NCERT Solutions for Class 11 Biology Chapter 17 Locomotion and Movement

NCERT Solutions for Class 11 Biology Chapter 17: Locomotion and Movement

NCERT Solutions for class 11 Chapter 17 Locomotion and Movement: The chapter on Locomotion and Movement is important for students approaching the home exams. This article introduces NCERT solutions designed to help students explain the concepts of further learning and how to write to get good grades on exams. The solutions are presented in very simple language for ease of understanding.

NCERT CBSE chapter 17 Locomotion and Movement of class 11 explains that movement is a key characteristic of living organisms, and both plants and animals exhibit a diverse range of movements. Among these, voluntary movements are referred to as locomotion. There are some structures involved in locomotion and their mechanisms, including the skeletal system, functions of joints and bones, muscular system, and disorders related to the skeletal system like arthritis. Revise the basic concepts of Locomotion and Movement for quick revision and class notes.

Q1: Draw the Diagram of a Sarcomere of Skeletal Muscle Showing Different Regions.

Answer:

Q2: Define the Sliding Filament Theory of Muscle Contraction​.

Answer: 

According to this theory, when a muscle contracts, the thin filaments slide over the thick filaments, causing the myofibrils to shorten.

Within each muscle fibre, there are alternating light and dark bands that contain specific contractile proteins called actin and myosin, respectively. Actin is a thin protein found in the light band (I-band), while myosin is a thick protein found in the dark band (A-band).

Q3: Describe the Important Steps in Muscle Contraction.

Answer: 

During the contraction of striated muscles, the thick filaments slide over the thin filaments through a repetitive process of binding and releasing myosin on the filament. This entire process occurs sequentially.

Step 1:

Muscle contraction begins with signals that travel along a nerve fibre and reach the myoneural junction, which is the connection between a nerve cell and the membrane of the muscle fiber. This leads to the release of a neurotransmitter called acetylcholine into the junction cleft, generating an action potential on the sarcolemma.

Step 2:

The action potential triggers the release of calcium ions from the sarcoplasmic reticulum into the cytoplasm.

Step 3:

The increased calcium ions in the cytoplasm activate binding sites on the thin filaments. Calcium ions bind to troponin, a protein on the thin filaments, causing tropomyosin (which covers the binding sites on actin) to move away. This exposes active actin sites, allowing myosin heads to bind to them.

Step 4:

At this stage, myosin heads attach to the exposed actin sites and form cross-bridges by utilising energy from ATP. The actin filaments are pulled by the myosin heads, resulting in a reduction of the H-zone. This is when muscle contraction occurs.

Step 5:

After the shortening phase, the myosin head releases ADP and inorganic phosphate. ATP molecules then bind to the myosin head, causing it to detach from actin breaking the cross-bridges.

Step 6:

The process of cross-bridge formation and breakdown continues until the stimulation ceases, leading to a decrease in calcium levels. As a result, the concentration of calcium ions decreases, causing tropomyosin to cover the actin filament once again resulting in muscle relaxation.

Q4: Write True or False. If false, Change the Statement so that It Is True.

• (a) Actin is present in the thin filaments
• (b) H-zone of striated muscle fiber represents both thick and thin filaments.
• (c) Human skeleton has 206 bones.
• (d) There are 11 pairs of ribs in man.
• (e) Sternum is present on the ventral side of the body.

Answer:

a. True

b. False: The H-zone of a striated muscle fibre only includes the thick filament’s centre, which is unaffected by the thin filament.

c. True

d. False: The human body have 12 pairs of ribs in total.

e. True

Q5: Write the Difference Between :

• (a) Actin and Myosin
• (b) Red and White muscles
• (c) Pectoral and Pelvic girdle

Answer:

(a) Actin is a type of thin contractile protein found in light bands known as isotropic bands. Myosin, on the other hand, is a thick contractile protein found in dark bands referred to as anisotropic bands

(b) Red muscle fibres are characterised by their smaller size and thinness. They appear red due to the abundance of myoglobin, a pigment that stores oxygen. These fibers are responsible for slow and sustained contractions.

In contrast, white muscle fibres are thicker and larger in size. They appear white because they contain only a small amount of myoglobin. These fibers are specialized for fast contractions but for shorter durations.

(c) Pectoral: the skeletal support where the forelimbs are attached. It consists of two bones, namely the clavicle and scapula.

Pelvic girdle: The skeletal support where hind limbs are attached consists of three bones, namely the ileum, pubis, and ischium.

Q6: Match Column I with Column II:

Column I	Column II
(a) Smooth muscle	(i) Myoglobin
(b) Tropomyosin	(ii) Thin filament
(c) Red muscle	(iii) Sutures
(d) Skull	(iv) Involuntary

Answer:

Column I	Column II
(a) Smooth muscle	(iv) Involuntary
(b) Tropomyosin	(ii) Thin filament
(c) Red muscle	(i) Myoglobin
(d) Skull	(iii) Sutures

Q7: What Are the Different Types of Movements Exhibited By the Cells of Human Body?

Answer:

1. Amoeboid movement:

Leukocytes show amoeboid movement. When there is tissue damage, these blood cells move in an amoeboid fashion, forming temporary protrusions called pseudopodia. They migrate from the circulatory system to the site of injury, initiating an immune response.

2. Ciliary movement:

Reproductive cells, such as sperm and ova, demonstrate ciliary movement. This type of movement aids in the passage of ova through the fallopian tubes towards the uterus.

3. Muscular movement:

Muscle cells in the human body exhibit muscular movement. They contract and relax to generate movement. Examples include movements of the limbs, tongue, and jaws.

Q8: How Do You Distinguish Between a Skeletal Muscle and a Cardiac Muscle?

Answer:

Skeletal Muscle:

Skeletal muscles have a voluntary function. The cells of these muscles are non-branched and lack intercalated discs. They are involved in activities such as movement and maintaining body posture.

Cardiac Muscle:

Cardiac muscles have an involuntary function. The cells of these muscles are branched and connected by intercalated discs. Cardiac muscles specifically work to pump and regulate the heart

​Q9: Name the Type of Joint Between the Following:

• (a) atlas/axis
• (b) carpal/metacarpal of thumb
• (c) between phalanges
• (d) femur/acetabulum
• (e) between cranial
• (f) between pubic bones in the pelvic girdle

Answer:

(a) Pivotal joint

(b) Saddle joint

(c) Hinge joint

(d) Ball and socket joint

(e) Fibrous joint

(f) Socket joint

​​Q10: Fill in the Blank Spaces:

• (a) All mammals (except a few) have __________ cervical vertebra.
• (b) The number of phalanges in each limb of human is __________
• (c) Thin filament of myofibril contains 2 ‘F’ actins and two other proteins namely __________ and __________.
• (d) In a muscle fibre Ca++ is stored in __________
• (e) __________ and __________ pairs of ribs are called floating ribs.
• (f) The human cranium is made of __________ bones.

Answer:

(a) seven

(b) 14

(c) troponin and tropomyosin

(d)​ sarcoplasmic reticulum

(e) 11th & 12th

(f) eight