Chapter 17 of Class 11 Biology is titled Locomotion and Movement. This chapter explains how different parts of the body help in movement and how muscles and bones work together. From walking and running to the beating of the heart – movement is a basic activity of life. The chapter covers types of muscles, structure of muscles, mechanism of muscle contraction, bones and joints, and various disorders related to the musculoskeletal system.
I chose to write about this chapter because many students find it both interesting and a little tricky. It contains diagrams, processes, and a mix of biology and basic physics. If you’ve ever wondered how your hand lifts, how your legs coordinate while running, or how an athlete moves faster – this chapter holds the answers. It’s also quite relevant from NEET point of view, especially the sliding filament theory of muscle contraction. Understanding this chapter gives a solid foundation in human physiology and also builds awareness of our body movements and structure in real life.
What is Movement and Locomotion?
Movement means any change in position or shape of a body part. Locomotion is a type of movement that helps an organism move from one place to another.
Types of Movement
- Amoeboid Movement: Seen in leucocytes and macrophages
- Ciliary Movement: Helps in movement of ova in fallopian tube
- Muscular Movement: Seen in limbs and other parts
Types of Muscles
There are three types of muscles explained in the chapter:
| Muscle Type | Structure | Location | Voluntary/Involuntary |
|---|---|---|---|
| Skeletal | Striated | Attached to bones | Voluntary |
| Smooth | Unstriated | Internal organs | Involuntary |
| Cardiac | Striated, branched | Heart | Involuntary |
Structure of Muscle Fibre
Each muscle fibre is made of many myofibrils. These have repeating units called sarcomeres, made of actin (thin) and myosin (thick) filaments.
Muscle Contraction Mechanism
This part of the chapter explains how muscles contract and relax. The Sliding Filament Theory explains how actin and myosin slide over each other with the help of ATP, causing contraction.
Steps involved:
- Nerve impulse reaches the muscle
- Calcium ions are released
- ATP is used to slide filaments
- Muscle contracts
- Calcium is reabsorbed and muscle relaxes
Skeletal System and Its Functions
The skeletal system includes all the bones and joints of the body. Humans have 206 bones in total. Major functions include:
- Supporting the body
- Protection of internal organs
- Helping in movement
- Blood cell formation (in bone marrow)
Types of Skeleton
- Axial Skeleton: Skull, vertebral column, rib cage
- Appendicular Skeleton: Limbs, pelvic and pectoral girdles
Types of Joints
- Fibrous Joints: Immovable (e.g., skull)
- Cartilaginous Joints: Slightly movable (e.g., vertebrae)
- Synovial Joints: Freely movable (e.g., knee, elbow)
Types of synovial joints include:
- Hinge joint (knee)
- Ball and socket (shoulder)
- Pivot (neck)
- Gliding (wrist)
Disorders of Muscular and Skeletal System
- Myasthenia Gravis: Autoimmune disorder where muscles become weak
- Muscular Dystrophy: Inherited disorder, muscle degeneration
- Arthritis: Inflammation of joints
- Osteoporosis: Loss of bone density, common in old age
Download PDF
Click here to download the official NCERT PDF of Chapter 17 – Locomotion and Movement
Download NCERT Class 11 Biology Chapter 17 PDF
