20- LOCOMATION AND MOVEMANT

CHAPTER NO.20 LOCOMOTION AND MOVEMENT

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RECAPITULATION:In this chapter of “Types of movement ”, we have learnt;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.Cells of the human body show three main types of movements There are three main types of movements shown by the cells of the human body, viz., amoeboid, ciliary and muscular.

1 Amoeboid (Pseudopodial) Movement:

2 Ciliary Movement:

3 Muscular Movement: .

4 Flagellar Movement:

1 is achieved by pseudopodia and involves the flow of cytoplasm as extensions of the organism. Movement occurs when the

cytoplasm slides and forms a pseudopodium in front to pull the cell forward.

Some examples of organisms that exhibit this type of locomotion are amoebae

(such as Amoeba) and slime molds, as well as some cells in humans suchas

leukocytes.

2 refers to the rhythmic movement of cilia, which causes movement of the fluid or the cell.Cilia are present in the epithelial lining such as the fallopian tube, respiratory tract, where they help in the movement of fluid as well as trap any external particles in the mucus.

3.This basic mechanism is used in the majority of vertebrates, including

humans. The universal property of this mechanism is to exert a force by

alternate contraction and relaxation. Movement of our limbs, jaws, tongue, etc.

require muscular movement. This is a more complex movement which involves muscle fibres, which have the ability to contract and relax. This type of movements is seen in all higher vertebrate

4 Human sperms (typical example of flagellated cells) exhibit the flagellar movement. The flagellum is the propulsion equipment for the movement of sperm towards the ovum. The whip like movement of the tail and the middle piece of the sperm.

“LETS US KNOW WHAT WE HAVE LEARNT

PART A VERY SHORT ANSWER QUESTIONS

(A)MCQ

1.Human body exhibits type of movment is:

(a) Amoeboid movement

(b) Ciliary movement

(c)Muscular movement

(d)All the above

2.Ciliary movement can be seen in_____

(a) In Oviduct

b) In Trachea

c) In Vasa Efferentia

d) All the above

3._______is not included under type of movememt in organisms.

(a) Muscular movement

b) Amoeboid movement

c) Joining process

d) Ciliary movement

(B )TRUE / FALSE

Our body like macrophages and leucocytes blood exhibit amoeboid movement.Movement of our limbs, jaws , tongue require Ciliary movement.

(C)Fill ups

The coordinated movement of in the trachea help us in removing dust particles .

Some specialised cells in our body like macrophages and leucocytes.blood exhibit movement.

PART (B ) Short Question / Answer

What is the significance of locomotion in animals?

PART (C ) Long question / answer

Explain types of movement with example?

ANSWER KEY PART A

(A)MCQ

1 (D)ALL OF ABOVE

2 (D) ALL OF ABOVE

3 (C) JOINING PROCESS

(B) TRUE \ FALSE

1 TRUE

2 FALSE

(C) FILL THE BLANKS :

1 Cilia

2 Amoeboid movement

PART B SHORT ANSWER TYPE QUESTIONS .

ANS 1 In animals, locomotion plays an important role in helping them to move from

one place to another. Animals move for many reasons to support their living.Therefore they walk, run, jump, fly, swim and to escape from their predators.

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INTRODUCTION:A muscle is a group of fibrous tissue in a human or animal body that has the ability to contract, producing movement in or maintaining the posture of parts of the body.Muscle is a specialised tissue of mesodermal origin. About 40-50 per cent of the body weight of a human adult is contributed by muscles.

PPROPERTIES OF MUSCLE TISSUE: The main properties of muscle tissue

are:

1. Contractility: Itis the ability of muscle cells to forcefully shorten.

2. Excitability: It is the ability to respond to a stimulus, which may be delivered from a motor neuron or a hormone.

3. Extensibility: It is the ability of a muscle to be stretched.

4. Elasticity: Itis the ability to recoil or bounce back to the muscle's original

length after being stretched.

TYPES OF NMIUSCLES: Muscles are of three types on the basis of location,appearance and nature of regulation of their activities.

|. Skeletal muscles

2. Visceral muscles

3, Cardiac muscles

1. Skeletal muscles: These muscles are closely associated with the skeletal

components of the body. They have a striped appearance under the microscope and hence are called striated muscles. As their activities are under the voluntary control of the nervous system, they are known as voluntary muscles too. They are primarily involved in locomotory actions and changes of body postures.

2. Visceral muscles: They are located in the inner walls of hollow visceral

organs of the body like the alimentary canal, reproductive tract, etc. They do not

exhibit any striation and are smooth in appearance. Hence, they are called

smooth muscles (nonstriated muscle). Their activities are not under the voluntary control of the nervous system and are therefore known as involuntary muscles. They help in the transportation of food through the digestive tract and gametes through the genital tract.

