Chapter———"——_____ |, 8 Locomotion and a ———————————— Meaning fined as “an action wh Movement is one of the significant living organisms. It can be det an Fe an oy ement is one ofthe significant features of living organisms. Fa" Of OS On ao onan le shifts position either involving its entire body or by one or organism from place to place is called locomotion. 17.1 Types of movements a) Amoeboid movement This type of movement is brought about by pseudopodia which are the characteristic features of amoeba, Here ectoplasm forms a blunt projection in the direction of its movement into which endoplasm flows. This fan Pseudopodia. b) Ciliary movement This kind of movement is brought about by cilia which are the microscopic hair like cytoplasmic extension cell. Each beat or lash of cilia consists of an effective stroke and recovery stroke. In the effective stroke the cjg becomes stiff where as in the recovery stroke the cilia returns to their original position. Ex: Paramoecium ¢) Muscular movement This is the basic type of movement exhibited by most of the animals including man. This kind of achieved by the muscles through the amazing and extra ordinary ability of converting chemical energy stored, nutrients into mechanical energy by alternate contraction and relaxation. 17.2 Muscle Muscle is a specialised tissue originated from the mesoderm. About 40-50% of the body weight of a adult man is due to muscles. They have the properties of excitability, extensibility, contractibility and elasticity. Types of Muscles : Based on their location, three Muscte ttre 1] it types of muscles are present (mausele cell 1. Striated muscle (Skeletal muscle) Sarcolemma These muscles are closely associated with the skeleton _and their activities are under the control of nervous system. Hence they are called voluntary muscles. They have striped appearance under the microscope and hence are called striated muscles. They are Diagrammatic cross sectional view of a muscle primarily involved in locomotary actions and changes showing muscle bundles and muscle fibres of body postures. : Fascicle (muscle bunda nT muscle (Visceral muscle or unstriatea muscle) - gm jocated 9 the inner walls of visceral organs {il ws Mo oF HEFLOUS System. Hence they are eating jit nan appearance. Hence called smooth muy go Mpa digestive Hael and gametes through genit : . reproductive tract etc. They are not involuntary muscles. They do not exhibit any striations es (non striated muscles). They help in transportation of al tract. " uscle diac ™ sles ae : ig pate 2 NT yolutary muscles. sem f the skeletal muscl ture ‘mscle is Made up of number of muscle bundles or fascicles held together by a collagenous (white fibres) * gonective tissue layer called fascia. Each muscle bundle contains a number of muscle fibres ggch muscle fibre is lined by the plasma membrane called sarcolemma that encloses the cytoplasm called ssrcoplas™. 4 sieotal muscle fibre is a syncitium as the sarcoplasm contains many nuclei The endoplasmic reticulum, i.e., sacroplasmic reticulum of the muscle fibres are the store house of calcium ions. , Toe sarcoplasm contains numerous parallely arranged filaments (contractile fibrils) called myofilaments or myofibrils. «+ Tee myofibrils are stacked in compartments called sarcomeres which are the structural and functional units of a muscle. + Nyofibrils contain two kinds of proteins namely Actin and Myosin that gives alternate light and dark bands due to their distribution pattern on the myofibrils. + The ight bands contain actin and is called ‘I’ band or Isotropic band. The dark band contains myosin and is lied ‘A’ band or Anisotropic band. Both proteins are arranged as rod-like structure, parallel to each other and also to the longitudinal axis of the myofibrils. ‘cn filaments are thinner than myosin filaments. Hence they are called thin and thick filaments respectively. Atthe centre of each “I” band is an elastic fibre called *Z? line which bisects it. The thin filaments are firmly anached to the *Z? line. ‘The thick filaments in the ‘A’ band are also held together by a thin fibrous membrane called ‘M? line. The” and “A? band are arranged alternately throughout the length of the myofibrils. The portion of the myofibrils between two successive ‘Z’ lines is considered as the functional unit of contraction and is called a sarcomere. Ina resting state the edges of thin filaments on either sides of the thick filaments partially overlap the free ends ofthe thick filaments leaving the central part of the thick filament. The central part of thick filaments not overlapped by thin filaments is called *H? zone.Structure of Contractile Proteins Actin and Myosin are the two types of contractile proteins. [Cross arm a. Actin > Each actin (thin filament) is made up of two ‘F” (filamentous) actins which are helically coiled around ca other. > Each ‘F” actin is polymer of monomeric “G” (globular) actins. > Two filaments of another protein called tropomyosin also run close to the ‘F’ actins throughout its lng > Acomplex protein namely troponin is distributed at regular intervals on the ‘tropomyosin’. > Inthe rest in state a subunit of troponin masks the active binding sites for myosin on the actin flamen's b. Myosin > Each myosin (thick filament) is a polymer of protein, peeve bcd aOnONICHS proses eaneu Mero} : yon ™ myosins constitute one thick filament sromyosin has t ach mere myosin Nas fo Important parts such as a globular head with a short arm and a tail b dis call : he globular head i led heavy meromyosin (HMM) and tail is called light meromyosin (LMM). ymponent i.e., the he . » The HMM comp rise cae and short arm projects outwards at regular distance and angle from cach other of a polymerized myosin filament. This is called as cross arm. , each globular head is an active ATPase enzyme Consisting of Actin bin muscle contraction ig site and ATP binding site. ism 01 mi etl Actin filament Myosin nm filament (Bre: 7 i eee (Formation of cross bridge) ey apps a ees Stages in cross bridge formation, rotation of head and breaking of cross bridge = ADP The mechanism of muscle contraction is described by the ‘sliding filament’ theory. It states that, contraction of muscle takes place by the sliding of the thin filaments over the thick filaments. 