NCERT Books for Class 11 Biology Chapter 20 - Locomotion and Movement - Free PDF Download
FAQs on Free Download of NCERT Books for Class 11 Biology Chapter 20 - Locomotion and Movement
1. What topics are covered in Chapter 20 of the NCERT Biology textbook?
Chapter 20 of the NCERT Biology class 11 textbook highlights the difference between movement and locomotion. The 3 types of movement exhibited by the human body are discussed. These are namely amoeboid, ciliary, and muscular movements. To understand muscular movements, students are made aware of the structure of the muscle and its basic structural and functional unit: a sarcomere. The mechanism of skeletal muscle contraction is explained in great detail with simplified diagrams. The various types of joints alongside disorders of the skeletal and muscular systems are also mentioned.
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3. What are contractile proteins?
Actin and myosin are the two major contractile proteins involved in skeletal muscle contraction. The NCERT textbook states that the proteins are arranged as rod-like structures, present parallel to each other. They are also longitudinal to the axis of the myofibrils. Microscopically, one can observe that actin filaments are thinner as compared to myosin filaments. This is the reason why actin and myosin filaments are commonly called thin and thick filaments respectively. Moreover, each actin filament is made of both filamentous and globular actin filaments. Similarly, myosin filaments are also polymerised filaments.
4. Explain the neural mechanism behind muscle contraction.
Skeletal muscle contraction is first initiated by a signal sent by the central nervous system (CNS) through the means of a motor neuron. The junction between a motor neuron and the sarcolemma of the adjoining muscle fiber that will receive the impulse is called the neuromuscular junction or the motor-end plate. Upon activation, a neurotransmitter like acetylcholine is released from the synaptic vesicles and is received by receptors present in the adjoining sarcolemma. The neural signal finally spreads across muscle fibers and results in muscle contraction.
5. Where is amoeboid and ciliary movement seen in the human body?
Some white blood cells (WBCs) like macrophages and leukocytes in the blood can be seen to exhibit amoeboid movement. The formation of pseudopodia is characteristic of this type of movement. In addition to this, some cytoskeletal elements like microfilaments are also involved in the amoeboid movement. Ciliary movement in humans is only observed in internal tubular organs which are lined by ciliated epithelium. Some examples of ciliary movement can be seen in the trachea and the female reproductive tract.