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Questions and Answers
What is the definition of a motor unit?
What is the definition of a motor unit?
What happens when a muscle group contracts?
What happens when a muscle group contracts?
What is the term for the process of activating more motor units to lead to the contraction of more muscle fibers?
What is the term for the process of activating more motor units to lead to the contraction of more muscle fibers?
Why does resistance training increase the strength of a muscle?
Why does resistance training increase the strength of a muscle?
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What is a common effect of aging on muscle?
What is a common effect of aging on muscle?
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What is the basis of electromyography?
What is the basis of electromyography?
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What is the term for the recording obtained through electromyography?
What is the term for the recording obtained through electromyography?
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What is the effect of recruiting more motor units on muscle contraction?
What is the effect of recruiting more motor units on muscle contraction?
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What determines the number of motor units activated?
What determines the number of motor units activated?
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What is the direct proportionality of the strength of the electrical signal?
What is the direct proportionality of the strength of the electrical signal?
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What is the term for the decline in ability of the muscle to maintain force despite stimulation?
What is the term for the decline in ability of the muscle to maintain force despite stimulation?
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What is the result of aerobic activities and endurance training on muscle composition?
What is the result of aerobic activities and endurance training on muscle composition?
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What is the term for the recording obtained through the detection of changes in skin voltage produced by action potentials?
What is the term for the recording obtained through the detection of changes in skin voltage produced by action potentials?
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What determines the strength of contraction in a muscle?
What determines the strength of contraction in a muscle?
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What is the term for the small amounts of muscle contractions to maintain postural tone?
What is the term for the small amounts of muscle contractions to maintain postural tone?
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What is the relationship between the amplitude of the EMG and the force of contraction?
What is the relationship between the amplitude of the EMG and the force of contraction?
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What is the term for the activation of additional motor units if a greater contraction strength is needed?
What is the term for the activation of additional motor units if a greater contraction strength is needed?
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What type of muscle fibers are most resistant to fatigue?
What type of muscle fibers are most resistant to fatigue?
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What is the term for a somatic motor neuron plus all of the muscle fibers it controls?
What is the term for a somatic motor neuron plus all of the muscle fibers it controls?
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The number of motor units activated is inversely proportional to the amount of work required.
The number of motor units activated is inversely proportional to the amount of work required.
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Skeletal muscle contracts when the heart activates motor units.
Skeletal muscle contracts when the heart activates motor units.
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The maximum clench force is the same among all individuals.
The maximum clench force is the same among all individuals.
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Electromyography measures the changes in voltage produced by action potentials in smooth muscle.
Electromyography measures the changes in voltage produced by action potentials in smooth muscle.
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As we age, muscle fibers tend to increase in number.
As we age, muscle fibers tend to increase in number.
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The arrangement of cells within a muscle is such that it is not possible to recruit more muscle fibers by activating more motor units.
The arrangement of cells within a muscle is such that it is not possible to recruit more muscle fibers by activating more motor units.
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The electrical signals from individual muscle fibers are large enough to be measured by electrodes placed on the surface of the skin.
The electrical signals from individual muscle fibers are large enough to be measured by electrodes placed on the surface of the skin.
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Most skeletal muscle is composed of only a few motor units.
Most skeletal muscle is composed of only a few motor units.
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Resistance training always results in a decrease in muscle strength.
Resistance training always results in a decrease in muscle strength.
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The strength of the electrical signal is directly proportional to the number of muscle fibers firing.
The strength of the electrical signal is directly proportional to the number of muscle fibers firing.
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Muscle fatigue is a permanent condition.
Muscle fatigue is a permanent condition.
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Aerobic activities and endurance training can decrease the number of mitochondria in muscle fibers.
Aerobic activities and endurance training can decrease the number of mitochondria in muscle fibers.
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The amplitude of the EMG is inversely proportional to the force of contraction.
The amplitude of the EMG is inversely proportional to the force of contraction.
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Muscle tonus is the same as muscle fatigue.
Muscle tonus is the same as muscle fatigue.
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The proportion of slow-oxidative fibers in a muscle determines its endurance.
The proportion of slow-oxidative fibers in a muscle determines its endurance.
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Electromyography is the term for the process of activating more motor units to lead to the contraction of more muscle fibers.
