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Phys Lect 14

Proprioception Gives the brain feedback of the muscles' position in space. Important of Precision in movement **NEGATIVE feedback system
Golgi Tendon Organs (GTOs) Located within the muscle TENDON. Provides sensory feedback on muscle TENSION.
Muscle Spindles Alligned parallel within the muscle fibers. Provides sensory feedback on muscle length/stretch.
Muscle spindle's efferent input (from the CNS) From Gamma motor neurons (different from alpha motor neurons that trigger muscle contraction). **Important in changing sensitivity of muscle spindle to length changes.
Muscle spindle's afferent output 1.Group 1a: Respond to velocity (RATE of stretch/ length change) as well as length. 2.Group II: Respond to length change ONLY (Inc firing with Inc length)
GTOs innervation Group 1b afferents. Carry impulses back to the CNS based on the level of tension. These nerve endings are found withing the collagen fibers of the tendon and when the fibers increase in tension, the squeeze the group 1b afferents.
Muscle spindles and GTO's response to STRETCH 1.Musc. Spin: Increase Firing. 2.GTO: No Effect
Muscle spindles and GTO's response to CONTRACTION 1.Musc. Spind: No effect (because it buckles withing the muscle). 2.GTO: Large Inc in firing
Function of the Gamma Motor Neuron Causes the muscle spindle to shorten during muscle contraction so that it can continue to provide proprioreceptive feedback during a contraction. **receives the same signal from CNS that alpha motor neuron does.
Effects of Gamma Activation on the muscle spindle? Shortens the spindle and increases its sensitivity.
What happens if a muscle spindle is disrupted? The afferent signals will be altered from the norm
Steps of the Myotatic Reflex **MONOSYNAPTIC REFLEX** 1.Muscle stretches, activating Muscle spindles. 2.Muscle spindle sends impulses down 1a afferents to spinal cord. 3.1a afferents directly synapse onto Alpha motor neuron of that same muscle. 4.Muscle contraction.
Muscle spindles' involvement in Muscle Strain Muscle strain causes inappropriate gamma motor activation -> muscle shortening -> Tenderpoint. **Counterstrain resets the muscle spindle & Gamma activation.
Hyperreflexia Indicates an Upper motor defect. **b/c there is a lose of the tonic inhibition of alpha motor nerves, allowing the hyper sensitivity.
Effect of myotatic reflex on antagonist muscle? The 1a afferent leaving the muscle spindle sends an EPSP to the agonist's alpha motor neuron, but an IPSP to the antagonist's alpha motor neuron. **Allows joint movement.
What is responsible for producing the Inverse myotatic reflex GTOs. **Produces OPPOSITE effect as the stretch reflex.
Mechanism of Inverse Myotatic reflex 1.Too much tension, activates GTO. 2.1b afferents carry impluse to CNS. 3.synapses onto Excitatory interneuron (antagonist alpha motor) and Inhibitory interneuron (agonist alpha motor). 4.Triggers agonist relaxation, antagonist contraction.
Flexor Reflex Produces a response in the ipsilateral limb and the OPPOSITE response in the contralateral limb. **Ex: stub toe: ipsilateral flexion, contralateral extension of legs.
Upper motor Vs Lower motor defects 1.Upper motor: Problems from the motor cortex down the spinal cord. 2.Lower motor: Problems with the alpha motor neurons to the muscle. **This is why stretch reflexes are tested.
If there is a Lower motor defect, where might the problem be? 1.Neuromuscular junciton. 2.Alpha Motor Neurons. **Pt will have DIMINISHED stretch reflexes.
Created by: WeeG



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