Cranial Neuropathies I, V, and VII–XII
Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw in Hankey's Clinical Neurology, 2020
This is a monosynaptic myotatic reflex in which the trigeminal nerve constitutes both the afferent limb (sensory division of V3) and the efferent limb (motor division of V3) of the reflex arc. Its first-order neuron is not in the gasserian ganglion, but located centrally in the mesencephalic nucleus in the midbrain: Afferent limb: Ia fibers in V3 division that carry proprioceptive sensory information from facial muscles and masseter. Collateral fibers synapse with the motor nucleus of CN V.Efferent limb: mandibular fibers that originate in the motor nucleus of CN V. Efferent (motor) fibers are sent to masticatory muscles via the motor division of V3.
Neurological disorders
Michael Horvat, Ronald V. Croce, Caterina Pesce, Ashley Fallaize in Developmental and Adapted Physical Education, 2019
Some muscles may function normally or fluctuate because of response in static strength or length of the muscle (United Cerebral Palsy (UCP), 2010; NINDS, 2013). In normal functioning, a slight stretching of the muscle stimulates the muscle spindle of the stretched muscle, causing the muscle to contract appropriately, which is essential for maintaining muscle tone and maintenance of posture. In spasticity, the stretch reflex is exaggerated and causes muscle tightness and abnormal postures. Spastic muscles may also demonstrate a clasp-knife response, in which a sudden passive movement creates an initial buildup in resistance, followed by a sudden release of tension accompanied by a positive stretch reflex, similar to the action of opening a knife. Additionally, voluntary movements of spastic muscles tend to be slow and uncoordinated, as children experience difficulty breaking free of stereotyped movements from their reflexes. Inadequate control of force may be observed at the beginning, middle, or end of a movement (Sugden & Keogh, 1990). As children mature and bones elongate, there is an increased amount of pull exerted by the muscles at the joint that exerts pressure on the muscles. This pressure causes tightening or contractures of muscles, such as the upward pull of the heel from a spastic gastrocnemius muscle. As a result, the child requires training programs to balance opposing muscle groups.
Neurological issues
Andrea Utley in Motor Control, Learning and Development, 2018
The best example of a monosynaptic reflex within the spinal cord is the myotatic reflex or the muscle-stretch reflex. The stimulus for the stretch reflex is excessive stretch on the muscle detected by the muscle spindle. For example, if the weight on the arm is suddenly increased, the arm is pulled down and the sensory neurons from the intrafusal fibers detect the change in length. This results in activity in these neurons and a nerve impulse being sent to the dorsal root of the spinal cord and then directly to an alpha motor neuron via a single synapse. The alpha motor neurons then transmit the nerve impulse back to the extrafusal muscle fibers of the muscles of the arm, causing the muscle to contract and limb position to be restored.
Effects of Botulinum Toxin A Injection on Ambulation Capacity in Patients with Cerebral Palsy
Published in Developmental Neurorehabilitation, 2019
Sibel Çağlar Okur, Mahir Uğur, Kazım Şenel
The mode of action of botulinum toxin includes extracellular binding to glycoprotein structures on cholinergic nerve terminals and intracellular blockade of the acetylcholine secretion. Thus, it prevents the release of acetylcholine at the neuromuscular junction, causing presynaptic neuromuscular blockade. BT affects the spinal stretch reflex by blockade of intrafusal muscle fibers with consecutive reduction of Ia/II afferent signals and muscle tone without affecting muscle strength (reflex inhibition).7 Thus, it allows muscles to become paralyzed for 3–6 months. Although its lethal dose is rather low, no significant side effect has been observed in the treated patients. Sometimes, it can cause temporary weakness in adjacent muscle groups, and local pain and tenderness may occur at the injection site. It is a reliable drug except for these side effects.8
Solution space: Monitoring the dynamics of motor rehabilitation
Published in Physiotherapy Theory and Practice, 2019
Jurjen Bosga, Wim Hullegie, Robert van Cingel, Ruud Meulenbroek
This analysis provides insight into the relative involvement of the various motor control processes, for instance by allowing the distinction of the extremely rapid myotatic reflex activity (i.e. physiological tremors) and the more slowly evolving visual and even slower cognitive monitoring processes. A particularly relevant PSD index for the solution space is the slope function (ß), which allows the quantification of the relative contributions of the different control processes in a particular motor pattern (Duarte and Zatsiorsky, 2001; Harrison and Stergiou, 2015). If ß is 0, this indicates that lower- and higher-frequency control processes have contributed equally to the production of the movement. A ß value < 0 reflects a systematic damping of the higher frequencies, denoting a relative decline in fast adaptive processes (e.g. physiological tremor, myotatic, or crossed reflexes) that contribute to movement execution. Accordingly, the smaller the negative value ß is, the stronger the contribution of the relatively slower control processes (e.g. visuomotor feedback) to the production of movement. In this article we use ß as a relative measure, that is, to indicate whether control processes were relatively slower or faster compared to previous measurements. Since ß as a relative measure is additive, we calculated the mean ß value of the three movement directions of each body segment. Next, we computed the absolute value of ß, subsequently denoted as |ß|. We used |ß| to facilitate reading, as higher absolute beta values represent more visual and cognitive control.
Effect of inhibitory kinesiotaping on spasticity in patients with chronic stroke: a randomized controlled pilot trial
Published in Topics in Stroke Rehabilitation, 2022
Mahdad Mehraein, Zahra Rojhani- Shirazi, Ahmad Zeinali Ghotrom, Nasrin Salehi Dehno
In a recent study by Puce et al. (2021), the effect of KT on knee extensor spasticity was investigated in para-swimmers.54 In line with our study, they reported a significant decrease in the amplitude of stretch reflex 48 hours after KT, but MAS score did not change following KT.54 Despite the similarity between our results, they examined athletes and measured spasticity by stretch reflex. The H-reflex and stretch reflex have the same spinal circuitry.55 However, for H-reflex, Ia afferent axons are excited electrically and stretch reflex is elicited by the mechanical stimulation of group Ia and II afferent axons.55 Hence, our study is the first to highlight the specific effect of KT on the reflex component of muscle tone, which is spasticity in patients with stroke.
Related Knowledge Centers
- Action Potential
- Alpha Motor Neuron
- Gamma Motor Neuron
- Muscle Contraction
- Muscle Spindle
- Reflex
- Spinal Nerve
- Spinal Cord
- Skeletal Muscle
- Golgi Tendon Reflex