3. Cardiac muscles: These muscles are located in the heart. Based on appearance, cardiac muscles are striated. They are involuntary in nature as the nervous system does not control their activities directly.

STRUCTURE OF SKELETAL MUSCLES:Each skeletal muscle consists of various integrated tissues. These tissues include the skeletal muscle fibers, blood vessels, nerve fibers, and connective tissue.Each skeletal muscle has three layers of connective tissue called “mysia’” -epimysium, perimysium and endomysium (Figure 1).

1. Each muscle is wrapped in a sheath of dense, irregular connective tissue called the epimysium, which allows a muscle to contract and move powerfully while maintaining its structural integrity. The

epimysium also separates muscle from other tissues and organs in the area, allowing the muscle to move independently.

2. Each skeletal muscle in our body is made of a number of muscle bundles or fascicles held together by a middle layer of connective tissue called perimysium.

3. Each muscle bundle contains a number of muscle fibres, encased in a thin connective tissue layer of collagen and reticular fibers called the endomysium. The endomysium contains the extracellular fluid and nutrients to support the muscle fiber. These nutrients are supplied via blood to the muscle tissue.

Each muscle fibre is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm. Muscle fibre is a syncitium as the sarcoplasm

contains many nuclei.A characteristic feature of the muscle fibre is the presence of a large number of parallelly arranged filaments in the sarcoplasm called

myofilaments or myofibrils or sarcomere. Each myofibril has alternate dark

and light bands on it.A detailed study of the myofibril (sarcomere) has established that the striated appearance is due to the distribution pattern of two important

proteins — Actin and Myosin. The light bands contain actin and is called I-

band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin. Both the proteins are arranged as rod-like structures, parallel to each other and also to the longitudinal axis of the myofibrils (Figure 2).Actin filaments are thinner as compared to the myosin filaments, hence are commonly called thin and thick filaments respectively. In the centre of each ‘I’ band is an elastic fibre called ‘Z’ line which bisects it.

The thin filaments are firmly attached to the ‘Z’ line. The thick filaments in

the ‘A’ band are also held together in the middle of this band by a thin fibrous membrane called ‘M’ line. The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils. The portion of the myofibril between two successive ‘Z’ lines is considered as the functional

unit of contraction and is called a sarcomere.In a resting state, the edges of thin filaments on either side of the thick

filaments partially overlap the free ends of the thick filaments leaving the

central part of the thick filaments. This central part of thick filament, not

overlapped by thin filaments is called the ‘H’ zone.

STRUCTURE OF CONTRACTILE PROTEIN

Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically

wound to each other.Each ‘F’ actin is a polymer of monomeric ‘G' (Globular) actins. Actin contain two other proteins - tropomyosin and troponin.Two filaments of tropomyosin run along the grooves of F-actin double helix Troponin has three units. It is distributed at regular intervals on the tropomyosin. In the resting state a subunit of troponin masks the active binding sites for myosin on the actin filaments (figure 3).‘

Each myosin (thick) filament is also a polymer of many monomeric proteins called Meromyosins constitute one thick filament (figure 4).

Each meromyosin has two parts-Heavy meromysin (HMM) or cross arm (globular head with a short arm}- It projects outward.

Light meromyosin (LMM) or tail. The globular head is an active ATPase

enzyme and has binding sites for ATP and active sites for actin.

FUNCTIONS OF MUSCLE TISSUE:

1. Itis responsible for the movement of body parts.

2. It maintains body equillibrium.

3. It helps in collecting informations about changes in external environment.

4. It provides support to skeletal structures.

5. It control facial expression and gestures.

LET US KNOW WHAT WE HAVE LEARNT!!

PART: (A) VERY SHORT ANSWER TYPE QUESTIONS:

A. Multiple Choice Questions:

1. What separates one sarcomere from another?

a) |-band

b) H-Zone

c) Z-Discs

d) A-band

2. Which of the following muscle tissue are voluntary in nature?

a) Cardiac muscle

b) Visceral muscle

c) Skeletal muscle

d) None of the above.

3. Which of the following statement is true?

a) Actin is a regulatory protein

b) Storage is one of the property of muscular tissue

c) Sarcomere are the functional unit of myofibril

d) H- zone contains all thin filaments

4. Which is most likely to extend the entire length of a muscle?

a) Sarcomere

b) Myofibril

c) Myosin filament

d) M-line

5. The ends of the actin filaments are anchored (attached) to the:

a) M-line

b) Z-line

c) Perimysium

d) Sarcomere

B. Fill Ups:

1. Skeletal muscles are also called -----

2. Actin filaments are thinner as compared to ----------filaments.

3. The light band is also called------

C. True/False:

1. Cardiac muscles are present only in the heart.

2. The distance between two successive Z-lines are called sarcomere.

3. Light band is called A band.

ANSWER KEY: PART-A

A. MCQs:

1. C)Z discs

2. C) Skeletal muscles

3. C) Sarcomere

4. B) Myofibril.

5. B) Z-line.

B. Fill Ups:

1. Voluntary muscles

2. Myosin

3. Isotropic band

C. True/False:

1. True

2. True

3. False

PART (B): SHORT ANSWER TYPE QUESTIONS

1. What are striated and non striated muscles?

2. Enlist four properties of muscle tissue.

3. Where are cardiac muscles located in our body?

PART (C): LONG ANSWER TYPE QUESTIONS:

