46 terms

Muscular System

Muscular System
T/F Functions of muscle include; heartbeat, muscle tone, and moving bones.
Myofibrils are composed primarily of
actin and myosin
The striated appearance of skeletal muscle fibers results from the
sarcomere organization
A sarcomere is best described as
a unit within a muscle fiber
What transmits muscle impulses into the cell interior?
Transverse tubules
The discoloration and swelling of a muscle strain is due to
ruptured blood vessels
A tendon is ______, whereas an aponeurosis is ______.
cordlike and connects muscles to bones; a broad sheet of dense connective tissue that connects muscles to muscles
Muscle fibers are basically a collection of
Transverse tubules and sarcoplasmic reticulum are well developed in
skeletal and cardiac muscle fibers
The functional unit of muscle contraction is
the sarcomere
Neurotransmitters are stored in vesicles in
motor neuron endings
Supplies energy for the synthesis of ATP
Creatine phosphate
The amount of oxygen liver cells require to support the conversion of lactic acid to produce glucose or glycogen is the
oxygen debt
Muscle cramps are most likely due to a temporary deficit of
Binding sites on the surface of actin allow the formation of cross-bridges with molecules of
Athletes usually experience muscle fatigue less quickly than nonathletes because they
produce less lactic acid
At a neuromuscular junction, the muscle fiber membrane folds, forming a
motor end plate
The toxin that causes botulism
prevents release of acetylcholine
Rigor mortis affects skeletal muscles a few hours after death, due to
a decrease in ATP and increased permeability to calcium
What is released at a neuromuscular junction?
The first event in muscle fiber contraction is that
acetylcholine is released from the end of the motor neuron
Actin filaments slide along ___________.
myosin filaments
The functional connection between a neuron and a skeletal muscle fiber is a
__________ degrades acetylcholine, keeping it from accumulating in the synapse
Arrange the following steps of muscle fiber contraction in the correct sequence.
1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released.
2. Thin filaments are pulled over the thick filaments.
3. Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites.
4. The impulse arrives at the synapse and travels through the transverse tubules.
5. The muscle fiber shortens and contracts.
6. Myosin heads bind to exposed active sites on actin, forming cross-bridges.
4, 1, 3, 6, 2, 5
A shift in metabolism that breaks down pyruvic acid to lactic acid is called
lactic acid threshold
What may occur if the respiratory and circulatory systems to supply enough oxygen to skeletal muscles when used strenuously for a minute or two?
Oxygen debt in muscles
When ATP levels are low, the relationship between ATP and creatine phosphate is that
creatine phosphate supplies energy to regenerate ATP from ADP and phosphate
The characteristic reddish brown color of skeletal muscle comes from which substance?
A motor unit is
a motor neuron and the muscle fibers connected to it
During muscle contraction ATP supplies energy for
myofilament movement
Skeletal muscles help maintain body temperature in that
the more active they are, the more heat is released
What is the minimum strength of stimulation required to contract a muscle fiber is called
Threshold stimulus
The increase in the number of motor units activated as a result of more intense stimulation is called
In a recording of a muscle twitch, the delay between the time a stimulus is applied and the time the muscle responds is called the
latent period
A muscle fiber exposed to a series of stimuli of increasing frequency combines individual twitches (summation) which results in
complete sustained contraction
Activities such as distance swimming and distance running are most likely to stimulate development of
slow fatigue-resistant fibers
What 3 things occur when a muscle undergoes atrophy in response to disuse
1. there is a reduction in capillary networks.
2. the size of actin and myosin filaments decreases.
3. the muscle gets smaller.
Compared to skeletal muscle, smooth muscle
contracts more slowly and relaxes more slowly
The structures that connect cardiac muscle cells are
intercalated discs
Bones and muscles function as mechanical devices called
The more movable end of a muscle is its
The muscle that causes an action is the
A muscle that assists the agonist is a(n)
The muscle that opposes a particular action is called the
Fibers of muscles whose motor neurons are severed
may be replaced by fat or fibrous connective tissue