A) Movements shown by human cells
by Jyoti Jha
1. •• brought up by the action of specific type of muscles
2. B) Types of muscular tissues
3. Three types
4. c) Muscular movement
5. 2)ARRANGEMENT: Muscle fibres are arranged In bundles. Big muscle is surrounded by a sheath ,epimysium .inside big muscle are some bundles called muscle fasciculus. Muscle fasciculus is surrounded by a sheath, perimysium. Inside perimycin are individual muscle fibre which is again surrounded by a sheath called endomysium. (All these sheaths were of connective tissue) And all these things are held together by a collagenous connective tissue layer called Fascia .Also some blood and nerve Fibres are present.
6. 4)Externally covered by a membrane called sarcolemma which invaginates to form a system of T-tubules.
6.1. New Topic
7. 3)EACH STRAITED MUSCLE FIBRES:: long, cylindrical,straight, unbranched,blunt ends . 40mm in length,10-100um in dia.
8. 9) Structure of A- band under electron microscope: • formed of thick tadpole shaped Myosin / primary / A-filaments. • each myosin filament 1.2um long , 100 angstrom in dia • formed of about 200 myosin protein molecules. • free at both the ends. • has small ridges called cross bridges or heads. • thick myosin filaments of A-band are held together by thin fibrous membrane called M-line.
9. 8) Sarcomere: ( about 2.5 um long) •part of myofibril b/w two adjacent Z-lines is Sarcomere. • structural & functional unit of striated muscle fibre. •formed of 1complete A-band &half of I-band on either side.
10. 10) structure of I- band: • formed of thin actin / secondary /I-filaments. • Each actin filament is about 2um long , 50 angstrom in dia . • formed of about 3000 actin protein molecules. • Attached to Z- line on one side while partially overlaps myosin filament on other side. • has no cross bridges.
11. 11) structure of myosin protein: • myosin is thicker protein than actin protein. •1500 angstrom long •20-40angstrom in diameter •formed of 6 polypeptide chains •differentiated in two parts ( tail & head) •Tail- formed of 2 polypeptide chains intercoiled to form double helix & form light meromyosin (LMM). •Head- two in number , each of them is formed of 2 globular meromyosin proteins &form heavy meromyosin (HMM). • Myosin is polymer & monomeric unit is meromyosin. Heads lie at tip of arms to form cross arms ( cross arms of different myosin oriented in different direction). •head form cross bridges with actin filaments in presence of enzyme myosin ATPase present on head.
12. 12) Actin is thinner protein than myosin. • actin filament is formed of 3 types of proteins: ( Actin , tropomyosin, troponin protein) a) Actin protein - also known as fibrous / F-actin & it forms the backbone of actin filament. •F-actin is formed by polymerization of G-actin. • G-actin are arranged in beaded form. • F- actin is formed of 2 polypeptide chains intercoiled to form a double helix. • G - actin molecules has active sites having ADP molecules which act as binding for heads of myosin. b) Tropomyosin - formed of 2 polypeptide chains & is spirally coiled around F- actin • basically it lies in the depression ( groove) of F- actin. •each Tropomyosin molecule covers 7 active sites of actin molecule during relaxed state. c) Troponin - present on Tropomyosin • oval shaped globular protein •troponin and Tropomyosin blocks the active site of actin so that myosin head don't bind ( when no muscle contraction occurs)
13. 5) sarcoplasm (cytoplasm of muscle fibre) has: • numerous, Oval , large sized mitochondria •Glycogen granules( muscle fibre has high energy requirements) • a network of sarcoplasmic reticulum ( ER of muscle fibre) storehouse of calcium ions, plays a major role in muscle contraction •Nucleus ( multinucleated,spindle shaped) present just below the sarcolemma.
14. Straited muscle
14.1. •Straited / striped / skeletal voluntary muscle •Smooth /unstraited / visceral /involuntary muscle •Cardiac muscle
14.1.1. Straited muscles are basically involved in muscular contraction