The results from this lab are consistent with what is expected from a healthy subject. The use of the tendon hammer elicited a reflex of the Achilles tendon. When comparing the stretch reflex with the voluntary reflex, the voluntary reflex exhibited a longer latency. The mechanism is that the use of a reflex hammer, tapped on the tendon causes the muscle to stretch, and according to Purves (2008), this evokes excitation of the Ia sensory axons, innervating the muscle spindles. This excitation reaches the alpha motor neurons in the spinal cord or brainstem and then return to the muscle that has been stretched. It is important to note that muscles are ways under a degree of tension, which is mediated by group II afferents; this reflex circuit is responsible for maintaining the level of tension in muscle, called muscle tone. Purves goes on to explain that the stretch reflex is a negative …show more content…
Due to the nature of the experiment, it is quite painful, the participant chose to stop the experiment at this point so a fused tetanus was not achieved. As the frequency increased the muscle fibres did not have time to relax before the next action potential came along which causes the force that is generated each time, to be summed. At low frequencies, each action potential generated in the muscle fibre will lead to a single twitch in the muscle fibre related; this is observed is the second experiment. As the frequency was increased however, each twitch was summed with the next which lead to temporal summation. At the highest frequencies, the force produced was much greater but the individual twitches were still noticeable. If the experiment were to continue to the highest level of motor neuron activation, the single twitches become one fused tetanus where the individual peaks and dips are no longer