આ MCQ મોડ્યુલ આના પર આધારિત છે: NCERT Exercises and Solutions: Locomotion and Movement
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NCERT Exercises and Solutions: Locomotion and Movement
🎓 Class 11
Biology
CBSE
Theory
Ch 17 – Locomotion and Movement
⏱ ~8 min
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આ મૂલ્યાંકન આના પર આધારિત હશે: NCERT Exercises and Solutions: Locomotion and Movement
મૂલ્યાંકન બનાવવામાં તેમની સામગ્રી સામેલ કરવા ચિત્રો, PDF અથવા Word દસ્તાવેજ અપલોડ કરો.
Locomotion and Movement - Summary and NCERT Exercise Solutions
This final part of Chapter 17 gathers the whole chapter into a single view and then works through every NCERT exercise question in full. Use the summary to check that nothing is missing from your understanding, and the solutions to check the exact form in which answers are expected.
Chapter Summary
Movement is an essential feature of all living beings. Protoplasmic streaming, ciliary movements, movements of fins, limbs, wings and so on are some forms exhibited by animals. A voluntary movement which causes the animal to change its place is called locomotion. Animals move generally in search of food, shelter, mate, breeding ground, better climate, or to protect themselves.
The cells of the human body exhibit amoeboid, ciliary and muscular movements. Locomotion and many other movements require coordinated muscular activities.
Three types of muscles are present in our body. Skeletal muscles are attached to skeletal elements; they appear striated and are voluntary in nature. Visceral muscles, present in the inner walls of visceral organs, are non-striated and involuntary. Cardiac muscles are the muscles of the heart; they are striated, branched and involuntary. Muscles possess excitability, contractility, extensibility and elasticity.
Muscle fibre is the anatomical unit of muscle. Each muscle fibre has many parallelly arranged myofibrils. Each myofibril contains many serially arranged units called sarcomere, which are the functional units. Each sarcomere has a central ‘A’ band made of thick myosin filaments, and two half ‘I’ bands made of thin actin filaments on either side of it marked by ‘Z’ lines.
Actin and myosin are polymerised proteins with contractility. The active sites for myosin on resting actin filament are masked by a protein, troponin. Myosin head contains ATPase and has ATP binding sites and active sites for actin.
A motor neuron carries a signal to the muscle fibre which generates an action potential in it. This causes the release of Ca++ from the 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 the sarcoplasmic reticulum, which inactivates the actin. Cross bridges are broken and the muscles relax.
Repeated stimulation of muscles leads to fatigue. Muscles are classified as Red and White fibres based primarily on the amount of red coloured myoglobin pigment in them.
Bones and cartilages constitute our skeletal system. The skeletal system is divisible into axial and appendicular. Skull, vertebral column, ribs and sternum constitute the axial skeleton. Limb bones and girdles form the appendicular skeleton. Three types of joints are formed between bones or between bone and cartilage — fibrous, cartilaginous and synovial. Synovial joints allow considerable movements and therefore play a significant role in locomotion.
The one-line logic of the chapter: a nerve signal raises sarcoplasmic calcium → calcium unmasks actin → myosin heads form cross bridges and pull → thin filaments slide over thick ones → sarcomeres shorten → bones move about joints → the body moves. Every fact in this chapter sits somewhere on that chain.
| Item | Number |
|---|---|
| Total bones in the human body | 206 |
| Axial skeleton | 80 |
| Bones of the skull (cranial + facial) | 22 (8 + 14) |
| Ear ossicles per middle ear | 3 (malleus, incus, stapes) |
| Vertebrae | 26 — cervical 7, thoracic 12, lumbar 5, sacral 1 fused, coccygeal 1 fused |
| Pairs of ribs | 12 — true 7, vertebrochondral (false) 3, floating 2 |
| Bones per limb | 30 |
| Carpals / tarsals | 8 / 7 |
| Metacarpals / metatarsals | 5 / 5 |
| Phalanges per limb | 14 |
| Bones fused in each coxal bone | 3 — ilium, ischium, pubis |
🎯 Interactive: Rapid Revision Quiz
Answer, then reveal. Select a question to begin.