2 Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via motor neuron. }. Amotor neuron along with the muscle fibres connected to it constitute a motor unit. 4 The junction between the motor neuron and sarcolemma of the muscle fibre is called neuro-muscular junction or motor end plate. 5. Aneural signal reaching this junction releases a neurotransmitter (Acetyl choline) which generates an action potential in the sarcolemma. 6 This spreads through the muscle fibre and causes the release of Ca™* into the sarcoplasm. Increase in Ca“ level leads to the binding of Ca’* with a sub unit of troponin on the actin filaments and remove ‘he masking of active sites for myosin. By utilizing the energy from ATP hydrolysis, the myosin head binds to the exposed active sites on actin fibres ‘oform a eross bridge. This cross bridge pulls the attached actin filaments towards the centre of ‘A’ band, The ‘Z’ line attached to ‘bese actins is also pulled inwards that causes contraction of sarcomere. During contraction of muscles, the ‘I’ bands gets reduced whereas ‘A’ bands retain the length.4% os Locomotion sr ; e 11. The myosin releases ADP and Pi and goes back to its relaxed state. A new ATP binds to the myosin 4, the cross-bridge is broken. The ATP is again hydrolysed by the myosin head and the cycle of <_ and breaking is repeated causing further sliding. 12. This process continues till the Ca" are pumped back into the sarcoplasmic cistemae result in the mag actin filaments, This causes the retum of *Z’ lines to their original position i.e, relaxation. NB of ad we format 13. The reaction time of the fibres can vary in different muscles. Repeated activation of the muscles can lead to accumulation of lactic acid due to anaerobic breakdown of glycogen in the muscle that causes fatigue (gi, : in) > Muscle contains a red coloured pigment called “myoglobin” which stores oxygen. > In few muscles, myoglobin content is high and that gives red colour. Such muscles are called red fy, ‘These fibres contain more mitochondria which can utilize large amount oxygen for the synthesis of me Hence these muscles are called aerobic muscles. > On the other hand, some of the muscles contain less amount of myoglobin and hence they are called wy, fibres which contain less number of mitochondria, The contain sarcoplasmic reticulum is high in they ‘These muscles depend on anaerobic process for energy. Thad Maximally contracted ‘Two sarcomeres ‘Mechanism of sliding filament theory of muscle contraction 17.3 Skeletal System > Skeleton system consists of a frame work of bones and a few cartilages. > This system has significant role in the movement shown by the body. Bone and cartilage are specialized connective tissues. Bone has very hard matrix due to calcium salts whi cartilage has highly pliable matrix due to chondroitin salts. In human body the skeletal system is made up of 206 bones and few cartilages. The skeletal system is divided into two major divisions namely, axial skeleton and appendicil > skeleton.temporal bone Occipital one Occipttat condyle sists of skull, vertebral column, sternum and ribs, Skull > The facial region is made up of 14 skeletal elements which form the front part of the skull. > Asingle U-shaped hyoid bone is present at the base of the buccal cavity and is also included in the skull, > Each middle ear contains three tiny bones — Malleus, Incus and Stapes collectively called Ear Ossicles, Vertebral Column > Vertebral column is made up of 26 serially arranged units called vertebrae and is placed on dorsal side of the body. > It extends from the base of the skull and constitutes the main framework of the trunk. Each vertebra has a central hollow portion (neural canal) through which spinal cord passes. First vertebra is the atlas and it articulates with the occipital condyles of the skull. Frontal bone Sphenotd bond Ethmold bond Lacrimat hone Nasal bone Zygomattc bone Mauitla Mandibte Hyold bone Dingrammatle view of human skull prises 80 bones distributed along the main axis of the body. > Itis composed of 22 bones arranged in two sets namely, cranial bones and facial bones. > There are 8 cranial bones which form the hard protective outer covering called cranium for the brain. These bones are Frontal bones (b), Parietal bones (b), Temporal bones (b) and Occipital bones (b). Cervical vertebra Thoracic vertebra Lumbar Intervertebral — vertebra dise Sacrum’ Coceyx Vertebral column (right lateral view)The vertebral column is differentiated into several vertebra — “eet 1 namely. cervieal (7), thoracic (19), 5 » Lay (5), sacral (a) (five bones fused) and Caudal (caceygeal) 1 vertebra (Four bones fused) > The number of cervical vertebrae are seven in almost all mammals including human beings, The vertebral column protects the spinal cord, supports the the ribs and musculature of the back 3) Sternum (breast bone) > Iisa flat bone on the ventral midline of thorax to which ribs attach. 