Elbow Flexion Unloading Response - Essay Example

Minor Assignment 2 Question Attach a graph that plots the EMG data from the sheet of the PRAC_2_datafile. Make sure you label all axes and units. Question 2: In this example of the elbow flexion unloading response (i.e. the task performed during the laboratory), state the muscle from which the data from sheet 1 was recorded, and whether the weight was removed unexpectedly or was self-removed by the subject. What was the latency of the response Answer: The data from sheet 1 showed the elbow flexion unloading response of the biceps.

The weight was removed unexpectedly as we can see the unloading reflex in the bicep provoked by the load release. The latency time is about 55 milliseconds. Question 3: Attach a graph that plots the EMG data from sheet 2 of the PRAC_2_datafile. Make sure you label all axes and units. (2 marks)Question 4: In this example of the elbow flexion unloading response (i.e. the task performed during the laboratory), state the muscle from which the data from sheet 1 was recorded, and whether the weight was removed unexpectedly or was self-removed by the subject.

What was the latency of the response Answer: The data from sheet 1 showed the elbow flexion unloading response of the biceps. The weight was self-removed as we observed the reduced EMG activity of the biceps, starting before the onset of the unloading. The latency time is about 50 milliseconds. Question 5: Based on evidence from the laboratory and/or the literature, explain the major reflex pathway that causes the reduction in agonist EMG in the unexpected unloading response. Include the series of neural events from just prior to the release of the weight until the end of the first agonist (biceps) response.

Answer: Anticipation in the postural domain is an example of the ability of the CNS to predict the consequence of the mechanical effect of movement on posture and helps minimize a forthcoming disturbance. A classical example was provided by the pioneering work of Belenkiy et al. (1967). They showed that, during arm raising while standing, the prime mover activity in the biceps brachii was preceded by activation of a leg muscle, the biceps femoris, starting 100 ms before the movement onset. This anticipatory postural adjustment was initiated in order to minimize the movement-related postural disturbances and to preserve the postural functions continuously exerted during the movement.

The anticipatory adjustments serve three main goals: (1) minimizing the disturbance of balance during movement; (2) minimizing the disturbance of the postural orientation of body segments, which serve as a reference frame for the organization of movement; (3) assisting the movement performance in terms of velocity or force. Question 6: Based on your answer to question 6, what can you infer about the contribution of this reflex pathway to steady isometric contractions Include reference to the fusimotor system in your answer.

Answer: When an individual can control the timing of a known external perturbation, the CNS exerts differential control over activity in the components of the medial back muscles. This does not occur when a similar perturbation is delivered unexpectedly. In addition, when the perturbation was self-initiated, there was increased baseline activity prior to unloading. This response was also observed in the biceps, which is considered to limit the impact of the disturbance by effecting a general increase in the stiffness of the arm (Biryukova et al. 1999).oluntary movements. Biofizica 12:135-141