1. Explain the structure of skeletal muscles with the help of diagram.

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Muscle is a specialized tissue of mesodermal origin. About 40-50 percent of the body weight of human adult is contributed by muscles.Muscles have specialized properties like excitability, contractility,extensibility, and elasticity. Movement of our limbs, jaws, tongue, etc.require muscular movements.

The contractile property of muscles are effectively used for locomotion and other movements by human beings and other

multicellular organisms.Locomotion requires a perfect coordinated activity of muscular,

skeletal and neural system.

Myofilaments and Contractile proteins:

Each organized muscle eg. Skeletal muscle is made up of a number of muscle bundles.

Each muscle bundle contains a number of muscle fibres.In each muscle fibre there is presence of a large number of parallely

arranged filaments called myofilaments or myofibrils - Actin and Myosin.Each actin (thin) filament is 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.In the 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 called Meromyosins constitute one thick filament.Each meromyosin has two important parts, a globular head with a

short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM).

The HMM component, i.e.; the head and short arm projects outwards at regular distance and angle from each other from the surface of a polymerised myosin filament and is known as cross arm.The globular head is an active ATPase enzyme and has binding sites

for ATP and active sites for actin.

Mechanism of muscle contraction:Most satisfactory theory of muscle contraction is Sliding filament theory proposed by A.F. Huxley, H. E. Huxley and J. Hansen in

1954.Sliding filament theory states that contraction of muscle fibre takes

place by the sliding of the thin filaments over the thick filament.A motor neuron along with the muscle fibre connected to it constitute a motor unit.The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor end plate.

Muscle contraction is initiated by a neural signal sent by the central nervous system via a motor neuron to a neuro-muscular junction.A neural signal reaching this junction releases a neurotransmitter

Acetyl! choline.|t generates an action potential in the sarcolemma and this spreads —through the muscle fibre.

It causes release of calcium ions into the sarcoplasm.

Increase in calcium ions level leads to binding of calcium with a

subunit of troponin on actin filaments.

It removes the masking of active sites for myosin. The myosin head now binds to the exposed active sites on actin to form a cross bridge.This pulls the attached actin filaments towards the centre of 'A’ band.

The Z line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e.. contraction.During shortening of the muscle, i.e., contraction, the “I” bands get reduced, whereas the 'A' bands retain the length.The myosin, releasing the ADP and Pi, goes back to its relaxed state.

A new 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** lons are pumped back to the

sarcoplasmic cisternae resulting in the masking of actin filaments.This causes the return of 'Z' lines back to their original position, i.e.,relaxation. The reaction time of the fibres can vary in different

muscles.Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen in them, causing fatigue. Muscle contains a red coloured oxygen storing pigment

called myoglobin.Myoglobin content is high in some of the muscles which gives a

reddish appearance. Such muscles are called the Red fibres.These muscles contain plenty of mitochondria which can utilise the

large amount of oxygen stored in them for ATP production also called aerobic muscles.Some of the muscles possess very less quantity of myoglobin and

therefore, appear pale or whitish. These are the White fibres.Number of mitochondria are also few in them, but the amount of

sarcoplasmic reticulum is high. They depend on anaerobic process for energy.

“LET US KNOW WHAT WE HAVE LEARNT ?”

PART A: VERY SHORT ANSWER TYPE QUESTIONS

(A) MCQs

1. Calcium, during muscle contraction binds with

(a) Tropomyosin

(b) Troponin

(d) none of the above

2. In contracted state of a skeletal muscle fibre

(a) A band retains its length

(b) | band retains its length

(d) both (a) and (b)

3. Where does the stimulation of muscle fibers by a motor neuron take place

(a) myofibril

(b) transverse tubules

(d) neuromuscular junction

4. Which substance causes action potential at the neuromuscular junction

(a) Tropomyosin

(b) Troponin

(d) both (a) and (b)

5. Increase in level of which ions play a role in exposing the active sites of actin filaments?

(a) Mg++

(b) Ca++

(d) K+

(B) TRUE/FALSE:

1. Binding of calcium ions with the subunit of troponin causes the masking of the active sites of actin filaments.

2. During muscle contraction A bands get reduced and | bands retain the length.

3. During contraction the myosin head pulls the attached actin filaments towards the centre of 'A' band.

(C) FILL IN THE BLANKS:

1. Mechanism of muscle contraction is best explained by theory.

2. lines come back to its original position during relaxation of muscle.

