CBSE Class 11 Biology Locomotion and Movement Revision Notes

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Locomotion and Movement Revision Class 11 Biology Revision Notes

Class 11 Biology students should refer to the following concepts and notes for Locomotion and Movement Revision in standard 11. These exam notes for Grade 11 Biology will be very useful for upcoming class tests and examinations and help you to score good marks

Locomotion and Movement Revision Notes Class 11 Biology

Human Physiology
(Locomotion and Movement)
1.1 MOVEMENT

Movement is one of the most important characteristics of living organisms.
 
Nonliving objects do not move.
 
Types of Movement
 
Cells of the human body exhibit three main types of movements which are followings :-
(i) Amoeboid (ii) Ciliary (iii) Muscular.
 
(i) Amoeboid movement :
 
Some specialised cells in our body like macrophages and leucocytes in blood exhibit amoeboid movement.
 
It is effected by pseudopodia formed by the streaming of protoplasm (as in Amoeba). Cytoskeletal elements like micro filaments are also involved in amoeboid movement.
 
(ii) Ciliary movement :

Ciliary movement occurs in most of our internal tubular organs which are lined by ciliated epithelium. The coordinated movements of cilia in the trachea help us in removing dust particles and some of the foreign substances inhaled alongwith the atmospheric air. Passage of ova through the female reproductive tract
is also facilitated by the ciliary movement.
 
(iii) Muscular movement :

Movement of our limbs, jaws, tongue, etc, require muscular movement. The contractile property of muscles are effectively used for locomotion and other movements by human beings and majority of multicellular organisms.
 
Note : Locomotion requires a perfect coordinated activity of muscular, skeletal and neural systems.
 
1.2 LOCOMOTION (locus = place + moveo = to move) : Locomotion is the movement of an animal as a whole from one place to another.
 
Locomotion in different animals

(i) Locomotion in Protozoa : Locomotion in protozoans by the help of cilia, flagella and pseudopodia.
 
(ii) Locomotion in Porifera : Sponges are sedentary or fixed animals which are attached to some substratum.
 
(iii) Locomotion in Coelentrates : Locomotion in coelentrates is largely due to the contraction of the epidermal muscle fibres following type of movements take place in coelentrates –
(a) Swimming (b) Floating (c) Climbing
(d) Walking (e) Gliding (f) Somersaulting
 
(iv) Locomotion in Helminths : In helminths (platyhelminthes and aschelminthes) locomotion not required by adult due to parasitic adaptations. However in miracidia (a larva) locomotion by cilia, in cercaria larva by tail. In Ascaris 15% locomotion by cuticle fiber. In planaria locomotion by cilia and muscles.
 
(v) Locomotion in Annelids : Leech, Earthworm and Nereis have well developed circular and longitudinal muscles in the body wall that help these animals to move about. Parapodia and setae helpful for locomotion in nereis. In earthworm also locomotion by setae.
 
(vi) Locomotion in Arthropods : In arthropods locomotion takes place with the help of jointed legs, and a pair of wings.
 
(vi) Locomotion in Mollusca : In all the molluscs, the locomotory organ is a thick walled, muscular, broad or laterally compressed foot. In some molluscs, the foot is modified into eight or ten arms
 
(viii) Locomotion in Echinodermata : In echinoderms such as starfish, the locomotory organs are tubefeet which act on hydraulic pressure phenomena.
 
(ix) Locomotion in vertebrates : In vertebrates, locomotion takes place with the help of skeletal muscles, and skeleton. The locomotory organs are a pair of legs.
 
2. Muscular Tissues
 
 Contraction for motility in the cells results essentially from the interaction of two contractile proteins, actin and myosin. These tissues are obviously responsible for movements of organs and locomotion of the body in response to stimuli.
 
 These develop from embryonic mesoderm except for those of the iris and ciliary body of eyes, which are ectodermal in origin.
 
