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Related Concept Videos

Motor Unit Stimulation01:20

Motor Unit Stimulation

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When the neuron of a motor unit fires an action potential, it triggers a series of events, leading to a twitch contraction in the muscle fibers. The process of excitation-contraction coupling is crucial in relaying the action potential to the muscle fibers.
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
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Motor Units01:13

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The motor unit is a fundamental component of the neuromuscular system and plays a crucial role in coordinating muscle contractions. It consists of a somatic motor neuron, which connects and controls multiple skeletal muscle fibers, forming a single functional segment. The axon of the motor neuron branches out and establishes synaptic connections known as neuromuscular junctions with individual muscle fibers within the motor unit.
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The Neuromuscular Junction01:19

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The nervous system consists of complex motor neuron circuits, including upper motor neurons originating from the cerebral cortex and lower motor neurons starting in the spinal cord, coordinating both voluntary and involuntary movements. Among these, somatic motor neurons activate skeletal muscles and are classified into alpha, beta, and gamma types. Alpha neurons are vital for voluntary movement coordination, while gamma neurons adjust muscle spindle sensitivity, and the function of beta...
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Hierarchy of Motor Control01:18

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The hierarchy of motor control refers to the different levels of organization and processing involved in controlling movement in the body. These levels range from higher cortical areas involved in planning and decision-making to lower spinal cord reflexes that respond automatically to external stimuli.
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Related Experiment Video

Updated: Jun 29, 2025

The Preparation of Oblique Spinal Cord Slices for Ventral Root Stimulation
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The Preparation of Oblique Spinal Cord Slices for Ventral Root Stimulation

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Intrinsic motoneuron properties in typical human development.

Ghazaleh Mohammadalinejad1,2,3, Babak Afsharipour1,2,3, Alex Yacyshyn1,2

  • 1Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.

The Journal of Physiology
|March 30, 2024
PubMed
Summary
This summary is machine-generated.

Motoneuron excitability decreases with age, with children and adolescents showing higher firing rates than adults. Selective serotonin reuptake inhibitors (SSRIs) also increase motoneuron excitability, similar to developmental changes.

Keywords:
motor unitsonion skinpersistent inward currentsserotonintibialis anteriortorque steadiness

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Area of Science:

  • Neuroscience
  • Motor Control
  • Developmental Biology

Background:

  • Motoneuron properties, including firing patterns and excitability, change during development and are influenced by neuromodulators like serotonin.
  • Persistent inward currents (PICs) are crucial for motoneuron excitability and self-sustained firing.

Purpose of the Study:

  • To investigate age-related changes in self-sustained firing and excitability of tibialis anterior motoneurons.
  • To examine the effect of selective serotonin reuptake inhibitors (SSRIs) on motoneuron excitability.

Main Methods:

  • Electrophysiological recordings were used to measure motoneuron firing properties (ΔF, firing rates, secondary ranges) in different age groups (7-17, 18-28, 32-53 years).
  • Comparison was made between participants taking SSRIs and age-matched controls.
  • Muscle fiber activity of tibialis anterior motoneurons was recorded.

Main Results:

  • Self-sustained firing (ΔF) was significantly higher in the young development group (7-17 years) compared to young adult and adult groups, indicating a developmental decrease in PIC-mediated firing.
  • Participants taking SSRIs exhibited higher ΔF than their age-matched controls, suggesting increased spinal serotonin facilitates motoneuron PICs.
  • Both young development and SSRI groups showed increased firing rates and steeper secondary ranges, consistent with PIC-mediated depolarization.
  • The young development group also displayed greater unsteadiness in dorsiflexion torque profiles.

Conclusions:

  • Human motoneuron excitability, influenced by PICs, decreases from childhood to adulthood.
  • SSRIs increase motoneuron excitability, mimicking some developmental changes.
  • These findings highlight the dynamic nature of motoneuron excitability and its modulation by development and neurochemicals.