ANSWER KEY : PART (A)

(A) MCQs

Answer 1: (b) Explanation : Increase in calcium ions level leads to binding of calcium with a subunit of troponin on actin filaments.

Answer 2: (a) Explanation : during shortening of the muscle, i.e.,contraction, the “I” bands get reduced, whereas the 'A' bands retain the length.

Answer 3: (d) Explanation : The stimulation takes place at the junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor end plate

Answer 4 : (c) Explanation : eural signal reaching this junction releases a

neurotransmitter Acetyl choline.

Answer 5 : (b) Explanation : Increase in calcium ions level leads to binding of calcium with a subunit of troponin on actin filaments. It removes the masking of active sites of actin filaments for myosin.

(B) TRUE/FALSE

1. False ; The binding of calcium with a subunit of troponin on actin filaments removes the masking of active sites for myosin.

2. False; During muscle contraction | bands get reduced and A bands retain the length.

3. True ; During contraction the myosin head binds to the exposed active

sites on actin filaments to form a cross bridge & pulls the actin filaments

towards the centre of 'A' band. The Z line attached to these actins are also

pulled inwards causing a shortening of the sarcomere, i.e.. contraction.

(C) FILL IN THE BLANKS :

ANSWER 1: Sliding filament theory

ANSWER 2: Z lines

PART B : SHORT ANSWER TYPE QUESTIONS

1. What is the role of calcium ions in muscle contraction ?

2. How the relative size of different bands and zones varies during contraction and relaxation of muscles ?

PART C : LONG ANSWER TYPE QUESTIONS

1. Explain the sliding filament theory for the mechanism of muscle contraction ?

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INTRODUCTION:HUMAN SKELETAL SYSTEM

+Skeletal system consists of a framework of bones and a few cartilages.This system has a significant role in movement .Bone and cartilage are specialised connective tissues.The bone has a very hard matrix due to calcium salts in it.The cartilage has slightly pliable matrix due to chondroitin salts.In human beings, this system is made up of 206 bones and a few cartilages.

Skeletal system is grouped into two principal divisions

skeleton.The skull, vertebral column, sternum and ribs constitute axial skeleton.

The bones of the limbs alongwith their girdles constitute the appendicular

skeleton.

THE AXIAL SKELETON

THE SKULL The skull is composed of two sets of bones -Cranial(8)and facial(14) that totals to 22 bones. Cra nial= They form the hard protective outer covering,cranium for the brain.A single U-shaped bone called hyoid is present at the base of the buccal

cavity and it is also included in the skull.Each middle ear contains three tiny bones - Malleus, Incus and Stapes,

collectively called Ear Ossicles.

The skull region articulates with the superior region of thevertebral column

with the help of two occipital condyles (dicondylic skull).Our vertebral column (Figure 2) is formed by 26 serially arranged units called vertebrae and is dorsally placed.It extends from the base of the skull and constitutes the main

framework of the trunk .First vertebra is the atlas and it articulates with the occipital condyles. vertebral column is differentiated into cervical (7),

thoracic (12), lumbar (5), sacral (1-fused) and coccygeal (1-fused)regions starting from the skull. The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back.

Sternum is a flat bone on the ventral midline of thorax.There are 12 pairs of ribs.Each rib is a thin flat bone connected dorsally to the vertebral column and

ventrally to the sternum.It has two articulation surfaces on its dorsal end and is hence called bicephalic.First seven pairs of ribs are called true ribs. Dorsally, they are attached to the

thoracic vertebrae and ventrally connected to the sternum with the help of

hyaline cartilage.The 8th, 9th and 10th 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 2 pairs (11* and 12th) of ribs are not connected ventrally and are therefore, called floating ribs.Thoracic vertebrae, ribs and sternum together form the rib cage (Figure 3).

we THE APPENDICULAR SKELETON

The bones of the limbs alongwith their girdles constitute the appendicular skeleton. Each limb is made of 30 bones.

The bones of the hand (fore limb) are humerus, radius and ulna, carpals

(wrist bones (8), metacarpals (palm bones(-5) and phalanges (digits 14 in

number) (Figure 20.9). Femur (thigh bone - the longest bone). Tibia and fibula, tarsals (ankle bones( 7), metatarsals (5) and phalanges (digits - 14) are

the bones of the legs (hind limb) (Figure

A cup shaped bone called patella cover the knee ventrally (knee cap).Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with the axial skeleton. Each girdle is formed of two halves.