 The muscle cells are always elongated, slender and spindle-shaped, fibre-like cells, These are, therefore called muscle fibres. These possess large numbers of myofibrils formed of actin and myosin. Muscle cells lose capacity to divide, multiply and regenerate to a great extent.
 
• Study of muscle is called myology.
 
• Based on their location, three types of muscles are identified: (i) Skeletal (ii) Visceral and (iii) Cardiac.
 
2.1 SKELETAL OR STRIATED OR STRIPED MUSCLES

• Most muscles of body are striated. These generally bring about voluntary movements under conscious control of brain and, hence, called voluntary muscles.
 
• Most of these are inserted at both ends upon bones in different parts of the body depend upon these muscles. Hence, these are also called skeletal muscles.
 
• Movements of limbs and the body solely depend upon these muscles. Hence these are also called somatic muscles.
 
• These are also called phasic type of muscles, because contraction in these is rapid, but brief and fatigue occurs quickly.
 
 Each organised skeletal muscle in our body is made of a number of muscle bundles or fascicles held together by a common collagenous connective tissue layer called fascia. Each muscle bundle contains a number of muscle fibres.
CBSE Class 11 Biology Locomotion and Movement Revision Notes
Diagrammatic cross sectional view of a muscle showing muscle bundles and muscle fibres

2.1 (i) Fine structure of striated muscle fibres :

• Striated muscle fibres shows transverse striation in the form of regular alternate dark A (anisotropic) and light I (isotropic) bands.
 
(a) A- band :
The ‘A’ band contains about 120Å thick and 1.8 μ long “myosin filaments”. A slender transverse line, the ‘M’ or Hansen’s line is visible in middle of each ‘A’ band. The major, middle region of ‘A’ band is comparatively lighter, but its terminal parts appear darker. The middle lighter region is called ‘H’ zone.
 
(b) I-band : The I band contains about 60Å thick and 1.0 μ long “actin filament” which are twice as many as myosin filaments. Each I band is divided into two equal halves by a thin, fibrous and transverse zig-zag partition, called ‘Z’ band (‘ Z’ disc) or Krause’s membrane. Each segment of a fibril between two adjacent ‘Z’ bands is called a sarcomere. It is 2.3 μ long in uncontracted mammalian striated fibres.
 
Note : Due to the geomatric bonding pattern, the end of each myosin filament is, thus, encircled by the ends of six actin filaments (hexagon), while the end of each actin filaments is encircled by the ends of three myosin filaments (trigon).
 
2.1 (ii) Ultrastructure of myofilaments :

• At the molecular level, each myosin filament is composed of about 500 thread-like myosin molecules.
 
• Three different kinds of proteins participate in the composition of actin filaments. The major part of an actin filament is a coiled double helical strand whose each arm is a linear polymer of small and globular molecules (monomers) actin protein. Another coiled double helical, but thiner, strand runs along the whole length of actin strand. Each arm of this strand is a polymer of fibre-like molecules of tropomyosin protein. The third protein is troponin.
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2.1 (iii) Structure of Contractile Proteins :

(a) Actin : Each actin filament is made up of the following components-

(A) F- actin : In each actin filament, two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins.

(B) Tropomyosin : Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length.

(C) Troponin : It is a complex protein which 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.

(b) Myosin : 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 fllament 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.

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2.1 (iv) Working of striated muscles :

 H.E. Huxley and A.F. Huxley in 1954 proposed a theory to explain the process of muscular contraction. This theory is known as ‘sliding

filament theory’.
• It was observed that when a fibril contracts :

(a) Its ‘A’ bands remain intact,

(b) ‘I’ bands progressively shorten and eventually disappear when the fibril has shortened to about 65% of its resting length.

(c) At this stage, ‘H’ zones also disappear because the actin filaments of both sides in each sarcomere reach, and may even overlap each other at the “M” line, and the ‘Z’ lines now touch the ends of myosin filaments.

(d) Sarcomere shortens

Note: It was further observed that if a fibre is mechanically streched, the zones of overlap between thick and thin filaments are shorter than in resting condition, resulting in wider ‘H’ zones.

