NCERT Solutions for Class 11 Biology Chapter 17 (2025-2026)

Movement is one of the most characteristic features of living organisms. Chapter 17 of Class 11 Biology, Locomotion and Movement, explores the distinction between movement and locomotion, and examines how animals achieve various types of movements. The chapter explains the structure and functions of different types of muscles, the skeletal system in humans, the mechanism of muscle contraction, and the various types of joints that facilitate movement. It also covers different types of body movements and disorders related to the muscular and skeletal systems. This chapter is part of the comprehensive NCERT Solutions Class 11 Biology series, which covers all chapters in detail.

The NCERT Solutions for Locomotion and Movement provided here offer detailed, step-by-step explanations for all textbook questions, helping students strengthen their conceptual understanding, clear doubts effectively, and prepare efficiently for both school exams and competitive tests like NEET.

NCERT Solutions for Class 11 Biology Chapter 17 - All Exercise Questions

Locomotion and Movement
Easy
Q.
Draw the diagram of a sarcomere of skeletal muscle showing different regions.
Locomotion and Movement
Easy
Q.
Define sliding filament theory of muscle contraction.
Locomotion and Movement
Difficult
Q.
Describe the important steps in muscle contraction.
Locomotion and Movement
Medium
Q.
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.
Locomotion and Movement
Difficult
Q.
Write the difference between:
(a) Actin and Myosin
(b) Red and White muscles
(c) Pectoral and Pelvic girdle
Locomotion and Movement
Easy
Q.
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
Locomotion and Movement
Easy
Q.
What are the different types of movements exhibited by the cells of human body?
Locomotion and Movement
Easy
Q.
How do you distinguish between a skeletal muscle and a cardiac muscle?
Locomotion and Movement
Easy
Q.
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
Locomotion and Movement
Easy
Q.
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.

Download the PDF of NCERT Solutions for Class 11 Biology Chapter 17 –Locomotion and Movement

Class 11 Chapter 17 Biology Questions & Answers –Locomotion and Movement

Q1. Draw the diagram of a sarcomere of skeletal muscle showing different regions.

Solution: The diagram of a sarcomere of skeletal muscle showing different regions:

 

Q2. Define sliding filament theory of muscle contraction.

Solution: According to the sliding filament theory of muscle contraction, contraction of muscle fibres to produce contractile force takes place by the sliding of the thin filaments (actin fibres) over the thick filaments (myosin) found in the sarcomere of the muscle cell.

[Explanation: Sliding filament theory best describes the molecular basis of muscle contraction. It explains how myofibrils (actin and myosin) interact to produce contractile force. In sarcomere, actin forms thin filaments and myosin forms thick filaments. Sarcomere consists of two bands- A-band (Dark band) and I-band (Light band). A-band is the region of myosin thick filaments while I-band is the region of actin filaments which are not superimposed with myosin filaments. Actin filaments of I-band are connected to an elastic fibre called Z-line. There is a region in the central part of sarcomere that does not overlap with actin fibres is called H-zone. During the process of muscle contraction, thick filaments (myosin fibres, A-band) remains constant while thin filaments (actin fibres, I-band) change their length and slide over the myosin filaments. Actin filaments interact with the myosin head that results in pulling the actin filaments towards the centre of the sarcomere. In this process, length of sarcomere decreases and Z-lines of sarcomere come closer.]

 

Q3. Describe the important steps in muscle contraction.

Solution: Muscle contraction is explained by sliding filament theory. According to sliding filament theory, contraction of muscle fibers to produce contractile force takes place by the sliding of the thin filament (actin fibers) over the thick filaments (myosin) found in the sarcomere of the muscle cell. Important steps in muscle contraction are as follows:

1. Central nervous system sends signal for initiation of muscle contraction via a motor neuron.

2. Neural signal reaches motor end plate (the junction between a motor neuron and sarcolemma of the muscle fiber) and releases a neurotransmitter (acetylcholine) which generates an action potential in the sarcolemma that spreads through the muscle fiber and causes the release of calcium ions into the sarcoplasm.

3. Calcium ions bind to troponin that removes tropomyosin from the active sites of actin. These exposed active actin sites are now available to interact with myosin.

5. Heads of myosins form cross bridges by interacting with active sites on actin filaments and pull them towards the center of A-band by utilising the energy from ATP hydrolysis. Z line which is attached to actin filaments are also pulled inwards that shortens the sarcomere resulting in contraction. In this process, I-bands get shortened while the lengths of A-bands remain the same.

