Muscles and Muscle Tissue
Both actin and myosin are found in the ________.
A band
Which of the following statements is true?
Skeletal muscle cells are long and cylindrical with many nuclei.
What causes the power stroke?
release of ADP and Pi
Which of the following surrounds an individual muscle cell?
Endomysium
What is the functional role of the T tubules?
Enhance cellular communication during muscle contraction
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.
What cellular event is indicated by A?
Exocytosis; Neurotransmitters stored in synaptic vesicles are released into the synaptic cleft by exocytosis.
The longer a muscle is when it starts contracting, the more tension it can generate in the contraction.
False
Contain abundant amounts of glycogen.
Fast (glycolytic), fatigue-resistant fibers
Which of the following is the correct sequence of events for muscle contractions?
Motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments
The cell membrane of a muscle fiber is the _____.
Sarcolemma
The molecular interaction described as a cross bridge involves the binding of which two proteins?
A and C
The myosin filaments are located in the ______.
A band
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.
Marathons
Aerobic Pathway
In which phase of the muscle twitch shown in the figure would the maximum amount of ATP be consumed by myosin head groups?
B
Which of the following corresponds to a single fascicle ?
B
Which of the structures is surrounded by the connective tissue sheath known as the perimysium?
B
Which of the following interactions must occur first so that the others can take place?
B binds to troponin
Why would inflammation of the knee joint be a "good thing" when there's been an acute quadriceps injury?
Because fluid accumulation reduces joint movement
What causes the myosin head to disconnect from actin?
Binding of ATP
In which phase in the figure would the net movement of Ca2+ INTO the sarcoplasmic reticulum (SR) be greatest?
C
Which structure in the figure corresponds to a single skeletal muscle cell?
C
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.
Sarcomeres are functional units of ____ muscle.
Cardiac and Skeletal only
Which of the following is true about smooth muscle?
Certain smooth muscle cells can actually divide to increase their numbers.
What is name given to the regularly spaced infoldings of the sarcolemma?
Transverse or T tubules
The binding of calcium to which molecule causes the myosin binding sites to be exposed ?
Troponin
Muscle tone _____.
a state of sustained partial contraction
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 an isotonic contraction, the muscle ____.
changes in length and moves the ʺloadʺ
Drag the appropriate labels to their respective targets.
T tubule->A band, I band-Sarcolemma-->Triad-->Terminal Cisterns--> Myofibrils
Continued sustained smooth contraction due to rapid stimulation.
Tetanus
______ has an affinity for myosin binding sites in the absence of calcium.
Tropomyosin
What is the role of tropomyosin in skeletal muscles?
Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.
The interaction between which protein and ion initiates muscle coupling?
Troponin; Calcium Ions
A skeletal muscle contracts with varying force and length of time in response to the body's needs at the time.
True
Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments.
True
An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, sliding stops.
True
Cardiac muscle has a limited regenerative capacity.
True
Excitability is the ability of a cell to receive and respond to stimulus by changing its membrane potential.
True
In the muscles of the limbs, the origin is usually the immobile muscle attachment.
True
One of the functions of skeletal muscle contraction is production of heat.
True
The alternating contraction and relaxation of the longitudinal and circular layers mixing substances in the lumen and squeezing them through an organ's internal pathway is characteristic of smooth muscle.
True
The force of muscle contraction is controlled by multiple motor unit summation or recruitment.
True
When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length.
True
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.
A sarcomere is the distance between two ____.
Z discs
A muscle that is lengthening while it produces tension is performing a(n) ____ contraction.
eccentric
Exhaustion of glycogen storage within a muscle fiber would have the biggest effect on ________.
fast glycolytic fibers
During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________.
lactic acid
Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the events of excitation-contraction coupling occur.
latent
The thicker filaments are the ____ filaments.
myosin
Rigor mortis occurs because ________.
no ATP is available to release attached actin and myosin molecules
The _____ shorten(s) during muscle contraction.
sarcomere
Myoglobin _____.
stores oxygen in muscle cells
When a sarcomere contracts and thin filaments move over thick filaments you would expect to see ________.
the I bands to appear smaller
Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?
white fast twitch fibers
Drag the appropriate labels to their respective targets.
From top left to bottom right: Z Disc; H zone;I band; A band; M Line.
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.
Glycolysis
Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?
Glycolysis
The ____ contains only the actin filaments.