• It was observed that when a fibril relax : All the phenomenona occur in reverse way to relax the muscle i.e. the muscle comes in normal condition.

Note : These observations led Huxley to propose that shortening of the fibrils in contraction is brought about by sliding movement of actin filaments over myosin filaments towards “M” line by means of rapidly forming and breaking cross bridges or rachets at the spurs of myosin filaments. Thus, the sarcomere were recognised as the ‘ultimate units of contraction

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2.1 (v) Mechanism of Muscle Contraction

 Mechanism of muscle contraction is best explained by the sliding filament theory which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments.

 Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron.
A motor neuron along with the muscle fibres 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 motorend plate.

 A neural signal reaching this junction releases a neurotransmitter (Acetyl choline) which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm.

 Increase in Ca2+ 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.
 Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.

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 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. It is clear from the above steps, that 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 crossbridge 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 Ca2+ ions 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.

Note : Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen in them, causing fatigue.

Note : On the basis of quantity of myoglobin pigment muscles are categories as

(A) Red muscle fibre : Muscle contains a red coloured oxygen storing pigment called myoglobin. Myoglobin rich muscles gives a reddish appearance. Such muscles are called the Red fibres. These muscles also contain plenty of mitochondria which can utilise the large amount of oxygen stored in them for ATP production. These muscles, therefore, can also be called aerobic muscles.

(B) White muscle fibre : Muscles possess very less quantity of myoglobin, 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.

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2.2 VISCERAL OR SMOOTH MUSCLES OR NON STRIATED

 These are called smooth, plain nonstriated involuntary or unstriped muscles due to absence of striations.

 These occur in the walls of hollow internal organs (alimentary canal, gall bladder, bile ducts, respiratory tracts, uterus, urinogenital ducts, urinary bladder, blood vessels, etc.), in capsules of lymph glands, spleen etc., in iris and ciliary body of eyes, skin dermis, penis and other accessory genitalia, etc.

 Smooth muscles of skin dermis, called errector pilli muscles, are associated with hair roots, and are responsible for flesh (erection of hairs). Those of penis form a muscular network which helps in its erection and limping.

• Structure : Smooth muscle fibre is unbranched goose-spindle shaped, uninucleated and has no sarcolemma. Contraction is slow, involuntary under the control of ANS.

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 Functionally smooth muscles are of two types –

(1) Single-unit smooth muscle : Single unit smooth muscle fibres are composed of muscle fibres closely joined together, contract as a single unit. e.g., urinary bladder, gastrointestinal tract, small arteries and small veins.

(2) Multi-unit smooth muscles : are composed of more independent muscle fibres, contract as separate units e.g. – hair root muscle, muscles on the wall of large blood vessels, ciliary muscles, muscles of iris and bronchi.

2.3 CARDIAC MUSCLES

  Heart wall (also the wall of large veins just where these enter into the heart) is made up of cardiac muscles and, hence, called myocardium.

 Structurally, these muscles resemble striated muscles but, functioning independently of the conscious control of brain, these are involuntary like the smooth muscles.

 Cardiac muscle cells of fibres are comparatively shorter and thicker, cylindrical, mostly uninucleate with a central nucleus, somewhat branched and covered by a sarcolemma. 

3. classification of body muscles
The total number of muscles in the body of adult man is 639. The muscles that act together to produce a movement are called synergists and the muscle that act in opposition to each other are antagonists. According to the type of motion they cause, the muscles are divided into the following types.

(i) Flexor and Extensor : Muscles that bend one part over another joint is called flexor. Extensor muscle is antagonist of flexor muscle. The contraction of an extensor extends a joint by pulling one of the articulating bone apart from another.

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(ii) Pronator and Supinator : The contraction of a pronator rotates the forearm to turn the palm downward or backward Supinator is antagonist of pronator. A supinator contracts to rotate the forearm and thus to make palm face upward or forward.

