NCERT Textbook: Locomotion & Movement | Biology Class 11 - NEET PDF Download

 Page 1


LOCOMOTION AND MOVEMENT 217
Movement is one of the  significant features of living beings. Animals and
plants exhibit a wide range of movements. Streaming of protoplasm in
the unicellular organisms like Amoeba is a simple form of movement.
Movement of cilia, flagella and tentacles are shown by many organisms.
Human beings can move limbs, jaws, eyelids, tongue, etc. Some of the
movements result in a change of place or location. Such voluntary
movements are called locomotion. Walking, running, climbing, flying,
swimming are all some forms of locomotory movements. Locomotory
structures need not be different from those affecting other types of
movements. For example, in Paramoecium, cilia helps in the movement of
food through cytopharynx and in locomotion as well. Hydra can use its
tentacles for capturing its prey and also use them for locomotion. We use
limbs for changes in body postures and locomotion as well. The above
observations suggest that movements and locomotion cannot be studied
separately. The two may be linked by stating that all locomotions are
movements but all movements are not locomotions.
Methods of locomotion performed by animals vary with their habitats
and the demand of the situation. However, locomotion is generally for
search of food, shelter, mate, suitable breeding grounds, favourable
climatic conditions or to escape from enemies/predators.
17.1 TYPES OF MOVEMENT
Cells of the human body exhibit three main types of movements, namely,
amoeboid, ciliary and muscular.
LOCOMOTION AND MOVEMENT
CHAPTER  17
17.1 Types of
Movement
17.2 Muscle
17.3 Skeletal
System
17.4 Joints
17.5 Disorders of
Muscular and
Skeletal System
2024-25
Page 2


LOCOMOTION AND MOVEMENT 217
Movement is one of the  significant features of living beings. Animals and
plants exhibit a wide range of movements. Streaming of protoplasm in
the unicellular organisms like Amoeba is a simple form of movement.
Movement of cilia, flagella and tentacles are shown by many organisms.
Human beings can move limbs, jaws, eyelids, tongue, etc. Some of the
movements result in a change of place or location. Such voluntary
movements are called locomotion. Walking, running, climbing, flying,
swimming are all some forms of locomotory movements. Locomotory
structures need not be different from those affecting other types of
movements. For example, in Paramoecium, cilia helps in the movement of
food through cytopharynx and in locomotion as well. Hydra can use its
tentacles for capturing its prey and also use them for locomotion. We use
limbs for changes in body postures and locomotion as well. The above
observations suggest that movements and locomotion cannot be studied
separately. The two may be linked by stating that all locomotions are
movements but all movements are not locomotions.
Methods of locomotion performed by animals vary with their habitats
and the demand of the situation. However, locomotion is generally for
search of food, shelter, mate, suitable breeding grounds, favourable
climatic conditions or to escape from enemies/predators.
17.1 TYPES OF MOVEMENT
Cells of the human body exhibit three main types of movements, namely,
amoeboid, ciliary and muscular.
LOCOMOTION AND MOVEMENT
CHAPTER  17
17.1 Types of
Movement
17.2 Muscle
17.3 Skeletal
System
17.4 Joints
17.5 Disorders of
Muscular and
Skeletal System
2024-25
218 BIOLOGY
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 microfilaments are also involved in amoeboid 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.
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. Locomotion requires a perfect coordinated activity of muscular,
skeletal and neural systems. In this chapter, you will learn about the
types of muscles, their structure, mechanism of their contraction and
important aspects of the skeletal system.
17.2 MUSCLE
You have studied in Chapter 8 that the cilia and flagella are the outgrowths
of the cell membrane. Flagellar movement helps in the swimming of
spermatozoa, maintenance of water current in the canal system of sponges
and in locomotion of Protozoans like Euglena. 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. They have
special properties like excitability, contractility, extensibility and
elasticity. Muscles have been classified using different criteria,
namely location, appearance and nature of regulation of their
activities. Based on their location, three types of muscles are
identified : (i) Skeletal (ii) Visceral and (iii) Cardiac.