Each half of pectoral girdle consists of a clavicle and a scapula . Scapula is a

large triangular flat bone situated in the dorsal part of the thorax between the

second and the seventh ribs.The dorsal, flat, triangular body of scapula has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion.The clavicle articulates with this. Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus) form the shoulder joint.Each clavicle is a long slender bone with two curvatures. This bone is commonly called the collar bone.Pelvic girdle consists of two coxal bones .Each coxal bone is formed by the fusion of three bones-ilium, ischium and pubis.At the 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.

LET US KNOW WHAT WE HAVE LEARNT!

PART A MCQs

1. How many bones does the adult human body have ?

a. 210

b. 206

c. 180

d. 126

2. The axial skeleton is comprised of

a.80 bones

b. 126bones

c. 26 bones

d. 206 bones

3.false ribs are formed by

a. first 7 pairs of ribs

b. 8" 9 10" pairs of ribs

c. last 2 pairs of ribs

d. 7", 8" 9" pairs of ribs

4. which of the following is not a part of appendicular skeleton

a. vertebral column

b. ulna

c. tarsal

d. pelvic girdle

5.Acetabulum is a cavity found in

a. fore limb

b. pelvic girdle

c.pectoral girdle

d. sternum

2.FILL UPS

1. is a flat bone on the ventral midline of thorax.

2. is the longest bone of the human skeleton system.

3. A cup shaped bone that covers the knee is called .

3.true /false

1.each coxal bone is formed by fusion of two bones .

2.There are 12 pairs of ribs.

PART B SHORT ANSWER TYPE QUESTIONS

a.Name the constituents of axial skeleton?

B. Name three bones of ear ossicles?

c. Name various bones of fore limb?

PART C LONG ANSWER TYPE QUESTIONS

1 .Write a note on appendicular skeleton.

2.Write a note on axial skeleton.

3.Write a note on human skeletal system.

ANSWER KEY PART A

Multiple choice questions

1.b ) 206 bones (the adult human skeleton contain 206bones)

2.a) 80 bones(80 bones forms the axial skeleton system)

3.b)8",9° 10" pair of ribs(These three pairs of ribs do not articulate directly

with the sternum but joins the seventh rib with the help of hyaline cartilage

these are called false ribs)

4 a) vertebrae all other bones are part of appendicular skeleton)

5.b)pelvic girdle(At the point of fusion of coxal bones a cavity called

acetabulum is formed which is a part of pelvic girdle)

Q2 FILL UPS

1.sternum

2.femur(thigh bone)

3.patella

TRUE / FALSE

1.false(each coxal bone is formed by fusion of three bones illium,ischium and

pubis)

2.true

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JOINTS:Joints are essential for all types of movements involving the bony parts of the body. Joints hold the skeleton together and support movement. Joints are points of

contact between bones and cartilages.

Force generated by muscies is used to carry out movement through joints, where

the joint acts as a fulcrum. The movability of these joints vary depending upon

different factors.Joints have been classified into three major structural forms, namely, fibrous,cartilaginous and synovial.

FIBROUS JOINTS :Fibrous joints are joints connected by fibrous tissue consisting mainly of collagen.These are fixed joints where bones are united by a layer of white fibrous tissue of varying thickness. In the skull, the joints between the bones are called sutures.Such immovable joints are also referred to as synaethroses. These joints do not allow any movement.

CARTILAGINOUS JOINTS:Cartilaginous joints are connected entirely by cartilage (fibro cartilage or hyaline).Cartilaginous

joints allow more movement between bones than a fibrous joint but less than the highly mobile synovial joint. Cartilaginous joints also forms the growth regions of immature long bones and the intervertebral discs of the spinal column

SYNOVIAL JOINTS:Synovial joints are characterised by the presence of a fluid filled synovial cavity between the articulating surfaces of the two bones. Such an arrangement allows considerable movement. These joints help in locomotion and many other movements.

Examples —Ball and socket joint ( Between humerus and pectoral girdle )

MUSCULAR AND SKELETAL DISORDERS:The human body, like most machines, undergoes wear and tear over time,because of age or misuse. This wear and tear lead to disorders. The muscular and skeletal system is also subject to diseases and this affects the human body adversely. Below are mentioned a few Muscular and Skeletal Disorders.LIST OF DISORDERS

Myasthenia gravis: It is the abnormal weakening and rapid fatigue of certain

muscles. It is due to a breakdown in communication between nerves and muscles.

Muscular Dystrophy: This is mostly hereditary. It causes progressive weakness

and degeneration of skeletal muscle, which controls movement.

Tetany: It is caused due to low blood calcium and is characterized by rapid or wild spasms.

Arthritis: Inflammation of one or more joints. Arthritis leads to the limited

movement of joints and pain.