NCERT Exercises — Complete Solutions
Question 1
Draw the diagram of a sarcomere of skeletal muscle showing different regions.
A sarcomere is the portion of a myofibril between two successive ‘Z’ lines. Label the following regions:
Regions to label and their content:
- ‘Z’ line — elastic fibre to which the thin actin filaments are attached; two successive ‘Z’ lines bound one sarcomere.
- ‘A’ band (dark, anisotropic) — the central region occupied by the thick myosin filaments; it retains its length during contraction.
- ‘I’ band (light, isotropic) — the region of thin actin filaments only; a sarcomere carries two half ‘I’ bands, one on either side of the ‘A’ band.
- ‘H’ zone — the central part of the ‘A’ band not overlapped by thin filaments, i.e. thick filaments alone.
- ‘M’ line — the line in the middle of the ‘H’ zone holding the thick filaments together.
Question 2
Define sliding filament theory of muscle contraction.
The sliding filament theory states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments.
In other words, actin and myosin filaments do not themselves shorten. The myosin heads form cross bridges with actin and pull the thin filaments towards the centre of the ‘A’ band, so the ‘Z’ lines are drawn inwards and the sarcomere shortens. Consequently, during contraction the ‘I’ bands get reduced and the ‘H’ zone narrows, whereas the ‘A’ band retains its length.
Question 3
Describe the important steps in muscle contraction.
The important steps, in order, are:
- Muscle contraction is initiated by a signal sent by the central nervous system via a motor neuron.
- A motor neuron along with the muscle fibres connected to it constitutes a motor unit. The junction between the motor neuron and the sarcolemma of the muscle fibre is the neuromuscular junction or motor-end plate.
- A neural signal reaching this junction releases a neurotransmitter, acetyl choline, which generates an action potential in the sarcolemma.
- This action potential spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm.
- The increase in Ca++ level leads to the binding of calcium with a subunit of troponin on the actin filaments, thereby removing the masking of the active sites for myosin.
- Utilising the energy from ATP hydrolysis, the myosin head binds to the exposed active sites on actin to form a cross bridge.
- This pulls the attached actin filaments towards the centre of the ‘A’ band. The ‘Z’ lines attached to these actins are also pulled inwards, causing a shortening of the sarcomere, i.e. contraction. The ‘I’ bands get reduced while the ‘A’ bands retain their 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++ ions are pumped back to the sarcoplasmic cisternae, resulting in the masking of actin filaments. This causes the return of the ‘Z’ lines to their original position, i.e. relaxation.
Question 4
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.
(c) Human skeleton has 206 bones.
(d) There are 11 pairs of ribs in man.
(e) Sternum is present on the ventral side of the body.
(a) True. Each actin (thin) filament is made of two ‘F’ actins helically wound to each other, along with tropomyosin and troponin.
(b) False. Corrected statement: The H-zone of a striated muscle fibre represents only the thick filaments. The H zone is the central part of the ‘A’ band that is not overlapped by the thin filaments, so it contains thick (myosin) filaments alone.
(c) True. In human beings the skeletal system is made up of 206 bones and a few cartilages — 80 axial and 126 appendicular.
(d) False. Corrected statement: There are 12 pairs of ribs in man. Of these, 7 pairs are true ribs, 3 pairs (8th–10th) are vertebrochondral or false ribs and the last 2 pairs (11th and 12th) are floating ribs.
(e) True. The sternum is a flat bone on the ventral midline of the thorax.
