40 Questions
Which type of muscle fibers lack striations?
Smooth muscle fibers
What is the function of flexor muscles?
To bring bones together
Which muscle type is characterized by being smaller, branched, and uninucleate?
Cardiac muscle fibers
What is the function of extensor muscles?
To move bones away
Which muscle type is multinucleate?
Skeletal muscle fibers
What is the function of tendons?
To attach muscles to bones
What is the function of intercalated disks in cardiac muscle fibers?
To attach cells to each other
Which muscle type appears striped or striated under the microscope?
Skeletal muscle fibers
What is the function of the sarcolemma in skeletal muscle fibers?
To surround and protect the muscle fiber
What is the function of the sarcoplasmic reticulum in skeletal muscle fibers?
To store and release calcium ions
Which protein prevents myosin-actin attachment at rest?
Tropomyosin
What is the major calcium reservoir in muscle cells?
Sarcoplasmic reticulum
What initiates a muscle action potential?
ACh receptor-channel
Which protein allows actin-myosin binding by binding to calcium?
Troponin
What is the role of ATP in muscle contraction?
ATP rotates the myosin head
What happens during the power stroke in muscle contraction?
Actin filament moves toward M line
What causes the conformational change in troponin-tropomyosin complex?
Calcium binding to troponin
What is the function of the dihydropyridine (DHP) receptor?
Alters the conformation of DHP receptor
What is the role of the ryanodine receptor-channel in muscle contraction?
Releases calcium from the sarcoplasmic reticulum
What happens when the DHP receptor opens the ryanodine receptor channels?
Calcium is released from the sarcoplasmic reticulum
Which ion(s) are involved in creating the neuronal action potential?
Na+
Which ion(s) are involved in creating the muscle action potential?
Ca++
Which type of muscle contraction involves muscle shortening while lifting a load?
Concentric contraction
Which type of muscle contraction generates force but does not result in muscle shortening?
Isometric contraction
Which type of muscle fibers are characterized by being slow-twitch and fatigue-resistant?
Type I fibers
Which type of muscle fibers are characterized by being fast-twitch and fatigue-resistant?
Type IIa fibers
Which type of muscle fibers are characterized by being fast-twitch and fatigable?
Type IIb fibers
Which type of muscle fibers are characterized by being fast-twitch and highly fatigable?
Type IIx fibers
Which disorder is characterized by a deficiency of the enzyme myophosphorylase?
McArdle's disease
Which protein is responsible for the conversion of glycogen to glucose 6-phosphate?
Glycogen phosphorylase
During the relaxation phase of a muscle twitch, what ion(s) are moved in what direction(s)?
Ca++ is moved out of the sarcoplasm
What ion(s) create the neuronal action potential during a muscle twitch?
Na+
What ion(s) create the muscle action potential during a muscle twitch?
K+
What type of contraction occurs when a muscle generates force but doesn't shorten?
Isometric contraction
What type of contraction occurs when a muscle shortens while lifting a load?
Isotonic contraction
Which type of muscle fiber is characterized by slow-twitch properties?
Type I fibers
Which type of muscle fiber is characterized by fast-twitch properties?
Type IIb fibers
Which disorder is characterized by a deficiency of dystrophin?
Duchenne muscular dystrophy
Which disorder is characterized by a deficiency of myophosphorylase, leading to the inability to convert glycogen to glucose 6-phosphate?
McArdle's disease
During strenuous exercise, what is the process called that restores energy expended during exercise?
Oxygen debt
Study Notes
Muscle Fibers
- Smooth muscle fibers lack striations
- Skeletal muscle fibers are characterized by being multinucleate
- Cardiac muscle fibers are branched, uninucleate, and have intercalated disks
- Skeletal muscle fibers appear striped or striated under the microscope
Muscle Functions
- Flexor muscles decrease the angle between two bones
- Extensor muscles increase the angle between two bones
- Tendons connect muscles to bones, transmitting forces from muscle to bone
Muscle Physiology
- The sarcolemma is the plasma membrane of skeletal muscle fibers, regulating ion movement and muscle contraction
- The sarcoplasmic reticulum is a calcium reservoir in skeletal muscle fibers, releasing calcium ions during muscle contraction
- Troponin and tropomyosin are proteins that prevent myosin-actin attachment at rest
- Calcium ions initiate muscle contraction by binding to troponin, causing a conformational change in the troponin-tropomyosin complex
- ATP is essential for muscle contraction, providing energy for myosin-actin binding and muscle relaxation
- During the power stroke, the myosin head binds to actin, generating force and shortening the muscle
Muscle Contraction
- The dihydropyridine (DHP) receptor is a voltage-gated calcium channel, opening ryanodine receptor-channel and releasing calcium ions
- The ryanodine receptor-channel releases calcium ions, initiating muscle contraction
- During muscle contraction, sodium ions create the neuronal action potential, while calcium ions create the muscle action potential
- Isotonic contraction involves muscle shortening while lifting a load
- Isometric contraction generates force but does not result in muscle shortening
Muscle Fiber Types
- Slow-twitch fibers are fatigue-resistant, characterized by slow contraction velocities
- Fast-twitch fibers are fatigable, characterized by fast contraction velocities
- Fast-twitch and highly fatigable fibers have high contraction velocities and fatigue easily
Disorders
- McArdle's disease is characterized by a deficiency of the enzyme myophosphorylase, leading to the inability to convert glycogen to glucose 6-phosphate
- Duchenne muscular dystrophy is characterized by a deficiency of dystrophin
Muscle Twitch and Relaxation
- During the relaxation phase of a muscle twitch, calcium ions are pumped back into the sarcoplasmic reticulum, and sodium ions are pumped out of the cell
- Sodium ions create the neuronal action potential, while calcium ions create the muscle action potential during a muscle twitch
- Isometric contraction occurs when a muscle generates force but doesn't shorten
- Isotonic contraction occurs when a muscle shortens while lifting a load
Test your knowledge of skeletal muscle cellular physiology with this quiz. Learn about muscle attachment, flexors and extensors, and antagonistic muscle groups.
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