Terms in this set (99)
Depends on oxygen delivery and aerobic mechanisms.
Slow (oxidative), fatigue-resistant fibers
Have very fast-acting myosin ATPases and depend upon anaerobic metabolism during contraction.
Fast (oxidative or glycolytic), fatigable fibers
Red fibers, the smallest of the fiber types.
Slow (oxidative), fatigue-resistant fibers
Contain abundant amounts of glycogen.
Fast (oxidative or glycolytic), fatigable fibers
Abundant in muscles used to maintain posture.
Slow (oxidative), fatigue-resistant fibers
The stimulus above which no stronger contraction can be elicited, because all motor units are firing in the muscle.
The phenomenon in which the contraction strength of a muscle increases, due to increased Ca2+ availability and enzyme efficiency during the warm-up.
Continued sustained smooth contraction due to rapid stimulation.
The situation in which contractions become stronger due to stimulation before complete relaxation occurs.
How a smooth increase in muscle force is produced.
Multiple motor unit summation
A sarcomere is the distance between two ________.
The ________ contains only the actin filaments.
The thicker filaments are the ________ filaments.
Both actin and myosin are found in the ________.
The myosin filaments are located in the ________.
Serves as the actual "trigger" for muscle contraction by removing the inhibition of the troponin molecules.
A neurotransmitter released at motor end plates by the axon terminals.
A metabolic pathway that provides for a large amount of ATP per glucose because oxygen is used. Products are water and carbon dioxide and ATP.
Normally stored in the terminal cisternae of the sarcoplasmic reticulum.
Used to convert ADP to ATP by transfer of a high-energy phosphate group. A reserve high-energy compound.
With muscular dystrophy ________.
muscle fibers degenerate and atrophy
Which muscle cells have the greatest ability to regenerate?
Most muscles contain ________.
A mixture of fiber types
Fatigued muscle cells that recover rapidly are the products of ________.
intense exercise of short duration
The strongest muscle contractions are normally achieved by ________.
increasing the stimulation up to the maximal stimulus
Which of the following would be recruited later in muscle stimulation when contractile strength increases?
motor units with larger, less excitable neurons
Which of the following is not a usual result of resistance exercise?
increase in the number of muscle cells
In skeletal muscle contraction, calcium apparently acts to ________.
remove the blocking action of tropomyosin
Calcium ions bind to the ________ molecule in skeletal muscle cells.
Stores Oxygen in the muscle cells
An elaborate network of membranes in skeletal muscle cells that functions in calcium storage is the ________.
A sarcomere is ________.
the area between two Z discs
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.
Creatine phosphate functions in the muscle cell by ________.
storing energy that will be transferred to ADP to resynthesize ATP
After nervous stimulation of the muscle cell has ceased, the calcium ________.
level in the cytoplasm drops
The major function of the sarcoplasmic reticulum in muscle contraction is to ________.
regulate intracellular calcium concentration
The striations of a skeletal muscle cell are produced, for the most part, by ________.
the arrangement of myofilaments
Which of the following are composed of myosin
During muscle contraction, myosin cross bridges attach to which active sites?
Which of the following surrounds the individual muscle cell?
Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are ________.
Rigor mortis occurs because ________.
no ATP is available to release attached actin and myosin molecules
What acts as a stimulus to initiate a muscle contraction
a change in the pH of a muscle
The term aponeurosis refers to ________.
a sheetlike indirect attachment to a skeletal element
The oxygen-binding protein found in muscle cells is ________.
The contractile units of skeletal muscles are ________.
The site of calcium regulation in the smooth muscle cell is ________.
One functional unit of a skeletal muscle is ________.
The functional role of the T tubules is to ________.
enhance cellular communication during muscle contraction
The role of calcium ions in muscle contraction is to ________.
bind to regulatory sites on troponin, changing the configuration
The warm-up period required of athletes in order to bring their muscles to peak performance is called ________.
