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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

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