Osteoporosis: The chances of contracting this disease increases with age,resulting in reduced bone mass and fragile bones, thus increasing chances of fracture. Low levels of oestrogen are a common cause.

Gout: This too is the inflammation of joints, but due to an accumulation of uric acid crystals.

LET US KNOW WHAT WE HAVE LEARNT!

PART-A VERY SHORT ANSWER TYPE QUESTIONS

(a) MULTIPLE CHOICE QUESTIONS

1. The joint in our elbow is an example of

A Hinge joint

B Ball and socket joint

C Pivot joint

D Gliding joint

2. The type of joint between the skull bones are is

A Fibrous

B Cartilaginous joint

C Synovial joint

D Hinge joint

3 The joint between atlas and axis is

A Saddle joint

B Angular joint

C Pivot joint

D Cartilaginous joint

4 Which of these is an autoimmune disorder?

A Arthritis

B Osteoporosis

C Gout

D Myasthenia gravis

5 Which of these disorders is caused due to low calcium ions in body fluid

A Muscular dystrophy

B Gout

C Tetany

D Osteoporosis

(b) TRUE / FALSE

1. Decreased levels of oestrogen causes osteoporosis.

2. All joints in the human body are movable.

3. Arthritis leads to the limited movement of joints.

(b)FILL IN THE BLANKS

1. Joints of bones help in the of body.

2. is caused due to accumulation of uric acid crystals.

PART B SHORT QUESTION / ANSWERS

1. Define “joint ”. How many types of joints are there in human body?

PARTC— LONG QUESTION / ANSWERS

1. Describe various disorders of muscular and skeletal system.

ANSWER KEY

PART A VERY SHORT ANSWER TYPE QUESTIONS

(a) MULTIPLE CHOICE QUESTIONS

1. (A) Hinge joint

2 (A) Fibrous joint

3 (C) Pivot joint

4 (D) Myasthenia gravis

5 (C) Tetany

(b) TRUE & FALSE

1. True

2. False

3. True

(c) FILL IN THE BLANKS

1. Movement

2. Gout

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RECAPITULATION:In this chapter of “Locomotion and movement”, we have learnt;

Locomotion is the voluntary movement of an individual from one place to another.

1. Contractile Proteins Each thin filament (actin) is made of two ‘F’ actins helically wounded to each other.

2. 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.

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

(3)Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with the axial skeleton.

(4)Joints — are points of contact between bones, or between bones and cartilage.

a. Fibrous joints— do not allow any movements. Present in flat skull

bones to form cranium.

b. Cartilaginous joints— bones are held together with the help of cartilage present in vertebrae. Permits limited movements.

c. Synovial joints— fluid filled synovial cavity, provide considerable movements. Ball and socket joint, hinge joints, pivot joints, gliding joints etc.

5. Disorders of Muscular and Skeletal System Myasthenia gravis, Muscular Dystrophy, Osteoporosis, Arthritis, Gout, Tetany

LET US KNOW WHAT WE HAVE LEARNT!

NCERT EXERCISE QUESTIONS WITH SOLUTIONS

Q2. Define sliding filament theory of muscle contraction.

Ans1. The sliding filament theory describes the process of muscle contraction in

which the thick filaments (myosin) of muscle fibres slide past the thin filaments

(actin), resulting in the shortening of the myofibril. Each muscle fibre consists of

alternate light and dark bands. They contain a unique contractile protein called

actin and myosin respectively. Myosin is a thick contractile protein found in the dark

band and is known as the A-band or Anisotropic band. Actin is a thin contractile protein found in the light band and is known as the I-band or Isotropic band. Each l-band is bisected by an elastic fibre known as the Z line. The thin filament (actin) is firmly attached to the Z line. The H-zone is the central portion of the thick filament (myosin) that is not overlapped by the thin filament. Sarcomere, the functional unit of contraction, is the portion of the myofibril between two successive Z lines.During muscle contraction, the myosin heads come into close contact with the thin

filaments. As a result, the thin filaments are pulled towards the centre of the

sarcomere as well as the Z line attached to the actin filaments is also pulled, causing

shortening of the sarcomere. The length of the A-band or anisotropic band remains

constant as its original length whereas the I-band or isotropic band shortens and the

H-zone disappears.

Q3. Describe the important steps in muscle contraction.

Ans 2. During skeletal muscle contraction, the thick filament slides past the thin

filament (actin) via repeated binding, releasing myosin along the filament. This entire process takes place in sequential order.

Step 1: Muscle contraction is initiated by a signal that is sent by a CNS (Central

nervous system) through a motor neuron. A neuromuscular junction or motor-end

plate is a junction between a motor neuron and the sarcolemma of the muscle fibre.

When a signal reaches the neuromuscular junctions, Acetylcholine (a

neurotransmitter) is released which results in the generation of an action potential in

the sarcolemma.

