Muscle Spasms

  • Medical Author:
    Benjamin Wedro, MD, FACEP, FAAEM

    Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

What is smooth muscle?

Smooth muscle is located in the walls of hollow internal structures in the body, like the arteries, intestines, bladder, and iris of the eye. They tend to circle the structure and when they contract, the hollow structure is squeezed. These muscles are involuntary and are controlled by the unconscious part of our brain function using the autonomic nervous system. The autonomic nervous system can run in the background, regulating processes within the body. There is a balance between the sympathetic system (adrenergic nerves) that speeds things up and the parasympathetic system (cholinergic nerves) that slows things down. These names are based on the type of chemical that is used to transmit signals at the nerve endings. Adrenaline (epinephrine from the sympathetic nervous system) allows the body to respond to stress. Imagine seeing a bear in the woods; your heart beats faster, your palms get sweaty, your eyes dilate, your hair stands on end, and your bowels move, all because the sympathetic nervous system is activated. Acetylcholine is the chemical that is the anti-adrenaline and is involved in the parasympathetic nervous system that acts to calm us down. Smooth muscle has the same basic contraction mechanism as skeletal muscle, though different proteins are involved.

What is a muscle spasm?

A muscle spasm, or muscle cramp, is an involuntary contraction of a muscle. Muscle spasms occur suddenly, usually resolve quickly, and are often painful.

A muscle spasm is different than a muscle twitch. A muscle twitch, or fasciculation, is an uncontrolled fine movement of a small segment of a larger muscle that can be seen under the skin. Continue Reading

Reviewed on 4/21/2016
References
REFERENCE:

Bucholz, R.W., J.D. Heckman, and C.M. Court-Brown. Rockwood and Green's Fracture in Adults. 6th ed. Philadelphia: Lippincott, Williams & Wilkins, 2006.

Daroff, R.B., et al. Bradleys' Neurology in Clinical Practice, 6th edition. Philadelphia: Elsevier/Saunders, 2012.

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