Chapter 20 Locomotion and Movement 

In Year 11, Biology is compulsory for students who wish to pursue a course in Medicine. Biology lessons 11 Chapter 20 Locomotion and Movement cover topics such as the human skeletal system, joints, disorders of the human skeletal and muscular system, the human musculature and types of human movement. 

Vidyakul scholars have included over 700 exercises from over 50 books to help students practice on countless questions. Solutions are prepared to help students study the chapter in a holistic way. Continue reading this article to learn more about the NCERT Biology Class 11 Chapter 20 notes.

CBSE CLASS 11 BIOLOGY CH-20

Points to Remember

We have summarized a few important points from the entire chapter for students to refer to while studying.

• The movements of an animal resulting in a change of location or place is called locomotion.

• Amoeboid motion helps in ingestion of food and locomotion as well.

• Ciliary movements of cells lining the trachea of humans helps to remove the invading microbes and dust particles.

•  Based on their location, in humans, muscles are broadly classified into three categories: skeletal muscles, smooth muscles and cardiac muscles.

• Cardiac muscles are also striated, but these muscles are branched and involuntary.

• A motor neuron carries signal to the muscle fibre, which generates an action potential in it.

• Skeletal muscle consists of numerous physiological units called myofibrils.

Topics and Sub-topics

Chapter 20 of Class 11 Biology discusses the movement of humans and the mechanism which allows living beings to move from one place to another. The chapter contains 10 questions for students to test their conceptual understanding.

Furthermore, Vidyakul’s experts provide practice questions to allow students to hone their skills. Also, there are personalized tests for each student to evaluate their performance.

Thus, students can check the list of important topics from the table below.

Section Name	Topics
Ex. 20.1	Types of Movement
Ex. 20.2	Muscle
Ex. 20.2.1	Structure of Contractile Proteins
Ex. 20.2.2	Mechanism of Muscle Contraction
Ex. 20.3	Skeletal System
Ex. 20.4	Joints
Ex. 20.5	Disorders of Muscular and Skeletal System

Frequently Asked Questions

• Does calcium ion concentration in blood cause tetany in some cases? Compare fluctuation in blood calcium with tetany.

In the regulation of muscle contraction, calcium plays a significant role. The parathyroid hormone (PTH) that is secreted by the parathyroid gland increases the calcium level in the blood. In hypoparathyroidism (PTH deficiency), the level of calcium in the blood dips which causes an increase in the excitability of muscles and nerves resulting in convulsions and cramps. It also produces sustained contractions of the muscles of the face, hands, feet, and larynx. This disorder is referred to as parathyroid tetany.

• How does the slipped disc affect the lower back and overall health?

The bones are protected by the intervertebral discs that are situated in between the vertebrae. They absorb the shocks from everyday activities such as lifting, walking, and twisting. Each of the vertebral discs has two parts, one is the soft inner portion that is gelatinous and the other is a tough outer ring. In case of any weakness or injury, the inner part protrudes through the outer ring and is called the slipped disc which can cause added pressure on the muscles and nerves surrounding it and affects the health in ways listed below:

• Numbness and pain in one side of the body

• Pain that intensifies at night

• Induces pain that can spread up to the legs and arms

• Produces pain after walking or sitting

• An unexplained weakness of the muscles

• Burning sensation, aching, tingling in the area affected.

If left untreated, the slipped disc can cause severe damage to the nerves which can be permanent. In some cases, it can cause the nerve impulses to cut off to cauda equina nerves in the legs and lower back which can result in loss of bladder control.

• Describe the significance of Ca2+ ions in the contraction of muscles.

Calcium plays a key role in the muscle contraction process. During contraction of muscles, from the motor endplate, an action potential passes over the sarcolemma and further into the T-tubules and sarcoplasmic reticulum and triggers it to produce Ca2+ ions into the sarcoplasm. The binding of calcium ions to the troponin causes its shape and position to change which in turn modifies the position and shape of tropomyosin that binds the troponin. This shift presents the active sites on the molecule, F-actin which prompts the myosin cross-bridges to bind to these active sites.

• State the differences between the pectoral and pelvic girdle.

Both structures are known to provide support to the lower and upper parts of the body. Following are the differences:

Pectoral Girdle	Pelvic Girdle
It is called a shoulder girdle as it occurs in the shoulder region.	It is called the hip girdle as it occurs in the hip region.
It is divided into two parts – One scapula and one clavicle.	One pelvic girdle is formed by two innominate bones where each bone has 3 parts – ilium, pubis, and ischium.
Not articulated with the vertebral column.	Articulated with the vertebral column.
Articulation of the axial skeleton and upper limb is brought about by the clavicle and scapula.	The innominate at its mid-lateral surface has a deep cup-shaped acetabulum where the head of the femur connects the two parts of the pelvic girdle for the formation of the pubic symphysis.
Associated bones are light and not subjected to much stress.	Associated bones are hard and subjected to much stress.
Functions – lifting, holding, etc.	Functions – standing, running, jumping, etc.

 

• What are the different types of movements?

Movement is a process of changing position or location. Different organisms have different types of movements.

Based on the mode of locomotion, movements are of three types:

1. Amoeboid movement:  This movement is the most common mode of locomotion in all eukaryotic cells. This type of movement takes place in the phagocytes of a cell and is most commonly seen in amoeba.

2. Ciliary and flagellar movement: This movement occurs in internal tubular organs which are lined by ciliary epithelium. Some of our internal tubular organs exhibit ciliary movement.

3. Muscular Movement: This is a more complex movement which involves muscle fibres, which have the ability to contract and relax. This type of movement is seen in all higher vertebrates.

Practice Questions

• Old people usually suffer from inflamed and stiff joints, name the condition. State the reasons for the symptoms.

• List two hormones causing fluctuation of Ca++ level.

• What is Gout?

• What is the significance of locomotion in animals?

• Where do muscle contractions derive their energy from?

• Define the following terms with respect to the rib cage:

a) Bicephalic ribs

c) True ribs

c) Floating ribs

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