NCERT Class 11 Biology Chapter 20 Notes Locomotion And Movement- Download PDF Notes

CBSE Quick Revision Notes Class 11 Biology Chapter 17: Locomotion and Movement are fundamental characteristics of all living organisms. Movement refers to a change in the position of a body or a part of the organism. Locomotion, a type of movement, involves the displacement of an organism from one place to another. Locomotion and Movement NCERT Notes for Class 11 Biology help you revise these major concepts given in the book in a short period of time during board exam preparation. CBSE Class 11 Biology Chapter 17 notes will help you with quick revision.

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This Story also Contains

1. NCERT Class 11 Chapter 17 Notes
2. Introduction
3. Types of Movement
4. Muscle
5. Skeletal System
6. Joints
7. Disorders of The Skeletal System
8. Subject Wise NCERT Exemplar Solutions
9. Most Important Questions for Class 11 Biology Chapter 20 Locomotion and Movement
10. Subject-Wise NCERT Solutions
11. Approach to Solve Questions of Class 11 Biology Chapter 20 Locomotion and Movement
12. Chapter-Wise NCERT Class 11 Notes Biology

This chapter explores different types of movements in muscular systems that facilitate locomotion and the mechanism behind muscle contraction. Understanding these concepts is essential to comprehending how organisms interact with the environment and perform daily activities. Having revision notes and NCERT Solutions handy is beneficial to save you time. Download the CBSE Notes for Class 11 Biology to use offline anywhere. Students must go through each topic in the chapter in Class 11 Notes Biology most easily and effectively as possible with the help of NCERT Notes for Class 11.

Also, Students can refer,

• NCERT Solutions for Class 11 Biology Chapter 20 Locomotion and Movement.
• NCERT Exemplar Class 11 Biology Chapter 20 Solutions Locomotion and Movement.

NCERT Class 11 Chapter 17 Notes

The summarized notes are given below:-

Introduction

Movement is important for survival as it helps in searching for food, escaping predators, and reproduction in animals. Locomotion is carried out by a well-organised, muscular and skeletal system controlled by the nervous system. Different organisms have evolved various forms of movement.

Types of Movement

The types of movement are described below-

Amoeboid:

Amoeboid movement is seen in unicellular organisms like Ameoba, and in certain cells of multicellular organisms such as leucocytes, it involves the formation of temporary projections called pseudopodia, which helps in engulfing food and movement.

Ciliary:

Ciliary movement is by small hair-like structures called cilia that beat in a coordinated manner. This type of movement is seen in the respiratory tract and the reproductive tract. Paramecium, an unicellular organisms use cilia for locomotion in water.

Muscular:

Muscular movement is the most advanced form of movement seen in higher animals, including humans. It is based on the contraction and relaxation of muscle fibres and is responsible for various functions such as walking, running, breathing and pumping blood.

Muscle

Muscles are made up of muscle fibres, which are composed of protein filaments called actin and myosin. These proteins play an important role in muscle contraction. Muscles are classified based on the structural function into three types:

Skeletal muscles: These are voluntary muscles attached to bones and help in movement.

Visceral Muscles: These are involuntary muscles found in internal organs like the stomach and intestine.

Cardiac Muscles: These are involuntary muscles found only in the heart and help in continuous contraction for pumping blood.

Structure of Skeletal Muscle in Detail

Skeletal muscle is a striated, voluntary muscle responsible for body movement. It is made up of muscle fibres, which are long, cylindrical and multinucleate cells. These fibres are grouped into bundles surrounded by connective tissues like epimysium, perimysium and endomysium. Each muscle fibre contains myofibrils that are further composed of repeating units called sarcomere- the functional unit of contraction. Sarcomere contains thick(myosin) and thin(actin) filaments arranged in an overlapping pattern that gives skeletal muscles a striated appearance. Skeletal muscles are richly supplied with nerves and blood vessels, ensuring proper contraction and oxygen supply. It is attached to bones by tendons, enabling movement through contraction and relaxation.

