\"Myofibrils are made up of thick and thin myofilaments that are organized into

Question

"Myofibrils are made up of thick and thin myofilaments that are organized into repeating functional units called sarcomeres" (Martini, 2014, p. 296). The interaction between the thick and thin filaments within the sarcomeres are what causes muscle contraction. The thick and thin filaments account for the bonded appearance that is seen on each myofibril. What proteins make up the thick and thin filaments?

Muscle contraction begins when nerve impulses cause sarcomeres in the muscle fibers to compress, lengthwise like accordions. With this known what causes a person to have a charlie horse?

Explanation / Answer

Thick filaments are made up of protein myosin, whereas thin filaments are made up of protein actin, and small amounts of trponin and tropomyosin.

Myosin is made up of 6 polypeptide chains. Of which 4 are low molecular weight light chains and two are high molecular weight heavy chains. It contain a tail and two heads that bind to actin on thin filament during muscle contraction. Actin contain myosin binding site for binding of myosin head. Tropomyosin acts as a regulatory protein under relaxed condition of skeletal muscle covering myosin binding sites of actin blocking myosin binding to actin. Troponin is a regulatory protein in thin filament which undergo conformational change when Ca+ attach to it moving tropomyosin away from myosin binding site on actin and aids in muscle contraction.

Charlie horse or muscle spasms is involuntary muscle contraction or cramp seen mainly in calf muscle signaling nerve from spinal cord to muscle to contract.

It is due to inefficient blood flow to muscle

Excess exercising

Nerve compression in spine

Low potassium calcium sodium

dehydration

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