Skeletal 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.
Visceral muscles 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 assist, for example, in the transportation of food
through the digestive tract and gametes through the genital tract.
2024-25
Page 3


LOCOMOTION AND MOVEMENT 217
Movement is one of the  significant features of living beings. Animals and
plants exhibit a wide range of movements. Streaming of protoplasm in
the unicellular organisms like Amoeba is a simple form of movement.
Movement of cilia, flagella and tentacles are shown by many organisms.
Human beings can move limbs, jaws, eyelids, tongue, etc. Some of the
movements result in a change of place or location. Such voluntary
movements are called locomotion. Walking, running, climbing, flying,
swimming are all some forms of locomotory movements. Locomotory
structures need not be different from those affecting other types of
movements. For example, in Paramoecium, cilia helps in the movement of
food through cytopharynx and in locomotion as well. Hydra can use its
tentacles for capturing its prey and also use them for locomotion. We use
limbs for changes in body postures and locomotion as well. The above
observations suggest that movements and locomotion cannot be studied
separately. The two may be linked by stating that all locomotions are
movements but all movements are not locomotions.
Methods of locomotion performed by animals vary with their habitats
and the demand of the situation. However, locomotion is generally for
search of food, shelter, mate, suitable breeding grounds, favourable
climatic conditions or to escape from enemies/predators.
17.1 TYPES OF MOVEMENT
Cells of the human body exhibit three main types of movements, namely,
amoeboid, ciliary and muscular.
LOCOMOTION AND MOVEMENT
CHAPTER  17
17.1 Types of
Movement
17.2 Muscle
17.3 Skeletal
System
17.4 Joints
17.5 Disorders of
Muscular and
Skeletal System
2024-25
218 BIOLOGY
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 microfilaments are also involved in amoeboid 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.
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. Locomotion requires a perfect coordinated activity of muscular,
skeletal and neural systems. In this chapter, you will learn about the
types of muscles, their structure, mechanism of their contraction and
important aspects of the skeletal system.
17.2 MUSCLE
You have studied in Chapter 8 that the cilia and flagella are the outgrowths
of the cell membrane. Flagellar movement helps in the swimming of
spermatozoa, maintenance of water current in the canal system of sponges
and in locomotion of Protozoans like Euglena. 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. They have
special properties like excitability, contractility, extensibility and
elasticity. Muscles have been classified using different criteria,
namely location, appearance and nature of regulation of their
activities. Based on their location, three types of muscles are
identified : (i) Skeletal (ii) Visceral and (iii) Cardiac.
Skeletal 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.
Visceral muscles 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 assist, for example, in the transportation of food
through the digestive tract and gametes through the genital tract.
2024-25
LOCOMOTION AND MOVEMENT 219
muscle fibre is lined by the plasma membrane called sarcolemma
enclosing the sarcoplasm. Muscle fibre is a syncitium as the sarcoplasm
contains many nuclei. The endoplasmic reticulum, i.e., sarcoplasmic
reticulum of the muscle fibres is the store house of calcium ions. 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. Each myofibril has alternate dark and light bands on it. A
detailed study of the myofibril 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
As the name suggests, Cardiac muscles are the muscles of heart.
Many cardiac muscle cells assemble in a branching pattern to form a
cardiac muscle. Based on appearance, cardiac muscles are striated. They
are involuntary in nature as the nervous system does not control their
activities directly.
Let us examine a skeletal muscle in detail to understand the structure
and mechanism of contraction. 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 (Figure 17.1). Each
Fascicle
(muscle bundle)
Muscle fibre
(muscle cell)
Sarcolemma
Blood capillary
Figure 17.1 Diagrammatic cross sectional view of a muscle showing muscle bundles
and muscle fibres
2024-25
Page 4


LOCOMOTION AND MOVEMENT 217
Movement is one of the  significant features of living beings. Animals and
plants exhibit a wide range of movements. Streaming of protoplasm in
the unicellular organisms like Amoeba is a simple form of movement.
Movement of cilia, flagella and tentacles are shown by many organisms.
