The stretch reflex also called the myotatic reflex, the muscle stretch reflex and sometimes the kneejerk reflex, is a preprogrammed response by the body to a stretch stimulus in the muscle. The management of spasticity in multiple sclerosis david a. Although misunderstood for the most part and discounted by most research literature as a simple organ of reflex. Some of the simplest nerve pathways consist of little more than two neurons that communicate across a single synapse.
Microsoft powerpoint chap 6 reflexes compatibility mode. Acoustic reflex or attenuation reflex contraction of the stapedius and tensor tympani muscles in the middle ear in response to high sound intensities. Describe the function and mechanism of a stretch reflex. Some sources suggest that with extensive training, the stretch reflex of certain muscles can be voluntarily controlled so that there is little or no reflex contraction in response to a sudden stretch. Biceps stretch reflex definition of biceps stretch reflex. Its called the myotatic reflex, perhaps you better know this as the stretch reflex. Muscle stretch reflex definition of muscle stretch reflex. Accommodation reflex coordinated changes in the vergence, lens near object.
Homonymous and heteronymous reflex connections of the abdominal muscles were investigated by the application of a tap to the muscle belly and observation of surface electromyographic responses. The stretch reflex is a monosynaptic reflex that regulates muscle length through neuronal stimulation at the muscle spindle. Stretch reflexes initiated by muscle spindles must maintain healthy muscle tone. Developmental reflexes and neurological structure in infant. Pdf stretch reflexes in human abdominal muscles iain. Mar 09, 2016 a muscle in eccentric contraction subjected to a load that causes it to rapidly lengthen triggering a myostatic reflex response called the stretch reflex. It is located within the fleshy parts of the muscle. The alpha motor neurons resist stretching by causing contraction, and the gamma motor neurons control the sensitivity of the reflex. Understanding the stretch reflex or myotatic reflex. Stretching and flexibility physiology of stretching. To fully understand the stretch reflex, try the following exercise. The role of muscle spindles in the development of the. Pdf spinal mechanisms of the functional stretch reflex. Human nervous system basic organization of movement.
Initiated by golgi tendon organ located in muscle tendon. The central lesion causing the umns disrupts the balance of supraspinal inhibitory and excitatory inputs directed to the spinal cord, leading to a state of disinhibition of the stretch reflex. A reflex is built into the nervous system and does not need the intervention of conscious thought to take effect. Altered reflex sensitivity after repeated and prolonged. Our rationale for using the msr to investigate changes in neuromuscular control was threefold. The stretch reflex is inherent in the squat if you dont pause and drive your hips up hard at the right time. The golgi tendon organ records the change in tension, and the rate of change of the tension, and sends signals to the spine to convey this information see section. And for the muscle stretch reflex, the lower motor neurons make up the efferent part of the reflex that causes the response of contraction of the muscle that was stretched. As noted above, the basis for this simple spinal reflex is a monosynaptic excitation of the motor neurons of the stretched muscle. The muscle spindles are responsible for detecting the. Muscle stretch reflex reflex arc components monosynpatic.
Skeletal muscle tone and the misunderstood stretch reflex. Stretch reflex definition of stretch reflex by the free. Changes in length and tension of muscle fibers rate of changes in length and tension 2. It is a simple preprogrammed response by the human body in response to the muscle being passively stretched e. The sensory organ is a fusiform shaped structure called the muscle spindle. The ability of the muscles to undergo a stretch and accumulate energy to produce a forceful and fast contraction in the shortening phase is known as muscle resiliency.
Nerve impulses follow routes through the nervous system called nerve pathways. Obviously, it is easier to stretch, or lengthen, a muscle when it is not trying to contract. Physiologically spasticity is defined as a motor disorder characterized by a velocity dependent increase in the tonic stretch reflexes muscle tone with exaggerated tendon jerks. This results in the contraction of the stretched muscle and relaxation of the opposing muscles. In contrast to this, a phasic stretch reflex consists of a synchronous motor neurone discharge caused by brief stimulation of muscle spindles or their afferent nerve pathways.