Step 2: This spreads through the muscle fibres, resulting in the release of calcium

ions from the sarcoplasmic reticulum into the sarcoplasm.

Step 3: The increased calcium ions (Ca2+) in the sarcoplasm leads to the

activation of actin sites. Calcium ions (Ca2+) bind with the subunit of troponin on

actin filaments and thus remove the masking of active sites for myosin. Hence, active

sites on actin are exposed and this allows myosin heads to attach to this site.

Step 4: The myosin head now attaches to the exposed site of actin to form a cross-

bridge by utilizing energy from ATP hydrolysis. The actin filaments are pulled towards the centre of the A-band. The Z line attached to the actin filaments is also pulled,causing shortening of the sarcomere, i.e., the contraction of the muscle occurs. It is clear from the above steps, that during contraction, the length of the A-band or anisotropic band remains constant as its original length whereas the |-band or isotropic band gets reduced.

Step 5: After muscle contraction, the myosin head goes back to its relaxed state,

releasing ADP and inorganic phosphate (Pi). Anew ATP molecule binds and detaches myosin, thus the cross-bridges are broken.

Step 6: This process of formation and breaking down is repeated causing further

sliding. This process continues until the calcium ions are pumped back to the

sarcoplasmic cisternae. Hence, the calcium ions concentration decreases. This

results in masking the actin filaments and leading to muscle relaxation.

Q4. Write true or false. If false change the statement so that it is true.

(a) Actin is present in thin filament

(b) H-zone of striated muscle fibre represents both thick and thin filaments.

(d) There are 11 pairs of ribs in man.

(e) Sternum is present on the ventral side of the body.

Ans 3.

(a) True- Actin is present in thin filament

(b) False- H-zone of striated muscle fibre represents both thick and thin filaments.

Corrected statement: H-zone of the striated muscle fiber represents only thick

filaments

(d) False- There are 11 pairs of ribs in man Corrected statement: There are 12 pairs of ribs in man.

(e) True- Sternum is present on the ventral side of the body

Q7. What are the different types of movements exhibited by the cells of human

body?

Ans 4. Movement is considered to be one of the fundamental characteristics which is

observed in the living entities. The different types of movements exhibited by the human body cells are:

1. Amoeboid Movement — Leucocytes found in blood exhibit this type of movement.

Leucocytes from the circulatory system move towards the injury site when there is a

damage to the tissue in order to initiate an immune response.

2. Muscular movement — The muscle cells exhibit this type of movement

3. Ciliary movement — Sex cells (sperms and ova) exhibit this type of movement.

This movement facilitates the passage of ova via the fallopian tube on its way to the uterus.

Q.8. How do you distinguish between a skeletal muscle and a cardiac muscle?

Ans 8. The differences between a skeletal muscle and a cardiac muscle is as follows:

Q.9. Name the type of joint between the following:-

(a) atlas/axis

(b) carpal/metacarpal of thumb

(d) femur/acetabulum

(e) Between cranial bones

(f) Between pubic bones in the pelvic girdle

Answers:The types of joints are as follows:

(a) atlas/axis — Pivot joint

(b) carpal/metacarpal of thumb — Saddle joint

(d) femur/acetabulum — Ball and socket joint

(e) Between cranial bones — Fibrous joint

(f) Between pubic bones in the pelvic girdle — cartilaginous joint

Q10. Fill in the blank spaces:

(a) All mammals (except a few) have cervical vertebra.

(b) The number of phalanges in each limb of human is

namely___ and .

(d) In a muscle fibre Ca++ is stored in

(e) and pairs of ribs are called floating ribs.

(f) The human cranium is made of bones

Answers:

(a) Seven

(b) Fourteen

(d) Sarcoplasmic reticulum

(e) Eleventh, twelfth

(f) Eight

A207

RECAPITULATION:Dear students, we have learnt all about muscle contraction and skeletal system in previous assignments , now we are going to revise important

questions and diagrams of this chapter.

ONE MARK QUESTIONS

Q1. Name the functional contractile unit of a muscle.

Ans. The functional contractile unit of a muscle is known as a sarcomere.

Q2. Define a sarcomere.

Ans. Sarcomere, the functional unit of contraction, is the portion of the

myofibril between two successive Z lines.

Q3. Name of the longest bone of the human body.

Ans. The femur also called the thigh bone is the longest bone of the human body.

Q4. Give the name of the first vertebra.

Ans. The name of the first vertebra is Atlas.

Q5. How many bones are present in the human skeleton?

Ans. The human skeleton contains 206 bones.

Q6. Name the proteins which help in muscle contraction.

Ans. Myosin and actin

Q7. Differentiate between A-band and I-band.

Ans. A-band is a dark band having myosin filaments.I-band is a light band having thin filament

Q8. Which type of movable joint makes the hip joint?