The main effect of the warm-up period of athletes, as the muscle contractions increase in strength, is to ________.
enhance the availability of calcium and the efficiency of enzyme systems
During vigorous excercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________.
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
In an isotonic contraction, the muscle ________.
changes in length and moves the load
The muscle cell membrane is called the ________.
Smooth muscle is significantly different from striated muscle in several ways. Which of the following is true?
Smooth muscle contracts in a twisting way
The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________.
the site of calcium regulation differs
The cells of single-unit visceral muscle ________.
exhibit spontaneous action potentials
Which of the following statements is not true concerning developmental aspects of muscle?
There is no biological basis for the difference in strength between women and men
Which of the following is true about smooth muscle contraction?
Certain smooth muscle cells can actually divide to increase their numbers.
Smooth muscle is characterized by all of the following except ________.
there are more thick filaments than thin filaments
Muscle tissue has all of the following properties
The giant protein titin maintains the organization of the ________ assisting in muscle stretching.
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.
Muscle tone is ________.
a state of sustained partial contraction
The sliding filament model of contraction involves ________.
actin and myosin sliding past each other and partially overlap
After nervous stimulation stops, ACh in the synaptic cleft is prevented from continuing stimulation of contraction by ________.
acetylcholinesterase destroying the ACh
The most distinguishing characteristic of muscle tissue is ________.
the ability to transform chemical energy into mechanical energy
Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers
a long, relaxing swim
Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions?
multiunit smooth muscle
Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped ________.
no muscle tension could be generated
An individual has just ingested a chemical that binds irreversibly to the ACh receptors in the sarcolemma. By itself it does not alter membrane potential, yet prevents normal neurotransmitter binding. Ignoring the effects on any other system, the consequence to skeletal muscle would be ________.
no contraction at all by nervous mechanisms, but contraction if stimulated by an external electrode
Only ________ muscle cells are alwyas multinucleated
Claudication might more simply be called ________.
The end of the muscle that typically moves when a muscle contracts is called the ________.
In the synaptic cleft of a neuromuscular junction, an enzyme called ________ is always present.
The time in which cross bridges are active is called the period of ________.
________ (color) fibers are slow (oxidative) fibers
Only ________ muscle cells commonly branch
A smooth, sustained contraction is called ________.
Define physiologic muscle fatigue
Fatigue occurs when ATP production fails to keep pace with ATP use even though the muscle still receives stimuli
Compare red and white muscles relative to their speed of action and endurance
Red muscles tend to have a slow (oxidative) rate and fatigue resistance, whereas white muscle cells have a fast (oxidative) rate and fatigue easily
Briefly, what causes rigor mortis?
Following the death of an individual, ATP is rapidly consumed and cannot be replaced. Because cross bridge detachment and calcium active transport is ATP driven, calcium leakage from the sarcoplasmic reticulum causes attachment of cross bridges, and lack of ATP prevents detachments
What ultimately stops muscle stimulation when the motor neuron ceases firing?
The ultimate switch is the enzyme acetylcholinesterase. When the neuron stops releasing ACh, the muscle would not stop contracting if the acetylcholinesterase did not split the ACh into its two components, acetyl and choline, making them release their binding sites
A long-distance runner is about to enter a 5-mile race. Beforehand, he spends several minutes warming up. During the warm-up period, the phenomenon of treppe is occurring in body muscles being used. What is treppe and why does it occur?
Treppe is the staircase phenomenon in which muscles increase their strength of contraction due to increased availability of calcium. Additionally, the increased warmth due to activity causes an increase in the efficiency of muscle enzyme systems.
What are the two special inclusions of skeletal muscle cells and how would they be useful to the cell?
Skeletal muscle cells require a lot of rapidly available fuel to burn in order to function properly. They also require a lot of oxygen to burn this fuel efficiently. Glycosomes store glycogen which can be quickly converted to glucose, which in turn can be burned to produce ATP. Myoglobin is a chemical much like hemoglobin in blood cells which can store large quantities of oxygen.