Consists of netlikeramified collection of knobby nerve endings among tendon fascicles. While stretching tissues may take years, changes in the nervous system are immediate. Spinal reflexes and descending motor pathways section 3. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The stretch reflex myotatic reflex is a muscle contraction in response to stretching within the muscle. Likewise, secondary type ii sensory fibers respond to muscle length changes but with a. Passive stretch of a muscle produced by tapping its tendon stretches the spindle intrafusal fibers. In general, the reflex activity of human back muscles has received very little attention in the past, compared with limb muscles. The deep tendon or muscle stretch reflexes neupsy key. The stretch reflex also prevents us from tearing our muscles, tendons, and ligaments. We feel there is only one method to box squat, but many have these less effective methods. Muscle stretch reflex organ systems mcat khan academy. On the subject of the stretch reflex, however, someone said that the stretch reflex does not last four seconds as a study. When using the stretch reflex, the same muscles are involved in the down phase as in the up phase.
Stretching of a spindle distorts its central chain region, which stimulates dendritic endings of sensory nerves. If the reflex was mediated by the brain precious time could be lost before the protective impulse to contract reached a stretched muscle, resulting in. Developmental reflexes and neurological structure in infant behavior. If you compare traditional training to a messy hardware reorganization, then relax into stretch is an efficient software upgrade. Khan academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at. So theres some variety for how the information travels in reflexes, depending on the reflex. The stretch and golgi tendon reflexes work in tandem to control muscle length and tension. Because the stimulus for the stretch reflex is stretching the muscle, this reflex helps what. Check the deep tendon reflexes using impulses from a reflex hammer to stretch the muscle and tendon.
When a muscle is stretched, primary type ia sensory fibers of the muscle spindle respond to both changes in muscle length and velocity and transmit this activity to the spinal cord in the form of changes in the rate of action potentials. To use the stretch reflex to get a more explosive contraction, you must program it in advance. The functional response of sensory axons to muscle stretch was assessed in wildtype and erbb2. Pdf musculoarticular stiffness of the triceps surae ts increases with age in prepubescent children, under both passive and active conditions. Muscle stretch reflexes are usually named after the muscle being tested table 63. The myotatic reflex the development of muscle tension.
Using only the muscles of that hand, lift your left index finger, then slam it back onto. The stretch reflex myotatic reflex is a muscle contraction in response to stretching within the. The muscle stretch reflex msr is a monosynaptic volley involving the stretchsensitive muscle spindles, i. The simplest of these pathways, including a few neurons. By stretching the muscle and following with an isometric contraction of that muscle, its possible to reduce the activity or tone of that muscle and trick the myotatic reflex to allow for a more. Inform what is the length of the muscle, what is skeletal motor nerve axis of the nervousits instantaneous tension, and how rapidly is its system. The pathway starts when the muscle spindle is stretched caused by the tap stimulus in the knee jerk reflex. These changes were associated with a clear immediate reduction in the reflex sensitivity. This is the dynamic component which some think of as the dynamic stretch reflex. When the doctor taps your patellar tendon just below your knee, it stretches your patellar tendon, your quadriceps tendon, and your quadriceps muscles. The golgi tendon reflex also called inverse stretch reflex, autogenic inhibition, tendon reflex is an inhibitory effect on the muscle resulting from the muscle tension stimulating golgi tendon organs gto of the muscle, and hence it is selfinduced.
It is only one of the several components of the upper motor neuron syndrome umns. The role of the stretch reflex the muscle spindle is a long thin nerve receptor found within the muscle. If a skeletal muscle, like in this drawing, heres a skeletal muscle in the arm. It follows that if the homonymous stretch reflex of abdominal muscles have a monosynaptic component, then a similar. Stretch reflexes can have an important role in force enhancement during ssc exercise article pdf available in journal of applied biomechanics 4. Human nervous system human nervous system basic organization of movement. Change in muscle length here is a similar reflex in the arm, showing muscle length. Reduced stretch reflex sensitivity after exhausting stretch shortening cycle exercise article pdf available in european journal of applied physiology and occupational physiology 7256. Information from this receptor transmits information to the spinal cord regarding muscle length and the speed of lengthening.
