Related Experiment Video
Updated: Aug 20, 2026

In vitro Functional Characterization of Mouse Colorectal Afferent Endings
Published on: January 21, 2015
Excitability of the motor cortical representation of the external anal sphincter
1Club d'Electrophysiologie Périnéale, Service de Physiologie-Explorations Fonctionnelles, Hôpital Henri Mondor, Assistance Publique-Hôpitaux de Paris, 51 avenue de-Lattre-de-Tassigny, 94010, Créteil, France. jean-pascal.lefaucheur@hmn.ap-hop-paris.fr
Abstract:
This study was designed to assess the excitability of the motor cortical representation of the external anal sphincter by using transcranial magnetic stimulation (TMS). In six healthy volunteers, the rest motor threshold and the duration of the cortical silent period were determined with single TMS pulses, and the intracortical inhibition and facilitation were measured with paired TMS pulses. Values obtained from the anal sphincter were compared with those obtained from a muscle in the right hand. All subjects completed the study. Rest motor threshold and intracortical facilitation were similar in both muscles. In contrast, cortical silent period duration and intra-cortical inhibition were less for the anal sphincter than for hand muscle. This study has opened new perspectives for the investigation of anal sphincter cortical control in humans.
Related Concept Videos
Motor Unit Stimulation
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...
Generation of Action Potential in Skeletal Muscles
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...
The Micturition Reflex
The process begins with bladder filling, where the bladder wall stretches as urine accumulates. This stretching activates the urine storage reflex, mediated by the sacral spinal segments and the pontine storage center. Efferent sympathetic impulses stimulate the detrusor muscle to relax and the internal urethral sphincter to contract, facilitating urine...
Muscle Contraction
Muscle Contraction
Somatic Spinal Reflexes
One of the most well-known somatic spinal reflexes is the stretch reflex, which is activated by the sudden stretching of a muscle. This reflex involves the activation of specialized sensory receptors called muscle spindles, which are located in the muscle tissue and detect changes in the length and speed of muscle contractions. When a muscle is suddenly...

