Motor Nerve And The Muscle Stimulus example essay topic

Introduction The experiment involved an examination of contractile responses of a skeletal muscle. This is completed using an electrical stimulus, a dissected motor nerve is stimulated to achieve the desired muscle contractions. Then the stimulation of the muscle itself was observed, allowing for a comparison of voltage (force) requirements. This comparison of voltage's is obtained by finding and recording the threshold and maximal for both the motor nerve and the muscle stimulus. The threshold records the minimal stimulus required to achieve a muscle contraction where as the maximal obtains the maximum contraction force that the muscle can produce. This demonstrates the effective purpose of the nervous system.

Complete tetanus is observed, causing the motor nerve and maximal stimulus voltage, increasing frequency until the muscle no longer shows a relaxation period. This can be observed when maximum contraction has been obtained in the muscle. The final demonstration was the neuromuscular junction blockage, this shows how the nerve transmits a signal to the muscle. By blocking the junction the signal can no longer be completed, when the muscle is stimulated a contraction is still achieved... Understanding how a motor nerve works is essential when comparing the voltage required for the motor nerve stimulus and the muscle nerve stimulus. Materials and Methods The skin on the right hand limb of the frog was carefully removed to expose the muscle tissue beneath of the entire leg.

Next the sciatic-tibial nerve was exposed using only glass rods, as they did not affect the nerve. The gastrocnemius muscle was then dislodged from the leg, at the posterior end, by cutting the tendon. This muscle was then tied to the displacement transducer, and the knee pinned to the board so that muscle contractions could be measured. A sleeve stimulating electrode was then placed on the nerve to carry out the experiment. To begin, the muscle was stimulated to produce a twitch every five seconds.

With a duration of. 05 msec, and a voltage of zero, the nerve was stimulated. The voltage was increased until a contraction of the muscle occurred. This first contraction is called the stimulus threshold. The voltage was then further increased until a maximal muscle twitch strength was recorded. This is the voltage where the strength of the contraction stops increasing.

Next the muscle was stimulated at different frequencies until tetanus occurred. This was accomplished using the maximal stimulus voltage. With a rest period of 30 sec between each trial, the frequencies were slowly increased from points between 1 and 40. The trial where there was no evidence of any muscle relaxation between twitches was where tetanus occurred.

At this time, the nerve stimulating electrode was removed from the frog and a direct muscle stimulating wire was placed in the gastrocnemius muscle. The stimulator was then set to 1 pulse per 5 sec, and the duration to. 05 sec. The voltage was then increased to obtain the threshold and maximal stimulus values. Finally, the muscle stimulating electrodes were disconnected and the nerve stimulating electrode was reconnected. 1 mL of D-tubocurarine was injected into the muscle, in various locations.

The contractions of the muscle were observed every five seconds at maximal stimulus until no contraction occurred. When this point was reached, the muscle stimulating electrode was again reconnected and the result was observed... This was also accomplished at the maximal stimulus for the inter muscle stimulation. Answers to Questions 3.

The receptor for hypoxic drive is the peripheral chemoreceptors, located in the carotid bodies of the carotid artery. 4. Apnea is the transient (doesn't last forever) stoppage of breathing, which often occurs after a period of forced breathing (such as hyperventilation). Hyperventilation is an increased frequency of breathing which results in the increased intake of 02 and the increased blow off of CO 2. Hyperventilation lowers the amount of CO 2 so much that breathing becomes very slow and eventually stops. 5.

Because breathing is regulated by CO 2 and not O 2, CO 2 stimulates the peripheral chemoreceptors, which are responsible for the rate and depth of breathing. Therefore when breathing a concentration of 100% O 2, the activity of the peripheral chemoreceptors is decreased because CO 2 is not present to stimulate them. 6. Composition of Air: Name of Element % of Earth Atmosphere at sea level Nitrogen 78.08% Oxygen 20.95% Argon 0.93% Carbon Dioxide 0.03% Neon 0.0018% Helium 0.0005% Krypton 0.0001% Xenon 0.0001% 7. Because CO 2 drives our breathing (stimulates the chemoreceptors which increases both rate and depth of breathing) and not O 2, a patient exhibiting a weak respiratory drive while under anesthesia should be given CO 2 rather than O 2.