1.A motor unit contains only one type of muscle fiber. Different muscle fiber ty

Question

1.A motor unit contains only one type of muscle fiber. Different muscle fiber types will fatigue at different rates. If you want to achieve a maximal muscle contraction, you need to recruit the motor units with the fastest fatigue rate last.
Identify the order (first to last) that motor unit types are recruited to achieve a maximal contraction.

Question 7 options:

123

fast-twitch oxidative-glycolytic muscle fibers

123

fast-twitch glycolytic muscle fibers

123

slow-twitch oxidative muscle fibers

2.General. In the experiments, you stimulated the muscle with electrodes. In reality, there are no electrodes to contract our skeletal muscle. Stimulating muscle with electrodes in the experiments is analogous to which event in regular skeletal muscle contraction?

Question 15 options:

A)

Achetylcholine binding to its receptor at the neuro-muscular junction

B)

Myosin binding to actin during crossbridge cycling

C)

Ca2+ ions entering the motor neuron to release neurotransmitter

D)

Ca2+ ions leaving the sarcoplasmic reticulum to bind to troponin

E)

Achetylcholinesterase breaking down ACh in the synaptic cleft

123

fast-twitch oxidative-glycolytic muscle fibers

123

fast-twitch glycolytic muscle fibers

123

slow-twitch oxidative muscle fibers

Explanation / Answer

1q). The slow twitch fibers are abundant in the long muscles, they are always oxidative. These muscle fibers appear red due to their high content of myoglobin, they are generally fatigue resistant so that required in endurance sports. The motor units of the slow twitch fbers are smaller than the fast twitch fibers. These are frequently used because they are fatigue resistant.

The fast –twitch fiber can split ATP rapidly in short –duration twitches so that, power sports require these fibres. Anaerobic pathways are generated in these fibres so that higher fatigue occurs during ATP generation.

Thus, the order of recruiting the muscles to achieve a maximal contraction is,

Slow twitch oxidative muscle fibers, fast-twitch oxidative-glycolytic muscle fibers, fast-twitch glycolytic muscle fibers.

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