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23 views13 pages

L 1

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prakharsample7
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Muscular movements: External body parts: Collect information Maintenance of equilibrium Capturing and ingestion of food Locomotion Offence and defence Breathing ‘© Most important characte ‘¢ Change in position or place by the entire body or by ‘one or more of its parts ‘¢ Animals possess two forms of movements: + movements of body parts * Locomotion ‘© Two collectively referred to as muscular movements ‘© Study of movement: Kinesiology Muscular movements: Internal body parts: «© Circulation of blood ‘* Gaseous exchange: movements of diaphragm assist chest in the flow of air through respiratory tract «* Peristalsis for passage of food and urine ‘© Movements of genital tract and uterine wall during egg laying and childbirth Non-muscular movements: Inside the cell + Four major type: © Ciliary movements: 4 Swimming (Paramecium and other ciliates) & Take part in propulsion of excretory products in urinary tubules and flame cells Occurs in most of ou by ciliated epithelium internal tubular organs lined @ Cilia present in trachea, oviducts and vasa efferentia help in pushing out dust particles, eggs and sperms Nedaritin '* Pseudopodial movements: @ Helps to make movement in leukocytes and macrophayes & ASfected by pseudopodia formed by the streaming of protoplasm and helps in creeping (Amoebo) & Cytoskeletal elements like microfilaments also involved in amoeboid movement Flagellar movements: @ Flagella of choanocytes maintains a regular current ‘of water in the body (Sponges) @ Perform locomotion in Eugienoids, other flagellar protists and sperms & Helps in circulation of food (Hy Bhebunt TRE (ote) ToT (snsibibog) Te T ( Popo) ‘© The light bands contain actin and is called band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin © Myofibrils are arranged in a number of sections: {Band ABand | Band ‘Sarcomeres ee _F*». Sane, @ Sercomeres are delinested by & very thin ond comparatively dense Z-line (Krause's membrane) * A dark A-band present in the centre of the sarcomere '* Adjacent to this lies a light Lband 1 u | « At the centre ofthe A-band, a comparatively less dark zone. ZDisc Mline 7 Disc (not overlapped by thin flaments) Is present: H-zone Thick Filament (Myosin) (Hensen zone) Thin Filament (Actin) ‘© In the centre of H-zone, Muiine is present formed by threads that connects the myofilaments ‘© Ziline is located at the centre of the I-band Vedanta, Muscle Contraction protein is a complex of three globular peptides 1 2 ‘Troponin 7: binding to tropomyosin as well as to the other two troponin components Troponin |: inhibiting the F-actin- myosin interaction, also binding to other components of troponin . Troponin C: calcium binding polypeptide Structure of Contractile Proteins ‘© Each actin (thin) filament made of two ‘F* (filamentous) actins helically wound to each other '* Each ‘F' actin is a polymer of monomeric ‘G’ (Globular) actins ‘© Two filaments of another protein, tropomyosin also run close to the *F’actins throughout its length * A complex protein Troponin Is distributed at regular Intervals on the tropomyosin ‘2 In resting state: a subunit of troponin masks the active binding sites for myosin on the actin filaments ‘* Each myosin (thick) filament is also a polymerised protein © Many monomeric proteins: Meromyosins constitute one thick filament, '* Each meromyosin has two important parts, 2 globular head with a short arm and a tall, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM) ‘* HMM component, ie; the head and short arm projects ‘outwards at regular distance and angle from each other from the surface of a polymerised myosin filament: known as cross arm ‘© The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin ‘After this, an enzyme cholinesterase present along with receptor sites for acetylcholine, breaks down diffuses back to the axon and is reused to synthesize more acetylcholine for transmission of subsequent impulses ‘* At the opening of each transverse tubule onto the muscle fibre surface, the action potential spreads inside the muscle fibre ‘* At each point where a transverse tubule touches part of the sarcoplasmic reticulum, it causes the sarcoplasmic reticulum to release Ca* ions ‘# Increase in