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Textbook for Class XI

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CONTENTS 1. 2. 3. 4. 5.

Types of movement Muscle Skeletal system Joints Disorders of muscular and skeletal system

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Locomotion is referred to as the voluntary movement performed by animals. The method varies depending upon the habitat and demand of the situation. Typically, locomotion is carried out in search of shelter, food, mate, suitable climatic conditions, breeding grounds, escaping from predators. Locomotion is the voluntary movement of an individual from one place to another. Walking, running, climbing, swimming are the examples of locomotion. All locomotion are movement but all movements are not locomotion. Types of Movement Cells of the human body show three main types of movements:

Macrophages and leucocytes in blood exhibit amoeboid movements. Coordinated movement of cilia in trachea to remove dusts particles and passage of ova through fallopian tube is example of Ciliary movements.

Movement of limbs, jaw, tongue, etc. need muscular movement. Contractile property of muscles is used in movement in higher organism including human beings.

Muscle Muscles are specialized tissues of mesodermal origin. They have property like excitability, contractility, extensibility and elasticity. Based on their location, three types of muscles are identified

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Skeletal Muscles

Visceral Muscles Form inner wall of Associated with skeletal internal visceral organs, system, alternate light non-striated, involuntary and dark bands (striated), muscle, assists in voluntary and movement of food locomotory and change in through digestive tract body posture function. and gametes.

Cardiac Muscles Muscles of heart, having branching pattern, alternate light and dark bands, involuntary in action.

Skeletal Muscle is made up of muscles bundles (fascicles), held together by collagenous connective tissue called fascia.

Each muscle bundle contains a number of muscle fibres. Each muscle fibre is lined by plasma membrane called sarcolemma enclosing sarcoplasm. Partially arranged myofibrils are present in muscle bundle having alternate light and dark bands due to presence of protein- actin and myosin Light bands contain actin and is called I-band (isotropic band) and dark band contains myosin, called A-band (anisotropic band). Both bands are present parallel to each other in longitudinal fashion. In centre of each I-band is elastic fibre called ‘Z’ line. In the middle of A-band is thin fibrous ‘M’ line. The portion of myofibrils between two successive ‘Z’ lines is the functional unit of contraction called a sarcomere.

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At resting stage thin filament overlaps the thick filament. The part of thick

filament not overlapped is called ‘H’ zone. Structure of contractile Protein Each thin filament (actin) is made of two ‘F’ actins helically wounded to each other. Two filaments of another protein, tropomyosin runs close to it. A complex protein Troponin is distributed at regular intervals on the tropomyosin.

Each myosin filament is made of many monomeric proteins called Meromyosins. Each meromyosin has globular head with short arm and tails. Globular head has ATP binding sites. Mechanism of muscle contraction •

The mechanism of muscle contraction is explained by sliding mechanism theory in which thin filament slide over thick filament.

Muscle contraction start with signal sent by CNS via motor neuron. Neural signal release neurotransmitter ( Acetyl choline) to generate action potential in the sarcolemma.

This causes the release of Ca ++ from sarcoplasmic reticulum.

Ca ++ activates actin which binds to the myosin head to form a cross bridge.

These cross bridges pull the actin filaments causing them to slide over the myosin filaments and thereby causing contraction.

Ca ++ are then returned to sarcoplasmic reticulum which inactivate the actin. Cross bridges are broken and the muscles relax.

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Muscles are classified as: Red fibres (aerobic muscles-) contain myoglobin that has plenty of mitochondria to use large amount of oxygen stored in them. White fibres-the muscle fibres containing less number of myoglobin are called white fibres. Skeletal System Framework of bones and cartilage forms the skeletal system. In human beings, it consists of 206 bones and some cartilages. The two principle division of skeletal system are: 1. Axial Skeleton (80 bones)- includes skull, vertebral column, sternum and ribs constitute axial system.

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The skull (22 bones) is composed of cranial and facial bones. Cranial (8 bones) forms protective covering for brain (cranium). The facial region consists of 14 skeletal systems that form front part of skull. Hyoid bone (Ushaped) forms the base of buccal cavity.

The middle ear bone (Malleus, Incus and Stapes) collectively called Ear Ossicles. Skull joins with vertebral column with two occipital condyle.

Vertebral column consists of 26 serially arranged vertebrae. First vertebra is atlas that combines with occipital condyle. Other includes Cervical-7, thoracic -12, lumbar -5, sacral – 1 coccoygeal -1.

12 pairs of ribs connected dorsally to vertebral column and ventrally to sternum. 11th and 12th rib bones are not connected with sternum and are called floating ribs.

Appendicular Skeleton- includes bones of limbs and girdles. Each limb contains 30 bones.

