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90 Cards in this Set

  • Front
  • Back
Which of these statements about skeletal muscles is false?
Their fibers branch.
They store nutrient reserves.
They support soft tissues.
They pull on tendons.

answer: their fibers branch
Which type of muscle tissue has the greatest effect on the body's heat production?
skeletal muscles does each of these except
pump blood

skeletal muscle
-produces movement
-ventilate the lungs
-maintain posture
the capillaries that wrap around each muscle fiber are located within the
MUSCLES are attached to BONES by TENDONS or
a thin layer of connective tissue that surrounds a muscle fascicle is called the
What is the function of the muscle cell deature indicated by the arrow?
(Sarcoplasmic reticulum)
storage of calcium
what is the function of the nucleus of the muscle cell?
houses the genetic material of the cell
what is the function of the transverse tubules?
-part of coupling the action potential to contraction

The transverse tubules are a conduit for the passage of the action potential from the sarcolemma to the sarcoplasmic reticulum.
What is the function of the mitochondria?
making of ATP-the "power house" of the cell
Which arrangement of the sarcomere gives rise to the structure (band or line) H?
the region of the resting sarcomere that only contains THICK filaments

(lighter region where only thick filaments are found)
what does the Z line do?
marks the boundary between adjacent sarcomeres
what does the M line do?
is the point of connection for adjacent THICK filaments
what does I band do?
the region of the sarcomere that contains only THIN filaments

The I band extends from the A band of one sarcomere to the A band of the neighboring sarcomere and is the region where only thin filaments are found.
Which thick filament binds to ACTIN once its active binding sites are exposed?
the action potential in skeletal muscle fibers is generated by the
titin is an
elastic protein
sarcomere is best defined as
a repeating unit of striated muscle
Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?
Acetylcholine is degraded by acetylcholinesterase.
The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?
Acetylcholine is released by axon terminals of the motor neuron.
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons
extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
Calcium entry into the axon terminal triggers which of the following events?
Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
Acetylcholine binds to its receptor in the sarcolemma and triggers
the opening of ligand-gated cation channels
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
Calcium release from the sarcoplasmic reticulum initiates the contraction.
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
A series of proteins that control calcium release.
What is name given to the regularly spaced infoldings of the sarcolemma?
transverse or T tubules
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Calcium ions.
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
A myosin head bound to actin
What structure is the functional unit of contraction in a skeletal muscle fiber?
The sarcomere
Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?
Calcium ions are stored in the sarcoplasmic reticulum.
After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
ATP binds to the myosin head.
How does the myosin head obtain the energy required for activation?
The energy comes from the hydrolysis of ATP.
What specific event triggers the uncovering of the myosin binding site on actin?
Calcium ions bind to troponin and change its shape.
When does cross bridge cycling end?
Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
when an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium chanels
what means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
the binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
How is acetylcholine (ACh) removed from the synaptic cleft?
acetylcholinesterase (AChE; an enzyme)
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cisternae of the sarcoplasmic reticulum
The neuromuscular junction is a connection between a neuron and a_____.
muscle fiber

The neuromuscular junction is a connection between two cells -- a neuron and a muscle fiber. Overall, the neuromuscular junction allows action potentials in the neuron to generate action potentials in the muscle fiber. This is accomplished through the release of the chemical acetylcholine from the synaptic terminal of the neuron.
The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________.
synaptic terminal

Acetylcholine-filled vesicles are found in the synaptic terminals of motor neurons. The synaptic terminal is at the end of the neuron's axon, so you can think of the axon "terminating" at the synaptic terminal.
What is the synaptic cleft?
the space between the synaptic terminal and the motor end plate
Inside a neuron, acetylcholine is contained within __________.
What causes the vesicles inside a neuron to fuse with the plasma membrane?
an action potential in the neuron
Acetylcholine receptors are primarily located __________.
on the motor end plate
An action potential in the muscle fiber causes __________.
the muscle fiber to contract
The role of acetylcholinesterase in the neuromuscular junction is to __________.
remove acetylcholine from the synaptic cleft
Myofibrils are____.
made of a series of sarcomeres
Z lines define the edges of which of the following?
Myosin molecules form what part of the sarcomere?
thick filament
Which of the following is involved in the power stroke?