Ca level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin. Mechanism of Muscle Contraction © Best explained by sliding filament theory which states that contraction of a muscle fibre takes place by sliding of thin filaments over thick filaments ‘¢ Muscle contraction initiated by a signal sent by the CNS. via a motor neuron * A motor neuron along with the muscle fibres connected to it constitute a motor unit ‘* Junction between a motor neuron and the sarcolemma of the muscle fibre: Neuromuscular junction or motor-end plate © A neural signal reaching this junction releases a neurotransmitter, Acetylcholine which generates an Neder action potential in the sarcolemma ‘© The head of each myosin molecule contains an enzyme myosin ATPase «= In the presence of myosin ATPase, Ca*" and Mg ons, ATP breaks ‘down into ADP and inorganic phosphate, releasing energy in the head = Utlising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actn to form across bridge ‘© This pulls the attached actin flaments towards the centre of bana © The Z line attached to these actins are also pulled inwards thereby ‘causing a shortening of the sarcomere, Le, contraction + Chemical events associated with muscle contraction: Albert Szent Gyorgi (1942) Vedat, Cocked" crose-bridge Sign, Sliding Myosin Filament lament Cross-bridge pulls actin lament ‘© During shortening of the muscle, i.e., contraction, the ‘I bands get reduced, whereas the ‘A’ bands retain the length ‘* Myosin, releasing the ADP and P, goes back to its relaxed state ‘* Anew ATP binds and the cross-bridge is broken ¢ The ATP is again hydrolysed by the myosin head and the cycle of cross bridge formation and breakage is repeated causing further sliding ‘© The process continues till the Ca” ions are pumped back to the sarcoplasmic cisternae resulting in masking of actin filaments ‘This causes the return of ‘Z' lines back to their original. Cori’s Cycle Cori’s Cycle Proposed by Cori and Cor vie Mook oad Repeated activation of muscles leads to accumulation of lactic acid due to anaerobic breakdown of glycogen in them, causing fatigue This cycle occurs in the muscles and liver During anaerobic respiration, lactic acid is produced in the muscles Lactic acid is carried in the blood to the liver where and Glycogen releases glucose into blood which is reconverted to glycogen in muscles; cycle is repeated. MUSCLE Types of muscles > The body muscles show four general forms: ‘© Broad, thin, sheetdike muscles, e.g., obliquus ‘externus and transversus, which form the flexible abdominal wall Slender, ribbon-like muscles, eg, biceps and deltoideus of the limb * Long, tapering muscles, e.g., gastrocnemius of the 1d limbs ‘© Ring - like sphincter muscles, e.g., sphincter ani, that surrounds the anus and constricts to close it Vedanta Types of muscles Flexor and extensor © Flexor: muscle that bends one part of a limb on another at a joint e.g. biceps that bring the forearm ‘* Flexor and extensor towards the upper arm > On the basis of movement: «© Pronator and supinator Extensor: antagonist of flexor muscle; contraction of BYabeiictorend edductor an extensor extends a joint by pulling one of the articulating bone apart from another, e.g. triceps that * Depressors and elevators ee cant cco © Sphincters and dilators ‘© Protractor and retractor Pronator and supinator © The contraction of a pronator rotates the forearm to turn the palm downward or backward © Supinator is antagonist of pronator; contracts to rotate the forearm and thus to make palm face upward or forward Depressors and elevators © Depressors: lower a part that lowers down the lower jaw to open the mouth depressor mandibulae © Elevators: (antagonistic to depressor) raise a part ex masseter that lifts up the lower jaw to close the mouth Abductor and adductor © Abductor: contracts to draw a bone away from the body midline e.g. deltoideus that draws the forelimb to the side © Adductor: draws a bone towards the body midline 24g, latissimus dorsi that presses the entire forelimb against the Sphincters and dilators ‘© Sphincters decrease the size of the apertures to close them while dilators widen the apertures. Protractor and retractor © Protractor muscle pulls the lower jaw, tongue and the head forward © Retraction is opposite to protraction; draws the lower Jaw, tongue and the head backward

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