Tag: muscles and their structure

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Multiple choice zoology movement and locomotion in man structure of skeletal muscle muscles and their structure skeletal muscles

Cross bridges of sarcomere in skeletal muscle are made up of 

  1. Actin

  2. Myosin

  3. Troponin

  4. Tropomyosin
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • Active sites for myosin (Thick filament) are present on actin which are masked by troponin in resting state. when  Ca++ level increases it leads to the binding of calcium with a subunit of troponin on actin(thin) filaments and thereby remove the masking of active sites for myosin.
  • Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge. thus myosin forms cross bridges.
  • This pulls the attached actin filaments towards the centre of ‘A’ band.
  •  The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction.
  • Hence cross bridges of sarcomere in skeletal muscle are made up of myosin.
  • So, the correct answer is 'Myosin'.
Multiple choice zoology movement and locomotion in man structure of skeletal muscle muscles and their structure skeletal muscles

State whether the following statements are true or false.
Intercalated discs make up striations in the skeletal muscle.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Intercalated discs support synchronized contraction of cardiac tissues. They occur at the Z line of the sarcomere and can be visualized easily when observing a longitudinal section of the tissue. Three types of cell junction make up an intercalated disc.

So, the option is 'False'.

Multiple choice zoology movement and locomotion in man structure of skeletal muscle muscles and their structure skeletal muscles

Which muscles having functionally multinucleated conditions?

  1. Cardiac muscle

  2. Smooth muscle

  3. Voluntary muscle

  4. All of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

There are cardiac, skeletal and smooth muscle cells of which only skeletal or voluntary muscle cells are multinucleated. Such cells are syncytial. Skeletal muscle cells arise in the embryo as uninucleated entities. Later the cells fuse to give rise to the multinucleated muscle fibre.

So the correct answer should be option C "voluntary muscles".

Multiple choice zoology movement and locomotion in man structure of skeletal muscle muscles and their structure skeletal muscles

Consider the following statements each with one or two blanks.
(i) Each half of pectoral girdle consists of a (A) and a (B) 
(ii) (C) is a condition of rapid spasms (wild contractions) in muscle due to low $Ca^{++}$ in body fluid.
(iii) Each organised skeletal muscle In our body is made of a number of (D) held together by a common collagenous connective tissue layer called (E) Which one of the following options correctly fills the blanks in any two of the statements ?

  1. (C) - Muscular dystrophy, (D) - fascia, (E) - fascicle

  2. (A) - clavicle, (B) - scapula, (C) - Tetany

  3. (A) - ilium, (B) - ischium, (D) - fascicles, (E) - fascia

  4. (C) - Myasthenia gravis, (D) - fascicles. (E) - fasda
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Each half of pectoral and pelvic girdle consist of clavicle & scapula, tetany is a condition of rapid spasms in muscle due to low calcium ion in body fluid.

So, the correct option is '(A) - clavicle, (B) - scapula, (C) - Tetany'.

Multiple choice zoology locomotion and movement contractile protein structure of muscle muscles and their structure

The important muscle proteins that helps in the movement are 

  1. Actin and myosin

  2. Troponin

  3. Tropomyosin

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Skeletal muscle fiber is made up of two types of filaments. They are thick filament (myosin) and thin filament (actin). Contraction of a muscle fiber takes place by the sliding of the thin filaments over the thick filaments.
  • Myosin (thick) filament is also a polymerized protein. Many monomeric proteins called meromyosins constitute one thick filament. 
  • Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length. A complex protein troponin is distributed at regular intervals on the tropomyosin.
  • Hence, the important muscles proteins that help in the movement are actin and myosin, troponin and tropomyosin.
  • So, the correct answer is 'All of the above'.
Multiple choice zoology locomotion and movement contractile protein structure of muscle muscles and their structure

In resting stage, binding sites for myosin on actin filaments are masked by

  1. Troponin

  2. Light meromyosin

  3. Heavy meromyosin

  4. Calcium ions
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Skeletal muscle fiber is made up of two types of filaments. They are thick filament (myosin) and thin filament (actin). Contraction of a muscle fiber takes place by the sliding of the thin filaments over the thick filaments.
  • Myosin (thick) filament is also a polymerized protein. Many monomeric proteins called meromyosins constitute one thick filament. 
  • Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length
  •  In the resting state a subunit of troponin masks the active binding sites for myosin on the actin filaments.
  • So, the correct answer is 'Troponin'.
Multiple choice zoology locomotion and movement contractile protein structure of muscle muscles and their structure

Thick filaments in muscles are polymerised proteins of

  1. Meromyosin

  2. Actin

  3. Troponin

  4. Tropomyosin

  5. Keratin
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Myofibrils are composed of two types of filaments i.e thin filament (actin) and thick filament (myosin).
  • Actin filaments are thinner as compared to the myosin filaments, hence are commonly called thin and thick filaments respectively
  • Each myosin (thick) filament is a polymerized protein. Many monomeric proteins called meromyosins constitute one thick filament (Myosin).
  • Hence thick filaments in muscles are polymerized proteins of meromyosin.
  • So, the correct answer is 'Meromyosin'.
Multiple choice zoology locomotion and movement contractile protein structure of muscle muscles and their structure

 The thin filaments of myofibril contain  __(A)_ actin and two filaments of (B) protein along with  (C)_  protein for masking binding site for myosin. 

  1. A - 1F B - troponin C - Tropomyosin

  2. A - 1F B - tropomyosin C - troponin

  3. A - 2F B - troponin C - tropomyosin

  4. A - 2F B - tropomyosin C - troponin
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Thin filaments of myofibril contain one filament of actin and two filaments of troponin, along with tropomyosin protein.

So, the correct option is 'A - 1F B - troponin C - Tropomyosin'.

Multiple choice zoology locomotion and movement contractile protein structure of muscle muscles and their structure

ATPase activity in muscle fibre lies with

  1. Light meromyosin

  2. Head of heavy meromyosin

  3. Troponin

  4. Short arm of heavy meromyosin
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • The myofibril is composed of two types of filaments. They are thick filament(Myosin) and Thin filament(Actin).
  • Increase in Ca++ level leads to the binding of calcium with a subunit of troponin i.e troponin-C on actin filaments and thereby remove the masking of active sites for myosin. Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.
  • Each myosin (thick) filament is also a polymerized protein. Many monomeric proteins called Meromyosins constitute one thick filament. Each meromyosin has the globular head which is an active ATPase enzyme and has binding sites for ATP and active sites for actin. Hence ATPase activity in muscle fibre lies with Head of heavy meromyosin.
  • So, the correct answer is 'Head of heavy meromyosin'.