Which type of muscle CANNOT contract without being stimulated by the nervous system?
B. skeletal
Which muscle characteristic describes the ability of muscle to respond to a stimulus?
B. excitability
The molecular interaction described as a "cross bridge" involves the binding of which two of the letters below?
A. A and C
The protein troponin is shown in this figure to be bound to which substance?
C. calcium ion
How many motor units are illustrated in the figure?
D. 2
If both of the neurons in the figure were activated, more muscle fibers would contract than if either neuron alone were active. This mechanism for control of the force of muscle contraction is known as ______.
A. recruitment
In which phase of the muscle twitch shown in the above figure would the maximum amount of ATP be consumed by myosin head groups?
C. B
In which phase in the figure would the net movement of Ca2+ into the sarcoplasmic reticulum (SR) be greatest?
A. C
What result would be expected if an additional stimulus, equal in intensity to the first, were to be applied to the muscle at the 60 millisecond (ms) time point?
B. The muscle would increase in tension to a level greater than that measured at the beginning of phase C.
The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure?
C. 1 and 7
What event directly triggers the release of neurotransmitter shown in A?
C. diffusion of Ca2+ into the axonal terminus
What specific neurotransmitter is released from the axonal terminus as shown in A?
A. acetylcholine
The smallest contractile unit of a muscle fiber is ________.
D. the sarcomere
The major role of the sarcoplasmic reticulum is to regulate ________.
B. intracellular levels of Ca2+
Thick myofilaments are made of ________.
C. myosin
The sliding filament model of contraction states that ________.
A. during contraction the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree
A muscle that is lengthening while it produces tension is performing a(an) ________ contraction.
D. eccentric
The response of a motor unit to a single action potential of its motor neuron is called ________.
C. a muscle twitch
Slow oxidative muscle fibers are best suited for ________.
B. running a marathon
Isometric contraction leads to movement of a load. True or False
False
Which protein inhibits interaction between actin and myosin to prevent skeletal muscle contraction; and which ions remove the inhibition?
B. tropomyosin; calcium ions
Excitation-contraction coupling includes all EXCEPT which of the following events?
C. release of acetylcholine from axon terminals at the neuromuscular junction
What is a cross bridge cycle?
D. It is the cycle in which an energized myosin head binds to actin and performs a power stroke, then binds to ATP in order to detach and re-energize.
Which pathway for regenerating ATP provides the majority of the energy used for muscle activity during 30 minutes of light to moderate exercise?
A. aerobic respiration
Which muscle fiber type is best suited for endurance activities, such as long-distance jogging?
C. slow oxidative fibers
Cross bridge formation between myosin heads and actin molecules is caused by the elevation of calcium ion concentration in the cytosol. During rigor mortis, this elevation of calcium ion concentration in the cytosol is permanent because ________.
A. mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps
Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the neurotransmitter is released by exocytosis, diffuses across the synaptic cleft, and binds to its receptors.
C. latent
What structure in skeletal muscle cells functions in calcium storage?
B. sarcoplasmic reticulumin
What does excess postexercise oxygen consumption represent?
C. the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
Creatine phosphate functions in the muscle cell by ________.
D. storing energy that will be transferred to ADP to resynthesize ATP
What is the primary function of wave summation?
D. produce smooth, continuous muscle contraction
The major function of the sarcoplasmic reticulum in muscle contraction is to ________.
D. regulate intracellular calcium concentration
The contractile units of skeletal muscles are ________.
A. myofibrils
What is the functional role of the T tubules?
C. enhance cellular communication during muscle contraction
What is the role of calcium ions in muscle contraction?
D. bind to regulatory sites on troponin to remove contraction inhibition
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
D. refractory period
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.
B. glycolysis
Muscle tone is ________.
A. a state of sustained partial contraction
The sliding filament model of contraction involves ________.
D. actin and myosin sliding past each other and partially overlapping
Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________.
C. no muscle tension could be generated
What part of the sarcolemma contains acetylcholine receptors?
D. motor end plate
The force of muscle contraction is controlled by multiple motor unit summation or recruitment. True or False
True
Binding of calcium to calmodulin is a step in excitation-contraction coupling of ________ cells.
A. smooth muscle
The type of muscle found in the walls of most hollow organs is ________.
D. unitary smooth muscle
What special feature of smooth muscle allows it to stretch without immediately resulting in a strong contraction?
C. stress-relaxation response
Which of the following describes the cells of unitary smooth muscle?
A. They exhibit spontaneous action potentials.
Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments. True or False
True
Cardiac muscle makes most of its ATP via anaerobic pathways. True or False