The myosin head pivots at the head after it binds to actin, causing the thin filament to be pulled towards the center of the sarcomere. This motion causes the muscle to shorten during contraction.
Which of the following proteins contains the active site involved in cross-bridge formation?

The active site on actin is where myosin heads bind. In the absence of calcium, these active sites are covered by the regulatory protein tropomyosin.
When the sarcomere is at rest, what is covering the active sites on actin?

Tropomyosin is the rope-like regulatory protein that covers the active sites on actin, preventing cross-bridges from forming.
When calcium is released inside a muscle cell, what does it bind to?
myosin molecules form cross-bridges when they attach to
What happens immediately after the myosin head binds to the active site on actin?
The myosin head detaches from the active site on actin.
ATP binding leads to which of the following actions?
detaching and resetting cross-bridges
Which component of a thin filament binds to calcium once the calcium ion is released from the sarcoplasmic reticulum?
Triads in skeletal muscle fibers function in __________.
calcium ion release
During neuromuscular transmission, the axon terminals release __________.
The muscle action potential penetrates into a fiber along the __________.
transverse tubules
In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.
sarcoplasmic reticulum
Cycling of myosin cross-bridges results in ___________.
Repeated cycling of cross-bridges causes all of these effects.
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
arrival of an action potential
The binding of calcium to which molecule causes the myosin binding sites to be exposed?

Yes, when calcium binds to troponin, troponin releases tropomyosin, exposing the myosin binding sites.
A myosin head binds to which molecule to form a cross bridge?
What causes the myosin head to disconnect from actin?
binding of ATP
What energizes the power stroke?
hydrolysis of ATP
A single muscle action potential will normally be followed by __________.
a single pulse of calcium ion release
to increase muscle tension, the nervous system can______.
- increase the number of active motor units
-recruit larger motor units
-increase the stimulation frequency
When a muscle contraction develops tension but doesn't shorten the muscle, the contraction is called __________.
What is the type of chemical reaction used to rebuild ADP into ATP?
dehydration synthesis
Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?
Which of the following processes produces 36 ATP?
Krebs cycle and oxidative phosphorylation
The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.
-Glycogen is synthesized from glucose molecules.
-Oxygen rebinds to myoglobin.
-ATP is used to rephosphorylate creatine into creatine phosphate.

does NOT include:

Pyruvic acid is converted back to lactic acid.
Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?
white fast twitch fibers
The biochemical reaction that consumes the majority of a muscle's ATP is the __________.
actin myosin cross-bridge cycle
Muscle fatigue occurs due to a buildup of __________ and __________ in pH.
lactic acid; decrease

(the lower the pH, the more acidic)
Anaerobic glycolysis provides energy for muscle contraction when the supply of __________ is limited.
The __________ type of muscle fiber has relatively few mitochondria.
Which of these is NOT a property of slow muscle fibers?
they are large in diameter

IS property of slow muscle fibers:

They are rich in myoglobin.
They contract slowly.
They resist fatigue.
Which of these is true of cardiac muscle fibers?
-cardiac fibers branch
-cardiac fibers have a long twitch duration compared to skeletal fibers
-cardiac fibers have a single nucleus
the intercalated disk is not a site of
neuromuscular transmission

it is a site of:
-myofibril attachment
-force transmission
-action potential propagation
All of the following are found in both skeletal and cardiac muscle fibers except __________.
intercalated disks

Found in skeletal and cardiac muscle fibers:
Smooth muscle contracts when calcium binds to __________ and activates __________.
calmodulin; myosin light chain kinase
Which of these is not a function of smooth muscle?
pushing blood into the arteries

Functions of smooth muscle:
-adjusting airway diameter
-elevating skin hairs
-churning the stomach contents