Structure of Sarcomere

The sarcomere is the functional unit of a striated muscle fibre responsible for muscle contraction. It is composed of a thick filament arranged in a highly organised repeating pattern between two lines and consists of different bands and zones that contribute to muscle contraction. Z lines are dark, thin protein bands that define the boundary of a sarcomere. Thin filaments are made up of actin, troponin and tropomyosin proteins. Actin filaments are attached to the Z line and extend to the centre of the sarcomere. Thick filaments are made up of myosin molecules with globular heads that form cross-bridges with actin during contraction. I-band(Isotropic band) is the region containing only thin filaments and shortens during muscle contraction. A-band(Anisotropic band) is the region containing the entire length of the thick filament and remains constant during contraction. The central region of the A-band contains only thick filaments called the H-zone and disappears during muscle contraction as actin slides over myosin. The M-line of the sarcomere holds the thick filament together and provides structural support to the myosin filaments.

Structure Of Contractile Protein:-

The two main contractile proteins in muscles are actin(thin filaments) and myosin(thick filaments). Actin filaments are made up of globular actin(G-actin) subunits that polymerise to form filamentous actin(F-actin). These filaments are associated with regulatory proteins like troponin and tropomyosin, which control muscle contraction and consist of myosin molecules, each with a tail and head. The myosin head has ATPase activity, which provides energy for contraction. During contraction, the myosin heads bind to actin filaments, forming cross bridges that pull actin towards the sarcomere's entre, leading to the shortening of the muscle fibre.

Mechanism of Muscle Contraction (Sliding Filament Theory):-

• A motor neuron releases the neurotransmitter acetylcholine at the neuromuscular junction.

• Acetylcholine binds to the receptors on the muscle fibre, triggering an action potential across the muscle membrane.

• The action potential travels through T-tubules, reaching the sarcoplasmic reticulum, which releases calcium ions into the sarcoplasm.

• Calcium ions play an important role in initiating muscle contraction by binding to troponin, a protein on actin filaments.

• Troponin undergoes a conformational change, causing tropomyosin to move away, exposing the myosin binding sites on actin.

• The myosin heads are attached to the exposed binding sites and actin filaments, forming cross bridges.

• Myosin is in an energised state, carrying ATP that is hydrolysed into ADP and inorganic phosphate.

• Once the cross-bridge is formed, myosin heads pivot, pulling the actin filament toward the centre of the sarcomere.

• This action is called power stroke, which results in muscle contraction.

• A new ATP molecule binds to myosin, causing it to detach from actin, which prevents continuous binding and allows relaxation.

• The ATP bound to myosin is hydrolysed, re-energising the myosin to return to its original position.

• Once the nerve impulse stops, calcium ions are pumped back into the sarcoplasmic reticulum.

• Troponin and Tropomyosin cover the myosin binding sites again, preventing further cross-bridge formation.

Skeletal System

• Consists of a framework of bones and a few cartilages.

• The human endoskeleton consists of 206 bones: Axial skeleton- 80 bones, and Appendicular skeleton– 126 bones

Axial Skeleton:

The axial skeleton forms a central framework of the body consisting of 80 bones. It includes the skull, vertebral, column, ribs, and sternum. The skull has 22 bones, protects the brain, and houses sensory organs. The vertebral column has 33 vertebrae, providing structural support and flexibility and allowing movement while protecting the spinal cord. The rib cage has 12 pairs of ribs and a sternum that protect vital organs like the heart and lungs. The skeleton maintains posture, protects vital organs, and serves as an attachment for muscles involved in the movement.

Ribs- 12 Pairs

• 1st to 7th pair: True ribs(Vertebro sternal ribs)
• 8,9,10th pair: Vertebro- chondral ribs
• 11th, and 12th pairs: Vertebral ribs (Floating ribs)
• Thoracic Vertebrae, ribs, and Sternum form the rib cage.

Appendicular Skeleton:

The appendicular skeleton consists of 126 bones that facilitate movement and include the limbs and girdles. The. The pectoral girdle consists of clavicles and scapulae connecting the upper limbs to the axial skeleton. The upper limbs include the humerus, radius, ulna, carpal, metacarpals, and phalanges. The pelvic girdle supports the body's weight and consists of hip bones(ilium, ischium and pubis). The lower limbs include the femur, tibia, fibula, tarsal, metatarsal, and phalanges. The skeleton plays an important role in locomotion and manipulation of objects.

Joints

Joints are the points of articulation between two or more bones, facilitating movement and flexibility. They are classified based on structure and function:

Fibrous joints, for example, sutures in the skull are immovable.

