12/19/2023 0 Comments Neuron all or none principle![]() If a stimulus is above a certain threshold, a nerve or muscle fiber will fire. If you have a population of, for example, 5 neurons, the population response is no longer all or none, even if the individual units follow the principle. The all-or-none law is a principle that states that the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus. Thus with any load of work you notice how the Type I fibers are always firing. The 'all-or-none' principle refers to the roughly accurate concept that neurons fire all-or-none action potentials, individual muscle fibers contract fully or not at all, etc. This recruits the most powerful motor units in the body, the Type IIx and you see the Type IIa and Type I are helping. In the bottom picture, there are many plates on the bar requiring near maximal exertion of the exercise. The Type IIa is doing most of the work with the help of the Type I. In the middle picture there are more plates on the bar and thus more force to overcome. With the top picture, the load is light for the exerciser and the Type I motor units have been innervated. Learning Tip: Notice in the above graphic how the author is depicting the motor unit with ONE nerve innervating multiple muscle fibers on the left side of the graphic. Jennifer Hill, Exercise Physiology Student. Therefore Type I motor units are always firing no matter what the intensity. ![]() When the load becomes even greater, the Type IIx will be recruited with the help of the Type IIa and Type I motor units. The all-or-none law is illustrated in the right side of Figure 35, which demonstrates that any stimulus large enough to produce an action potential produces. When the load is increased, the Type IIa (fast twitch) will be recruited with the help of the Type I fibers. The action potential will be the same size and is propagated at the same speed, regardless of whether the stimulus just meets threshold or exceeds it by 2, 3, or 20 times. With light intensity exercise the Type I (slow twitch) motor units are recruited. If a stimulus is strong enough to destabilize the neuronal membrane, the neuron produces an action potential in that case, we say the neuron has fired. Motor unit recruitment depends on the force/resistance of the exercise. This is the all-or-none response of motor units. When the neuron ceases to fire, all of the muscle fibers innervated by the nerve will also cease to contract. ![]() When the neuron impulse fires, all of the muscle fibers innervated by the nerve will contract. Steps are resting states, depolarization, repolarization,hyperpolarization (undershoot). What is the All-or-None Response of Motor Units? Study with Quizlet and memorize flashcards containing terms like Explain the following steps in an action potential make sure to include where the ions are, the membrane potential, and what gates are opened and closed. ![]() The Motor Unit: What two different anatomical constituents compose a motor unit? Motor Unit, All-or-None Response of Motor Units and Motor Unit Recruitment ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |