CBSE Class 11 Biology Revision Notes Chapter 20

CBSE Class 11 Biology Revision Notes Chapter 20 – Locomotion and Movement

Chapter 20 of Class 11 Biology deals with the topics of Locomotion and Movement. In this chapter, students study different types of movements and body structures involved in these movements. There are certain complex topics in this chapter that students may find difficult to understand and gain proper knowledge of. But with the help of the Class 11 Biology Chapter 20 notes, students can grab a thorough and in-depth knowledge of all the concepts. These notes summarise all the important topics covered in the chapter, which makes them ideal for last-minute preparations and revisions.

Access Class 11 Biology Chapter 20 – Locomotion and Movement Notes

Class 11 Biology Chapter 20 notes are available to download online at Extramarks. The notes cover a summarised view of the complete syllabus of the Biology chapter 20 Locomotion and Movement for Class 11 students. The various topics and subtopics of Locomotion and Movement have been explained in these notes in a clear and concise manner.

Locomotion and Movement

Movement is when living organisms move from one place to another. In case the movement changes the location or position of a living organism, it is called locomotion. Climbing, running, and walking are examples of locomotion.

There are three kinds of movements

• Ciliary
• Amoeboid
• Muscular

Ciliary Movement

It is the kind of movement that occurs in organisms that are covered with ciliated epithelium. With the help of this, dust particles inhaled during breathing are captured, and the egg from the fallopian tube into the uterus is moved.

Amoeboid Movement

Some immune cells like white blood cells and macrophages possess this type of movement. Amoeba moving through pseudopods also have this kind of movement.

Muscular Movement

Muscle movement is seen in the chin, tongue, limbs, etc. The bones, muscles and nervous system are all involved in locomotion.

Muscle

Muscle tissue or Muscle is essentially mesoderm. It is an association of cells that is responsible for body movement. The three main muscle types are skeletal muscle, cardiac muscle and smooth muscle.

Skeletal muscles are under the control of our will and the control of the somatic nervous system and are thus voluntary muscles. Because of the characteristic striations in them, they are striated muscles. These muscles are responsible for keeping the body in posture and performing multiple body movements. These are attached to the bones via tendons.

Cardiac muscles are the heart muscles responsible for the rhythmical contraction and relaxation of the heart. These muscles are involuntary and have cross stripes with branching patterns.

Smooth muscles are also known as visceral muscles. These lack striations. These muscles are responsible for maintaining involuntary body movements. They are located in the walls of both the digestive tract and reproductive tract.

Structure of Muscle

Several muscle bundles in skeletal muscle form a fascicle. Several muscle fibres compose a single muscle bundle. The plasma membrane that is arranged on the muscle fibres is known as sarcolemma. The sarcolemma of the muscle membrane surrounds the sarcoplasm. In muscle fibres, there are several nuclei called syncytium. The endoplasmic reticulum in the muscle fibres is known as the sarcoplasmic reticulum. The calcium ions participate in the contraction of the muscles, and these ions are stored in the sarcoplasmic reticulum. Muscle fibres contain parallel strands known as myofibrils of myofilaments. The fibrous tissue named epimysium is present around the skeletal muscle.

The characteristic stripes of skeletal muscles are because of the presence of actin and myosin proteins. The light stripes are also called isotropic bands and have actin protein. But the dark stripes are known as anisotropic bands that have myosin protein. Thin filaments are called actin, and thick ones are called myosin ones.

In the centre of each actin stripe, an elastic fibre present is named the Z-line. The part of myofibrils between two consecutive Z-lines is called a sarcomere which is called the functional unit of muscle contraction.

Structure of Contractile Protein

Actin and myosin are the two main contractile proteins. The monomer unit of actin is called globular actin or G-actin. The polymer of G-actin forms F-actin or F-filament. Two of the F-actin twist around each other to form actin molecules. The protein tropomyosin surrounds the F-actin. Another protein called troponin is evenly distributed in tropomyosin.

The monomeric unit of myosin is known as meromyosin. Each meromyosin comprises two parts: a spherical head and a long tail. The spherical head has ATPase activity and actin-binding sites.

