BMS 507 - Mastering A&P Ch 10
Which of these is/are 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
When comparing slow muscle fibers to fast muscle fibers, slow fibers
-are rich in the red protein myoglobin -take about three times as long to reach peak tension -generate much less tension -have much smaller fiber diameters
Muscular force can be adjusted to match different loads by
-involving more muscle fibers in the contraction -recruiting larger motor units -varying the frequency of action potentials in motor neurons -recruiting more motor units
During anaerobic glycolysis,
-oxygen is not consumed -pyruvic acid is produced -ATP is produced -carbohydrate is metabolized
In rigor mortis
-sustained contractions occur -the myosin heads are attached to actin -ATP is depleted -calcium ions keep binding to troponin
Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell
95
At what point during excitation contraction coupling does exocytosis play a role?
During acetylcholine release from the synaptic terminal
The area in the center of the A band that contains no thin filaments is the
H band
The region of the sarcomere that always contains thin filaments is the
I band
Which of the following best describes the term titin?
Protein that accounts for elasticity of resting muscle
A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction?
Reduces the muscle's ability for contraction
Which type of muscle tissue has the greatest effect on the body's heat production?
Skeletal
Which of the following types of muscle fibers are best adapted for prolonged contraction such as standing all day?
Slow fibers
What is the function of the triad?
Storage of calcium
Which of the following hormones directly stimulates growth of muscle tissue, leading to increased muscle mass?
Testosterone
Which region of the sarcomere gives rise to the structure (band or line) indicated by the arrow?
The region of the resting sarcomere that only contains thick filaments
Which of the following become connected by myosin cross-bridges during muscle contraction?
Thin filaments and thick filaments
Which of the following best describes the term Z line?
Thin filaments are anchored here
Sarcomere is best defined as ________
a repeating functional unit of striated muscle
The skeletal muscle complex known as the triad consists of
a transverse tubule and two terminal cisternae
Triggering of the muscle action potential occurs after
acetylcholine binds to chemically-gated channels in the motor end plate
Thin filaments are mostly made of the protein
actin
Creatine phosphate
acts as an energy reserve in muscle tissue
During the recovery period the body's need for oxygen is increased because
additional oxygen is required to restore energy reserves
A resting muscle generates most of its ATP by
aerobic metabolism of fatty acids
After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs
an oxygen debt
A(n) ________ can be described as a broad tendinous sheet
aponeurosis
In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases
calcium ions
Smooth muscle contracts when calcium binds to __________ and activates __________
calmodulin; myosin light chain kinase
Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for
contraction
The capillaries that wrap around each muscle fiber are located within the __________
endomysium
The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the
endomysium
The dense layer of connective tissue that surrounds an entire skeletal muscle is the
epimysium
Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives
exocytosis
Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of
fast fibers
In the liver, during the Cori cycle,
glucose is produced from lactic acid
Cardiac muscles cells have a sarcolemma that is more permeable to calcium, which causes them to __________
have contractions that last longer than skeletal muscle fibers
Fast fibers
have low resistance to fatigue and quick twitches
Muscle fibers differ from "typical cells" in that muscle fibers
have many nuclei
The muscle weakness of myasthenia gravis results from
loss of acetylcholine receptors in the end-plate membrane
When acetylcholine binds to receptors at the motor end plate, the sarcolemma becomes
more permeable to sodium ions
During activities requiring aerobic endurance,
most of the muscle's energy is produced in mitochondria
Receptors for acetylcholine are located on the
motor end plate
During the recovery period following exercise, all of the following are true except
muscle fibers are unable to contract
Skeletal muscle fibers are formed from embryonic cells called
myoblasts
Thick filaments are made of the protein
myosin
Cross-bridges are portions of
myosin molecules
Each skeletal muscle fiber is controlled by a motor neuron at a single
neuromuscular junction
At peak levels of muscle exertion the mitochondria can supply
only about one-third of the energy required by the muscle
Resting smooth muscle can be stretched without affecting tension development because of its __________
plasticity
The advantage of having many nuclei in a skeletal muscle fiber is the ability to
produce large amounts of muscle proteins
Fast muscle fibers can adapt to aerobic metabolism by generating more mitochondria in response to
repeated, exhaustive stimulation
After death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasmic reticulum into the sarcoplasm. This results in a condition known as
rigor mortis
The plasma membrane of a skeletal muscle fiber is called the
sarcolemma
The repeating unit of a skeletal muscle fiber is the
sarcomere
Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber
shortens
The structural theory that explains how a muscle fiber contracts is called the ________ theory
sliding filament
The narrow space between the synaptic terminal and the muscle fiber is the
synaptic cleft
At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium, come together to form a
tendon
The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n)
tendon
An infection by the bacterium Clostridium tetani can cause the disease called
tetanus
The action potential is conducted into a skeletal muscle fiber by
transverse tubules
The complex of a transverse tubule and two adjacent terminal cisternae is known as a
triad
The protein that regulates muscle contraction by controlling the availability of active sites on actin is called
tropomyosin
At rest, active sites on the actin are blocked by
tropomyosin molecules
Active sites become exposed when calcium bind to
troponin
At rest, the tropomyosin molecule is held in place by
troponin molecules
The rapid rise and fall in force produced by a muscle fiber after a single action potential is a(n)
twitch
Each thin filament consists of
two actin protein strands coiled helically around each other
In a sarcomere, cross-bridge attachment occurs specifically in the
zone of overlap