anatomy Dynamic study
Which of the following is the dark band seen on myofibrils?
A band
What causes the myosin head to release its attachment to actin?
A new ATP molecule binds to the myosin head.
_______ is required to detach cross-bridges and reactivate the myosin head.
ATP
Layers of smooth muscle in the reproductive tract of the female are important for __________. All of the listed responses are correct. Unselected movement of oocytes Unselected delivery of a newborn during parturition Unselected movement of sperm if present
All of the listed responses are correct.
Which of the following may cause muscle atrophy? All of the listed responses are correct. Unselected A lack of regular stimulation of muscle fibers Unselected Wearing a cast on a broken limb Unselected Paralysis
All of the listed responses are correct.
Which of the following is NOT found in the endomysium? all of these are present in the endomysium. Unselected Capillary networks Unselected Nerve fibers Unselected Myosatellite cells
All of these are present in the endomysium.
What is the term for the ability of cardiac muscle cells to contract without neural stimulation?
Automaticity
What must bind to troponin in order to expose the active sites on actin?
Calcium ions
In smooth muscle cells, calcium binds to which regulatory protein to initiate contraction?
Calmodulin
The cardiovascular system uses which types of muscle?
Cardiac and smooth
What provides ATP for the first 15 seconds of a muscle contraction?
Creatine phosphate
Which of the following would NOT be an effective source of energy for muscle contraction?
DNA
Which of the following would NOT be an effective source of energy for muscle contraction? DNA Unselected Glycogen Unselected ATP Unselected Creatine phosphate
DNA
Which connective tissue layer wraps around the entire muscle?
Epimysium
Which of the muscle fiber types is best adapted for a rapid contraction but fatigues easily?
Fast fibers
What structure is responsible for the spread of action potential between visceral smooth muscle cells?
Gap junctions
Which of the following is an example of an isometric contraction?
Holding a heavy stack of books above the ground
What is the effect of acetylcholine on the motor end plate of the muscle cell membrane?
Increasing the permeability to Na+, causing Na+ to diffuse into the muscle cell
What is the name of the structure that contains gap junctions and desmosomes and joins the plasma membranes of two cardiac muscle cells together?
Intercalated discs
Pushing both hands against a nonmoving wall represents which type of muscle contraction?
Isometric
How does the release of calcium ions from the terminal cisternae initiate contraction?
It triggers the binding of myosin to actin.
What happens in the muscle fiber during the Cori cycle?
Lactic acid is shuttled to the liver and glucose is shuttled back to the muscle fiber from the liver.
Why is control over leg muscles LESS precise than control over the muscles of the eye?
Many muscle fibers in the legs are controlled by a single motor neuron.
The H band contains which structures?
Only myosin in the thick filaments
Which of the following is NOT a characteristic of smooth muscle tissue?
Presence of striations
Where is the site of calcium storage in the skeletal muscle fibers?
Sarcoplasmic reticulum
Which type of tissue is responsible for holding your head upright while you are reading this question?
Skeletal muscle tissue
What are the three types of muscle tissue?
Skeletal, cardiac, and smooth
Marathon runners rely on which muscle fiber type for endurance?
Slow fibers
Which of the following activities describes an isotonic eccentric contraction?
Slowly lowering a book out in front of you with the arm extended.
Structurally, how do smooth muscle cells differ from skeletal muscle cells?
Smooth muscle cells lack myofibrils and sarcomeres.
Which type of muscle tissue causes contraction of the urinary bladder, forcing urine out of the body?
Smooth muscle tissue
Cardiac muscle has the feature of automaticity, which is the ability to contract without neural stimulation. Which of the following statements accurately explains this feature?
Specialized pacemaker cells within the heart determine the rate of contraction of heart muscl
Which structure in a muscle fiber or muscle cell is continuous with the sarcolemma and carries the signal to contract deep into the muscle cells?
T tubules
The transmission of an action potential along the T tubules stimulates the release of calcium from which structure in the sarcomere?
Terminal cisterna
What is happening during the contraction phase of a single twitch?
The muscle is producing tension.
What causes the myosin head to reenergize itself once the power stroke has occurred?
The myosin head splits a fresh ATP molecule.
What happens during the power stroke?
The thin filaments slide toward the M line
What is a characteristic of cardiac muscle that is NOT true of skeletal muscle?
They lack terminal cisternae
What structures make up a triad?
Two terminal cisternae and a T tubule
When would we use the contractile proteins in our skeletal muscle cells to provide energy?
When our diet contains too few proteins or calories
Which of the following has been correlated with muscle fatigue?
a decline in pH within the muscle, which alters enzyme activities
Smooth muscle contractions in the respiratory passageways cause __________.
a decrease in diameter, making it harder for air to flow
The thin filaments consist of __________.
a pair of F-actin molecules twisted together
A single stimulation-contraction-relaxation sequence in a muscle fiber is known as ________.
a twitch
The thick filaments consist of __________.
about 300 myosin molecules twisted around one another
The neurotransmitter required to trigger skeletal muscle contraction is __________.
acetylcholine (ACh)
The sliding of __________ over ___________ causes shortening of skeletal muscle fibers.
actin; myosin
The length of time a muscle can continue to contract while supported by mitochondrial activities is referred to as __________.
aerobic endurance
What are the two mechanisms used to generate ATP from glucose?