Electromyography is the term for the process of activating more motor units to lead to the contraction of more muscle fibers.
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Recruitment is the process of deactivating motor units to reduce muscle contraction strength.
Recruitment is the process of deactivating motor units to reduce muscle contraction strength.
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The strength of contraction depends on the type of muscle fibers contributing to the force of contraction.
The strength of contraction depends on the type of muscle fibers contributing to the force of contraction.
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Angiogenesis in active muscles can decrease blood flow to the muscle.
Angiogenesis in active muscles can decrease blood flow to the muscle.
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Study Notes
Skeletal Muscle Contraction
- Skeletal muscle contraction occurs when the brain or spinal cord activates motor units, consisting of a motor neuron and the muscle cells it innervates.
- A muscle group contraction involves thousands of individual muscle cells, called fibers, contracting.
- Most skeletal muscle is composed of hundreds of motor units.
Motor Unit Recruitment
- The number of motor units activated is proportional to the amount of work required.
- Activating more motor units leads to the contraction of more muscle fibers, known as recruitment.
- Recruitment allows for increased muscle force by activating more motor units.
Muscle Fiber Characteristics
- Individual muscle fibers can increase in diameter through resistance training, allowing for more powerful contractions.
- Muscle fibers are lost with age, resulting in a decline in strength.
Electromyography (EMG)
- EMG measures the electrical signals generated by muscle contractions, with the strength of the signal directly proportional to the number of motor units firing.
- EMG recordings are measured in millivolts (mV).
Muscle Fatigue
- Muscle fatigue occurs when muscle cells are no longer able to sustain the force of contraction.
- The rate of muscle fatigue depends on the proportion of slow-oxidative, fast-oxidative, and fast-glycolytic fibers within a given muscle.
Muscle Adaptation
- Aerobic activities and endurance training can change the composition of muscle fibers, increasing blood flow and ATP production.
- This adaptation leads to increased muscle endurance and strength.
Key Terminology
- Electromyogram (EMG): recording of muscle contraction electrical signals.
- Motor unit: a somatic motor neuron and the muscle fibers it controls.
- Graded contraction: variable strength in muscle contraction.
- Recruitment: activation of additional motor units for increased contraction strength.
- Fatigue: decline in muscle force despite stimulation.
- Muscle tonus: small amounts of muscle contractions to maintain postural tone.
Skeletal Muscle Contraction
- Skeletal muscle contraction occurs when the brain or spinal cord activates motor units, consisting of a motor neuron and the muscle cells it innervates.
- A muscle group contraction involves thousands of individual muscle cells, called fibers, contracting.
- Most skeletal muscle is composed of hundreds of motor units.
Motor Unit Recruitment
- The number of motor units activated is proportional to the amount of work required.
- Activating more motor units leads to the contraction of more muscle fibers, known as recruitment.
- Recruitment allows for increased muscle force by activating more motor units.
Muscle Fiber Characteristics
- Individual muscle fibers can increase in diameter through resistance training, allowing for more powerful contractions.
- Muscle fibers are lost with age, resulting in a decline in strength.
Electromyography (EMG)
- EMG measures the electrical signals generated by muscle contractions, with the strength of the signal directly proportional to the number of motor units firing.
- EMG recordings are measured in millivolts (mV).
Muscle Fatigue
- Muscle fatigue occurs when muscle cells are no longer able to sustain the force of contraction.
- The rate of muscle fatigue depends on the proportion of slow-oxidative, fast-oxidative, and fast-glycolytic fibers within a given muscle.
Muscle Adaptation
- Aerobic activities and endurance training can change the composition of muscle fibers, increasing blood flow and ATP production.
- This adaptation leads to increased muscle endurance and strength.
Key Terminology
- Electromyogram (EMG): recording of muscle contraction electrical signals.
- Motor unit: a somatic motor neuron and the muscle fibers it controls.
- Graded contraction: variable strength in muscle contraction.
- Recruitment: activation of additional motor units for increased contraction strength.
- Fatigue: decline in muscle force despite stimulation.
- Muscle tonus: small amounts of muscle contractions to maintain postural tone.
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Description
Learn about the contraction of skeletal muscles, motor units, and how the brain and spinal cord activate them. Discover how muscle fibers work together to achieve movement.