Question 5
Write the difference between:
(a) Actin and Myosin
(b) Red and White muscles
(c) Pectoral and Pelvic girdle
(a) Actin and Myosin
| Actin | Myosin |
|---|---|
| Forms the thin filament | Forms the thick filament |
| Made of two ‘F’ (filamentous) actins, each a polymer of ‘G’ (globular) actins | Made of many monomeric meromyosins |
| Carries tropomyosin and troponin; troponin masks the myosin binding sites at rest | Has a globular head with a short arm (heavy meromyosin, the cross arm) and a tail (light meromyosin) |
| Has active sites for myosin | Head is an active ATPase enzyme with ATP binding sites and active sites for actin |
| Present in the ‘I’ band and the overlapping part of the ‘A’ band; attached to the ‘Z’ line | Present throughout the ‘A’ band; held at the ‘M’ line |
| Slides over the thick filament during contraction | Remains in place; its heads pull the actin |
(b) Red and White muscles
| Red muscles (red fibres) | White muscles (white fibres) |
|---|---|
| Myoglobin content is high, giving a reddish appearance | Myoglobin content is very less, so they appear pale or whitish |
| Contain plenty of mitochondria | Number of mitochondria is few |
| Amount of sarcoplasmic reticulum is comparatively less | Amount of sarcoplasmic reticulum is high |
| Utilise the large amount of stored oxygen for ATP production — aerobic muscles | Depend on the anaerobic process for energy |
| Resist fatigue; suited to prolonged activity | Fatigue quickly; suited to rapid powerful bursts |
(c) Pectoral and Pelvic girdle
| Pectoral girdle | Pelvic girdle |
|---|---|
| Helps in the articulation of the upper limbs with the axial skeleton | Helps in the articulation of the lower limbs with the axial skeleton |
| Each half consists of a clavicle and a scapula | Consists of two coxal bones, each formed by the fusion of ilium, ischium and pubis |
| The head of the humerus fits into the glenoid cavity, a depression below the acromion | The thigh bone articulates with the acetabulum, a cavity at the point of fusion of the three bones |
| The two halves are not fused to each other ventrally | The two halves meet ventrally to form the pubic symphysis, containing fibrous cartilage |
| Scapula is a large triangular flat bone in the dorsal part of the thorax between the 2nd and 7th ribs, with a spine projecting as the acromion | Forms a rigid basin that transmits the weight of the body to the legs |
Question 6
Match Column I with Column II:
| Column I | Column II |
|---|---|
| (a) Smooth muscle | (i) Myoglobin |
| (b) Tropomyosin | (ii) Thin filament |
| (c) Red muscle | (iii) Sutures |
| (d) Skull | (iv) Involuntary |
| Column I | Column II | Why |
|---|---|---|
| (a) Smooth muscle | (iv) Involuntary | Smooth (visceral) muscle in the inner walls of visceral organs is non-striated and involuntary |
| (b) Tropomyosin | (ii) Thin filament | Two filaments of tropomyosin run close to the ‘F’ actins throughout the length of the thin filament |
| (c) Red muscle | (i) Myoglobin | Red fibres have a high content of the red oxygen-storing pigment myoglobin |
| (d) Skull | (iii) Sutures | The flat skull bones fuse end-to-end by dense fibrous connective tissue in the form of sutures to form the cranium |
Answer: (a)–(iv), (b)–(ii), (c)–(i), (d)–(iii).
Question 7
What are the different types of movements exhibited by the cells of human body?
The cells of the human body exhibit three main types of movement: amoeboid, ciliary and muscular.
- Amoeboid movement: shown by some specialised cells such as macrophages and leucocytes in blood. It is effected by pseudopodia formed by the streaming of protoplasm, and cytoskeletal elements like microfilaments are also involved.
- 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 in removing dust particles and some of the foreign substances inhaled along with the atmospheric air, and the passage of ova through the female reproductive tract is also facilitated by ciliary movement.
- Muscular movement: movement of our limbs, jaws, tongue and so on requires muscular movement. The contractile property of muscles is effectively used for locomotion and other movements by human beings and majority of multicellular organisms.
