Muscles chapter 9
Which of the following is the correct order for the phases of a muscle twitch?
1. latent phase 2. contraction phase 3. relaxation phase
What do facilitated diffusion and active transport have in common?
Both are a type of carrier-mediated transport
Why does Jonathan continue to breathe heavily after running his daily half-marathon?
He requires more oxygen to restore levels of ATP and creatine phosphate
What would you expect to see when a sarcomere contracts?
I bands appear smaller
What happens when acetylcholine stimulates its receptors in the neuromuscular junction?
Na+ can move into the post-synaptic cell
Where would you expect to find numerous gap junctions in muscular tissue?
The intercalated discs of cardiac muscle
Which of the following is true concerning isotonic eccentric contraction?
The muscle lengthens while tension remains constant
Which of the following systems provides Jonathan the most energy while he's winning the first point in racquetball?
The phosphagen system
The 100-meter dash is a brief run requiring explosive speed. On completion of the dash, the runners will continue to breathe hard for several seconds to minutes even though they are no longer running. Which of the following provided the best explanation?
The runners' use of stored oxygen, glucose, and creatine phosphate is being replenished which requires a prolonged increase of oxygen intake.
Which of the following marks the boundaries of a sarcomere?
Z discs
What is muscle tone?
a state of sustained partial contraction
A neuron stimulus reaches a muscle fiber which has only partially relaxed from a single previous stimulation. Which result is most likely?
a stronger contraction due to temporal summation
Which of the following muscle proteins is most associated with excitability?
acetylcholine receptors in the synapse
After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?
acetylcholinesterase breaks apart ACh
What does the sliding filament model of contraction involve?
actin and myosin sliding past each other and partially overlapping
Troponin is a major protein in thin filaments. Which of the following is not a function of the troponin?
binding potassium ions
Mitochondria are especially prominent in which of these?
cardiac muscle
The rubbery matrix of cartilage is secreted by __________, whereas _________ produce the fibers and ground substance that form the matrix of fibrous connective tissue.
chondroblasts, fibroblasts
he ability of muscle to shorten when stimulated is known as ______ and is unique to muscle tissue.
contractility
Which of the following surrounds an individual muscle cell?
endomysium
What is the functional role of the T tubules?
enhance conduction of electrical signals through a muscle cell
Which of these is false about smooth muscle?
extensive overlap between thin and thick filaments
Which of these would be impacted most by exhausting glycogen storage within a muscle fiber?
fast glycolytic fibers
Which of the following is caused by smooth muscle contraction?
goosebumps
How is cardiac muscle different than skeletal muscle?
has gap junctions that allow many muscle cells to contract in unison, unlike skeletal muscle
The training regimen of a competitive weight lifter is designed partly to:
increase the average number of myofibrils per muscle fiber
Which of these involves shortening a muscle while maintaining constant tension?
isotonic contraction
What is the purpose of a triad?
it releases Ca2+ when a muscle fiber is excited
Which of the following is a factor that affects the velocity and duration of muscle contraction?
load on the fiber
What type of histological section divides a structure along its long axis?
longitudinal section
Athletes who train at high altitudes increase their red blood cell count, which increases their oxygen supply during exercise. Which of these is a result of increased oxygen supply?
more aerobic respiration
Which of the following is the correct sequence of events for muscle contractions?
motor neuron electrical signal neurotransmitter release muscle cell electrical signal release of calcium ions from sarcoplasmic reticulum ATP-driven power stroke sliding of myofilaments
Which of these may be the result of absence or inhibition of acetylcholinesterase at a synapse?
muscle cramps
Myasthenia gravis is an autoimmune disorder resulting in the loss of ACh receptors from skeletal muscle fibers. Which of the following is most likely to be a symptom of myasthenia gravis?
muscle weakness
Why does rigor mortis occur?
no ATP is available to release attached actin and myosin molecules
All cells in ____ epithelium reach the basement membrane, but only cells that reach the apical surface have cilia.
pseudostratified columnar
What structure in skeletal muscle cells stores calcium?
sarcoplasmic reticulum
Sarcomeres are functional units of
skeletal muscle
Which muscle type is striated and has the longest muscle cells?
skeletal muscle
Which of the following statements about muscle types is true?
skeletal muscle cells are long and cylindrical with many nuclei
Which of these would be impacted most by addition of more mitochondria to a muscle fiber?
slow oxidative fibers
Which of these release very little calcium from sarcoplasmic reticulum?
smooth muscle
Which of the following is an accurate difference between skeletal muscle to smooth muscle?
smooth muscle contracts and relaxes more slowly than skeletal muscle
Which of these may contract without nervous stimulation?
smooth muscle, cardiac muscle
What term describes alternating light and dark bands in skeletal muscle?
striations
Where are acetylcholine receptors found?
synapse
What releases acetylcholine into the synaptic cleft to stimulate muscle contraction?
synaptic vesicles
Where is most lactate produced by skeletal muscle converted to pyruvate?
the liver
Why do all muscle cells respond when electrically stimulated?
they are electrically excitable
Drugs called calcium channel blockers may be used to lower blood pressure by causing arteries to relax. How do you suppose these drugs work?
they prevent extracellular calcium from entering smooth muscle, thus allowing the muscle to relax.
What is the purpose of motor nerve varicosities as they relate to smooth muscle?
they release neurotransmitter molecules onto smooth muscle cells
Which of the following muscle proteins is most associated with contractility?
thick (myosin) filaments
What structures form the triads of a muscle fiber?
two terminal cisterns and one T tubule
Skeletal muscle is termed ____ because it is usually subject to conscious control.
voluntary
Two solutions are separated by a selectively permeable membrane that only allows water to pass through. Which of these occurs If solution A has a higher solute concentration than solution B?
water will pass down its concentration gradient from solution B to A
