CBSE Class 11 Biology – Locomotion and Movement | NCERT-Based Study Module & Revision Notes

Course & Examination Details

• Course: CBSE Class 11 Biology
• Prescribed By: Central Board of Secondary Education
• Based On: NCERT
• Unit: Unit V – Human Physiology
• Chapter: Chapter 20 – Locomotion and Movement
• Chapter Importance: High conceptual weightage; frequently assessed through diagrams, short answers, long answers, and MCQs in CBSE Class 11 examinations

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Locomotion and Movement Class 11 Biology – NCERT Study Module & Revision Notes

CBSE Board Examination Relevance

This chapter is commonly assessed through:

• Definitions and distinctions between movement and locomotion
• Structure and functions of bones and joints
• Types of muscles and mechanism of muscle contraction
• Disorders of skeletal and muscular systems
• Assertion–Reason and case-based questions

A clear understanding of this chapter also builds a foundation for Human Physiology topics in Class 12 and competitive exams like NEET (UG).

Introduction: Movement and Locomotion

Living organisms exhibit various types of movements. Movement refers to the change in position of body parts or the whole organism, while locomotion is the movement of the entire body from one place to another. In humans, locomotion and movement are achieved by the coordinated functioning of the skeletal system, muscular system, and nervous system.

This chapter explains:

• The structural framework that supports movement
• The role of muscles in producing force
• The molecular mechanism behind muscle contraction

1. Types of Movement

Human body shows different types of movements:

1. Amoeboid movement: Found in white blood cells using pseudopodia
2. Ciliary movement: Found in respiratory tract and fallopian tubes
3. Muscular movement: Responsible for locomotion and movement of limbs

Muscular movement is the most prominent type in humans and depends on skeletal muscles.

2. Skeletal System

The skeletal system provides support, protection, and framework for movement.

2.1 Functions of the Skeletal System

• Provides shape and support to the body
• Protects vital organs (skull protects brain, rib cage protects heart and lungs)
• Serves as attachment sites for muscles
• Helps in movement and locomotion
• Stores minerals like calcium and phosphorus
• Produces blood cells in bone marrow

2.2 Components of the Skeletal System

The human skeletal system consists of:

• Bones
• Cartilage
• Ligaments
• Joints

An adult human has 206 bones, grouped into axial and appendicular skeleton.

2.3 Axial Skeleton

The axial skeleton consists of 80 bones and includes:

(a) Skull

• Composed of 22 bones
• 8 cranial bones protect the brain
• 14 facial bones form the face
• Hyoid bone supports tongue and larynx

(b) Vertebral Column

• Consists of 26 vertebrae
• Regions: cervical, thoracic, lumbar, sacral, coccygeal
• Provides support and protects spinal cord

(c) Rib Cage

• Consists of 12 pairs of ribs and sternum
• Protects heart and lungs
• Aids in respiration

2.4 Appendicular Skeleton

The appendicular skeleton consists of 126 bones and includes:

(a) Pectoral Girdle

• Composed of clavicle and scapula
• Attaches upper limbs to axial skeleton

(b) Upper Limbs

• Consist of humerus, radius, ulna, carpals, metacarpals, phalanges

(c) Pelvic Girdle

• Formed by hip bones
• Attaches lower limbs and supports body weight

(d) Lower Limbs

• Include femur, tibia, fibula, tarsals, metatarsals, phalanges

3. Joints

Joints are points where two or more bones meet. They allow movement and flexibility.

3.1 Types of Joints

(a) Fibrous Joints

• Immovable
• Found in skull

(b) Cartilaginous Joints

• Slightly movable
• Found between vertebrae

(c) Synovial Joints

• Freely movable
• Have synovial fluid

Examples of synovial joints:

• Ball and socket joint: Shoulder, hip
• Hinge joint: Elbow, knee
• Pivot joint: Atlas and axis
• Gliding joint: Wrist, ankle

4. Muscular System

Muscles are specialized tissues capable of contraction and relaxation.

4.1 Types of Muscles

(a) Skeletal Muscles

• Striated and voluntary
• Attached to bones
• Responsible for movement and posture

(b) Smooth Muscles

• Non-striated and involuntary
• Found in internal organs like intestine and blood vessels

(c) Cardiac Muscles

• Striated and involuntary
• Found only in heart
• Show rhythmic contractions

4.2 Structure of Skeletal Muscle

A skeletal muscle consists of:

• Muscle bundles (fascicles)
• Muscle fibres
• Myofibrils

Each muscle fibre is bounded by sarcolemma and contains sarcoplasm.

5. Myofibrils and Sarcomere

Myofibrils are made of repeating units called sarcomeres, which are the functional units of muscle contraction.

5.1 Structure of Sarcomere

• Actin filaments: Thin filaments
• Myosin filaments: Thick filaments

Key bands:

• A band: Dark band with myosin
• I band: Light band with actin
• Z line: Boundary of sarcomere
• H zone: Lighter area in A band

6. Muscle Contraction

Muscle contraction occurs due to interaction between actin and myosin filaments.

6.1 Sliding Filament Theory

Proposed by Huxley and Hanson, this theory explains muscle contraction as sliding of actin over myosin.

Steps of Muscle Contraction

1. Motor neuron releases acetylcholine
2. Action potential spreads over sarcolemma
3. Calcium ions released from sarcoplasmic reticulum
4. Myosin heads bind to actin forming cross-bridges
5. ATP provides energy for sliding of filaments
6. Sarcomere shortens causing contraction

6.2 Role of ATP and Calcium

• ATP provides energy for detachment and reattachment of myosin heads
• Calcium ions expose binding sites on actin by moving tropomyosin

7. Muscle Relaxation

• Occurs when stimulation stops
• Calcium ions are pumped back into sarcoplasmic reticulum
• Cross-bridges break
• Muscle returns to original length

8. Disorders of Skeletal and Muscular System

(a) Myasthenia Gravis

• Autoimmune disorder
• Weakness of skeletal muscles

(b) Muscular Dystrophy

• Genetic disorder
• Progressive muscle degeneration

(c) Arthritis

• Inflammation of joints
• Causes pain and stiffness

(d) Osteoporosis

• Decrease in bone density
• Common in elderly

9. Coordination of Skeletal and Muscular Systems

Movement occurs due to:

• Contraction of skeletal muscles
• Support from bones
• Flexibility at joints
• Control by nervous system

Agonist and antagonist muscles work together to produce smooth movement.

Quick Revision Notes (CBSE Exam Focus)

• Movement ≠ locomotion
• Humans have 206 bones
• Nephron is not related to locomotion
• Skeletal muscles are voluntary
• Sarcomere is functional unit of muscle
• Sliding filament theory explains contraction
• ATP and Ca²⁺ are essential for contraction
• Joints enable movement

NCERT & CBSE Compliance Confirmation

✔ Strictly based on NCERT Class 11 Biology
✔ Terminology and concepts as per textbook
✔ No out-of-syllabus content
✔ Ideal for CBSE Class 11 board examinations

Conclusion

The chapter “Locomotion and Movement” explains how the human body achieves movement through a well-coordinated interaction of bones, muscles, and joints. Understanding the skeletal framework, types of muscles, and molecular mechanism of muscle contraction is essential for mastering Human Physiology and scoring well in CBSE Class 11 Biology examinations.