Question 8
How do you distinguish between a skeletal muscle and a cardiac muscle?
| Feature | Skeletal muscle | Cardiac muscle |
|---|---|---|
| Location | Attached to the skeletal elements; primarily involved in locomotory actions and changes of body postures | Muscles of the heart |
| Appearance | Striated | Striated |
| Branching | Unbranched, cylindrical fibres | Branched fibres, with the cells joined end-to-end |
| Regulation | Voluntary — under the direct control of the nervous system | Involuntary — not under voluntary control |
| Nuclei | Multinucleate (syncitium) | Uninucleate or binucleate cells joined by intercalated discs |
| Fatigue | Fatigues on repeated stimulation | Does not fatigue; contracts rhythmically throughout life |
The clearest single distinction: both are striated, but skeletal muscle is unbranched and voluntary while cardiac muscle is branched and involuntary.
Question 9
Name the type of joint between the following:
(a) atlas/axis (b) carpal/metacarpal of thumb (c) between phalanges (d) femur/acetabulum (e) between cranial bones (f) between pubic bones in the pelvic girdle
| Articulation | Type of joint |
|---|---|
| (a) Atlas / axis | Synovial — pivot joint |
| (b) Carpal / metacarpal of thumb | Synovial — saddle joint |
| (c) Between phalanges | Synovial — hinge joint |
| (d) Femur / acetabulum | Synovial — ball and socket joint |
| (e) Between cranial bones | Fibrous joint (sutures) — immovable |
| (f) Between pubic bones in the pelvic girdle | Cartilaginous joint — the pubic symphysis, containing fibrous cartilage |
Question 10
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 __________
(c) Thin filament of myofibril contains 2 ‘F’ actins and two other proteins 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.
(a) seven (7). The number of cervical vertebrae is seven in almost all mammals, including human beings.
(b) 14. Each limb has 14 phalanges — the digits of the hand and of the foot alike.
(c) tropomyosin and troponin. Two filaments of tropomyosin run close to the ‘F’ actins throughout their length, and the complex protein troponin is distributed at regular intervals on the tropomyosin.
(d) the sarcoplasmic reticulum. Ca++ is stored in the sarcoplasmic reticulum (in its cisternae) and released into the sarcoplasm when an action potential spreads through the fibre.
(e) 11th and 12th. The last two pairs of ribs are not connected ventrally and are therefore called floating ribs.
(f) 8. Cranial bones are 8 in number and form the hard protective outer covering, the cranium, for the brain. (The skull as a whole has 22 bones — 8 cranial plus 14 facial.)
🎯 Competency-Based Questions
Q1. A student writes in an examination: "During contraction the sarcomere shortens because the A band shortens." Identify the error, give the correct statement, and state the observation that proves the student wrong.
The error is in the cause. The sarcomere does shorten, but not because the ‘A’ band shortens.
Correct statement: the sarcomere shortens because the thin filaments slide over the thick filaments towards the centre of the ‘A’ band, pulling the ‘Z’ lines inwards. Consequently the ‘I’ bands get reduced and the ‘H’ zone narrows.
The proof is the direct microscopic observation that the ‘A’ band retains its length throughout contraction. Since the ‘A’ band marks the extent of the thick filaments, its constancy shows the filaments themselves do not shorten — only their overlap changes.
Q2. Both an elderly woman with osteoporosis and a young man with muscular dystrophy find it hard to climb stairs. Explain why the same difficulty arises from entirely different tissue-level causes, and predict what an X-ray would show in each case.
Climbing stairs needs (i) muscles able to generate force and (ii) bones able to bear load and act as levers about joints. The two conditions attack different halves of that requirement.
Osteoporosis is an age-related disorder characterised by decreased bone mass and increased chances of fractures, with decreased levels of estrogen being a common cause. The muscles may be adequate, but the skeleton is fragile and painful to load.
