CBSE Class 11 Biology Revision Notes Chapter 17 Locomotion and Movement

Locomotion and Movement explains how organisms and body parts move using muscles, bones and joints.

In CBSE Class 11 Biology, this chapter covers movement types, muscle contraction, skeletal system, joints and related disorders.

Locomotion and Movement explains different forms of movement shown by living organisms. Some movements change the position of a body part, while locomotion changes the place or location of the whole organism. Walking, running, swimming, climbing and flying are examples of locomotion.

Use CBSE Class 11 Biology Revision Notes Chapter 17 for 2026–27 to revise types of movement, muscle structure, skeletal muscle, sarcomere, sliding filament theory, skeletal system, axial skeleton, appendicular skeleton, joints and disorders of muscular and skeletal systems.

Key Takeaways

• Movement: A change in position of the body or any body part.
• Locomotion: A voluntary movement that changes the location of an organism.
• Muscle contraction: Explained by the sliding filament theory of actin and myosin.
• Skeletal system: Made of 206 bones and supports movement, posture and protection.

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Locomotion and Movement Class 11 Biology Notes: Chapter Overview

Movement is a major feature of living organisms. Amoeba shows protoplasmic streaming, Paramoecium uses cilia, Euglena uses flagella, and humans move limbs, eyelids, jaws and tongue.

All locomotions are movements, but all movements are not locomotions.

Difference Between Movement and Locomotion

Locomotion is generally used for finding food, shelter, mate, breeding ground, favourable climate or escaping from predators.

Types of Movement in CBSE Class 11 Biology Notes Chapter 17

Cells of the human body show three main types of movement.

These movements help in defence, transport and body movement.

Amoeboid Movement

Amoeboid movement occurs through pseudopodia formed by streaming of protoplasm.

Leucocytes use amoeboid movement to move towards foreign particles.

Ciliary Movement

Ciliary movement occurs in internal tubular organs lined by ciliated epithelium.

Cilia move in a coordinated manner and help transport materials.

Muscular Movement

Muscular movement is produced by muscle contraction.

Muscular movement is important for locomotion and many body functions.

Muscle in Locomotion and Movement Class 11 Notes

Muscle is a specialised tissue of mesodermal origin. In an adult human, muscles form about 40–50% of body weight.

Muscles are classified based on location, appearance and control.

Types of Muscles in Class 11 Biology Chapter 17 Notes

The human body has three types of muscles.

Skeletal Muscles

Skeletal muscles are closely associated with bones. They appear striped under the microscope and are called striated muscles.

Skeletal muscles are mainly involved in locomotory actions.

Visceral Muscles

Visceral muscles occur in the walls of hollow organs such as the alimentary canal and reproductive tract.

They do not show striations.

Cardiac Muscles

Cardiac muscles are found in the heart.

Cardiac muscles are not directly controlled by the voluntary nervous system.

Skeletal Muscle Structure in Locomotion and Movement Class 11 Notes

A skeletal muscle is made of muscle bundles or fascicles held together by fascia.

Each muscle fibre is covered by sarcolemma and contains sarcoplasm.

Muscle Fibre

The sarcoplasmic reticulum stores calcium ions needed for muscle contraction.

Myofibril and Sarcomere in CBSE Class 11 Biology Notes Chapter 17

Myofibrils show alternate dark and light bands due to the arrangement of actin and myosin.

Sarcomere is the functional unit of muscle contraction.

Actin and Myosin Filaments

The striated appearance of skeletal muscle is due to the arrangement of actin and myosin.

Structure of Contractile Proteins

Muscle contraction depends on actin, myosin, tropomyosin and troponin.

Actin Filament

Each actin filament is made of two F-actin strands helically wound around each other.

In the resting state, a subunit of troponin masks the active binding sites for myosin on actin.

Myosin Filament

Each myosin filament is made of many meromyosin units.

The myosin head uses ATP energy during contraction.

Sliding Filament Theory in Locomotion and Movement Class 11 Biology Notes

Sliding filament theory explains muscle contraction. It states that contraction occurs when thin actin filaments slide over thick myosin filaments.

This theory is one of the most important concepts in Chapter 17.

Steps in Muscle Contraction

Muscle contraction begins with a signal from the central nervous system.

A motor neuron and the muscle fibres connected to it form a motor unit.

Cross Bridge Cycle

Repeated cross bridge formation and breakage causes further sliding.

Muscle Relaxation

Muscle relaxes when calcium ions are pumped back into the sarcoplasmic reticulum.

Relaxation requires ATP because calcium must be actively pumped back.

Red Fibres and White Fibres

Muscle fibres are grouped based on myoglobin content and energy production.

Red fibres store more oxygen and are suited for sustained activity.

Muscle Fatigue

Repeated activation of muscles can cause fatigue.

Fatigue reduces the ability of muscles to contract efficiently.

Skeletal System in CBSE Class 11 Biology Revision Notes Chapter 17

The skeletal system is made of bones and cartilages. It supports movement and body posture.

The skeletal system protects organs and provides attachment sites for muscles.