aerobic respiration and glycolysis
What allows the contraction cycle to repeat so that shortening of the sarcomere happens? All of the choices are correct. Unselected Calcium levels remain high in the sarcomere. Unselected ATP is continuously supplied by the mitochondria. Unselected The active site on actin remains exposed.
all are correct
What can happen when multiple stimuli are applied to a muscle fiber before it completely relaxes and tension production is gradually increasing? All of the listed answers are correct. Unselected Incomplete tetanus Unselected Complete tetanus Unselected Wave summation
all are correct
A blending of epimysium, perimysium, and endomysium that forms a broad sheet at the end of a muscle is known as __________.
an aponeurosis
As a result of physical inactivity, muscle cell and myofibrils will be reduced in size and number, respectively. This condition is known as __________.
atrophy
Unlike skeletal muscles, cardiac muscle fibers do not require autonomic stimulation to depolarize and contract. This property is known as ___________.
automaticity
Mitochondrial activities are relatively efficient, but their rate of ATP generation is limited by the __________.
availability of oxygen
The first step in the contraction cycle in skeletal or cardiac muscles is when ______ binds to ________.
calcium; troponin
Depolarization of the skeletal muscles at the NMJ occurs as a result of acetylcholinebinding and opening the _____________.
chemically gated sodium channels
During __________, the muscle fiber is rapidly and continuously being stimulated and is never allowed to relax completely.
complete tetanus
The length of a sarcomere determines the degree of tension produced. For optimal contraction, the ideal range of sarcomere length is 75 percent to 130 percent of its normal length. This is because at this range, there is a maximal number of _______ that can be formed during contraction.
cross-bridges
In an isotonic contraction, __________.
cross-bridges must produce enough tension to exceed the load to be moved
After contraction, a muscle fiber returns to its original length because of __________.
elastic forces and the movement of opposing muscles
Excitation-contraction coupling forms the link between __________.
electrical activity in the sarcolemma and the initiation of a contraction
During the recovery period, the body's oxygen demand is __________.
elevated above normal resting levels
The connective tissue layer that surrounds a single muscle fiber and joins it to other muscle fibers is __________.
endomysium
Nerves and blood vessels are contained within the connective tissues of the __________.
epimysium, perimysium, and endomysium
The perimysium surrounds a bundle of muscle fibers called a __________.
fascicle
The primary source of energy in a resting muscle fiber is ___________.
fatty acids
Which of the following produces ATP from glucose anaerobically?
glycolysis
Voluntary control over swallowing, defecation, and urination is provided by muscles that __________.
guard entrances and exits
A muscle producing almost peak tension during rapid cycles of contraction and relaxation is said to be in __________.
incomplete tetanus
The process of complete tetanus is reached by __________.
increasing the rate of stimulation until the relaxation phase is completely eliminated
What is the type of contraction in which the muscle does not change length and the contraction does not produce tension that exceeds the load?
isometric
During anaerobic muscle metabolism, _______ is produced as the end product of glycolysis.
lactate
When glycolysis produces pyruvic acid faster than it can be used by the mitochondria, the pyruvic acid is converted to __________, which lowers the pH of body fluids.
lactic acid
Heat released from contracting muscles functions to __________.
maintain body temperature
All the muscle fibers and the single motor neuron that innervates them are called a __________.
motor unit
Inherited disorders that produce progressive muscle weakness and deterioration within muscles are called ______________.
muscular dystrophies
One of the distinct features of the skeletal muscle fibers is that they are multinucleated. The multinucleation is the result of the fusion of embryonic cells called __________.
myoblasts
Skeletal muscles develop from the conjoining of a group of embryonic cells knows as _______.
myoblasts
Presence of _______ in the sarcoplasm provides a ready supply of oxygen for aerobic respiration in muscle tissue.
myoglobin
Which of the following is NOT found in a thin filament? Myosin Unselected Troponin Unselected Tropomyosin Unselected Actin
myosin
What structure below is part of the crossbridge?
myosin head
The amount of tension produced by an individual muscle fiber ultimately depends on the __________.
number of pivoting cross-bridges
Skeletal muscles generate maximum tension when the maximum number of cross-bridges can form in the zone of _______.
overlap
The connective tissue layer that surrounds a bundle of skeletal muscle fibers is called __________.
perimysium
The wave-like contraction created by smooth muscle cells is known as ________.
peristalsis
When lifting a heavy weight, more motor neurons are called into action to overcome the weight by creating a greater tension. This phenomenon is known as _________.
recruitment
Myofibrils are formed as a result of repeating functional units called __________.
sarcomeres
The repeating functional units seen in the myofibrils are __________.
sarcomeres
A high blood concentration of the enzyme creatine phosphokinase (CPK) usually indicates __________.
serious muscle damage
Extensive blood vessels, mitochondria, and myoglobin are found in the greatest concentration in __________.
slow fibers
The type of skeletal muscle fiber best suited for endurance-type activities is __________.
slow fibers
What type(s) of muscle tissue do(es) NOT contain sarcomeres?
smooth
The connective tissue fibers of the epimysium, perimysium, and endomysium extend beyond the skeletal muscle cells to form a bundle of connective tissue that joins the muscle cells to a bone. This bundle is called a(n) __________.
tendon
The regulatory protein responsible for elasticity of skeletal muscles is _________.
titin
The regulatory protein responsible for binding to calcium for contraction to proceed is _____.
troponin