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Related Concept Videos

Alterations in Muscle Tone lll01:11

Alterations in Muscle Tone lll

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Rigidity and myotonia are distinct abnormalities of muscle tone that affect resistance and relaxation during movement. Although both involve altered muscle contraction, they arise from different neurological and muscular mechanisms.CharacteristicsRigidity is characterized by uniform resistance to passive movement across the entire range, independent of speed, affecting flexors and extensors equally. It may appear as lead-pipe rigidity (smooth, constant resistance) or cogwheel rigidity...
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Alterations in Muscle Tone ll01:12

Alterations in Muscle Tone ll

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Alterations in muscle tone are common manifestations of neurological disorders and reflect dysfunction within different nervous system regions. Spasticity, paratonia, and dystonia represent distinct forms of hypertonia, each with unique mechanisms, clinical features, and diagnostic importance.CharacteristicsSpasticity happens from upper motor neuron lesions and is characterized by velocity-dependent resistance to passive movement. Clinical features include:Exaggerated deep tendon reflexesClonus...
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Disorders of the Skeletal Muscle01:28

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The clinical conditions affecting the skeletal muscle tissue are broadly categorized as musculoskeletal and neuromuscular disorders.
Musculoskeletal disorders
Musculoskeletal disorders involve injuries and conditions affecting the skeletal muscles and associated connective tissues. These disorders can arise from acute biomechanical stresses or chronic overuse and can occur across different age groups. Common injuries include sprains, fractures, and muscular strains, often resulting from...
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Isotonic and Isometric Muscle Contractions01:22

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Two primary types of muscle contractions are isotonic and isometric, each serving unique functions and involving distinct mechanisms. Both isotonic and isometric contractions are integral to the body's complex system of movement and stability. Isotonic exercises contribute significantly to functional strength and movement, while isometric contractions are crucial for maintaining posture and joint stability.
Isotonic contractions
Isotonic contractions occur when a muscle changes length while...
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Relaxation of Skeletal Muscles01:29

Relaxation of Skeletal Muscles

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The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open....
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Cross-bridge Cycle01:26

Cross-bridge Cycle

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As muscle contracts, the overlap between the thin and thick filaments increases, decreasing the length of the sarcomere—the contractile unit of the muscle—using energy in the form of ATP. At the molecular level, this is a cyclic, multistep process that involves binding and hydrolysis of ATP, and movement of actin by myosin.
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Isometric and Eccentric Force Generation Assessment of Skeletal Muscles Isolated from Murine Models of Muscular Dystrophies
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Aging interferes central control mechanism for eccentric muscle contraction.

Wan X Yao1, Jinqi Li2, Zhiguo Jiang3

  • 1Department of Kinesiology, Health, and Nutrition, College of Education and Human Development, The University of Texas at San Antonio San Antonio, TX, USA.

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Summary

Elderly adults show greater brain activation for eccentric contractions (EC) than concentric contractions (CC), possibly compensating for age-related motor control deficits. This highlights unique cortical control mechanisms in older individuals.

Keywords:
brain activationconcentric contractioneccentric contractionfMRImovement stability

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Area of Science:

  • Neuroscience
  • Motor Control
  • Aging Research

Background:

  • Previous studies indicate greater cortical motor network activation during eccentric contractions (EC) compared to concentric contractions (CC) in young adults.
  • It remains unclear if older adults, who experience greater difficulty with EC, utilize similar cortical control mechanisms.

Purpose of the Study:

  • To investigate age-related differences in cortical activation patterns during EC and CC of the first dorsal interosseous (FDI) muscle.
  • To determine if elderly individuals exhibit unique cortical control strategies for EC movements.

Main Methods:

  • Functional magnetic resonance imaging (fMRI) was used to examine brain activity in 11 young and 9 elderly adults.
  • Participants performed both EC and CC of the FDI muscle under identical conditions of angular distance and velocity.

Main Results:

  • Movement stability was reduced in EC compared to CC in the elderly group, but not in the young group.
  • Both age groups showed greater activation in the motor control network for EC than CC.
  • The age-related bias towards EC activation was more pronounced in the elderly, particularly in secondary and association cortices.
  • Conversely, the bias towards EC activation was greater in primary motor and sensory cortices in the young group.

Conclusions:

  • Elderly adults may exhibit increased activation in higher-order cortical areas to compensate for age-related motor control impairments during EC.
  • These findings offer insights for developing targeted therapies to address age-related movement deficits and prevent injuries.