6. Myosin goes into relaxed state by releasing ADP and Pi. Cross bridge is broken. A new ATP binds to myosin and upon ATP hydrolysis next cycle of cross-bridge formation starts. This process continues till the calcium ions are sent back into sarcoplasmic cisternae that results into masking of active sites on actin filaments

 

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.

(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.

Solution: (a) True

(b) False. H-zone of striated muscle fibre represents only thick filaments.

(c) True

(d) False. There are 12 pairs of ribs in man.

(e) True

 

Q5. Write the difference between :

(a) Actin and Myosin

(b) Red and White muscles

(c) Pectoral and Pelvic girdle

Solution: (a) Actin and Myosin

(b) Red and White muscles

Red muscles White muscles
Red muscles are thin and smaller in size. White muscles are thick and longer.
Red muscles contain large amount of myoglobin that gives them reddish colour. White muscles contain lesser myoglobin.
Red muscles contain large number of mitochondria which are used for generating energy (ATP) to perform their function White muscles contain a smaller number of mitochondria
The contractions are slow but sustained over a longer period of time. The contractions are fast but of short duration

(c ) Pectoral and Pelvic girdle

Pectoral Girdle Pelvic girdle
Pectoral girdles help in the articulation of upper limbs. Pectoral girdles help in the articulation of upper limbs.
Pectoral girdle consists of two bones- Clavicle and Scapula Pelvic girdle is composed of three bones- Ilium, Ischium and Pubic.

 

Q6. 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

Solution:

Column I Column II
(a) Smooth muscle  (iv) Involuntary
(b) Tropomyosin  (ii) Thin filament
(c) Red muscle  (i) Myoglobin
(d) Skull (iii) Sutures

 

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

Solution:  Four different types of movements are exhibited by the cells of human body:

1. Amoeboid movement: This kind of movement is shown by specialised cells like macrophages and leukocytes in the blood which migrate from bloodstream to the site of injury to perform their function. These cells move by the formation of pseudopodia (streaming of cytoplasm) in the direction of movement. Microfilaments of the cytoskeleton are involved in this kind of movement.

2. Ciliary movement: Ciliary movement is shown by cells of the ciliated epithelium lining internal tubular organs. Cells present in the lining of trachea perform ciliary movement to sweep the dirt and mucus out of the lung. In females, the ciliary movement shown by the cells lining the fallopian tubes helps in moving ova from ovary to uterus. Cilia are also found in the cochlear cells of the ear.

3. Muscular movement: Muscle cells exhibit contraction and relaxation movement. This kind of movement is involved in moving our limbs, jaws, tongue, etc.

4. Flagellar movement: Sperms swim by means of flagellum which shows flagellar movement.

 

Q8. How do you distinguish between a skeletal muscle and a cardiac muscle?

Solution:

 

Q9. 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

Solution: 

Bone Type of Joint
(a) atlas/axis Pivotal Joint
(b) carpal/metacarpal of thumb Saddle Joint
(c) between phalanges Hinge Joint
(d) femur/acetabulum Ball and socket Joint
(e) between cranial bones Fibrous joint
(f) between pubic bones in the pelvic girdle Cartilaginous joint (Pubic Symphysis)

 

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 __________ (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.

Solution: (a) All mammals (except a few) have seven cervical vertebra.

(b) The number of phalanges in each limb of human is 14.

(c) Thin filament of myofibril contains 2 ‘F’ actins and two other proteins namely troponin and tropomyosin.

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

(e) 11th and 12th pairs of ribs are called floating ribs.

(f) The human cranium is made of eight bones.

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NCERT Solutions for Class 11 Biology Chapter 17  – FAQs

1. What is the difference between locomotion and movement?

Movement refers to any change in position or place of any part of the body, such as bending of arms, beating of heart, or movement of food through the digestive tract. Locomotion is a specific type of movement where the entire body changes its position from one place to another, such as walking, running, swimming, or flying. All locomotion involves movement, but not all movements result in locomotion.

2. What are the three types of muscles found in the human body and their functions?

The three types of muscles are: (i) Skeletal muscles – voluntary, striated muscles attached to bones that help in body movement and locomotion, (ii) Smooth muscles – involuntary, non-striated muscles found in internal organs like the digestive tract, blood vessels, and urinary bladder that control internal movements, and (iii) Cardiac muscles – involuntary, striated muscles found only in the heart that pump blood throughout the body.