4) Ribs > > ‘There are 12 pairs of ribs. Each nb is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum. Each rib has two articulation surfaces on its dorsal end and is called bicephalic. First seven pairs of ribs are called true ribs. Dorsally they are attached to the thoracic vertebrae - and ventrally to the stermum with the help of hyaline cartilage The 8", 9" and 10™ pairs of ribs do not articulate directly with the sternum but join the seventh rib with the help of hyaline cartilage. These are called vertebrochondral (false) ribs. Last two pairs (11" and 12") of ribs are not connected ventrally and are called floating ribs. Thoracic vertebrae, ribs and sternum together form the rib cage. b) Appendicular Skeleton > > 1. Bones of Hand (Fore limbs): Humerus, Radius and Ulna, Carpals (wrist bones-8 in number), metacarpals (palm bones-5 in number) and Phalanges (digits bones —14 in number). 2. Bones of Legs (Hind limbs): Femur (thigh bone-the longest bone), Tibia and Fibula, tarsals (ankle bones-7 in number), Metatarsals (5 in number) and phalanges (digit-14 in number). ‘A cup shaped bone called patella cover the knee ventrally It includes the bones of limbs along with their (pectoral and pelvic). Each limb is made up of 30 bones. (knee cp). 3. Pectoral girdle: > Pectoral girdle helps in the articulation of upper limbs (hands). True ribs girdles Right pectoral girdle and uppet head and serves as the point of attach, ent Mba, rae cet” __ Seen made up of two halves. ws * rac ni of pectoral girdle consists of clavicle and a a. ceapul. scapula is 0 large triangular flat bone situated in the ee jorsal part of the thorax Between the second and the 7 covert DS. he dorsal, flat triangular body of scapula has a alghty elevated ridge called the spine which projects asa flat expanded process called the acromion, he clavicle or collar bone articulates with this. Femur > Below the acromion is a depression called the glenoid cavity which articulates with the head of the lj Tibia humerus to form the shoulder joint, If Fibula » Fach Clavicle is a long slender bone with two \ carvatures commonly called the collar bone, pelvic girdle: yy P| Metatarsats > Each pelvic girdle consists of two" coxal bones Ge Phalanges (innominate bones) Right pelvic girdle and lower limb bones (frontal view) > Each coxal bone is formed by the fusion of three bones namely, ilium, ischium and pubis. > Atthe point of fusion of the above bones is a cavity called acetabulum to which the thigh bone articulates. > The two halves of the pelvic girdle meet ventrally to form the pubic symphysis containing fibrous cartilage. 47.4 Joints > Joints are essential for all types of movements. > Joints are points of contact between bones or bones and cartilage. > The force generated by the muscles is used to carry out movement through joints, where the joint acts as a fulcrum (support). ‘wes of joints-There are three types of joints viz., Fibrous joints, Cartilagenous joints, Synovial joints ‘Fibrous joints. Tistype of joint is shown by the flat skull bones which fused end to end with the help of dense fibrous connective ‘nein the form of sutures to form cranium, Such kind of joints does not allow any movement. : LCartilagenous joints 'ee the bones are joined together with the help of cartilage. The joints found between adjacent vertebrae in the ‘zebral column is belongs to this category and permits limited movements. \Synovial joints (etaaterised by the presence of synovial cavity filled with fluid found between the articulating surfaces of the es, Such arrangement allows considerable movements which help in locomotion and many other ments, ‘land Socket joint ~ Between humerus and pectoral girdle, between Femur and Pelvic girdle, ’8¢ joint ~ Knee joint, Elbow joint of fore arm.1 — Between atlas and axis vertebrae. ng joint — Between the earpals ©. Saddle joint — Between carpal and metacarpal of thumb. 17.5 Disorders of Muscular and Skeletal system affecting neuromuscular junction leading to ting 1. Myasthenia gravis: It is an auto immune disorder weakening and paralysis of skeletal muscle. 2. Muscular dystrophy: It is a progressive degeneration of skeletal muscle mostly due to genetic disordey 3. Tetany: It causes rapid spasms (wild contractions) in muscle duc to low Ca" in body fluid 4. Arthritis: itis the inflammation of joints, 5. Osteoporosis: It is an age related disorder characterised by decreased bone mass and increased chance, of fractures. It is caused due to decreased levels of estrogen. 6. Gout: It is an inflammation of joints due to accumulation of uric acid crystals. Case Based Questions 1. Mechanism of muscle contraction is best explained by the sli contraction of muscle fibre takes place by the sliding of the thin filaments over the thick filaments. Th, stages regarding mechanism of muscle contraction are as follows: a =X ing filament theory which states ing a) out the phases that lead to muscle contraction. ‘Ans: Formation of cross bridge, sliding or rotation and breaking of cross bridge are the phases that lead to must contraction. b) Name the ions and the organelles which store them, which play an important role in muscle contraction ‘Ans: Ca” ions stored in sarcoplasmic reticulum play an important role in muscle contraction. c) What changes could be observed with respect to ‘H’ zone during contraction? ‘Ans: *H’ zone begins to decrease when contraction begins, continues to decrease as contraction process a completely disappears during maximum contraction.