The stimulus that initiates the reflex is the stretch of the muscle, and the response is contraction of the muscle being stretched. When you stretch a muscle there is an initial stretch reflex which is quick and strong. Reflex responses of the following abdominal muscles were. There is another reflex that occurs at the same time as the stretch reflex which is. Voluntary and reflex control of human back muscles during. The knee jerk is an example of the simplest type of reflex. Mar 25, 2020 when a stretch reflex is activated, it not only causes contraction of the synergistic muscles, but also caused relaxation i. The muscle stretch reflex throughout the menstrual cycle. The spinal stretch reflex, which provides proprioceptive sensory feedback to regulate motor output, has been used as a. This is a neuron mechanism that responds to a muscle being. The stretch reflex also called the myotatic reflex is a muscle contraction in order to response with the stretching within the muscle. To respond to stretch on a muscle through a reflex action, initiating a contraction to reduce that stretch and return to original position.
The electromyographic response to stretch consists of. Thus, when a muscle spindle is stretched and the stretch reflex is activated, the opposing muscle group must be inhibited to prevent it from working against the. Feb 01, 2014 the limitations of the tendon jerk as a marker of pathological stretch reflex activity in human spasticity. Biceps stretch reflex definition of biceps stretch. The role of muscle spindles in the development of the monosynaptic stretch re. When muscles contract possibly due to the stretch reflex, they produce tension at the point where the muscle is connected to the tendon, where the golgi tendon organ is located. Dynamic stretch reflex and static stretch reflexes. Reflexes can be tested as part of a neurological examination, often if there is an injury to the central nervous system. It is concluded that the longlatency component of the stretch reflex, m2, originates in skin andor subcutaneous nerve terminals and that no part of m2 originates in muscle stretch receptors.
The stretch reflex or myotatic reflex refers to the contraction of a muscle in response to its passive stretching by increasing its contractility as long as the stretch is. The deep tendon or muscle stretch reflexes table 38. The sudden stretch of a muscle activates stretch receptors within the muscle causing signals to be transmitted to the spinal cord by afferent sensory nerves. The stretch reflex of a muscle also plays an important role in maintaining body balance because it can generate the proper muscular response 2. Inverse stretch reflex inverse stretch golgi tendonnegative stretch reflex bisynaptic reflex. The stretch reflex is also referred to as the deep tendon reflex or myotatic reflex. The stretch reflex study guide by jennachild includes 14 questions covering vocabulary, terms and more. Muscle stretch reflexes are involuntary contractions of muscles induced by a brisk stretch of the muscle. A reflex contraction of a muscle in response to stretching of an attached tendon or of the muscle itself. Study 24 terms 11b the stretch reflex flashcards quizlet.
Are composed of a few intrafusal muscle fibers that. Altered activation patterns by triceps surae stretch reflex pathways in acute and chronic spinal cord injury. Muscle spindles and myotatic reflexes, part 1 movement. A reflex is a relatively simple motor response that does not involve a large number of interneurons or association neurons. The stretch reflex or the myotatic reflex is a system that monitors and maintains the length of a muscle. Primary afferent fibres are responsible for the stretch reflex, in which pulling the tendon of a muscle causes the muscle to contract. Muscle stretch reflex article about muscle stretch reflex. Okay, so lets begin by talking about a reflex, the simplest of all reflexes that we have through the circuits of our central nervous system. The stretch reflex and the contributions of c david marsden ncbi. It is a monosynaptic reflex that provides automatic regulation of skeletal muscle length.
The muscle spindle and the central nervous system the muscle spindle deserves special attention because of its important role as the prime organ of muscle sense. The bench press can be used to illustrate how the stretch reflex is used to elicit a more powerful muscle contraction. Pdf stretch reflex dynamics in spastic elbow flexor. Pdf reduced stretclex sensitivity after exhausting. This impulse results in the activation of more motor neurons at spinal level that send an impulse back to the muscle. Each spindle contains modified muscle fibers called spindle or intrafusel fibers inside spindle, innervated by gamma efferent fibers.