3. Explain the mechanism of muscle contraction (sliding filament theory).

Muscle contraction occurs through the sliding filament theory proposed by H.E. Huxley and J. Hanson. When a nerve impulse reaches the muscle fiber, calcium ions are released from the sarcoplasmic reticulum. These calcium ions bind to troponin, exposing binding sites on actin filaments. Myosin heads attach to these sites forming cross-bridges and pull the actin filaments towards the center of the sarcomere using ATP energy. This sliding of actin over myosin shortens the sarcomere, resulting in muscle contraction.

Q.1 Define vital capacity. What is its significance?

Ans-

Vital capacity refers to the volume of air a healthy person can inhale after a forced exhalation or the volume of air a person can exhale after a forced inhalation. It is the sum of Expiratory Reserve Volume (ERV), Tidal Volume (TV), and Inspiratory Reserve Volume (IRV). A normal adult person has a vital capacity of 3-5 litres.

Significance: Vital capacity is highest when physiological competence of the body is highest. It goes down as incompetence increases and becomes zero when respiration ceases. It implies that more the vital capacity, healthier is the body. Also, it helps in getting rid of the foul air and aids in supplying fresh air. Thus, the vital capacity enhances the exchange of gases between the body tissues and the environment.

Q.2 State the volume of air remaining in the lungs after a normal breathing.

Ans-

The volume of air that remains in the lungs after normal breathing is called FRC (functional residual capacity). This includes expiratory reserve volume (ERV, additional volume of air, a person can exhale by a forcible exhalation) and residual volume (RV, the volume of air remaining in the lungs even after a forcible exhalation). In a normal individual, ERV is about 1000 to 1100 mL while RV is about 1100 to 1200 mL.

Since, FRC = ERV + RV

FRC = 1000 (or 1100 mL) + 1100 (or 1200) mL

= 2100 or 2300 mL.

Thus, the volume of air remaining in the lungs after normal breathing is around 2100 mL to 2300 mL.

Q.3 Diffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why?

Ans-

The gaseous exchange (exchange of O2 and CO2) occurs in our body by simple diffusion between the blood capillaries around the alveoli and gases present in the alveoli. Alveoli are made up of thin and highly permeable layers of squamous epithelial cells. The reasons for gaseous diffusion in the alveolar region are as follows:

  1. Concentration and pressure: Diffusion is a concentration and pressure-dependent process. The barrier between the capillaries and alveoli is thin and it facilitates the gaseous diffusion from the region of higher to lower partial pressure. Pressure contributed by an individual gas in gaseous mixture is called its partial pressure. The partial pressure of O2 is high in the air present inside the lungs as compared to deoxygenated blood in lung capillaries. It means that there is a concentration gradient for O2 between the lungs and blood. Thus, O2 can easily diffuse from alveolar air into the blood of alveolar capillaries. A reverse concentration gradient is present for CO2, thus diffusion of CO2 takes place in the opposite direction.
  2. Nature of the membranes at the site of exchange: The region where diffusion takes place is made up three major layers namely; the thin squamous epithelium of alveoli, the endothelium of alveolar capillaries and the basement substance in between them. The total thickness of these three layers is less than a millimetre which makes it ideal to act as a site for the diffusion of gases.

Q.4 What are the major transport mechanisms for CO2? Explain.

Ans-

Blood is the medium for transport of CO2. There are three main ways by which CO2 is transported in the body:

  • By red blood cells (RBCs): The haemoglobin present in the RBCs carry about 20-25% CO2 as carbamino-haemoglobin. Haemoglobin transports CO2 as well as O2 and this transport of CO2 depends upon the partial pressure of these gases. If there is high partial pressure of O2, then CO2 is dissociated and O2 is acquired by haemoglobin (like in lungs where O2 is present in abundance). When oxygenated blood reaches the tissues, due to the high partial pressure of CO2, haemoglobin loses O2 and acquires CO2. This CO2 is transported to lungs for its exchange with O2.
  • By RBCs and plasma as bicarbonate ion: Nearly 70% of CO2 is transported in the form of bicarbonate ions. RBCs contain a very high amount of an enzyme called carbonic anhydrase. This enzyme is also present in minute amounts in plasma. A large part of CO2, as it diffuses into the blood plasma, combines with water to form carbonic acid with the help of enzyme carbonic anhydrase. Thereafter, the carbonic acid dissociates into bicarbonate and hydrogen ions by the action of the same enzyme. Thus, CO2 is transported in the form of bicarbonate ions.
  • Approximately 7% of CO2 is carried in dissolved state through plasma. CO2 combines with water to form carbonic acid.

