NCERT Solutions for Class 11 Biology Chapter 20

Locomotion and Movement Class 11

Chapter 20 Locomotion and Movement Exercise Solutions

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Exercise : Solutions of Questions on Page Number : 313

Q1 :  

Draw the diagram of a sarcomere of skeletal muscle showing different regions.


Answer :

The diagrammatic representation of a sarcomere is as follows:

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Q2 :  

Define sliding filament theory of muscle contraction.


Answer :

The sliding filament theory explains the process of muscle contraction during which the thin filaments slide over the thick filaments, which shortens the myofibril.

Each muscle fibre has an alternate light and dark band, which contains a special contractile protein, called actin and myosin respectively. Actin is a thin contractile protein present in the light band and is known as the I-band, whereas myosin is a thick contractile protein present in the dark band and is known as the A-band. There is an elastic fibre called z line that bisects each I-band. The thin filament is firmly anchored to the z line. The central part of the thick filament that is not overlapped by the thin filament is known as the H-zone.

During muscle contraction, the myosin heads or cross bridges come in close contact with the thin filaments. As a result, the thin filaments are pulled towards the middle of the sarcomere. The Z line attached to the actin filaments is also pulled leading to the shortening of the sarcomere. Hence, the length of the band remains constant as its original length and the I-band shortens and the H-zone disappears.

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Q3 :  

Describe the important steps in muscle contraction.


Answer :

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Q4 :  

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 :

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Q5 :  

Write the difference between:

(a) Actin and Myosin

(b) Red and White muscles

(c) Pectoral and Pelvic girdle


Answer :

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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 :

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Q7 :  

What are the different types of movements exhibited by the cells of human body?


Answer :

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Q8 :  

How do you distinguish between a skeletal muscle and a cardiac muscle?


Answer :

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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 bones

(f) between pubic bones in the pelvic girdle


Answer :

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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 :

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<< Previous Chapter 19 : Excretory Products and their Elimination Next Chapter 21 : Neural Control and Coordination >>

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