I band
Which of the following statements is NOT true regarding ATP production in muscles during periods of prolonged energy use, such as exercise?
In the absence of oxygen, creatine phosphate can drive aerobic respiration pathways for a few minutes.
During an exercise where muscles do not shorten, _____ contractions have occurred.
Isometric
When muscle tension develops but the load is not moved.
Isometric Contraction
When the muscle tension developed overcomes the load and muscle shortening occurs.
Isotonic Contraction
What level of strutural organization does the actin and myosin in a sarcomere of a muscle fiber represent?
Molecular
Each neuron shown in this figure innervates a group of muscle fibers. What is the term for a group of muscle fibers innervated by a single neuron?
Motor Unit
Which term best identifies a muscle cell?
Muscle Fiber
Determined by alternating motor units of a muscle organ even when the muscle is at rest.
Muscle Tone
The two proteins directly involved in muscle contraction are broadly called ____.
Myofilaments
The oxygen-binding protein found in muscle cells is ______.
Myoglobin
Which protein is indicated by the letter E?
Myosin
Approximately 80% of a muscle fiber's volume are the myofibrils. This characteristic reflects muscles ability to ________.
Produce movement through contractile force
The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT ____.
Pyruvic acid is converted back to lactic acid.
If both of the neurons were activated, more muscle fibers would contract than if either neuron alone were active. This mechanism for control of the force of muscle contraction is known as ______.
Recruitment
Which of the following events triggers the subsequent steps of excitation-contracting coupling?
Release of acetylcholine from axon terminals at the neuromuscular junction
What structure in skeletal muscle cells functions in calcium storage?
Sarcoplasmic Reticulum
Which of the following is NOT a normal function of muscle tissue?
Secreting Hormones
Which type of muscle requires somatic (voluntary) nervous stimulation for activation?
Skeletal
Of the following muscle types, which has the longest muscle cells and has obvious stripes called striations?
Skeletal muscle
Which of the following statements is FALSE?
Skeletal muscle cells use creatine phosphate instead of ATP to do work.
Of the following items below, which is the best description for why skeletal muscle stores glycogen?
Skeletal muscle is a heavy consumer of energy.
A relatively high percentage are found in successful marathon runners.
Slow (oxidative), Fatigue-resistant fibers
Abundtant in muscles used to maintain posture.
Slow (oxidative), fatigue-resistant fibers
Depends on oxygen delivery and aerobic mechanisms
Slow (oxidative), fatigue-resistant fibers
Red fibers, the smallest of the fiber types.
Slow (oxidative), fatigue-resistant fibers
If given the exact same amount of ATP, which of the three fiber types would be able to contract for the longest amount of time?
Slow Oxidative Fibers
Which muscle fiber type is best suited for endurance activities, such as long-distance jogging?
Slow oxidative fibers
Which muscle cells have the greatest ability to regenerate?
Smooth
AP generated by Motor Neuron ---Contraction of Skeletal Muscle Fiber
AP propagates along sarcolemma. AP travels down T tubules to triads. Voltage-sensitive proteins open Ca2+ channels. Sarcoplasmic reticulum releases Ca2+. Ca2+ levels in sarcoplasm increase.
The ability of muscle to shorten forcibly when adequately stimulated is known as _____, and sets muscle apart from other tissue types.
Contractility
tropo- iso- myo- sarco- dys-
Means turning, change, or affinity for. Means equal or same. Means muscle. Means flesh. Means abnormal, diseased.
Slow Oxidative muscle fibers are best suited for ____.
running a marathon
25 meter swim
Anaerobic Pathway
The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure?
1 and 7
During muscle contraction, myosin cross bridges attach to which active sites?
Actin Filaments
The region between which two points corresponds to the entire A(dark) band?
2 and 6
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
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.
After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?
Acetylcholinesterase breaks apart the ACh
A myosin head binds to which molecule to form a cross bridge?
Actin
Which protein is indicated by the letter A?
Actin
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
Arrival of an action potential
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Calcium ions
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.
What specific event triggers the uncovering of the myosin binding site on actin?
Calcium ions bind to troponin and change its shape.
Which statement best describes the importance of calcium in skeletal muscle contraction?
Calcium release from the sarcomplasmic reticulum binds to troponin to initiate muscle contraction.
What type of chemical reaction used to rebuild ADP into ATP?
Dehydration synthesis
The energy reserves for which of the ATP regenerating pathways will be depleted first during an extended period of light to moderate exercise?
