Question

You are accompanying your friend while she does her shopping. Before long, she asks you to help her carry her bags and SUDDENLY plops one of her bags in your arms; it is MUCH heavier than you thought and you almost collapse under the sudden weight. Explain how the muscles, spindles, Golgi Tendon Organs, nuclear chain spindles are involved – or even if they or some of these are indeed involved.

Answer 1

Answer: Muscles are composed of muscle fibers and these muscle fibers are composed of myofibrils, which are designated as the contractile units of our muscles. Our muscles are attached to bones by tendons which help them to move. Now, whenever we lift a heavyweight these fibers activate and as a result the muscle gets shortened in length, creating a muscle contraction, by causing the ends to draw closer together, and thus helps in movement.

When we lift more amount of weight than our muscles are able to support, The excess amount of weight places stress on the muscle tissue which in turn causes micro-tears in the muscle fibers also called as muscular hypertrophy. To avoid further damage from this trauma, an immediate response takes place in order to repair the damaged muscle fibers.

Muscle spindles are defined as the collections of specialized muscle fibers which are found within the muscle mass itself. These muscle fibers do not contribute more to the force generated by the muscle. But, they are the specialized receptors that signal

(a) the length and

(b) the rate of change of length of the muscle.

whenever we lift a heavy object which we are unable to lift then contraction of muscle occurs, in which no movement takes place as because the load upon the muscle exceeds the tension generated by our contracting muscle. This situation takes place generally when our muscle tries to push or pull an immovable object.

Muscle spindles or so-called stretch receptors are the primary receptors of the muscle. Another primary receptor that comes into play during the process of stretching is located in the tendon near the end of the muscle fiber and is known as Golgi tendon organ.

The Golgi tendon organ is one kind of specialized receptor which is located between the muscle and the tendon. Now, like the muscle spindle, which is found to be in parallel with extra-fusal muscle fibers, the Golgi tendon organ is primarily found to be in series with the muscle and it signals information about the amount of load or force which is being applied to the muscle.

The Nuclear chain fibers are one type of muscle spindle fibers and are so-named because their nuclei are all aligned in a single row in the center of the fiber. The primary job of nuclear chain fibers is to transmit signal information about the static length of the muscle. The nuclear chain fibers are generally long and thin fibers which get lengthened steadily whenever there is a stretch or load or tension being exerted on our muscles. Now, when these fibers are stretched, the stretch reflex nerves increases their signaling rates as their length steadily increases. This is generally the static component of the stretch reflex.