NCERT Solutions Class 11th Biology Chapter – 20 Locomotion and Movement
| Textbook | NCERT |
| class | Class – 11th |
| Subject | Biology |
| Chapter | Chapter – 20 |
| Chapter Name | Locomotion and Movement |
| Category | Class 11th Biology Question & Answer |
| Medium | English |
| Source | last doubt |
NCERT Solutions Class 11th Biology Chapter – 20 Locomotion and Movement
?Chapter – 20?
✍Locomotion and Movement✍
?Question & Answer?
1. Draw the diagram of a sarcomere of skeletal muscle showing different regions.
Answer: The diagram below shows the sarcomere of skeletal muscle showing different regions –
2. Define sliding filament theory of muscle contraction.
Answer: Sliding filament theory states that the muscle fibre contraction occurs due to the sliding of the thin filaments over thick filaments.
3. Describe the important steps in muscle contraction.
Answer: The mechanism of muscle contraction is explained well by the sliding filament theory which states that the muscle fibre contraction occurs due to the sliding of the thin filaments over the thick filaments.
Mechanism of muscle contraction –
Step 1 – Depolarization of Sarcolemma
1. The central nervous system (CNS) sends a signal through a motor neuron which arrives at the neuromuscular junction or the motor end plate
2. The junction present between the sarcolemma of the muscle fiber and the motor neuron is called the neuromuscular junction
3. The release of a neurotransmitter called acetylcholine is triggered when the signal arrives at the neuromuscular junction. The action potential in the sarcolemma is set by this release.
Step 2 – Release of Calcium ions
1. The sarcolemma transmits the action potential to the sarcoplasmic reticulum in order to release the calcium ions in the sarcoplasm
Step 3 – Conformational changes occurs in the Actin filaments
1. The calcium ions that are released, tends to bind to the troponin and tropomyosin located on the active filaments
2. This linkage causes a modification in the three-dimensional structure of the actin-troponin-tropomyosin complex. The active site for myosin which is located on the actin filament is exposed.
Step 4 – Activation of Myosin heads
1. The calcium ions release causes the myosin heads to get activated which inturn causes the release of energy in the form of ATP
2. Hydrolysis of ATP releases energy which causes the binding of myosin heads to the active sites found on the actin filaments hence forming a cross-bridge
Step 5 – Actin Filaments slide over Myosin
1. The myosin head rotates due to the formation of cross-bridge, pulling the actin filaments to the centre of the A-band which is the H-zone
2. The z-line which is attached to the actin filaments is pulled inwards too
3. Contraction of sarcomere occurs when the actin filaments are pulled in the opposite ends
4. During the process of contraction, the I-band shortens whereas the A-band maintains its length causing the muscles to contract.
4. Write true or false. If false change the statement so that it is true.
(a) Actin is present in thin filament
(b) H-zone of striated muscle fibre 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) Actin is present in thin filament – True
(b) H-zone of striated muscle fibre represents both thick and thin filaments – False Corrected statement: H-zone of the striated muscle fiber represents only thick filaments
(c) Human skeleton has 206 bones – True
(d) There are 11 pairs of ribs in man – False Corrected statement: There are 12 pairs of ribs in man.
(e) Sternum is present on the ventral side of the body – True
5. Write the difference between:
(a) Actin and Myosin
(b) Red and White muscles
(c) Pectoral and Pelvic girdle
Answer: The differences are as follows –
(a) Actin and myosin
| Actin | Myosin |
| Thin filaments (I-bands) of the myofilament are formed | Thick filaments (A-bands) of the myofilament are formed |
| It is built of globular actin monomers | It is built of meromyosin monomers |
| The regulatory proteins Tropnin and tropomyosin are linked with the actin | The regulatory proteins are not linked, instead each of the meromyosin is built of four light chains and two identical heavy chains |
(b) Red and white muscles
| Parameters | Red muscles | White muscles |
| Myoglobin content | High | Low |
| Amount of sarcoplasmic reticulum | Moderate | High |
| Fibers | Narrow and thin | Broad and thick |
| Mitochondria | Possess many | Few |
| Fatigue | Not fatigued | Fatigued |
| Type of respiration from which energy is derived | Aerobic | Anaerobic |
(c) Pectoral and Pelvic girdle
| Pectoral girdle | Pelvic girdle |
| Pectoral girdle is called as the shoulder girdle | Pelvic girdle is called as the hip girdle |
| Each part/half of the girdle consists of two bones – clavicle and scapula | Each part/half of the girdle consists of three bones – ischium, ilium and pubis |
| Forelimb articulation is offered | Hindlimb articulation is offered |
| Head of the humerus articulates with the glenoid cavity of the pectoral girdle | Head of the femur articulates with the acetabulum of the pelvic girdle |
6. 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 |
7. What are the different types of movements exhibited by the cells of human body?
Answer: Movement is considered to be one of the fundamental characteristics which is observed in the living entities. The different types of movements exhibited by the human body cells are:
1. Amoeboid Movement – Leucocytes found in blood exhibit this type of movement. Leucocytes from the circulatory system move towards the injury site when there is a damage to the tissue in order to initiate an immune response.
2. Muscular movement – The muscle cells exhibit this type of movement
3. Ciliary movement – Sex cells (sperms and ova) exhibit this type of movement. This movement facilitates the passage of ova via the fallopian tube on its way to the uterus.
8. How do you distinguish between a skeletal muscle and a cardiac muscle?
Answer: The differences between a skeletal muscle and a cardiac muscle is as follows-
| Skeletal muscle | Cardiac muscle |
| Linked to the primary bones | Located in the walls of the heart |
| Voluntary in nature | Involuntary in nature |
| Peripherally located nucleus | Centrally located nucleus |
| The muscle fibers of the skeletal muscles are unbranched | The muscle fibers of the cardiac muscles are branched |
| Intercalated discs are not found in the Muscle fibers of the skeletal muscles | Intercalated discs are found in the muscle fibers of the cardiac muscles |
| Brings about the locomotory actions of the body and maintains body posture | Responsible for the movement/motion of the heart |
9. 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 bones
(f) Between pubic bones in the pelvic girdle
Answer: The types of joints are as follows –
(a) atlas/axis – Pivot joint
(b) carpal/metacarpal of thumb – Saddle joint
(c) Between phalanges – Hinge joint
(d) femur/acetabulum – Ball and socket joint
(e) Between cranial bones – Fibrous joint
(f) Between pubic bones in the pelvic girdle – cartilaginous joint
10. 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) Fourteen
(c) Troponin, tropomyosin
(d) Sarcoplasmic reticulum
(e) Eleventh, twelfth
(f) Eight