Muscular dystrophy is a progressive degeneration of the skeletal muscle, mostly due to genetic disorder. Here the bones are normal but the muscle tissue generating the force is being lost.
X-ray prediction: in osteoporosis the bones would appear less dense, with a thinner cortex and possibly old compression fractures. In muscular dystrophy the bone density would be essentially normal, since the disorder is of muscle rather than bone.
Q3. Design a simple experiment on an isolated frog muscle to demonstrate that calcium is essential for contraction, and state the expected result and the control you would use.
Set-up: Take two comparable isolated muscle preparations with their nerve intact. Bathe muscle A in a normal physiological saline containing the usual calcium concentration, and muscle B in an otherwise identical saline from which calcium has been removed (or in which calcium is bound by a chelating agent). Stimulate the nerve of each with identical electrical pulses and record the tension developed.
Control: muscle A, in complete saline, is the control. Both preparations must come from the same animal, be of similar size, and be tested at the same temperature with the same stimulus — so that calcium is the only variable.
Expected result: muscle A contracts normally; muscle B develops little or no tension.
Explanation: the stimulus still releases acetyl choline and generates an action potential, but without calcium reaching the sarcoplasm in adequate amount the troponin subunit is not bound, the myosin active sites on actin stay masked, no cross bridges form, and no sliding occurs. Restoring calcium to muscle B's bath should restore contraction, which strengthens the conclusion.
Q4. Arrange the following in the order in which they are affected during a single contraction, and justify the order: troponin, sarcolemma, cross bridge, acetyl choline, Z line, sarcoplasmic reticulum.
Order: acetyl choline → sarcolemma → sarcoplasmic reticulum → troponin → cross bridge → ‘Z’ line.
Justification: the neural signal at the neuromuscular junction first releases acetyl choline. This generates an action potential in the sarcolemma, which spreads through the fibre and causes the sarcoplasmic reticulum to release Ca++ into the sarcoplasm. Calcium binds a subunit of troponin, unmasking the myosin active sites on actin. The myosin head then binds actin to form a cross bridge and rotates, pulling the actin inwards, so that finally the ‘Z’ line is drawn towards the centre and the sarcomere shortens.
The sequence is a chain of causes: each step exists only because the previous one occurred, which is why a block anywhere along it (as in myasthenia gravis at the junction, or tetany through calcium) abolishes or distorts normal contraction.
Q5. The human skeleton has 206 bones, of which 80 are axial. Work out the appendicular number from the chapter's own figures and check that the parts add up. Comment on what your arithmetic reveals about the girdles.
Appendicular total: 206 − 80 = 126 bones.
Building it up from the parts: each limb is made of 30 bones, and there are four limbs, giving 30 × 4 = 120. That leaves 126 − 120 = 6 bones for the girdles.
Checking the girdles: each girdle is formed of two halves. Each half of the pectoral girdle consists of a clavicle and a scapula, so the pectoral girdle is 2 × 2 = 4 bones. The pelvic girdle consists of two coxal bones, so 2 bones. Total 4 + 2 = 6 — exactly the remainder.
What this reveals: the pelvic girdle is counted as only two bones because each coxal bone is formed by the fusion of three bones — ilium, ischium and pubis. Six separate elements have become two. That fusion, together with the pubic symphysis joining the halves ventrally, is what turns the pelvis into a single rigid weight-bearing ring, in contrast with the four separate, loosely held bones of the pectoral girdle, which favour mobility instead.
🧠 Assertion–Reason Questions
For each pair, decide whether both statements are true and whether the reason correctly explains the assertion.
Assertion (A): The H zone contains only thick filaments.
Reason (R): The H zone is the central portion of the ‘A’ band which is not overlapped by the thin filaments.
Both A and R are true, and R is the correct explanation of A.