What is the relationship that occurs in the triad of a skeletal muscle cell?
The sarcoplasmic reticulum is a reservoir for calcium ions in the cell's normal resting state. The T tubule is a fold in the cell membrane between the sarcoplasmic reticuli. When an impulse is activated by a motor neuron, the voltage-regulated change causes SR foot proteins to open Ca2+ channels. The calcium ions are flushed out where they interact with the troponin complex to initiate a contraction. Once the axon stops firing, the membrane polarity is quickly restored and the calcium ions are pulled off the troponin and attracted back into the sarcoplasmic reticulum.
Briefly explain where the energy comes from in a one-minute sustained muscle contraction
1. The first 4-6 seconds of energy come from stored ATP in the muscle cell.
2. 6-15 seconds of energy come from the transfer of creatine phosphate and ADP (which come from the first few seconds of burn) to form additional ATP.
3. 15-60 seconds of energy come from glycolysis which by now has begun full production of ATP from glucose.
What are caveoli?
Folds on the surface of smooth muscle cells that correspond to T tubules in skeletal muscle cells
How is it that norepinephrine (NE) can inhibit smooth muscle action in airways, yet stimulate contractions in smooth muscles everywhere else in the body?
Airway passages have smooth muscle cells that are unique in that they have two receptor sites on their outer membrane. One receptor site accepts ACh as the neurotransmitter. When excited it causes the smooth muscle to contract. The second site accepts NE and the inhibitory effect is that the ACh dilates the airway.
How do the three muscle types respond to being stretched?
All three muscle types initially respond by contracting more forcefully. However, in smooth muscle cells the increased tension persists only briefly, and the muscle adapts to its new length and relaxes.
What is agrin?
Agrin is a growth factor of developing muscles. Agrin stimulates ACh receptors to cluster around a newly forming motor end plate.
Gary was injured in an automobile accident that severed the motor neurons innervating his quadriceps. Even though he has had extensive physical therapy, he is still suffering muscle atrophy. Why is the therapy not working?
In denervation atrophy, fibrous connective tissue replaces the muscle tissue that was lost. When atrophy is complete, fibrous tissue cannot be reversed to muscle tissue.
Aaron arrived at the hospital with the following symptoms: drooping eyelids; fatigue and weakness of his muscles; and difficulty talking, breathing, and swallowing. What was his diagnosis?
Aaron probably has myasthenia gravis (an autoimmune disease), which involves a shortage of ACh receptors at the neuromuscular junction.
Lynn has been waking up each night with intense pain in her calves. She does not feel that it is serious enough to seek medical attention but would like to know what is causing the pain. What would you tell her concerning this problem? She has been playing tennis all summer for several hours each day. Could this have anything to do with the night pain?
This is due to sustained spasm, or tetanic contraction, of the gastrocnemius muscle. The causes could be low blood sugar, electrolyte depletion (particularly sodium and calcium), dehydration, or irritability of the spinal cord neurons. The fact that Lynn has been playing tennis for several hours each day may have caused an electrolyte depletion. She should increase her intake of calcium
After removal of an elbow cast, Lauren noticed her arm was immovable. What happened to her arm?
Two things have occurred to Lauren while she was convalescing from her injury. First, the immobilization of the arm caused some muscle mass to atrophy. Second, the loss of muscle was replaced with tough connective tissue that locked her arm in place. With therapy the tissue can be stretched or torn enough to return the full range of motion.
When a geriatric client is admitted to the rehabilitation unit, an important nursing measure is to prevent the loss of muscle mass. What is the term used for loss of muscle mass and how can the patient prevent it?
Disuse atrophy is degeneration and loss of muscle mass. The size, shape, tone, and strength of muscles (including the heart) are maintained with mild exercise and increased with strenuous exercise. Promoting exercise to maintain a patient's muscle tone, joint mobility, and cardiovascular function is an important nursing function.
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