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Upper Arm Humerus, radius and ulna, 8-carpels, 5metacarpels, 14-phalanges,

Lower Limb Femur, tibia and fibula, 7-tarsals, 5metatarsals, 14-phalanges, cup shaped patella cover the knee.

Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with the axial skeleton. Pectoral girdle consists of a clavicle and a scapula. Pelvic girdle consists of two coxal bones. Each coxal bone is formed by the fusion of three bones – ilium, ischium and pubis. Joints Joints – are points of contact between bones, or between bones and cartilage. 1. Fibrous joints– do not allow any movements. Present in flat skull bones to form cranium. 2. Cartilaginous joints– bones are held together with the help of cartilage present in vertebrae. Permits limited movements. 3. Synovial joints– fluid filled synovial cavity, provide considerable movements. Ball and socket joint, hinge joints, pivot joints, gliding joints etc. Disorders of Muscular and Skeletal System • • • •

Myasthenia gravis- auto immune disorder affecting neuromuscular junction causing fatigue, weakening and paralysis of skeletal system. Muscular Dystrophy- degeneration of skeletal muscles due to genetic disorder. Osteoporosis – decreased bone mass in old age leading to chance of fracture due to decreased estrogen. Arthritis- inflammation of joints.

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Gout- inflammation of joints due to accumulation of uric acid crystals. Tetany- Rapid spasms in muscle due to low Ca ++ in body fluid

Summary Movement is an important feature of all living beings and locomotion is characteristic of protoctista and animalia. While in movement, an organ or organelle may shift from its original position and come back to it, in locomotion, the entire body of the animal or the protoctist moves away and is displaced from its original location .Ciliate protozoa or alga carry out locomotion by means of cilia, organelles made of microtubules. Ciliary beating begins with fast stroke and ends in a recovery stroke. Flagellum is long and whip like organelle made of microtubules. While cilia are many, flagella may be one or two. Muscles and bones help the vertebrates to locomote from one place to another, muscles are joined to bone by ligaments and one muscle is joined to the other by a tendon. Muscles are a tissue made of muscle cells, also called muscle fibres. Muscle fibres are made of thick and thin myofilaments made of myosin and actin protein molecules respectively. Muscles contract and relax to cause movement. Muscle contraction is explained by sliding filament theory of muscle contraction. Ca and ATP are required for muscle contraction. Vertebrate skeleton is made of bone and cartilage . Axial skeleton is made of skull and vertebral column and appendicular skeleton is made of girdles and limbs. Hereditary muscular and skeletal disorders are myaesthenia gravis and muscular dystrophy. Arthitis and Rheumatism are bone disorders. Osteoporosis to softening is the bones due to Ca and Vitamin D deficiency. Gout results from increase in level of uric acid in blood. Plant movements may be tropic movements or nastic movements. Movement is a characteristic of living beings. It means a temporary or permanent displacements of the body or its parts. Locomotion is the displacement of the entire body from one place to another. It is a characteristic of protoctists and animals. Cilia and flagella are organslles which help in movement. Ciliary protozoa Locomote with the help of cilia. Human sperms, certain algae like Chlamydomonas move from one place to another with the help of flagella. Cilia are many and move together causing a wavy motion. Flagella may be Plants and animals one or two and with whip like strokes help in Locomotion. Most animals carry out Locomotion with the help of muscles. Muscles are made of muscle fibres. Muscle fibres have protein filaments called myofilaments. Actin and myosin filaments in a muscle fibre (muscle cell) slide over each other to cause Locomotion. Hence the muscle is said to contract through sliding of these two kinds of myofilaments and this is termed sliding model of muscle contraction. Apart from actin and myosin protein molecules, two other protein molecules named Troponin and Tropomyosin participate in muscle movement. The unit of contraction is termed a sarcomere and it contains both the myofilaments which slide between Z lines.

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Nerve impulse stimulates muscle movement. Human skeleton is divided into axial skeleton which includes skull and vertebral column and appendicular skeleton comprised of bones of girdles and limbs. Bones are connective tissues made of ossein and cartilage which are also part of human skeleton. Bones are joined to each other by ligaments & to muscles by tendons. Muscular & Skeletal disorders include Muscular dystrophy, arthritis, Myaesthenia graive, Osteoporosis and gout.

Exercises 1. Distinguish between the following pairs of terms: (i) movement and locomotion (ii) thick and thin myofilaments (iii) tendon and ligament (iv) cilia and flagella (v) tropic and nastic movement 2. Enlist the steps in muscle contraction as explained by sliding filament theory. 3. Answer in one word or sentence (i) What is the shape of actin molecule? (ii) What is the chemical nature of troponin and tropomyosin? (iii) What is meant by recovery stroke of cilia? (iv) Give an example each of geotropism and phototropism. (v) Why do we say that vertebrate muscle contraction is energy dependent?