Human beings can move limbs, jaws, eyelids, tongue, etc. Some of the
movements result in a change of place or location. Such voluntary
movements are called locomotion. Walking, running, climbing, flying,
swimming are all some forms of locomotory movements. Locomotory
structures need not be different from those affecting other types of
movements. For example, in Paramoecium, cilia helps in the movement of
food through cytopharynx and in locomotion as well. Hydra can use its
tentacles for capturing its prey and also use them for locomotion. We use
limbs for changes in body postures and locomotion as well. The above
observations suggest that movements and locomotion cannot be studied
separately. The two may be linked by stating that all locomotions are
movements but all movements are not locomotions.
Methods of locomotion performed by animals vary with their habitats
and the demand of the situation. However, locomotion is generally for
search of food, shelter, mate, suitable breeding grounds, favourable
climatic conditions or to escape from enemies/predators.
17.1 TYPES OF MOVEMENT
Cells of the human body exhibit three main types of movements, namely,
amoeboid, ciliary and muscular.
LOCOMOTION AND MOVEMENT
CHAPTER  17
17.1 Types of
Movement
17.2 Muscle
17.3 Skeletal
System
17.4 Joints
17.5 Disorders of
Muscular and
Skeletal System
2024-25
218 BIOLOGY
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 microfilaments are also involved in amoeboid 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.
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. Locomotion requires a perfect coordinated activity of muscular,
skeletal and neural systems. In this chapter, you will learn about the
types of muscles, their structure, mechanism of their contraction and
important aspects of the skeletal system.
17.2 MUSCLE
You have studied in Chapter 8 that the cilia and flagella are the outgrowths
of the cell membrane. Flagellar movement helps in the swimming of
spermatozoa, maintenance of water current in the canal system of sponges
and in locomotion of Protozoans like Euglena. 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. They have
special properties like excitability, contractility, extensibility and
elasticity. Muscles have been classified using different criteria,
namely location, appearance and nature of regulation of their
activities. Based on their location, three types of muscles are
identified : (i) Skeletal (ii) Visceral and (iii) Cardiac.
Skeletal 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.
Visceral muscles 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 assist, for example, in the transportation of food
through the digestive tract and gametes through the genital tract.
2024-25
LOCOMOTION AND MOVEMENT 219
muscle fibre is lined by the plasma membrane called sarcolemma
enclosing the sarcoplasm. Muscle fibre is a syncitium as the sarcoplasm
contains many nuclei. The endoplasmic reticulum, i.e., sarcoplasmic
reticulum of the muscle fibres is the store house of calcium ions. 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. Each myofibril has alternate dark and light bands on it. A
detailed study of the myofibril 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
As the name suggests, Cardiac muscles are the muscles of heart.
Many cardiac muscle cells assemble in a branching pattern to form a
cardiac muscle. Based on appearance, cardiac muscles are striated. They
are involuntary in nature as the nervous system does not control their
activities directly.
Let us examine a skeletal muscle in detail to understand the structure
and mechanism of contraction. 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 (Figure 17.1). Each
Fascicle
(muscle bundle)
Muscle fibre
(muscle cell)
Sarcolemma
Blood capillary
Figure 17.1 Diagrammatic cross sectional view of a muscle showing muscle bundles
and muscle fibres
2024-25
220 BIOLOGY
myosin. Both the proteins are arranged as rod-like structures, parallel to
each other and also to the longitudinal axis of the myofibrils. 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 (Figure 17.2). 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.
Figure 17.2 Diagrammatic representation of (a) anatomy of a muscle fibre showing
a sarcomere (b) a sarcomere
(a)
(b)
2024-25
Page 5


LOCOMOTION AND MOVEMENT 217
Movement is one of the  significant features of living beings. Animals and
plants exhibit a wide range of movements. Streaming of protoplasm in
the unicellular organisms like Amoeba is a simple form of movement.
Movement of cilia, flagella and tentacles are shown by many organisms.