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(iii) Abductor and Adductor : An abductor contracts to draw a bone away from the body midline. Muscle that brings the limb away from midline is called abductor. An adductor draws a bone towards the body midline. Muscles that brings the limb towards midline is called adductor. Abductor muscle is antagonist of adductor muscle.

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(iv) Protractor and Retractor : Protractor muscle pulls the lower jaw, tongue and the head forward. Retraction is opposite to protaction. Retractor muscle draws the lower jaw, tongue and the head backward

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(v) Inversion and Eversion : Turning of feet so that the soles face one another in inversion. Eversion is the opposite of inversion. In this movement, the soles of the feet face laterally

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(vi) Rotation : Rotation is term that indicates the partial revolving of a body part on the part’s long axis.

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(vii) Errector      : Raises hairs of skin.

(viii) Levator      : Elevates a part of body.

(ix) Depressor    : Lowers a part of body.

(x) Sphincter      : Closes a natural orifice or passage.

(xi) Constrictor  : Causes constriction or squeezing.

4 Skeleta Systeml 

 Skeletal system consists of a framework of bones and a few cartilages. This system has a significant role in movement shown by the body.

 Bone and cartilage are specialised connective tissues. The former has a very hard matrix due to calcium salts in it and the latter has slightly pliable matrix due to chondroitin salts.

 The study of bone structure and treatment of bone disorder called osteology.

 The specialized branch of medicine that deals with preservation and restoration of skeletal system, joints is called orthopedics.

 Bones are made up of a protein called ossein and cartilage are made of a protein called chondrin.

Hence study of bones is called osteology and study of cartilage is called chondrology.

4.1 SKELETON
The hardened tissues of the body together form the skeleton (sclero = hard). Skeleton of invertebrates is most often secreted on the surface, forming a lifeless or dead exoskeleton. Whereas skeleton of vertebrates develops most often underneath the surface forming a living or growing endoskeleton.

 Three types of skeletons develop in vertebrates :

(1) Epidermal/Horny exoskeleton : These include hard and horny of keratinized derivatives of epidermal layer of skin, such as claws, most reptilian’s scales, bird feathers and mammalian hairs, horns, nails and hoofs, etc.

(2) Dermal/Bony skeleton : Dermal bony skeleton is derived from the dermis of skin. It includes bony scales and plates. In fishes, dermal scales become exposed due to wearing out of epidermis, and form exoskeleton.

(3) Endoskeleton : Greater part of vertebrate skeleton lies more deeply, forming the endoskeleton. Endoskeleton is formed by bones in vertebrates.

4.2 SKELETON IN DIFFERENT ANIMALS

(a) Invertebrate –

(i) Protozoa – No skeleton.

(ii) Porifera – Calcarius spicules + silicious spicules

(iii) Coelentrata – Calcareous (corals) and chitinous

(iv) Helminth – No skeleton, cuticle present.

(v) Annelida – No skeleton, cuticle present.

(vi) Arthropoda – Dead Chitinus exoskeleton.

(vii) Mollusca – Calcarius shell

(viii) Echinodermata – Dermal calcareous plates are present.

 
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Chapter 1 The Living World
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Chapter 2 Biological Classification
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Chapter 3 Plant Kingdom
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Chapter 4 Animal Kingdom
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Chapter 5 Morphology of Flowering Plants
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Chapter 6 Anatomy of Flowering Plants
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Chapter 7 Structural Organisation in Animals
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Chapter 8 Cell The Unit of Life
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Chapter 9 Biomolecules
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Chapter 10 Cell Cycle and Cell Division
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Chapter 11 Transport in Plants
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Chapter 12 Mineral Nutrition
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Chapter 13 Photosynthesis in Higher Plants
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Chapter 14 Respiration in Plants
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Chapter 15 Plant Growth and Development
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Chapter 17 Breathing and Exchange of Gases
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Chapter 18 Body Fluids and Circulation
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Chapter 19 Excretory Products and their Elimination
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Chapter 20 Locomotion and Movement
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