• They innervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating their contraction. (wikipedia.org)
  • They constitute a distinct subpopulation that differs in morphology, physiology and connectivity from α-MNs, which innervate extrafusal muscle fibers and exert force. (biomedcentral.com)
  • Each muscle spindle is built around 3-10 small intrafusal muscle fibres attached to the sheaths of the surrounding extrafusal skeletal muscle fibres, the ends of which are excited by small gamma efferent motor nerve fibres. (positivehealth.com)
  • This causes both the extrafusal & intrafusal muscle fibres to contract at the same time. (positivehealth.com)
  • The muscle fibers inside the spindles are called intrafusal fibers , while the rest of the muscle fibers (which form the bulk of the muscle in the body) are called extrafusal fibers . (ualberta.ca)
  • Fusimotor axons originate either from gamma motor neurons (γ-MNs), which only innervate intrafusal fibers of the muscle spindle, or from alpha motor neurons (α-MNs), which innervate extrafusal muscle and also send a β-skeletofusimotor collateral axon to innervate the muscle spindle [ 2 - 4 ]. (biomedcentral.com)
  • Like other neurons, α-MNs send axonal projections to reach their target extrafusal muscle fibers via axon guidance, a process regulated in part by neurotrophic factors released by target muscle fibers. (wikipedia.org)
  • The advantages of a γ-fusimotor system to control spindle sensitivity independently of force-generating extrafusal muscle fibers are not fully understood, nor are the mechanisms that generate the distinct γ- and α-MN subtypes in mammals. (biomedcentral.com)
  • "It was expected answers would describe in detail the role of troponin, tropomyosin and calmodulin in mediating muscle contraction" , the examiners rejoined. (derangedphysiology.com)
  • Troponin is a complex of three proteins that is integral to muscle contraction in skeletal and cardiac muscle , but not smooth muscle . (wikidoc.org)
  • Some of this calcium attaches to troponin, causing a conformational change that moves tropomyosin out of the way so that the cross bridges can attach to actin and produce muscle contraction. (wikidoc.org)
  • Therefore when a muscle is suddenly stretched a strong signal is transmitted to the spinal cord causing an instant v strong reflex contraction of the same muscle from which the signal originated. (positivehealth.com)
  • Local twitch response - defined as a transient visible or palpable contraction of the muscle and skin as the tense muscle fibres contract when pressure is applied through needle penetration or by transverse snapping palpation. (physio-pedia.com)
  • Coordinated contractions of cardiac muscle cells during systole propel blood out of the atria and ventricles to the blood vessels of the systemic and pulmonary circulatory systems . (wikidoc.org)
  • Unlike skeletal muscle , which contracts in response to nerve stimulation, and like single unit smooth muscle, cardiac muscle is myogenic , meaning that it is self-excitable stimulating contraction without a requisite electrical impulse coming from the central nervous system. (wikidoc.org)
  • If synchronization of cardiac muscle contraction is disrupted for some reason (for example, in a heart attack ), uncoordinated contraction known as fibrillation can result. (wikidoc.org)
  • Since cardiac muscle is myogenic, the pacemaker serves only to modulate and coordinate contractions. (wikidoc.org)
  • As a thank-you for using our site, here's a discounted rate for renewal or upgrade. (tabers.com)
  • Specialized pacemaker cells in the sinoatrial node normally determine the overall rate of contractions, with an average resting pulse of 72 beats per minute. (wikidoc.org)
  • In a relaxed muscle, tropomyosin blocks the attachment site for the myosin crossbridge, thus preventing contraction. (wikidoc.org)
  • They innervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating their contraction. (wikipedia.org)
  • Like other neurons, α-MNs send axonal projections to reach their target extrafusal muscle fibers via axon guidance, a process regulated in part by neurotrophic factors released by target muscle fibers. (wikipedia.org)
  • Further, mechanical interactions of the muscle spindle with muscle-tendon dynamics reveal how motor commands to the muscle (alpha drive) versus muscle spindle (gamma drive) can cause highly variable and complex activity during active muscle contraction and muscle stretch that defy simple explanation. (elifesciences.org)
  • Botulinum toxin type B may play a role in the treatment of refractory muscle-tension-muscle-contraction headaches in some patients. (medscape.com)
  • Gamma-motor neurons by stretching muscle spindle bodies, activate alpha-motor neurons leading to extrafusal muscle contraction. (epomedicine.com)
  • The function of α-motor neurones is to cause contraction of the muscle fibres they innervate. (teachmephysiology.com)
  • This in turn will cause the α-motor neurones to fire and lead to muscle contraction through the reflex arc. (teachmephysiology.com)
  • The contraction of muscle causes the intrafusal fibres to become slack, reducing Ia afferent firing. (teachmephysiology.com)
  • Local twitch response - defined as a transient visible or palpable contraction of the muscle and skin as the tense muscle fibres contract when pressure is applied through needle penetration or by transverse snapping palpation. (physio-pedia.com)
  • Much of muscle contraction occurs without conscious thought and is necessary for survival, like the contraction of the heart , or peristalsis (which pushes food through the digestive system ). (wikidoc.org)
  • Voluntary muscle contraction is used to move the body, and can be finely controlled, like movements of the eye, or gross movements like the quadriceps muscle of the thigh . (wikidoc.org)
  • Striated muscle contracts and relaxes in short, intense bursts, whereas smooth muscle sustains longer or even near-permanent contractions. (wikidoc.org)
  • It can contract more quickly and with a greater amount of force than oxidative muscle, but can sustain only short, anaerobic bursts of activity before muscle contraction becomes painful (often incorrectly attributed to a build-up of lactic acid ). (wikidoc.org)
  • BoNT-A causes degrees of flaccid (rather than rigid or tetanic) paralysis by blocking acetylcholine, required for muscle contraction, from release at the nerve terminal. (medscape.com)