Human beings can move limbs, jaws, eyelids, tongue, etc. Some of the
movements result in a change of place or location. Such voluntary
movements are called locomotion. Walking, running, climbing, flying,
swimming are all some forms of locomotory movements. Locomotory
structures need not be different from those affecting other types of
movements. For example, in Paramoecium, cilia helps in the movement of
food through cytopharynx and in locomotion as well. Hydra can use its
tentacles for capturing its prey and also use them for locomotion. We use
limbs for changes in body postures and locomotion as well. The above
observations suggest that movements and locomotion cannot be studied
separately. The two may be linked by stating that all locomotions are
movements but all movements are not locomotions.
Methods of locomotion performed by animals vary with their habitats
and the demand of the situation. However, locomotion is generally for
search of food, shelter, mate, suitable breeding grounds, favourable
climatic conditions or to escape from enemies/predators.
17.1 TYPES OF MOVEMENT
Cells of the human body exhibit three main types of movements, namely,
amoeboid, ciliary and muscular.
LOCOMOTION AND MOVEMENT
CHAPTER  17
17.1 Types of
Movement
17.2 Muscle
17.3 Skeletal
System
17.4 Joints
17.5 Disorders of
Muscular and
Skeletal System
2024-25
218 BIOLOGY
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 microfilaments are also involved in amoeboid 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.
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. Locomotion requires a perfect coordinated activity of muscular,
skeletal and neural systems. In this chapter, you will learn about the
types of muscles, their structure, mechanism of their contraction and
important aspects of the skeletal system.
17.2 MUSCLE
You have studied in Chapter 8 that the cilia and flagella are the outgrowths
of the cell membrane. Flagellar movement helps in the swimming of
spermatozoa, maintenance of water current in the canal system of sponges
and in locomotion of Protozoans like Euglena. 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. They have
special properties like excitability, contractility, extensibility and
elasticity. Muscles have been classified using different criteria,
namely location, appearance and nature of regulation of their
activities. Based on their location, three types of muscles are
identified : (i) Skeletal (ii) Visceral and (iii) Cardiac.
Skeletal 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.
Visceral muscles 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 assist, for example, in the transportation of food
through the digestive tract and gametes through the genital tract.
2024-25
LOCOMOTION AND MOVEMENT 219
muscle fibre is lined by the plasma membrane called sarcolemma
enclosing the sarcoplasm. Muscle fibre is a syncitium as the sarcoplasm
contains many nuclei. The endoplasmic reticulum, i.e., sarcoplasmic
reticulum of the muscle fibres is the store house of calcium ions. 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. Each myofibril has alternate dark and light bands on it. A
detailed study of the myofibril 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
As the name suggests, Cardiac muscles are the muscles of heart.
Many cardiac muscle cells assemble in a branching pattern to form a
cardiac muscle. Based on appearance, cardiac muscles are striated. They
are involuntary in nature as the nervous system does not control their
activities directly.
Let us examine a skeletal muscle in detail to understand the structure
and mechanism of contraction. 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 (Figure 17.1). Each
Fascicle
(muscle bundle)
Muscle fibre
(muscle cell)
Sarcolemma
Blood capillary
Figure 17.1 Diagrammatic cross sectional view of a muscle showing muscle bundles
and muscle fibres
2024-25
220 BIOLOGY
myosin. Both the proteins are arranged as rod-like structures, parallel to
each other and also to the longitudinal axis of the myofibrils. 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 (Figure 17.2). 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.
Figure 17.2 Diagrammatic representation of (a) anatomy of a muscle fibre showing
a sarcomere (b) a sarcomere
(a)
(b)
2024-25
LOCOMOTION AND MOVEMENT 221
17.2.1 Structure of Contractile Proteins
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 (Figure 17.3a).
Each myosin (thick) filament is also a polymerised protein. Many
monomeric proteins called Meromyosins (Figure 17.3b) 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.
Figure 17.3 (a) An actin (thin) filament (b) Myosin monomer (Meromyosin)
Actin binding sites
ATP binding sites
Head
Cross arm
(a)
(b)
17.2.2 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.
2024-25