Bio 250 Exam 3 Practice Questions and Correct Answers
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Course
BIO 250
Institution
BIO 250
What best describes how ACh changes the ion permeability of the sarcolemma? ACh binds to receptors in the junctional folds.
The end plate potential is primarily, and most directly, caused by the movement of Na+
__ diffuses into the muscle fiber through open chemically gated ion channels. Na+
__ ...
Bio 250 Exam 3 Practice Questions and
Correct Answers
What best describes how ACh changes the ion permeability of the sarcolemma?
✅ACh binds to receptors in the junctional folds.
The end plate potential is primarily, and most directly, caused by the movement of
✅Na+
__ diffuses into the muscle fiber through open chemically gated ion channels. ✅Na+
__ diffuses out of the muscle fiber through open chemically gated ion channels. ✅K+
__ binds to ACh receptors, causing them to open chemically gated ion channels.
✅ACh
Which of the following best describes the role of acetylcholinesterase molecules at the
neuromuscular junction? ✅acetylcholinesterase breaks down ACh, which allows
chemically gated ion channels to close.
Location of acetylcholinesterase ✅synaptic cleft
Protein in sarcolemma ✅ACh receptor
Ion entering muscle fiber through open chemically gated ion channels ✅Na+
Container of many neurotransmitter molecules ✅synaptic vesicle
Ion triggering exocytosis ✅Ca2+
Membrane surrounding muscle fiber ✅sarcolemma
Neurotransmitter at neuromuscular junction ✅acetylcholine
Portion of sarcolemma containing ACh receptors ✅junctional folds
How is an action potential generated at the neuromuscular junction (NMJ) is converted
to excitation in the muscle fiber? ✅an action potential in the motor neuron causes ACh
to be released into the synaptic cleft. Binding of ACh to sarcolemma receptors initiates
graded potentials.
, Which best describes the initial event in contraction? ✅Myosin heads bind to the newly
exposed myosin-binding sites on actin to form cross bridges
The swollen chamber of an organelle that lies on either side of a T tubule ✅
cistern ✅The swollen chamber of an organelle that lies on either side of a T tubule
voltage-sensitive tubule protein ✅a protein that changes shape as a result of an action
potential
A protein with heads that attach in cross bridging ✅myosin
A structure that forms a path from the membrane to the cell interior ✅T tubule
The protein that binds to calcium ✅troponin
Which of the following statements best summarizes excitation-contraction coupling?
✅A series of events in which an electrical stimulus is conveyed to a muscle fiber to
enact contraction.
myofilament with a knob-like head ✅myosin
myofilament stiffened and stabilized by tropomyosin ✅actin
the cytoplasm of a skeletal muscle fiber ✅sarcoplasm
bundle of skeletal muscle fibers enclosed by connective tissue called perimysium
✅fasicle
Sarcolemma ✅membrane of muscle cell
long, cylindrical cells ✅skeletal muscle fibers
contractile unit of muscle ✅sarcomere
made up of several sarcomeres ✅myofibrils
Location of higher concentration of Ca2+ needed for cross bridge formation and cycling:
✅cytoplasm
Actin status to begin cross bridge formation ✅actin-binding sites exposed
Molecule(s) bound to myosin head at start of cross bridge cycle ✅ADP and Pi
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