Muscle spindle essays
As these receptors are sensitive to both tension and pressure, they play a role in relaying information concerning muscle dynamics to the conscious and subconscious parts of the central nervous system.
They provide the brain with information concerning kinesthetic sense, or conscious appreciation of the position of body parts with respect to gravity. The local temperature of the preoptic region was controlled by implanting water perfused thermodes 32— Exp Neurol —32 Google Scholar Sato H Effects of skin cooling and warming on stretch responses of the muscle spindle afferent fibers from the cat's tibialis anterior.
Increase in the static stretch response during both cooling and heating was usually combined with the appearence of spontaneous discharges at rest.
Muscle spindle function
Acta Physiol Scand — Google Scholar Crowe A, Matthews PBC The effects of stimulation of static and dynamic fusimotor fibres on the response to stretching of the primary endings of muscle spindles. Primary type Ia sensory fibers large diameter spiral around all intrafusal muscle fibres, ending near the middle of each fibre. This, in turn, shortens the intrafusal fibers and causes their discharge to cease . This leads to a receptor potential that triggers action potentials in the muscle spindle afferent  . Golgi tendon organs are activated when the tendon attached to an active muscle is stretched. First, overactive input from gamma motor neurons or increased excitability at the central synapse can present as spasticity. Proprioceptors Proprioceptors are specialised sensory receptors that are located within joints, muscles, and tendons. Secondly, spasticity may be caused by problems with the renshaw cells. The result is a reduction in tension within the muscle and tendon. Acta Physiol Scand — Google Scholar Appelberg B Selective central control of dynamic gamma motoneurones utilised for the function classification of gamma cells. The sensory neuron of the GTO synapses with an inhibitory interneuron in the spinal cord, which in turn synapses with and inhibits a motor neuron that serves the same muscle.
Thus, whereas spindles facilitate activation of the muscle, neural input from GTOs inhibits muscle activation. Research examining the affect of the degeneration on intrafusal fibers have found that the proprioceptive function of muscle spindles is spared in muscular dystrophy.
Dysfunction in the Muscle Spindle Problems may arise in the functioning of the muscle spindle. The static component lasts as long as the muscle is being stretched. Muscle spindles have a capsule of connective tissueand run parallel to the extrafusal muscle fibers.
In a minority of muscle spindles the dynamic fusimotor innervation appears to be additionally activated by preoptic cooling. Exp Neurol — Google Scholar Sato H Midbrain neurones of rats responsive to hypothalamic temperature change and their local thermosensitivity.
Muscle spindle ppt
Both endings in muscle spindles are very sensitive to low-amplitude changes in muscle length, especially if these changes occur at a high frequency. Download preview PDF. The dynamic component lasts for only a moment in response to the initial sudden increase in muscle length. Unusual intrafusal fibres in human muscle spindles. Acta Physiol Scand — Google Scholar Crowe A, Matthews PBC The effects of stimulation of static and dynamic fusimotor fibres on the response to stretching of the primary endings of muscle spindles. The result is a reduction in tension within the muscle and tendon. The primary endings respond to its speed and the size of a muscle length change. It is concluded that changes of preoptic temperature influence the stretch response of muscle spindle afferents mainly by altering the activity of the static fusimotor innervation, its activation by preoptic cooling being the most consistent finding. In: Granit R ed Muscular afferents and motor control. This raises the resting potential of the endings, thereby increasing the probability of action potential firing, thus increasing the stretch-sensitivity of the muscle spindle afferents. Efferent nerve fibers of gamma motoneurons also terminate in muscle spindles; they make synapses at either or both of the ends of the intrafusal muscle fibers and regulate the sensitivity of the sensory afferents, which are located in the non-contractile central equatorial region. The Ia afferent signals are transmitted monosynaptically to many alpha motor neurons of the receptor-bearing muscle. The knee jerk can also be helpful in recognising thyroid disease.
This leads to a receptor potential that triggers action potentials in the muscle spindle afferent  .
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