Direct Phosphorylation of ADP by creatine phosphate
The sliding filament model of contraction states that ____.
During contraction, the thin myofilaments so that the actin and myosin myofilaments overlap to a greater degree
_____ is a missing protein in Duschenne 19s muscular dystrophy.
Dystrophin
A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate.
False
During isometric contraction, the energy used appears as movement.
False
Once a motor neuron has fired, all the muscle fibers in a muscle contract.
False
Have very fast-acting myosin ATPases and depend upon anaerobic metabolism during contraction.
Fast (oxidative), fatigue-resistant fibers
If the cell could no longer produce ATP, what would be the effect on the sarcoplasmic reticulum?
It would be unable to concentrate Ca++ in the sarcoplasmic reticulum
Which of the following processes produces 36 ATP?
Krebs cycle and oxidative phosphorylation
Which of the following is the correct order for the phases of a muscle twitch?
Latent, Contraction, Relaxation
Which of the following factors influence the velocity and duration of muscle contraction?
Load placed on the muscle
If a muscle fiber were to suddenly and permanently stop producing ATP the fiber would no longer be able to actively transport calcium out of the cytoplasm (sarcoplasm) and the intracellular calcium concentration would rise. Which of the following would you expect to happen?
Myosin would be able to bind to the exposed binding sites on thin filaments but it would not be able to detach.
Hypotherically, if a muscle were stretched to the point where thich and thin filaments no longer overlapped, ____.
No muscle tension could be generated
If both motor neurons shown in this figure were to develop action potentials and stimulate muscle fibers, would all the muscle cells shown here contract?
No, because neurons in this figure do not innervate every muscle cell shown.
Creatine phosphate functions in the muscle cell by ____.
Storing energy that will be transferred to ADP to resynthesize ATP
How does the myosin head obtain the energy required for activation?
The energy comes from the hydrolysis of ATP.
Based on what you know of the relationship between the thick and the thin filaments, what would happen if a disorder existed that caused a person to produce no tropomyosin?
The muscle tissues would never be able to relax.
What result would be expected if an additional stimulus, equal in intensity to the first, were to be applied to the muscle at the 60 millisecond (ms) time point?
The muscle would increase in tension to a level greater than that measured at the beginning of phase C.
The 100-meter dash is quick and short 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 is the best explanation for why this is so?
The runners' use of stored energy oxygen, glucose, and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake.
What structure is the functional unit of contraction in a skeletal muscle fiber?
The sarcomere
Although all the anatomical parts of muscle work together to give it its characteristics, which of the following proteins listed below would be most associated with the characteristics of excitability?
Thick (Myosin)Filaments
Direct phophorylation
Weight Lifting
Identify the correct sequence of the following events. a. Myosin generates a power stroke. b. Ca++ binds to troponin. c. ATP recharges the myosin head. d. Troponin removes tropomyosin from G actin. e. The sarcomere shortens. f. Myosin binds to actin.
b,d,f,a,e,c
Proper application of RICE--rest, ice, compression, and elevation--can effectively control inflammation due to an ankle sprain. Why would compression provided by a correctly wrapped elastic Ace bandage be helpful in preventing further inflammation?
because it immobilizes/stabilizes an injured ankle
During development embryonic cells will fuse to form muscle fibers. This will result in _______.
multi-nucleated muscle fibers that can extend as long as 30 centimeters
How a smooth increase in muscle force is produced.
multiple motor unit summation
what is the primary function of wave summation?
produce smooth, continuous muscle contraction
Which of the following are correctly paired?
skeletal muscle, voluntary control
The force of a muscle contraction is NOT affected by ____.
the amount of ATP stored in the muscle cells
A toxin released by certain bacteria can block the release of neurotransmitters into a neuromuscular synaps. What would result from such a block?
the loss of ability to contract the muscle
The contractile, or functional, unit of a muscle fiber is ____.
the sarcomere
Which muscle cell structure stores calcium ions that are used to trigger the contraction?
the sarcoplasmic reticulum
The mechanisms of contraction in smooth muscle is different from skeletal muscle in that ____.
the site of calcium binding site differs
An enzyme known as acetylcholinesterase is present in the synaptic cleft. What is its role?
to break down acetylcholine
A contraction in which the muscle does not shorten but its tension increases is called isometric contraction.
true
Which type of muscle is found in the body wall of hollow organs?
unitary smooth muscle
