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 zoology skeleton and movements contractile protein structure of muscle muscles and their structure

In skeleton muscle Z-line is connected to.

  1. Actin

  2. Myosin

  3. Tropomyosin

  4. Hensen's line
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • Each myofibril consists of a series of contractile units (sarcomeres) connected at a protein border (the Z line).
  •  Thin filaments(actin) of adjacent sarcomeres are present in the Z line between the thin filaments are thick filaments(myosin). 
  • The protein tropomyosin winds around the thin filaments and covers the myosin binding sites. Hence, In skeleton muscle, Z-line is connected to actin.
So, the correct answer is 'actin'.

Multiple choice zoology skeleton and movements contractile protein structure of muscle muscles and their structure

Major protein in thick filaments of skeletal muscle fibre is?

  1. Myosin

  2. Actin

  3. Tropomyosin

  4. Troponin
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • The main contractile components of a muscle fibre include:
  •  Thick filaments - The major protein of a thick filament is myosin. 
  • Thin filaments - The major proteins of a thin filament include actin, as well as troponin and tropomyosin. Hence, Major protein in thick filaments of skeletal muscle fibre is myosin.
So, the correct answer is 'myosin'.

Multiple choice muscle contraction locomotion and movements biology

Which statements about muscle contractions are true?
(i) Acetylcholine is released when neural signal reaches motor end plate
(ii) Muscle contraction is initiated by a signal sent by CNS via a sensory neuron
(iii) During muscle contraction, isotropic band gets elongated
(iv) Repeated activation of the muscle can lead to lactic acid accumulation.

  1. i and iv

  2. i and iii

  3. ii and iii

  4. i, ii and iii

  5. i and ii
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • Acetylcholine is the neurotransmitter used at the neuromuscular junction, it is the chemical that motor neurons of the nervous system release in order to activate muscles when acetylcholine is released when the neural signal reaches motor end plate. 
  • Repeated activation of muscle induces processes resulting in decreased performance (fatigue) as well as enhanced performance (potentiation).  Lactic acid is formed and accumulated in the muscle under conditions of high energy demand, rapid fluctuations of the energy requirement and insufficient supply of O2. Hence,  Repeated activation of the muscle can lead to lactic acid accumulation.
So, the correct answer is ' i and iv'.

Multiple choice muscle contraction locomotion and movements biology

Electron microscopic studies of the sarcomeres have revealed that during muscle contraction

  1. The width of A-band remains constant

  2. The width of the H-zone becomes smaller

  3. The width of I-band increases

  4. The diameter of the fibre increases
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During muscle contraction, the A - band with a length of 1.85 micrometers does not undergo any contraction. However, the I-bands and the H-zone shorten. This causes the Z lines to come closer together. So, the correct answer is 'The width of A-band remains constant'.

Multiple choice muscle contraction locomotion and movements biology

Which statement is correct for muscle contraction : - 

  1. Length of H-zone become decrease

  2. Length of A-band remains constant

  3. Length of I-band become increase

  4. Length of two Z-line become increase
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation
Upon muscle contraction, the A-bands do not change their length (1.85 micrometres in mammalian skeletal muscle), whereas the I-bands and the H-zone shorten. This causes the Z lines to come closer together.

So, the correct answer is 'A, B'.
Multiple choice muscle contraction locomotion and movements biology

Name the ion responsible for masking active sites for myosin for cross-bridge activity during muscle contraction.

  1. Potassium

  2. Calcium

  3. Magnesium

  4. Sodium
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. 
  • 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 the ion responsible for masking active sites for myosin for cross-bridge activity during muscle contraction is calcium.
  • So, the correct answer is 'Calcium'
Multiple choice muscle contraction locomotion and movements biology

Sarcoplasmic reticulum of muscle fibres is the storehouse of

  1. Calcium

  2. Sodium

  3. Chloride

  4. Potassium
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • The endoplasmic reticulum, i.e., sarcoplasmic reticulum of the muscle fibres is the storehouse of calcium ions.
  • A neural signal reaching this junction releases a neurotransmitter (Acetylcholine) which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm from the sarcoplasmic reticulum and initiate the mechanism of muscle contraction.
  • Hence sarcoplasmic reticulum of muscle fibres is the storehouse of calcium.
  • So, the correct answer is 'Calcium'.
Multiple choice muscle contraction locomotion and movements biology

Source of $Ca^{2+}$ for muscle contraction is both sarcoplasmic (endoplasmic) reticulum as well as extracellular fluid in case of
a.  Skeletal muscles
b. Smooth muscles
c. cardiac muscles 

  1. a only

  2. b and c only

  3. a and c only

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

Both smooth muscle and cardiac muscle utilise sarcoplasmic and extracellular fluid as source of calcium ion, which is in contrast to skeletal muscle which derive it from sarcoplasm only.