Muscle Contraction Mechanism

Sliding filament theory explains muscle contraction. The fine fibres slide over the thick fibres during the contraction of muscles. Muscle contraction starts as soon as the signal is transmitted from the central nervous system to the motor neurons. The junction where muscle fibres and muscle fibres come together is known as neuromuscular. Action potentials in the muscle plasma membrane are generated as neurotransmitters like acetylcholine are released at the neuromuscular junction.

Calcium ions from the sarcoplasmic reticulum into the sarcoplasm are released due to the action potential. The binding of calcium ions to troponin present on actin filaments is caused due to the increase in calcium levels. This shows the active myosin binding sites. The ATPase activity of myosin exposes sites that allow cross-bridging between myosin and actin. This causes shortening of the sarcomere, which results in muscle contraction. After this, the calcium ions are pumped back to the sarcoplasmic reticulum. This process hides the actin filaments by returning the muscle to its original position.

Formation of Lactic Acid in Muscles

When the muscles are reactivated, such as during running or exercise, the anaerobic breakdown of glycogen in the muscles leads to the accumulation of lactic acid the muscles, which leads to fatigue and muscle pain.

Skeletal System

Bones and cartilage from the skeletal system. This system helps the body to move. Bones are hard due to the presence of calcium salts, and cartilage is flexible due to chondroitin sulphate. An individual has 206 bones and a small amount of cartilage. There are two parts of the skeletal system one is the axial skeletal system, and the second is the appendicular skeletal system.

1. Axial skeletal system

A total of 80 bones are there in the axial skeletal system, including the sternum, skull, ribs, and vertebral column. 

22 facial and cranial bones make up the skull. The cranial bones protect the brain and are 8 in number. 14 bones make up the facial area which forms the front part of the skull. At the bottom of the mouth, there is a U-shaped hyoid bone. Each middle ear has three small bones: the incus, the malleus and the stapes. These bones are altogether known as ear ossicles. 

The spine or vertical column consists of 33 vertebrae. The vertebral column makes the basic structure of the trunk by extending from the skull base. The hollow central part that each vertebra has is called the neural tube. The spinal cord passes through this neural tube.

The first vertebra is known as the atlas and is connected to the occipital condyle. The vertebral column or spine is divided into 12 thoracics, 7 cervicals, 5 lumbar, 1 coccyx and 1 sacral starting from the skull. In mammals, the number of cervical vertebrae is preserved.

Ribs: First seven pairs of ribs are included as the true ribs. They are attached directly to the sternum, so they are called true ribs. Eighths, ninth and tenth pairs of the ribs are attached to the seventh pair rather than the sternum and therefore are called false ribs. The eleventh and twelfth are the last two pairs of ribs that are not connected to the sternum directly. These are called floating ribs. The ribs, thoracic vertebrae and sternum together form the rib cage.

The sternum is a flat bone situated at the midline of the chest. Twelve pairs of ribs are attached to the sternum or breastbone.

2. Appendicular skeletal system

Limb bones and girdles form the appendicular skeletal system. The single-limb consists of 30 bones. 

Forelimb bones: The bones of the front leg or arm or forelimb are the humerus, radius and ulna, wrist (8 carpal bones), metacarpal bone (5 palm bones), and phalanges (14 digit bones).

Hindlimb Bones: In the hind leg or limb, there are several bones present which are the femur, the thigh bone, which is the longest bone, the tibia and fibula, and 7 tarsals (the ankle bones), 5 metatarsals, and 14 phalanges. The bones on the knees are called the patella, which have a cup-like shape.

The pectoral girdle has two bones, the clavicle/collarbone and the scapula. The scapula has a cavity called the glenoid, which forms a hinge in the shape of a ball and socket joint with the humerus and is attached to the bones of the forelimbs.

The pelvic girdle has a cup-shaped cavity known as the acetabulum, which constitutes a spherical connection as a ball and socket joint with the femur attached to the hind leg’s bones, and the thigh muscles connected with the pelvic girdle.

