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Related Concept Videos

Action Potentials01:41

Action Potentials

Overview
Generation of Action Potential in Skeletal Muscles01:24

Generation of Action Potential in Skeletal Muscles

Every cell in the body maintains a membrane potential due to an uneven distribution of positive and negative charges across its plasma membrane. The membrane potential is measured in millivolts and quantifies the difference in charge across the membrane.
Like neurons, muscle cells are also regarded as excitable due to their capacity to change in response to stimuli, primarily due to voltage-gated ion channels embedded in their plasma membranes, which get activated by alterations in the cell's...
Action Potential01:14

Action Potential

Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information to the nervous system. An action potential is a specific "all-or-none" change in membrane potential that results in a rapid spike in voltage.
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
Action Potential01:14

Action Potential

Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information to the nervous system. An action potential is a specific "all-or-none" change in membrane potential that results in a rapid spike in voltage.
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
Local Anesthetics: Differential Sensitivity of Nerve Fibers01:24

Local Anesthetics: Differential Sensitivity of Nerve Fibers

Local anesthetics (LAs) block the sodium channels of nerve trunks, sensory nerve endings, and neuromuscular junctions. Although LAs can block all kinds of nerves, the sensitivity of nerve fibers differs according to nerve types and structures. LAs are known to block myelinated fibers faster than unmyelinated ones. Also, they block pain or sensory neurons at low concentrations without affecting the motor neurons involved in muscle contractions. This helps relieve labor pain without affecting the...
Excitatory and Inhibitory Effects of Neurotransmitters01:29

Excitatory and Inhibitory Effects of Neurotransmitters

When an action potential reaches the presynaptic axon terminal, it releases neurotransmitters from the neuron into the synaptic cleft at a chemical synapse. The released neurotransmitter can be excitatory or inhibitory. The critical criteria commonly used to determine whether a molecule is a neurotransmitter at a chemical synapse are the molecule's presence in the presynaptic neuron. Second, its release is in response to strong presynaptic depolarization. And lastly, the presence of specific...

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Related Experiment Video

Updated: Jul 15, 2026

The Ex vivo Preparation of Spinal Cord Slice for the Whole-Cell Patch-Clamp Recording in Motor Neurons During Spinal Cord Stimulation
06:55

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Published on: September 8, 2023

Axonal excitability properties in hemifacial spasm.

Arun V Krishnan1, Michael Hayes, Matthew C Kiernan

  • 1Institute of Neurological Sciences, Prince of Wales Hospital, University of New South Wales, Randwick, Sydney, New South Wales, Australia.

Movement Disorders : Official Journal of the Movement Disorder Society
|May 9, 2007
PubMed
Summary

Facial nerve studies reveal axonal depolarization in healthy individuals, suggesting a predisposition to ectopic activity. However, hemifacial spasm patients showed no distal nerve excitability changes, indicating a proximal impulse generator.

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The Ex vivo Preparation of Spinal Cord Slice for the Whole-Cell Patch-Clamp Recording in Motor Neurons During Spinal Cord Stimulation
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Published on: September 8, 2023

In Vivo Intracellular Recording of Type-Identified Rat Spinal Motoneurons During Trans-Spinal Direct Current Stimulation
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Assessment of Neuromuscular Function Using Percutaneous Electrical Nerve Stimulation
07:53

Assessment of Neuromuscular Function Using Percutaneous Electrical Nerve Stimulation

Published on: September 13, 2015

Area of Science:

  • Neuroscience
  • Clinical Neurology
  • Electrophysiology

Background:

  • Hemifacial spasm (HFS) involves involuntary facial muscle contractions due to facial nerve dysfunction.
  • The potential for the facial nerve to generate ectopic activity, a key factor in HFS, remains unclear.
  • Nerve excitability techniques offer insights into axonal ion channel function and membrane potential.

Purpose of the Study:

  • To investigate biophysical differences in the facial nerve that might predispose it to ectopic activity.
  • To assess facial nerve excitability in healthy controls and patients with hemifacial spasm.
  • To determine the location of the impulse generator in hemifacial spasm.

Main Methods:

  • Nerve excitability techniques were used to measure stimulus-response behavior, threshold electrotonus, and recovery of excitability.
  • Facial nerve excitability was assessed in 12 healthy control subjects and 9 hemifacial spasm patients.
  • Control subject data were compared to normative data from upper and lower limb nerves.

Main Results:

  • Control subjects exhibited relative "fanning-in" of threshold electrotonus, reduced superexcitability, and increased subexcitability in facial nerves compared to limb nerves.
  • These findings in controls suggest relative axonal depolarization, potentially predisposing the facial nerve to ectopic activity.
  • No significant differences in distal facial nerve excitability were found between affected and unaffected sides in HFS patients or compared to normative data.

Conclusions:

  • The healthy facial nerve shows biophysical properties consistent with a propensity for ectopic impulse generation.
  • The impulse generator for hemifacial spasm is likely located more proximally along the facial nerve.
  • Hemifacial spasm does not appear to result from a generalized disturbance of motor axon excitability.