The Musculoskeletal System Flashcards
The contraction of skeletal muscles is based on
A) actin filaments coiling up to become shorter.
B) myosin filaments coiling up to become shorter.
C) actin and myosin filaments both coiling up to become shorter.
D) actin cross-bridges binding to myosin and then flexing.
E) myosin cross-bridges binding to actin and then flexing.
E) myosin cross-bridges binding to actin and then flexing.
A skeletal muscle deprived of adequate ATP supplies will
A) immediately relax.
B) release all actin-myosin bonds.
C) enter a state where actin and myosin are unable to separate.
D) fire many more action potentials than usual and enter a state of “rigor.”
E) sequester all free calcium ions into the sarcoplasmic reticulum.
C) Enter a state where actin and myosin are unable to seperate.
The calcium ions released into the cytosol during excitation of skeletal muscle bind to A) troponin. B) tropomyosin. C) actin. D) myosin. E) transverse tubules.
A) Troponin
The muscles of a recently deceased human can remain in a contracted state, termed rigor mortis, for several
hours, due to the lack of
A) phosphorylated myosin.
B) ATP needed to break actin-myosin bonds.
C) calcium ions needed to bind to troponin.
D) oxygen supplies needed for myoglobin.
E) sodium ions needed to fire action potentials.
B) ATP needed to break actin-myosin bonds.
Calcium ions initiate sliding of filaments in skeletal muscles by
A) breaking the actin-myosin cross-bridges.
B) binding to the troponin complex, which then relocates tropomyosin.
C) transmitting action potentials across the neuromuscular junction.
D) spreading action potentials through the T tubules.
E) reestablishing the resting membrane potential following an action potential.
B) binding to the troponin complex, which then relocates tropomyosin.
In a relaxed skeletal muscle, actin is not chemically bound to A) myosin. B) troponin. C) tropomyosin. D) Z lines
A) Myosin
Skeletal muscle contraction begins when calcium ions bind to A) energized cross-bridges. B) myosin. C) actin. D) tropomyosin. E) troponin.
E) troponin.
The muscle spindle is
A) an actin-myosin complex.
B) a troponin-tropomyosin complex.
C) axons wound around muscle fibers.
D) a group of dendrite-encircled muscle fibers.
E) a muscle cell that makes up a muscle group.
D) a group of dendrite-encircled muscle fibers.
Sustained muscle contraction without relaxation between successive stimuli is called A) tonus. B) fused tetanus. C) an all-or-none response. D) fatigue. E) a spasm.
B) Fused tetanus
Skeletal, cardiac, and smooth muscle all have A) A bands and I bands. B) transverse tubules. C) gap junctions. D) motor units. E) thick and thin filaments.
E) thick and thin filaments
Calcium ions regulate contraction of smooth muscle cells by binding to A) troponin. B) tropomyosin. C) actin. D) myosin. E) calmodulin.
E) Calmodulin
Chitin is a major component of A) the skeleton of mammals. B) the hydrostatic skeletons of earthworms. C) the exoskeleton of insects. D) the body hairs of mammals. E) the skeleton in birds.
C) The exoskeleton of insects.
A ball-and-socket joint connects A) the radius to the ulna. B) the radius to the humerus. 3 C) the ulna to the humerus. D) the humerus to the scapula. E) the radius to the scapula.
D) The humerus to the scapula
The protein that acts as a calcium receptor in skeletal muscle is: A. actin B. troponin C. dystrophia D. titin
B) troponin
What is the role of calcium in muscle contraction?
A. its binding to a regulatory protein causes the protein to move, exposing actin binding sites to the myosin
heads
B. it provides energy for contraction
C. it blocks contraction when muscle relaxes
D. it is the neurotransmitter released by a motor neuron, and it initiates an action potential in a muscle fiber
E. it forms the heads of the myosin molecules in the thick filaments inside a muscle fiber
A. its binding to a regulatory protein causes the protein to move, exposing actin binding sites to the myosin
heads
