Human Anatomy 6
Smooth muscle cells
are spindle-shaped
The enzyme acetylcholinesterase causes acetylcholine to
break down
In response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases
calcium ions
Muscle cells
can only contract
Which of the following is characteristic of cardiac muscle?
cardiac muscle cells are striated
During which phase is the stimulus frequency so high that the relaxation phase is eliminated?
complete tetanus
A layer of collagen fibers that surrounds an entire muscle is called
epimysium
Which statement regarding isometric contractions is true?
examples are walking and running
A muscle ______ contains a sarcolemma, sarcoplasm, myofilaments, and myofibrils.
fiber
During moderated activity, which of the following is true regarding muscle metabolism?
glucose and fatty acids are catabolized
Regarding muscle fiber elongation
gravity may help lengthen a muscle fiber after elongation
Fast fibers
have high glycogen reserves
Skeletal muscle fibers differ from "typical cells" in that these muscle fibers
have many nuclei
The term used to describe muscular growth in response to usage is
hypertrophy
Which of the following occurs when tension production rises to a peak and very brief periods of relaxation occur?
incomplete tetanus
Glycolysis
is an anaerobic process
Anaerobic endurance
is exemplified by contractions of fast muscle fibers
Which of the following occurs when glycolysis produces pyruvate faster than it can be used by the mitochondria?
lactic acid is produced
Calcium ions are released from the sarcoplasmic reticulum during the _____ phase of contraction
latent
During activities requiring aerobic endurance
most of the muscle's energy is produced in mitochondria.
The specialized sarcolemma that contains acetylcholine receptors is the
motor end plate
Neurotransmitters that cause skeletal muscle contraction are normally stored in
motor neuron axon terminals
Exhaustion of energy reserves or decline in pH to production and dissociation of lactic acid causes
muscle fatigue
Which statement regarding the relaxation phase of a muscle twitch is true?
muscle tension falls to resting levels
Which of the following occurs as a result of motor units in a particular muscle being always active, even though their contractions do not produce enough movement to cause contraction?
muscle tone
Muscle fascicles are separated by
perimysium
The skeletal muscle structures that actively shorten and are responsible for muscle fiber contraction are called
sarcomeres
The skeletal muscles store calcium ions in the terminal cisternae of the
sarcoplasmic reticulum
Which of the following statements describes how muscles help maintain homeostasis?
skeletal muscle contractions help maintain body temperature
Which type of scenario is most likely?
small motor units are recruited first
Nonstriated, involuntary muscle is
smooth
What is the function of the transverse tubule?
to transmit electrical impulses to the cell's interior
During active-site exposure, calcium ions bind to which of the following?
troponin
Tropomyosin strands are held in position by which of the following?
troponin molecules
A single stimulus-contraction-relaxation sequence in a muscle fiber is known as a
twitch
Myofibrils are made primarily of
actin and myosin
The striated appearance of skeletal muscle results from
actin and myosin arrangement
When a calcium ion binds to troponin
active sites on actin are exposed
Which of the following sarcomere components is made up of proteins that connect the central portions of each thick filament to its neighbors?
M line
Which statement regarding skeletal muscle is true?
Skeletal muscles contain blood vessels