Ans. Ball and Socket joint.

Q9. Name the tissue which connects muscles to the bone?

Ans. Tendon is a fibrous connective tissue that connects muscles to the bones.

Q10. What is arthritis?

Ans. Arthritis is a condition that causes inflammation of one or more joints, pain and stiffness that can worsen with age.

TWO MARKS QUESTIONS:

Q1. Define a joint.

Ans: A joint is the part of the body at which two or more bones articulate to allow

movement. The surfaces of the two bones are opposite to each other at the joints.

These joints assist in the movement of bones in several different ways. The six types of freely movable joints are- ball and socket joint, saddle joint, pivot joint, hinge joint,condyloid joint, and gliding joint.

Q2. What are floating ribs? How many of them are there?

Ans: The last two pairs of ribs, i.e., the 11th and 12th pairs are known as the floating ribs. The floating ribs are smaller in size and have cartilaginous tips. They are only attached dorsally to the respective thoracic vertebrae, so they are also known as the vertebral ribs, and are free ventrally, hence the name "floating ribs".

Q3. Name the type of joint between the following: -

(a) atlas/axis

(b) carpal/metacarpal of thumb

(d) femur/acetabulum

(e) Between cranial bones

(f) Between pubic bones in the pelvic girdle

Ans. The types of joints are as follows:

(a) atlas/axis — Pivot joint

(b) carpal/metacarpal of thumb — Saddle joint

(d) femur/acetabulum — Ball and socket joint

(e) Between cranial bones — Fibrous joint

(f) Between pubic bones in the pelvic girdle — cartilaginous joint.

THREE MARKS QUESTIONS:

Q1. Explain the sliding filament theory of muscle contraction.

Ans. The sliding filament theory describes the process of muscle contraction in which

the thick filaments (myosin) of muscle fibres slide past the thin filaments (actin),resulting in the shortening of the myofibril. Each muscle fibre consists of alternate light and dark bands. They contain a unique contractile protein called actin and myosin respectively.yosin is a thick contractile protein found in the dark band and is known as the A-band

r Anisotropic band. Actin is a thin contractile protein found in the light band and is known s the I-band or Isotropic band. Each I-band is bisected by an elastic fibre known as the line. The thin filament (actin) is firmly attached to the Z line. Tne H-zone is the central ortion of the thick filament (myosin) that is not overlapped by the thin filament.

arcomere, the functional unit of contraction, is the portion of the myofibril between two uccessive Z lines.

During muscle contraction, the myosin heads come into close contact with the thin

filaments. As a result, the thin filaments are pulled towards the centre of the sarcomere as well as the Z line attached to the actin filaments is also pulled, causing shortening of the sarcomere. The A-band, or anisotropic band, stays the same length as before,whereas the I-band, or isotropic band, shortens and the H-zone vanishes.

Q2. What are the three types of muscle tissue? Write two characteristic points

about the structure of each of them?

Ans: Types of muscle tissue: - Muscle tissue is of three types- Skeletal, visceral (smooth) and cardiac.

(i) Skeletal/Striated Muscles:The cells of the skeletal muscles are straight, cylindrical, non-branched and ultinucleated. They show prominent striations and are thus called striated.

hey are voluntary muscles as their activities are under the voluntary control of the ervous system.

(ii) Visceral/Smooth/Non-Striated Muscles:

The cells of the smooth muscles are narrow, spindle-shaped and uni-nucleated. They

do not have any striation and are smooth in appearance, hence called smooth or non-

striated muscle.They are involuntary muscles as their activities are not directly controlled by the nervous system. They are controlled by the nervous system, endocrine system and different chemicals.

(iii) Cardiac Muscles:The cells of the cardiac muscles are cylindrical, branched and uni-nucleated. They are striated.

They are involuntary muscles as their activities are not directly controlled by the nervous system. They are controlled by the central nervous system, endocrine system and different chemicals.

3.Describe any three disorders of the muscular system.

Ans: Three disorders of the muscular system are

i)Myasthenia Gravis: This is a type of autoimmune disease.breakdown in communication between nerves and muscles causes this condition.t affects the neuromuscular junction that causes progressive weakening and aralysis of skeletal muscles. Symptoms are double vision, weakness in the arm nd leg muscles, and difficulties with speech and chewing.

ii) Muscular Dystrophy: It is a genetic disorder that causes weakness and

rogressive degeneration of skeletal muscles. Symptoms include trouble breathing

nd swallowing.

iti) Tetany: It refers to the rapid spasm (wild contraction) or the continued state of ontraction due to low Ca++ in the body fluid and hyperparathyroidism. Symptoms

nclude muscle spasms, speaking and breathing difficulty, numbness in hands and

seizures and heart problems.