That tradition presumes that muscle tone is fully determined by the monosynaptic stretch reflex, that tonic fusimotor activity is necessary for its production in normal. A reflex action mediated by the golgi tendon organs that, when the organs are stimulated by a prolonged stretch, cause the stretched muscle to relax. In the video where we went over the motor unit, we talked about lower motor neuron signs that can appear with abnormalities of. This stretch activates the muscle spindle which in turn sends an impulse to the spinal cord. Longlatency component of the stretch reflex in human. This article shall discuss the components of a reflex arc, the monosynaptic reflex and relevant. This is needed so that the execution is safe and under control throughout the entire range of motion. The stretch reflex myotatic reflex muscle spindle reference.
This is the key to all speed and power movements i. Once a stretch reflex occurs, the impulse is sent from the stretched muscle spindle, to the alpha motor neuron. The knee jerk reflex is an example of the stretch reflex and it is used to determine the sensitivity of the stretch reflex. The muscle stretch reflex is the most basic reflex pathway in the body and as such, understanding this allows understanding of more complex reflexes.
Technique with the arm gently flexed at the elbow, tap the biceps tendon with a reflex hammer. The stretch reflex is one of the simplest reflexes which contract a muscle that is being stretched. There is a second, weaker but longer acting, static stretch reflex. The strength of this reflex depends upon the rate of change. The response is the muscle contracting, jerking the arm up. Stretch reflex dynamics in spastic elbow flexor muscles. The muscle stretch reflex plays an important role in providing feedback during movements. Most discussions liken muscle tone in humans to the reflex tone described by sherrington in decerebrate animals. The kneejerk reflex is a great example of the stretch reflex. Dave yarnell wrote a great tribute to the culver city westside barbell club and its connections with the columbus, ohio, westside club. Clinical assessment of the deep tendon reflexes provides useful information regarding. Training the stretch reflex in the squat starting strength. The opinion that muscular hypertonus is a result of increased muscle stretch reflexes is frequently encountered in the literature berberich et al.
In simple terms of clinical neurology, spasticity is defined as increased resistance to passive movement due to a lowered threshold of tonic and phasic stretch reflexes burke et al. Pdf stretch reflexes can have an important role in force. That is, when a muscle is suddenly stretched or unstretched, a strong signal is transmitted to the spinal cord. Pdf changes in stretch reflexes and muscle stiffness with. For this reason the stretch reflex is known as a spinal cord reflex and is completely involuntary. A spinal reflex is a fast response that involves an afferent signal into the spinal cord and an efferent signal out to the muscle. One of the simplest reflexes thats a good example and that happens to be one of the most medically useful is called the muscle stretch reflex, muscle stretch reflex. Like the hammer tapping the knee, it stretches a muscle. To determine conduction time from tendon tap to response of the gastrocnemius muscle in the achilles tendon reflex arc. A reflex is defined as an involuntary, unlearned, repeatable, automatic reaction to a specific stimulus which does not require input from the brain.
Quantitation of muscle contraction can be done by force measurements or elec tromyographic recordings. Spasticity is the velocitydependent increase in muscle tone due to the exaggeration of stretch reflex. The stretch reflex can be a monosynaptic reflex which provides automatic regulation of skeletal muscle length, whereby the signal entering the spinal cord. Stretch reflex with passivestatic stretching ground up. The stretch reflex is mediated through a monosynaptic arc and it contributes to the maintenance of steady standing posture and to coordinate muscle movement. Muscle stretch reflex how is muscle stretch reflex abbreviated. Although these reflexes are often called deep tendon reflexes, this name is a misnomer because tendons have little to do with the response, other. The limbs should be in a relaxed and symmetric position, since these factors can influence reflex amplitude. Reflex responses are the simplest responses and the least affected by voluntary controls. Khan academy offers practice exercises, instructional videos, and a personalized learning dashboard. Stretching of a muscle causes impulses to be generated in the muscle spindles 2. Dec 16, 2016 the deep tendon or muscle stretch reflexes table 38. Jan 01, 2010 relax into stretch simply teaches your muscles to relax into a stretch. Muscle spindles are composed of a few intrafusal muscle fibers that lack actin and myosin in their central regions, are.1349 1064 440 688 1282 430 958 897 474 798 1556 1118 107 128 113 798 764 389 930 1175 288 24 1333 111 1457 92 454 114 133 151 1085 703 603 581 1264 1352 1009 1 51 1006 1221 968