So, the correct option is 'b and c only'

Multiple choice muscle contraction locomotion and movements biology

State whether the following statements are true or false.
Cross bridges pull the actin chain as the myosin heads return to their unenergized conformation.

  1. True

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

  • A sarcomere is the basic unit of muscle tissue in both cardiac and skeletal muscle. Myofibril activity is required for muscle contraction on the molecular level. 
  • When ATP binds to myosin, it separates from the actin of the myofibril, which causes a contraction.
  • The muscle contraction cycle is triggered by calcium ions binding to the protein complex troponin, exposing the active-binding sites on the actin.
  • ATP then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.
So, the correct option is 'True'.

Multiple choice muscle contraction locomotion and movements biology

Which response to overcooling does not involve muscle contraction?

  1. Blood vessels narrowing

  2. Hairs standing up

  3. Shivering

  4. Reduced sweating
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In response to over-cooling, 

muscles allow blood vessels narrowing(circular muscles), piloerection(hair standing up by erector pili muscles), and shivering.
Reduced sweating does not involve muscle contraction or relaxation.
So, the correct answer is 'Reduced sweating'.

Multiple choice muscle contraction locomotion and movements biology

During skeletal muscle contractions following events can occur:
I. I-band shortens
II. A-band shortens
III. H-zone shortens
IV. Sarcomere contract
V. ATP changes to ADP and Pi
Choose the option with incorrect events.

  1. Only I

  2. Only III

  3. IV and V

  4. Only II
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

I-band consists of only thin filaments. A-band consists of both the thin and thick filaments. H-zone is the band of thick filament only. For skeletal muscle contraction following events occur:

1. The nerve impulse is transmitted to the sarcolemma and it causes release of calcium ions from sarcoplasmic reticulum.
2. These calcium bind to the troponin and tropomyosin rotates. 
3. Then, the myosin binds to the tropomyosin. 
4. ATP is hydrolysed to detach the myosin from the tropomyosin and muscle can be relaxed.
The shortening of I-band and H-zone causes the contraction of sarcomere. 
A-band does not change.
Hence, the correct answer is 'only II'

Multiple choice muscle contraction locomotion and movements biology

Which responce to overcooling does not does not involve muscle contraction?

  1. Blood vessels narrowing

  2. Hairs standing up

  3. Shivering

  4. Reduced sweating
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Blood vessels narrowing, hairs standing up and shivering are all because of contraction of muscles. While reduced sweating is due to non-activation of sweat glands from the hypothalamus.

So, the correct option is 'reduced sweating'.

Multiple choice muscle contraction locomotion and movements biology

Which one of the following option gives the correct categorisation of structure of contractile proteins ?

Actin  Myosin
1 Troponin Actinin
2 Troponin tropomyosin HMM and LMM
3 'G' - actin Tropomyosin
4 Tropomyosin troponin $Ca^{++}$ binding site

  1. 1

  2. 2

  3. 3

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

Troponin is attached protein tropomyosin and lies within the groove between actin filaments in the muscle tissue. The calcium attaches the troponin which changes the shape exposing binding sites for myosin on the actin filament. So the correct answer is 1.

Multiple choice muscle contraction locomotion and movements biology

The energy of muscle contraction is most directly obtained from____________.

  1. Phosphocreatine

  2. ATP

  3. Anaerobic respiration

  4. Aerobic respiration
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Answer :
i) The contraction of skeletal muscles is an energy-requiring process. 
ii) To perform the mechanical work of contraction, actin and myosin utilize the chemical energy of the molecule Adenosine triphosphate (ATP).
iii) Adenosine triphosphate (ATP) is a complex organic chemical that provides energy to drive many processes in living cells, e.g. muscle contraction, nerve impulse propagation, and chemical synthesis. 
iv) Found in all forms of life, ATP is often referred to as the "molecular unit of currency" of intracellular energy transfer.

Therefore correct answer is option B- ATP.


Multiple choice muscle contraction locomotion and movements biology

ATP provides energy for muscle contraction by allowing for

  1. An action potential formation in the muscle cell

  2. Cross bridge detachment of myosin from actin

  3. Cross bridge detachment of myosin to actin
  4. Release of $C{a^{ + 2}}$ from sarcoplasmic rectulum
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
ATP enables the actin-myosin cross-bridge to detach, and release energy through its hydrolysis to enable the myosin head to return to its resting position.
So, the correct option is Cross bridge detachment of myosin from actin.