Tag: locomotion and movements

Questions Related to locomotion and movements

During contraction of muscles,

muscle contraction locomotion and movements biology

  1. Actin filament slide over actin

  2. Myosin filament slide over actin

  3. Actin filament slide over myosin

  4. None of the above

Show answer
Correct Option: C
Explanation:

Mechanism of muscle contraction is best explained by the sliding filament theory, which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments. The actin filament slide over myosin filament thus reduces the length of the sarcomere and contracts the muscle fibre.

So, the correct answer is option C.

Chemical ions responsible for muscle contraction are

muscle contraction locomotion and movements biology

  1. $Ca^{++}$ and $K^+$

  2. $Na^+$ and $K^+$

  3. $Na^+$ and $Ca^{++}$

  4. $Ca^{++}$ and $Mg^{++}$ ions

Show answer
Correct Option: D
Explanation:
  • When a nerve impulse reaches the neuromuscular junction, the calcium ions are released from the sarcoplasmic reticulum. Then the calcium ions trigger muscle contraction cycle by binding to the protein complex troponin, exposing the active-binding sites on the action. and this enables the myosin molecule heads to “grab and swivel” their way along the thin filament. This is the driving force of muscle contraction.
  • Magnesium ions also play a role in regulating muscle contractions. The magnesium acts as a natural calcium blocker to help muscles relax. 
  • Hence Chemical ions responsible for muscle contraction are Ca++ and Mg++ ions.
  • So, the correct answer is 'Ca++ and Mg++ ions'.

The muscular contraction in which the tension remains the same and the mechanical work is also done is called

muscle contraction locomotion and movements biology

  1. Isotonic contraction

  2. Tetanus

  3. Isomeric contraction

  4. Single muscle twitch

Show answer
Correct Option: A
Explanation:

Answer is- A

Isotonic contractions maintain constant tension in the muscle as the muscle changes length. This can occur only when a muscle's maximal force of contraction exceeds the total load on the muscle. Isotonic muscle contractions can be either concentric (muscle shortens) or eccentric (muscle lengthens).

Cardiac muscles are characteristic in that they contract

muscle contraction locomotion and movements biology

  1. Slowly and get fatigued

  2. Quickly and get fatigued

  3. Slowly and do not get fatigued

  4. Rhythmically and do not get fatigued

Show answer
Correct Option: D
Explanation:

Cardiac muscles have mixture of properties of both  striated and unstriated muscles. .These muscle continue  rhythmic contraction throughout life under the control  of A.N.S.

During muscle contraction

muscle contraction locomotion and movements biology

  1. Size of A-bands remains the same

  2. Size of H-zone becomes smaller

  3. Size of I-bands decreases

  4. All of the above

Show answer
Correct Option: D
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. 
  • 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 Size of A-bands remains the same, the Size of H-zone becomes smaller and Size of I-bands decreases.
  • So, the correct answer is 'All the above'

Which is true of muscle contraction

muscle contraction locomotion and movements biology

  1. Sarcolemma becomes permeable to $Ca^{2+}$ ions

  2. Sarcolemma becomes permeable $Na^+$ ions

  3. Sarcolemma becomes nonpermeable to $Na^+$ ions

  4. Concentration of $Ca^{2+}$ ions is reduced in myoplasm

Show answer
Correct Option: B
Explanation:

Acetylcholine release from synaptic vesicles and travels across synaptic cleft and binds with protein receptors in sarcolemma. This causes the sarcolemma to become more permeable to sodium ions which causes them enter. Now sarcolemma is elctro positive inside and negative outside. This new potential difference is called action potential and sarcolemma now is called as depolarised. So the correct answer is 'Sarcolemma becomes permeable Na+ ions'.

Correct order of stages of muscle contraction is

muscle contraction locomotion and movements biology

  1. Stimuli Neurotransmitter secretion $\rightarrow$ Release of calcium $\rightarrow$ Cross-bridges formation $\rightarrow$ Excitation of T-system $\rightarrow$ Sliding of actin filament

  2. Stimuli Neurotransmitter secretion $\rightarrow$ Excitation of T-system $\rightarrow$ Release of C$a^{2+}$ $\rightarrow$ Cross-bridges formation $\rightarrow$ Sliding of actin filaments $\rightarrow$ H band diminishes

  3. Stimuli Excitation of T-system $\rightarrow$ Neurotransmitter secretion $\rightarrow$ Crossbridges formation $\rightarrow$ Sliding of actin filaments $\rightarrow$ H band diminishes

  4. Stimuli $\rightarrow$ Neurotransmitter secretion $\rightarrow$ Cross-bridges formation $\rightarrow$ Excitation of T-system $\rightarrow$ Sliding of actin filaments

Show answer
Correct Option: B
Explanation:

  • Active sites for myosin(Thick filament) are present on actin which are masked by troponin-C in resting state. when  Ca++ level increases it leads to the binding of calcium with a subunit of troponin i.e Troponin-C 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. 
  • This pulls the attached actin filaments towards the center 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 the ‘I’ band and 'H' band get reduced, whereas the ‘A’ bands retain the length.

So, Correct answer is 'Stimuli Neurotransmitter secretion →→ Excitation of T-system →→ Release of $Ca^2+$ →→ Cross-bridges formation →→ Sliding of actin filaments →→ H band diminishes'

Involuntary muscular contraction is called

muscle contraction locomotion and movements biology

  1. Muscle sprain

  2. Muscle fatigue

  3. Muscle spasm

  4. Muscle twitch

Show answer
Correct Option: C
Explanation:
  • Muscle is a  bundle of fibrous tissue in a body that has the ability to contract, producing movement in or maintaining the position of parts of the body.
  • The total number of muscles in the human body comes in the range of 640-850.
  • Involuntary muscular contraction is called muscle spasm. Spasms of skeletal muscles are most common and are often due to overuse and muscle fatigue, dehydration, and electrolyte abnormalities.
  • So, the correct answer is 'Muscle spasm'.

Identify the events occurring in muscular contraction;

(i) H-zone disappears
(ii) A band widens
(iii) I-band reduces in width
(iv) The width of A band is unaffected
(v) M-line and Z-line come closer

muscle contraction locomotion and movements biology

  1. i, ii, v

  2. i, ii, iii

  3. i, iii, iv, v

  4. ii, iv, v

Show answer
Correct Option: C
Explanation:
  • Each myofibril has alternate dark and light bands on it. The light bands contain actin and are called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin.
  •  In the centre of each ‘I’ band is an elastic fibre called ‘Z’ line which bisects it. The thin filaments are firmly attached to the ‘Z’ line. The thick filaments in the ‘A’ band are also held together in the middle of this band by a thin fibrous membrane called’ line.
  •  Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge. 
  • This pulls the attached actin filaments towards the centre of ‘A’ band.
  •  The ‘Z’ line attached to these actions are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction.
  • Hence the events occurring in muscular contraction are  H-zone disappears, I-band reduces in width, The width of A band is unaffected and M-line and Z-line come closer.
  • So, the correct answer is 'i, iii, iv, v

Contraction period for a skeletal muscle is

muscle contraction locomotion and movements biology

  1. 4 sec

  2. 0.04 sec

  3. 0.2 sec

  4. 20 sec

Show answer
Correct Option: A
Explanation:

  • When an impulse reaches the muscle fibres of a motor unit, it stimulates a reaction in each sarcomere between the actin and myosin filaments. 
  • This reaction results in the start of a contraction and the sliding filament theory. And the Contraction period for a skeletal muscle is 4 sec.

    Hence, Contraction period for a skeletal muscle is 4 sec.
    So, the correct answer is '4 sec'.