Because the thin filaments extend inwards only part of the way into the ‘A’ band, its middle region is occupied by myosin alone. As contraction proceeds and the thin filaments slide further inwards, this zone narrows.
Assertion (A): Cardiac muscle is involuntary although it is striated.
Reason (R): Striation in a muscle is caused by the regular arrangement of actin and myosin, which is independent of whether the muscle is under voluntary control.
Both A and R are true, and R is the correct explanation of A.
Appearance and regulation are two separate bases of classification. Cardiac muscle is striated and branched yet involuntary; skeletal muscle is striated, unbranched and voluntary; visceral muscle is non-striated and involuntary. So striation cannot be used to predict voluntary control.
Assertion (A): Repeated stimulation of a muscle leads to fatigue.
Reason (R): Lactic acid accumulates due to the anaerobic breakdown of glycogen in the muscle.
Both A and R are true, and R is the correct explanation of A.
This is also why red fibres, with their high myoglobin and plentiful mitochondria, resist fatigue better than white fibres: they can meet their energy demand aerobically rather than relying on the anaerobic route that produces lactic acid.
Frequently Asked Questions - Summary and NCERT Exercises
What is locomotion and how does it differ from movement?
Movement is an essential feature of all living beings and includes protoplasmic streaming, ciliary movements and movements of fins, limbs and wings. A voluntary movement which causes the animal to change its place is called locomotion. So all locomotion is movement, but not all movement is locomotion. Animals move generally in search of food, shelter, mate, breeding ground, better climate or to protect themselves.
What are the different types of movements exhibited by human cells?
The cells of the human body exhibit amoeboid, ciliary and muscular movements. Amoeboid movement is shown by cells such as macrophages and leucocytes using pseudopodia; ciliary movement occurs in internal tubular organs lined by ciliated epithelium, such as the trachea and the female reproductive tract; and muscular movement moves the limbs, jaws and tongue.
What is the sliding filament theory in one sentence?
The sliding filament theory states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments, so that the sarcomere shortens while the lengths of the filaments themselves remain unchanged.
How many pairs of ribs are there in man, and which are floating ribs?
There are 12 pairs of ribs in man. The first seven pairs are true ribs, connected ventrally to the sternum by hyaline cartilage. The 8th, 9th and 10th pairs are vertebrochondral or false ribs, which join the seventh rib instead. The 11th and 12th pairs are not connected ventrally and are therefore called floating ribs.
What does the H zone contain?
The H zone is the central part of the 'A' band that is not overlapped by the thin filaments, so it contains only the thick myosin filaments. It narrows during contraction as the thin filaments slide further inwards.
How is a skeletal muscle distinguished from a cardiac muscle?
Both appear striated, but skeletal muscles are attached to skeletal elements, are unbranched and are voluntary in nature, whereas cardiac muscles are the muscles of the heart, are branched, are involuntary, and do not fatigue on repeated stimulation.
How many cervical vertebrae do mammals have?
The number of cervical vertebrae is seven in almost all mammals, including human beings. Animals with very long necks, such as the giraffe, have elongated cervical vertebrae rather than a greater number of them.
Where is calcium stored in a muscle fibre?
Calcium is stored in the sarcoplasmic reticulum, specifically in its cisternae. An action potential spreading through the fibre causes its release into the sarcoplasm, where it binds a subunit of troponin and unmasks the myosin binding sites on actin. Pumping calcium back into the cisternae re-masks actin and causes relaxation.
Which proteins other than actin are present in the thin filament?
Besides the two 'F' actins, the thin filament of a myofibril contains tropomyosin, two filaments of which run close to the 'F' actins throughout their length, and troponin, a complex protein distributed at regular intervals on the tropomyosin.
Which type of joint is present between the pubic bones of the pelvic girdle?
The two halves of the pelvic girdle meet ventrally at the pubic symphysis, which contains fibrous cartilage. It is therefore a cartilaginous joint, permitting only limited movement.
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