Biology · General Awareness

Muscle Biology

836 Questions

Muscle biology covers the structures, functions, and contraction mechanisms of skeletal, cardiac, and smooth muscles. Test questions target filaments, stimuli, and specific muscle roles. A clear understanding helps secure marks in biology sections.

Skeletal muscle controlCardiac muscle propertiesMuscle contraction mechanismActin and myosin filamentsMuscle functions

Muscle Biology Questions

Multiple choice muscle contraction locomotion and movements biology

During contraction of muscles,

  1. Actin filament slide over actin

  2. Myosin filament slide over actin

  3. Actin filament slide over myosin

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

Multiple choice muscle contraction locomotion and movements biology

Chemical ions responsible for muscle contraction are

  1. $Ca^{++}$ and $K^+$
  2. $Na^+$ and $K^+$
  3. $Na^+$ and $Ca^{++}$
  4. $Ca^{++}$ and $Mg^{++}$ ions
Reveal answer Fill a bubble to check yourself
D Correct answer
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'.
Multiple choice muscle contraction locomotion and movements biology

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

  1. Isotonic contraction

  2. Tetanus

  3. Isomeric contraction

  4. Single muscle twitch
Reveal answer Fill a bubble to check yourself
A Correct answer
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).

Multiple choice muscle contraction locomotion and movements biology

Cardiac muscles are characteristic in that they contract

  1. Slowly and get fatigued

  2. Quickly and get fatigued

  3. Slowly and do not get fatigued

  4. Rhythmically and do not get fatigued
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

Multiple choice muscle contraction locomotion and movements biology

During muscle contraction

  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
Reveal answer Fill a bubble to check yourself
D 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. 
  • 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'
Multiple choice muscle contraction locomotion and movements biology

Which is true of muscle contraction

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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'.

Multiple choice muscle contraction locomotion and movements biology

Correct order of stages of muscle contraction is

  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
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-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'

Multiple choice muscle contraction locomotion and movements biology

Involuntary muscular contraction is called

  1. Muscle sprain

  2. Muscle fatigue

  3. Muscle spasm

  4. Muscle twitch
Reveal answer Fill a bubble to check yourself
C Correct answer
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'.
Multiple choice muscle contraction locomotion and movements biology

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

  1. i, ii, v

  2. i, ii, iii

  3. i, iii, iv, v

  4. ii, iv, v
Reveal answer Fill a bubble to check yourself
C Correct answer
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
Multiple choice muscle contraction locomotion and movements biology

Contraction period for a skeletal muscle is

  1. 4 sec

  2. 0.04 sec

  3. 0.2 sec

  4. 20 sec
Reveal answer Fill a bubble to check yourself
A Correct answer
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'.

Multiple choice muscle contraction locomotion and movements biology

Which of the following is a source of energy for muscle contraction ?

  1. Actin

  2. ATP

  3. Myosin

  4. Actomyosin
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

'ATP' is the source of energy for muscle contraction.

So the correct answer is 'ATP'.

Multiple choice muscle contraction locomotion and movements biology

Following is given a randomly arranged list of events that occur at neuromuscular junction to trigger muscle contraction.
(i) Receptor sites on sarcolemma
(ii) Nerve impulse
(iii) Release of $Ca^{+2}$ from sarcoplasmic reticulum
(iv) The neurotransmitter acetylcholine is released (v) Sarcomere shorten
(vi) Synaptic cleft 
(vii) Spread of impulses over sarcolemma on T-tubules
Which of the following gives the correct sequence of these steps ?

  1. (ii) $\rightarrow$ (iv) $\rightarrow$ (i) $\rightarrow$ (vi) $\rightarrow$ (vii) $\rightarrow$ (v)
  2. (ii) $\rightarrow$ (iv) $\rightarrow$ (vi) $\rightarrow$ (i) $\rightarrow$ (vii) $\rightarrow$(iii) $\rightarrow$ (v)
  3. (i) $\rightarrow$ (ii) $\rightarrow$ (iii) $\rightarrow$ (iv) $\rightarrow$ (v) $\rightarrow$ (vi) $\rightarrow$ (vii)
  4. (vii) $\rightarrow$ (vi) $\rightarrow$ (v) $\rightarrow$ (iv) $\rightarrow$ (iii) $\rightarrow$ (i)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Muscle contraction:

a. As a nerve impulse( action potential) from a motor neuron arrives via its axon at the neuromuscular junction, the vesicles in the end plate release a neurotransmitter, the acetylcholine, into the nerve-muscle gap (synaptic cleft). 
b. Acetylcholine depolarises the postsynaptic muscle cell's sarcolemma and set up an action potential in the latter.
c. The action potential spreads deep into the interior of the muscle fibre via T- tubules and Z lines.
d. The incoming action potential changes the permeability of the SR, causing to release calcium ions.
e. The calcium ions bind to troponin molecules. 
f. The latter change shape and shift position.
So, the correct answer is '(ii) $\rightarrow$(iv)$\rightarrow$(vi)$\rightarrow$(i)$\rightarrow$(vii)$\rightarrow$(iii)$\rightarrow$(v)'.

Multiple choice muscle contraction locomotion and movements biology

Which of the following ions help in muscle contraction ?

  1. $K^+$ and $Mg^{++}$
  2. $Na^+$ and $K^+$
  3. $Ca^{++} $ and $Na^{++}$
  4. $Ca^{++}$ and $Mg^{++}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

' Ca${++}$ and Na${++}$ ' help in muscle contraction. So, the correct answer is (c).

Multiple choice muscle contraction locomotion and movements biology

Which of the following is incorrect regarding muscle contraction ?

  1. Actin and myosin make actomyosin

  2. Phosphate reserve comes from phosphoaeatine

  3. Chemical energy is converted into mechanical energy

  4. Mechanical energy is converted into chemical energy
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

During muscle contraction, actin and myosin form actomyosin, phosphate reserve comes from phosphocreatine and chemical energy is changed into mechanical energy. So, the correct answer is (d).