Neurophysiology Question Please answer all parts of the question, thanks! Imagin
ID: 122789 • Letter: N
Question
Neurophysiology Question
Please answer all parts of the question, thanks!
Imagine the signal on the left (labeled 'before'), is the response you see in the input region of a Ib sensory afferent when there is a low level of force in the muscle. Which of the signals on the right would correspond to the signal you would expect to see as the amount of force increases? Explain your choice of answer for the previous question in one sentence. Explain your choice of answer for the previous question in one sentence. Please be sure to discuss why you would or would not expect to see the both the amplitude and/or duration of the signal to change, and the reason each would or would not change. (Since the TA will not have your answer to the previous question, please start by reiterating your answer to the previous question, using the text provided: "I chose answer _____ because I would expect ....".)Explanation / Answer
A small introduction to GTO:
The Golgi tendon organ is an important neurological structure located within the muscular system. A Ib afferent nerve fiber enters the capsule bypassing the densely packed fibers and divides into branches that weave through the internal fascicle. When a tendon is stretched, some of the loosely packed collagen fibers will straighten. The Ib afferent endings get pinched between the straightening fibers, become depolarized, and open mechanically-gated ion channels. With an adequate stimulus, an action potential will result and propagate up the Ib afferent axon. As the signal reaches the dorsal root of the spinal cord it synapses with the Ib inhibitory interneuron.
I chose option E because:
1. A light load will cause the GTO to fire more frequently. As the load increases, there is a subsequent rise in the force of muscle contraction. As a result, the inhibitory discharge rate of the GTO also increases. Through this mechanism, the GTO limits the muscle to a safe level of contraction.
2. The initial discharge may be reduced by either self-adaptation or cross-adaptation of motor units. A motor unit will self-adapt if it has already been activated. Motor units can also undergo cross-adaptation in which the activation of one motor unit leads to the reduced dynamic discharge for a different motor unit firing after it.
3. The most obvious result of a malfunctioning GTO would be muscle damage in response to excessive tension. If a muscle is stretched too much, the GTO will become active and through autogenic inhibition, that same muscle will be inhibited to prevent further stretching. Therefore, if the GTO is not functioning properly a muscle tear may result.
4. Thus, if less muscle force is needed, excitatory input will synapse onto the Ib inhibitory interneuron to reduce muscle activation. Conversely, when more force is required, the descending input will operate to inhibit the Ib inhibitory interneuron, which will ultimately disinhibit muscle contraction.