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Physio-MuscleSpindle
| Question | Answer |
|---|---|
| Sensory receptors in muscle are important for proprioception and provide feedback for the precise control of movement | |
| Muscle spindles are sensitive to length changes in muscle; Golgi tendon organs sense muscle tension | |
| The sensory afferents of muscle spindles are the Ia and II fibers; the efferent inputs are the gamma motor neurons that are important for changing the sensitivity of the muscle spindle to length changes. | The sensory afferents from Golgi tendon organs are the Ib fibers. |
| Muscle spindles participate in the stretch (myotatic) reflex. Inappropriate muscle spindle activation is thought to cause muscle tender points | |
| Counterstrain is thought to work by resetting the muscle spindle to reduce inappropriate activation. | |
| Reflexes can result in joint movement as a result of effects on agonist and antagonist muscles. | |
| Activation of the myotatic reflex causes inhibition of the antagonist muscle via an inhibitory interneuron in the spinal cord | |
| The inverse myotatic reflex involves Golgi tendon organs and causes inhibition of the agonist and activation of the antagonist muscle via inhibitory and excitatory interneurons respectively. | |
| The flexor reflex causes responses in the ipsilateral and opposite responses in the contralateral leg | |
| Stretch reflexes can help to reveal sensory, lower or upper motor neuron, or neuromuscular transmission dysfunction | |
| The stretch reflex in lower limbs helps maintain posture | |
| Muscle spindles are important for proprioception (position sense) | |
| Explain the term “proprioception” and explain why proprioceptive feedback is essential for movement control | -proprioception (or ‘limb position’ sense) enables the fine control of movement |
| Describe the structure of muscle spindles and Golgi tendon organs with their respective locations in muscle | -Golgi Tendon Organs (GTOs) are found in the tendon region of the muscle -Muscle spindles are located in the belly of the muscle |
| List the afferent and efferent connections of muscle spindles | -Afferent:Group Ia and group II afferents *carry different types of information -Efferent: gamma motor neurons *important for changing the sensitivity of the muscle spindles to length changes |
| Name the variable sensed by the Golgi tendon organ | Golgi tendon organs sense muscle tension |
| Name the sensory afferent associated with the Golgi tendon organ | group Ib afferents |
| Describe the responses of muscle spindles and Golgi tendon organs to muscle stretch and contraction (Part 1) | When a muscle is stretched: -muscle spindles respond by increasing the firing rate -there is little if any response from the GTOs |
| Describe the responses of muscle spindles and Golgi tendon organs to muscle stretch and contraction (Part 2) | When a muscle contracts and shortens so that there will be some slack in the muscle spindle. As a consequence: -muscle spindle discharge drops to zero -Because tension is developed by the contracting muscle, the GTOs increase their discharge |
| Differentiate between type Ia and II sensory afferents in their responses to muscle stretch | -Type Ia afferents senses the velocity of stretch and the absolute length of the muscle -Type II afferents carry information regarding the absolute muscle length, and carry no information regarding the rate of stretch |
| Explain the function of gamma motor neurons in regulating the responses of muscle spindles | -Discharge of the gamma motor neurons causes the muscle spindle to shorten itself, so that it can maintain responsiveness during a muscle contraction -So gamma activation increases the sensitivity of the spindle |
| Describe the myotatic reflex and the role of muscle spindles in this reflex (Part 1) | The myotatic (stretch) reflex results in contraction of the stretched muscle via a monosynaptic connection of the Ia afferent with the alpha motor neuron innervating the stretched muscle |
| Describe the myotatic reflex and the role of muscle spindles in this reflex (Part 2) | -The stretch activates the muscle spindles, which sends information via the Ia afferent -The Ia afferent synapses onto the alpha motor neuron for the same muscle in the spinal cord -This leads to contraction of the muscle |
| Describe the myotatic reflex and the role of muscle spindles in this reflex (Part 3) | The purpose of the reflex is to limit inappropriate muscle stretching |
| Be able to predict the effect of changes in gamma motor neuron activation to the sensitivity of the myotatic reflex | |
| Explain how counterstrain treats muscle tender points by reference to effects on muscle spindles | -The osteopathic relevance of the muscle spindle is that inappropriate activation of the muscle spindles contributes to muscle tender points -Counterstrain may reset this system to remove the tender point |
| Explain how joint movement is produced by reference to agonist and antagonist muscles | Joint movement involves coordination of agonist and antagonist muscles -agonist muscle is the muscle that is contracting -antagonist muscle is the muscle that is inhibiting |
| Describe and explain the effect of the myotatic reflex on the antagonist muscle at a joint | -The myotatic (stretch) reflex also leads to inhibition of the antagonist muscle (causes knee jerk Rx) -The Ia afferent from the muscle spindle also synapses onto an interneuron in spinal cord that inhibits the alpha motor neuron of the antagonist muscle |
| List the components of the inverse myotatic reflex and describe the effects of this reflex on agonist and antagonist muscles. Be able to identify activation of this reflex given a description of the response to a change in muscle tension (Part 1) | -The inverse myotatic reflex: muscle tension triggers muscle relaxation |
| List the components of the inverse myotatic reflex and describe the effects of this reflex on agonist and antagonist muscles. Be able to identify activation of this reflex given a description of the response to a change in muscle tension (Part 2) | components: -GTOs *send information via Ib neurons into spinal cord -Inhibitory interneuron *synapses onto alpha motor neuron of the agonist mm *Inhibition of the agonist mm. |
| List the components of the inverse myotatic reflex and describe the effects of this reflex on agonist and antagonist muscles. Be able to identify activation of this reflex given a description of the response to a change in muscle tension (Part 3) | -Excitatory interneuron *synapses onto alpha motor neuron of the antagonist mm *Leads to activation of the antagonist muscle -Ex: Too much tension in a muscle leading to the muscle ‘giving’ under the weight |
| Describe how the flexor reflex triggers coordinated responses in the ipsilateral and contralateral limbs (Part 1) | -This reflex causes responses in the ipsilateral limb (the affected limb) and the opposite responses in the contralateral limb |
| Describe how the flexor reflex triggers coordinated responses in the ipsilateral and contralateral limbs (Part 2) | -Ex: stubbing the toe causes the stubbed limb to flex, but the contralateral limb extends to support the body. This is all achieved by a variety of excitatory and inhibitory interneurons in the spinal cord |
| Explain how the testing spinal reflexes can help to differentiate between sensory, lower motor and upper motor neuron dysfunction (Part 1) | Identifying whether a movement problem is because of a defect in the lower motor system (alpha motor neuron to muscle) or an upper motor problem (motor cortex and associated regions plus spinal cord) |
| Explain how the testing spinal reflexes can help to differentiate between sensory, lower motor and upper motor neuron dysfunction (Part 2) | If the reflexes are diminished it indicates a problem w/ either sensation or lower motor control |
| Describe the role of muscle spindles in the maintenance of posture | -Muscle spindles are incredibly important for proprioception and maintenance of posture -The legs on their own (i.e. muscle spindles) were as good as when all senses were intact at detecting sway |
| Describe the importance of muscle spindles for "position sense" | Muscle spindles are important for "position sense" as shown by the deficit in position sense when muscle spindles are disturbed |
Created by:
jgrayson