Axial Skeleton in Locomotion and Movement Class 11 Notes

The axial skeleton has 80 bones along the main axis of the body.

The skull, vertebral column, sternum and ribs form the axial skeleton.

Skull

The skull has cranial and facial bones.

The cranium protects the brain.

Vertebral Column

The vertebral column has 26 vertebrae.

The first vertebra is called atlas. It articulates with the occipital condyles.

Functions of Vertebral Column

The number of cervical vertebrae is seven in almost all mammals, including humans.

Ribs and Rib Cage

Humans have 12 pairs of ribs.

Thoracic vertebrae, ribs and sternum form the rib cage.

Appendicular Skeleton in Class 11 Biology Chapter 17 Notes

The appendicular skeleton includes limb bones and girdles.

Each limb has 30 bones.

Bones of Forelimb

Bones of Hindlimb

Femur is the longest bone in the human body.

Pectoral Girdle and Pelvic Girdle

Girdles attach limbs to the axial skeleton.

Pectoral Girdle

Each half of the pectoral girdle has one clavicle and one scapula.

The glenoid cavity forms the shoulder joint with the head of the humerus.

Pelvic Girdle

The pelvic girdle has two coxal bones.

Each coxal bone is formed by fusion of ilium, ischium and pubis.

Joints in CBSE Class 11 Biology Notes Chapter 17

Joints are points of contact between bones or between bones and cartilage. They help movement by acting as fulcrums.

Fibrous Joints

Fibrous joints do not allow movement. Skull bones fuse end-to-end with dense fibrous connective tissue called sutures.

Cartilaginous Joints

Cartilaginous joints allow limited movement. Adjacent vertebrae are joined by cartilage.

Synovial Joints

Synovial joints have a fluid-filled synovial cavity between articulating bone surfaces.

Synovial joints allow maximum movement.

Axial and Appendicular Skeleton Difference

Actin and Myosin Difference

Skeletal, Visceral and Cardiac Muscles Difference

Disorders of Muscular and Skeletal System

The muscular and skeletal systems may be affected by autoimmune, genetic, age-related and metabolic disorders.

Myasthenia Gravis

Myasthenia gravis affects the neuromuscular junction. It can cause fatigue, weakness and paralysis of skeletal muscles.

Muscular Dystrophy

Muscular dystrophy is a genetic disorder that causes progressive degeneration of skeletal muscles.

Tetany

Tetany causes rapid spasms or wild contractions in muscles due to low calcium ion levels in body fluids.

Arthritis

Arthritis is inflammation of joints. It can cause pain, stiffness and reduced joint movement.

Osteoporosis

Osteoporosis is an age-related disorder. It is marked by decreased bone mass and increased chances of fractures.

Decreased estrogen level is a common cause.

Gout

Gout is inflammation of joints due to accumulation of uric acid crystals.

Important Terms from Locomotion and Movement Class 11 Notes

NCERT-Based Exam Points

• All locomotions are movements, but all movements are not locomotions.
• Locomotion helps animals search for food, shelter, mate and favourable conditions.
• Human cells show amoeboid, ciliary and muscular movements.
• Macrophages and leucocytes show amoeboid movement.
• Ciliary movement helps remove dust from trachea.
• Ciliary movement helps passage of ova in the female reproductive tract.
• Muscle is of mesodermal origin.
• Muscles form about 40–50% of adult human body weight.
• Muscle properties include excitability, contractility, extensibility and elasticity.
• Skeletal muscles are striated and voluntary.
• Visceral muscles are smooth and involuntary.
• Cardiac muscles are striated, branched and involuntary.
• Skeletal muscle has fascicles, muscle fibres and myofibrils.
• Sarcolemma is the plasma membrane of muscle fibre.
• Sarcoplasmic reticulum stores calcium ions.
• Actin forms thin filaments.
• Myosin forms thick filaments.
• Sarcomere is the functional unit of contraction.
• I band contains actin.
• A band contains myosin.
• H zone is the central part of thick filament not overlapped by thin filament.
• Troponin masks active binding sites on actin in resting muscle.
• Myosin head has ATPase activity.
• Sliding filament theory explains muscle contraction.
• During contraction, I band reduces and A band remains same.
• Calcium ions are needed to expose active sites on actin.
• Myoglobin stores oxygen in muscles.
• Red fibres have more myoglobin and mitochondria.
• White fibres have less myoglobin and fewer mitochondria.
• Human skeletal system has 206 bones.
• Axial skeleton has 80 bones.
• Skull has 22 bones.
• Human skull is dicondylic.
• Vertebral column has 26 vertebrae.
• Cervical vertebrae are seven in almost all mammals.
• Humans have 12 pairs of ribs.
• First seven pairs of ribs are true ribs.
• Last two pairs are floating ribs.
• Each limb has 30 bones.
• Femur is the longest bone.
• Fibrous joints do not allow movement.
• Synovial joints allow considerable movement.
• Myasthenia gravis affects neuromuscular junction.
• Osteoporosis increases chances of fractures.
• Gout is due to uric acid crystal accumulation.

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