Cartilaginous joints, for example, intervertebral disc, allow limited movement

Synovial joints, for example, in the knee and shoulder, are highly movable and contain synovial fluid, which lubricates the joint and reduces friction. They are further categorised into hinge joints(elbow), ball and socket joints(the hip and shoulder), pivot joints(neck), gliding joints(wrist) and saddle joints(thumb). Joints play a critical role in the movement, providing stability and flexibility to the skeletal system.

Disorders of The Skeletal System

• Tetany: A medical condition characterised by involuntary muscle contractions and spasms that are usually caused by low calcium levels in the blood.

• Muscular dystrophy: A genetic condition leading to progressive muscle degeneration.

• Myasthenia gravis: An autoimmune disorder that weakens muscles by blocking nerve signals.

• Arthritis: Inflammation of joints, causing pain and stiffness.

• Osteoporosis: A condition where bones become weak and brittle due to calcium deficiency.

• Gout: A form of arthritis is caused by the accumulation of uric acid crystals in the joints, leading to severe pain, swelling, and inflammation.

Subject Wise NCERT Exemplar Solutions

• NCERT Exemplar Class 11 Solutions
• NCERT Exemplar Class 11 Maths
• NCERT Exemplar Class 11 Physics
• NCERT Exemplar Class 11 Chemistry
• NCERT Exemplar Class 11 Biology

Most Important Questions for Class 11 Biology Chapter 20 Locomotion and Movement

Below are a few solved questions:

Q1. What kind of muscles line the alimentary canal?

Answer:

• The smooth muscles in the inner walls of the alimentary canal are non-striated and involuntary.
• These muscles are responsible for the peristaltic movements that move food through the digestive tract.
• In comparison to the voluntary and striated skeletal muscles, smooth muscles are controlled by the autonomic nervous system, which guarantees the regular and steady contractions required to support vital physiological functions.

Q2. What is Osteoporosis?

Answer:

• Osteoporosis is a disease in which bone loses minerals and fibres from its matrix.
• There are more chances of fractures.
• It is caused by imbalances of hormones like calcitonin of the thyroid, parathormone of parathyroids, and sex hormones, and deficiencies of calcium and vitamin D.

Q3. What are the different kinds of arthritis?

Answer:

Arthritis is caused by the inflammation of the joints. Some types of arthritis are described here:

• Rheumatoid Arthritis (RA): It is diagnosed by the presence of rheumatoid factor (a type of immunoglobulin Igm). Rheumatoid arthritis is an inflammation of the synovial membrane in synovial joints.
• Osteoarthritis: It is also called degenerative joint disease. It is the most common type of joint disease. It is characterised by the progressive erosion of articular cartilage in synovial joints.
• Infectious Arthritis: These types of arthritis mostly occur due to bacterial and viral infection and are called bacterial and viral arthritis, respectively.
• Gout and Gouty Arthritis: This disease is due to a defect in purine metabolism that causes an excess of uric acid and its salts (urates). The level of uric acid is raised in the blood, and crystals of its salts (e.g., sodium urate) accumulate in the joints, resulting in gouty arthritis

Q4. What kind of movement do macrophages and leucocytes exhibit?

Answer:

Macrophages and leucocytes exhibit amoeboid movements.

Q5. What kind of joint is formed between the humerus and the pectoral girdle?

Answer:

The connection between the humerus and the pectoral girdle is defined by a ball-and-socket joint, specifically the glenohumeral joint,. This joint is created when the rounded head of the humerus fits into the shallow glenoid cavity of the scapula.

Subject-Wise NCERT Solutions

• NCERT Solutions for Class 11 Mathematics
• NCERT Solutions for Class 11 Chemistry
• NCERT Solutions for Class 11 Physics

• NCERT Solutions for Class 11 Biology

Approach to Solve Questions of Class 11 Biology Chapter 20 Locomotion and Movement

The student should focus on understanding the different types of movements and the detailed structure of muscles, especially the mechanism of muscle contraction. They should remember the difference between skeletal, smooth, and cardiac muscles and all the key joints in the body. They should practice drawing labelled diagrams of muscles and joints. They should solve the MCQ and subjective questions regularly and try to answer in a step-by-step explanation. They should relate structural features to their function for better memory and recall during the exam.

Chapter-Wise NCERT Class 11 Notes Biology

The chapterwise notes are given below: