor end plates.
E) actin.
26) Rigor mortis occurs at death due to a lack of
A) cAMP.
B) DNA.
C) RNA.
D) ATP.
E) tRNA.
27) When a calcium ion binds to troponin,
A) active sites on actin are exposed.
B) active sites on myosin are exposed.
C) actin heads will bind to myosin.
D) muscle relaxation occurs.
E) acetylcholine is released.
28) Which of the following is one of the steps that ends a contraction?
A) Sarcoplasmic reticulum absorbs sodium ions.
B) Acetylcholine binds to receptors on the sarcolemma.
C) Calcium ions bind to troponin.
D) Acetylcholine is broken down by acetylcholinesterase.
E) An action potential spreads across the entire surface of the muscle fiber.
29) In response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases
A) acetylcholine.
B) sodium ions.
C) potassium ions.
D) calcium ions.
E) acetylcholinesterase.
30) As a skeletal muscle contraction is initiated, acetylcholine binding alters the motor end plate membrane’s permeability to
A) acetylcholinesterase.
B) sodium ions.
C) calcium ions.
D) chloride ions.
E) potassium ions.
