BIO 250 EXAM 3 WITH ALL CORRECT & VERIFIED
ANSWERS/ALREADY GRADED A+
Which of the following best describes how ACh changes the ion permeability of the sarcolemma?
Correct answer-ACh binds to receptors in the junctional folds.
The end plate potential is primarily, and most directly, caused by the movement of Correct answer-
Na+
__ diffuses into the muscle fiber through open chemically gated ion channels. Correct answer-Na+
__ diffuses out of the muscle fiber through open chemically gated ion channels. Correct answer-K+
__ binds to ACh receptors, causing them to open chemically gated ion channels. Correct answer-
ACh
Which of the following best describes the role of acetylcholinesterase molecules at the
neuromuscular junction? Correct answer-acetylcholinesterase breaks down ACh, which allows
chemically gated ion channels to close.
Location of acetylcholinesterase Correct answer-synaptic cleft
Protein in sarcolemma Correct answer-ACh receptor
Ion entering muscle fiber through open chemically gated ion channels Correct answer-Na+
Container of many neurotransmitter molecules Correct answer-synaptic vesicle
Ion triggering exocytosis Correct answer-Ca2+
Membrane surrounding muscle fiber Correct answer-sarcolemma
Neurotransmitter at neuromuscular junction Correct answer-acetylcholine
Portion of sarcolemma containing ACh receptors Correct answer-junctional folds
How is an action potential generated at the neuromuscular junction (NMJ) is converted to excitation
in the muscle fiber? Correct answer-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? Correct answer-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 Correct answer-
cistern Correct answer-The swollen chamber of an organelle that lies on either side of a T tubule
voltage-sensitive tubule protein Correct answer-a protein that changes shape as a result of an
action potential
A protein with heads that attach in cross bridging Correct answer-myosin
, A structure that forms a path from the membrane to the cell interior Correct answer-T tubule
The protein that binds to calcium Correct answer-troponin
Which of the following statements best summarizes excitation-contraction coupling? Correct
answer-A series of events in which an electrical stimulus is conveyed to a muscle fiber to enact
contraction.
myofilament with a knob-like head Correct answer-myosin
myofilament stiffened and stabilized by tropomyosin Correct answer-actin
the cytoplasm of a skeletal muscle fiber Correct answer-sarcoplasm
bundle of skeletal muscle fibers enclosed by connective tissue called perimysium Correct answer-
fasicle
Sarcolemma Correct answer-membrane of muscle cell
long, cylindrical cells Correct answer-skeletal muscle fibers
contractile unit of muscle Correct answer-sarcomere
made up of several sarcomeres Correct answer-myofibrils
Location of higher concentration of Ca2+ needed for cross bridge formation and cycling: Correct
answer-cytoplasm
Actin status to begin cross bridge formation Correct answer-actin-binding sites exposed
Molecule(s) bound to myosin head at start of cross bridge cycle Correct answer-ADP and Pi
Energy state of myosin for beginning cross bridge formation: Correct answer-energized/clocked
myosin head
The molecules released just before power stroke Correct answer-ADP and Pi
Actin behavior during the power stroke Correct answer-ratchets toward the M line
Myosin head energy status during the power stroke Correct answer-pivots and returns to low
energy
the bond between the actin and myosin head weakens due to Correct answer-ATP
Only ____ of the myosin heads are detached from actin at any one time while calcium is present and
cycling continues. Correct answer-HALF
___ is not bound to myosin during the detachment step. Correct answer-ADP
ANSWERS/ALREADY GRADED A+
Which of the following best describes how ACh changes the ion permeability of the sarcolemma?
Correct answer-ACh binds to receptors in the junctional folds.
The end plate potential is primarily, and most directly, caused by the movement of Correct answer-
Na+
__ diffuses into the muscle fiber through open chemically gated ion channels. Correct answer-Na+
__ diffuses out of the muscle fiber through open chemically gated ion channels. Correct answer-K+
__ binds to ACh receptors, causing them to open chemically gated ion channels. Correct answer-
ACh
Which of the following best describes the role of acetylcholinesterase molecules at the
neuromuscular junction? Correct answer-acetylcholinesterase breaks down ACh, which allows
chemically gated ion channels to close.
Location of acetylcholinesterase Correct answer-synaptic cleft
Protein in sarcolemma Correct answer-ACh receptor
Ion entering muscle fiber through open chemically gated ion channels Correct answer-Na+
Container of many neurotransmitter molecules Correct answer-synaptic vesicle
Ion triggering exocytosis Correct answer-Ca2+
Membrane surrounding muscle fiber Correct answer-sarcolemma
Neurotransmitter at neuromuscular junction Correct answer-acetylcholine
Portion of sarcolemma containing ACh receptors Correct answer-junctional folds
How is an action potential generated at the neuromuscular junction (NMJ) is converted to excitation
in the muscle fiber? Correct answer-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? Correct answer-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 Correct answer-
cistern Correct answer-The swollen chamber of an organelle that lies on either side of a T tubule
voltage-sensitive tubule protein Correct answer-a protein that changes shape as a result of an
action potential
A protein with heads that attach in cross bridging Correct answer-myosin
, A structure that forms a path from the membrane to the cell interior Correct answer-T tubule
The protein that binds to calcium Correct answer-troponin
Which of the following statements best summarizes excitation-contraction coupling? Correct
answer-A series of events in which an electrical stimulus is conveyed to a muscle fiber to enact
contraction.
myofilament with a knob-like head Correct answer-myosin
myofilament stiffened and stabilized by tropomyosin Correct answer-actin
the cytoplasm of a skeletal muscle fiber Correct answer-sarcoplasm
bundle of skeletal muscle fibers enclosed by connective tissue called perimysium Correct answer-
fasicle
Sarcolemma Correct answer-membrane of muscle cell
long, cylindrical cells Correct answer-skeletal muscle fibers
contractile unit of muscle Correct answer-sarcomere
made up of several sarcomeres Correct answer-myofibrils
Location of higher concentration of Ca2+ needed for cross bridge formation and cycling: Correct
answer-cytoplasm
Actin status to begin cross bridge formation Correct answer-actin-binding sites exposed
Molecule(s) bound to myosin head at start of cross bridge cycle Correct answer-ADP and Pi
Energy state of myosin for beginning cross bridge formation: Correct answer-energized/clocked
myosin head
The molecules released just before power stroke Correct answer-ADP and Pi
Actin behavior during the power stroke Correct answer-ratchets toward the M line
Myosin head energy status during the power stroke Correct answer-pivots and returns to low
energy
the bond between the actin and myosin head weakens due to Correct answer-ATP
Only ____ of the myosin heads are detached from actin at any one time while calcium is present and
cycling continues. Correct answer-HALF
___ is not bound to myosin during the detachment step. Correct answer-ADP