Q.5 What will be the pO2 and pCO2 in the atmospheric air compared to those in the alveolar air?

(i) pO2 lesser, pCO2 higher

(ii) pO2 higher, pCO2 lesser

(iii) pO2 higher, pCO2 higher

(iv) pO2 lesser, pCO2 lesser

Ans-

(ii) pO2 higher, pCO2 lesser

In the atmosphere, O2 is present in large quantity and thus, its partial pressure is higher (159 mm Hg) than pO2 in alveolar air (104 mm Hg).

The pCO2 is lesser in atmosphere (0.3 mm Hg) as compared to pCO2 in alveoli (40 mm Hg).

Q.6 Explain the process of inspiration under normal conditions.

Ans-

The process of taking the air from outside the body into the lungs is called inhalation or inspiration. The process of inspiration involves the generation of the pressure gradient between the atmosphere and the lungs. Inspiration takes place when the pressure within the lungs is less (negative pressure) than the atmospheric pressure. The process of inspiration involves the following steps:

  • A negative pressure is generated within the lungs with the help of diaphragm and intercostal muscles (internal and external intercostal muscles)
  • Contraction of diaphragm increases the volume of the thoracic chamber in the anteroposterior axis.
  • Contraction of external intercostal muscles increases the volume of the thoracic chamber in the dorsoventral axis by lifting up the ribs and the sternum.
  • Increase in thoracic volume results in an increase in the pulmonary volume.
  • Increased pulmonary volume results in a decrease in intra-pulmonary pressure as compared to atmospheric pressure.
  • A decrease in intra-pulmonary pressure (negative pressure as compared to atmospheric pressure) allows the air to move into the lungs, i.e., inspiration or inhalation.

Q.7 How is respiration regulated?

Ans-

Respiration in human beings is a regulated process. It is regulated by the neural system according to the demands of the body tissues. It is mainly controlled by two regulatory regions present in the brain. These are:

(a) Respiratory rhythm centre: It is present in the medulla region of the brain and is mainly responsible for regulating the process of respiration. The areas adjacent to the respiratory rhythm centre are highly chemo-sensitive. They can sense the CO2 and H+ levels, whose increase activates the respiratory rhythm centre. Once activated, this centre adjusts the respiratory process, which helps in the elimination of CO2 and H+ from the body. Receptors associated with the aortic arch and carotid artery also sense the change in CO2 and H+ concentration and send signals to the respiratory rhythm centre to adjust the respiratory process.

(b) Pneumotaxic centre: It is present in the pons region of the brain. This centre can moderate the function of respiratory rhythm centre and reduces the duration of inspiration, which in turn changes the respiratory rate.

Q.8 What is the effect of pCO2 on oxygen transport?

Ans-

Oxygen binds to haemoglobin reversibly to form oxyhaemoglobin, which transports throughout the body to supply oxygen to different tissues. The binding of one molecule of haemoglobin with four molecules of oxygen depends on the partial pressure of oxygen (pO2). However, the partial pressure of CO2 also plays a significant role in the binding of oxygen with the haemoglobin molecule and its transport from lungs to tissues and vice-versa.

In alveoli, the pO2 is high but pCO2 is low. Thus, oxygen binds to haemoglobin and oxyhaemoglobin is formed. It transports the oxygen to body tissues. However, in tissues, the pCO2 is higher than pO2. Thus, O2 dissociates from haemoglobin and is released. Here, CO2 binds to haemoglobin to form carbamino-haemoglobin. CO2 Is thus transported to the lungs and is released in the lung cavity in exchange of O2. Thus, it can be stated that the affinity of haemoglobin for O2 increases as pCO2 decreases.

Q.9 What happens to the respiratory process in a man going up a hill?

Ans-

As a person goes up a hill (that is, at higher altitude), the level of O2 in the atmosphere decreases. So, less O2 is available for breathing and O2 level in the blood starts to decline. It results in an increase in the respiratory rate so as to meet the O2 demands of the body. Heart beat also increases to increase the supply of blood to the tissues so that every body tissue gets sufficient O2.

Q.10 What is the site of gaseous exchange in an insect?

