Structure and Functions of Muscle

Structure and Functions of Muscle

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  Jean Melanie VincentHaymo Physical Education Teacher MPhil Scholar Punjabi University ,Patiala MPED L.N.I.P.E , Gwalior Structure and Function of Skeletal Muscle
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  Skeletal Muscle – Humanbody contains over 400 skeletal muscles – 40-50% of total body weight – Functions of skeletal muscle – Heat production during cold stress – Force production for postural support – Force production for locomotion and breathing – The prime function of muscle is to convert chemical energy (ATP) into mechanical energy.
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  Structure of SkeletalMuscle – Epimysium – The entire muscle is surrounded by connective tissue called epimysium. – Perimysium – The bundle or fasciculus is also surrounded by a connective tissue called perimysium. – Fascicles – Endomysium – Many muscle fiber found in muscle bundle. The individual muscle fiber is surrounded by connective tissue called endomysium. – Tendon skeletal muscle is attaches to a bone with the help of connective tissue called tendon.
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  – Sarcolemma Each musclefiber contains sarcoplasm covered by membrane sarcolemma.in the sarcoplasm, ATP, CP, fat droplets are present. The sarcoplasmic reticulum (smooth endoplasmic reticulum) stores calcium, which is released into the sarcoplasm during muscle contraction. - Myofibrils Threadlike strands within muscle fibers. It is the smallest unit of a muscle fiber. Myofibril has dark and light bands in it. The dark band is known as A band and light one’s are as I band. These bands consists of two types of protein filaments known as actin(thin) and myosin(thick). Thin myofilaments are composed of 3 proteins: actin, tropomyosin, and troponin. - Thick myofilaments consist myosin molecules. A band consists of both actin and myosin filament and I band consist of only actin filament.
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  – Further divisionsof myofibrils – Z-line:-In the middle of A and I band, there is a Z line. – Sarcomere:- The portion between two Z line is called sarcomere. The sarcomere is the functional (contracting) unit of skeletal muscle. – H zone:-the area in the centre of the A band is called H zone.
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  Cross-Bridge Formation inMuscle Contraction
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  Function of SkeletalMuscle: – Motion -- Motion can be obvious body movements or less noticeable motions such as heartbeat and gut movement. – Stabilize body positions and regulate organ volume -- Sustained contractions of skeletal muscle maintain body posture without creating noticeable movement. Sustained contractions of smooth muscle prevent outflow from hollow organs and maintain them at an appropriate volume. – Thermogenesis -- A by-product of muscle contraction is heat production and is therefore important in homeostasis of body temperature.
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  Properties of skeletalmuscles – Excitability:-This is the ability to receive and respond to certain stimuli by producing electrical messages. – Contractibility :- Contractility is the ability to shorten and thicken (contract), thus generating force to do work. – Extensibility:- Extensibility is the ability to stretch without damaging the tissue. – Elasticity:- It is the property of muscle to lengthens during stretching by pulling force & can return again to its normal resting position. – Muscle tone:- it refers to the partially contracted state of the muscle in a constant state of readiness for action.