Joints

The connections between the bones or bones and cartilage are called joints. Joints act as fulcrums for the force exerted by the muscles to initiate movement and therefore are very important for locomotion. There are three major types of joints.

1. Synovial Joint: Between the two bones, a characteristic fluid-filled synovial cavity enables more movement and flexibility. For instance, hinge joints are knee and elbow joints, pivot joints are the neck, ball and socket joints are hip and shoulder joints, etc.
2. Fibrous Joints: Dense fibrous tissues forming sutures connect the bones. They are motionless and can be seen between the flat bones of the skull in the joints.
3. Cartilaginous Joints: Cartilage helps connect two bones. Such joints are movable parts situated between the vertebrae.

Disorders Related to Muscular and Skeletal Systems

Myasthenia Gravis: In this condition, neuromuscular nodes get affected, which causes skeletal muscle fatigue paralyzed, and weakness. It is an autoimmune disease.

Muscular Dystrophy: This disease causes progressive destruction of the skeletal system. It is a genetic disease.

Tetany: In this condition, the body fluids have low calcium ions causing rapid muscle spasms.

Arthritis: It is an inflammation of the joints.

Gout: When there is an accumulation of uric acid crystals in the joints, this condition is caused. As a result of this, there can be inflammation of the joints.

Osteoporosis: In this condition, the bone mass is reduced, which increases the risk of frequent fractures. It is related to decreased oestrogen levels and is related to age.

Importance of Biology Revision Notes:

Biology, an entirely theoretical and conceptual subject, requires concentration, practice, enough revisions and thorough study to have a good command of this subject. In Class 11, there are a total of 22 chapters in Biology. Each chapter consists of different concepts, logic and topics, and therefore students are required to study each chapter with the same attention and care. Memorising all the chapter topics is not easy for students. To help students with this, we have made available revision notes that cover the chapter elaborately. In these notes, all the essential topics have been covered so that students can have conceptual knowledge of the topic and understand the chapter easily. 

How are Extramarks Biology Notes Helpful?

• Chapter 20 Biology class 11 notes are prepared in such a way that students can understand the concepts very easily and precisely. 
• By going through these notes, again and again, students can perform well in their exams and score good marks. 
• In these notes, the most important things have been highlighted so that students can have a lasting impression about those important topics in mind.
• Some important questions have also been provided at the end of the chapter with these notes. By practising these questions, students can enhance their speed and accuracy.

Introduction on Chapter 20 of Class 11 Biology

Chapter 20 of Biology Class 11 is titled Locomotion and Movement, which introduces students to how human beings perform different movements in their bodies. As we know, movement is possible with the help of muscles and bones. This complete chapter revolves around the study of muscles and bones present in the human body. 

Topics Covered in Extramarks Notes

The notes of Class 11 Biology Chapter 20 cover all the important topics of this chapter. To help students get their confusion and doubts cleared, Extramarks offer this revision notes that offer simple and convenient explanations for various topics of the textbook.

Topics covered in these Chapter 20 Biology Class 11 notes include muscles joints, different types of joints, skeletal system, anatomy of various joints, muscular and skeletal system disorders, and types of movements such as voluntary or involuntary, amoeboid, and muscular movement. All these topics of this chapter have been covered in the notes creating a summarised view of the textbook chapter.

Biology Class 11 Chapter 20 Notes 

By downloading the Class 11 Biology chapter 20 notes, students will find it very convenient and easy to understand and revise the chapter. The notes are available to download for free from Extramarks. 

Locomotion and Movement Class 11 Notes

Locomotion and movement definition: When an organism moves from one location to another, this process is termed movement, and when a change in the area accompanies this movement, then it is called locomotion. Instances of Locomotion are walking, climbing, running, etc.

Types of movements: In this chapter notes, you will come across 3 types of movement types.

• Ciliary Movement: Organisms with organs lined with ciliated epithelium show this kind of movement. It is the movement that helps the ova to travel from the fallopian tube to the uterus.
• Amoeboid Movement: Some immune cells, such as macrophages, leukocytes, etc., show this movement.
• Muscular Movement: Organs such as jaws, limbs, and tongues show this movement.