Ans-

Insects have specialized structures called spiracles arranged in a series on the sides of its body. These are small openings through which the oxygen-rich air enters into the body. Spiracles are connected to a network of tubes called trachea which diffuses oxygen into the cells of the body. The transport of CO2 occurs in reverse direction, that is, from the trachea to the spiracles. Thus, the gaseous exchange occurs in the insects through the tracheal system.

Q.11 Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?

Ans-

Oxygen is transported in the blood by haemoglobin in the form of oxyhaemoglobin. Each haemoglobin molecule can carry a maximum of four O2 molecules. Binding of oxygen to haemoglobin is primarily affected by the partial pressure of O2 (pO2). However, the partial pressure of carbon dioxide (pCO2), H+ concentration and temperature also affect the binding of oxygen to haemoglobin. When the partial pressure of oxygen is high like in alveoli, haemoglobin binds with oxygen and forms oxyhaemoglobin. However, in tissues where pO2 is low, oxygen dissociates from oxyhaemoglobin. The per cent saturation of haemoglobin with oxygen at various pO2 can be studied using the oxygen dissociation curve. The oxygen dissociation curve is a sigmoid curve which is obtained by plotting the percentage saturation of haemoglobin with O2 against pO2.

The oxygen dissociation curve is sigmoid in shape because the binding of oxygen molecules to haemoglobin is co-operative. It means that binding of first O2 molecule to the haemoglobin increases the affinity of haemoglobin for another oxygen molecule. As a result, the haemoglobin attracts more oxygen and thus, the graph showing the percentage saturation of haemoglobin with O2 against pO2 appears sigmoid.

Q.12 Have you heard about hypoxia? Try to gather information about it, and discuss with your friends.

Hypoxia is a condition, wherein the tissues are not oxygenated adequately due to decreased supply of oxygen to the lungs. The oxygen deprivation can have severe adverse effects on various body cells and thus, several important biological processes get hampered. In general, hypoxia results in a pathological condition. There are various types of hypoxia depending upon the reason of inadequate oxygen supply to the body:

  1. Hypoxic hypoxia or generalized hypoxia: This results because of an inadequate saturation of blood with oxygen due to a reduced supply of oxygen in the air, decreased lung ventilation or respiratory disease.
  2. Anaemic hypoxia: This is due to decreased haemoglobin concentration.
  3. Stagnant hypoxia: This is due to poor circulation of the blood.
  4. Histotoxic hypoxia: This occurs when the tissues are unable to use oxygen due to cyanide or carbon monoxide poisoning.

Q.13 Distinguish between

(a) IRV and ERV

(b) Inspiratory capacity and expiratory capacity.

(c) Vital capacity and Total lung capacity.

Ans-

(a) IRV and ERV:

IRV ERV
IRV (Inspiratory Reserve Volume) is the additional volume of air that a person can inhale by a forceful inspiration. ERV (Expiratory Reserve Volume) is the additional volume of air that a person can exhale by a forceful expiration.
It is approximately 2500-3500 mL. It is approximately 1000-1100 mL.

(b) Inspiratory capacity and expiratory capacity:

Inspiratory capacity Expiratory capacity
Inspiratory capacity is the volume of air that can be inhaled after a normal expiration. Expiratory capacity is the volume of air that can be exhaled after a normal inspiration.
It includes tidal volume and IRV. It includes tidal volume and ERV.

(c) Vital capacity and Total lung capacity:

Vital capacity Total lung capacity
Vital capacity refers to the volume of air a healthy person can inhale after a forced exhalation or the volume of air a person can exhale after a forced inhalation. Total lung capacity is the total volume of air present in the lungs after a forced inhalation.
It includes ERV, IRV, and tidal volume. This includes ERV, IRV, residual volume and tidal volume.
It is about 4000 mL. It is about 5000-6000 mL.

Q.14 What is Tidal volume? Find out the Tidal volume (approximate value) for a healthy human in an hour.

Ans-

Tidal volume is the volume of air that is inhaled or exhaled during normal respiration. It is about 500 mL. A healthy person breathes about 12-16 times in a minute.

The approximate value of tidal volume for a healthy human per hour can be calculated as follows:

The tidal volume of a healthy human in an hour = Tidal volume per breath X Number of times an adult human being breathes per minute X 60 minutes

= 500 mL X 12-16 times per minute X 60 minutes

= 3,60,000 – 4,80,000 mL

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