Tag: muscle contraction

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Questions Related to muscle contraction

Multiple choice biology locomotion and movement locomotion in animals bones and movements muscle contraction types of muscles muscles

${Ca}^{2+}$ and ${Mg}^{2+}$ ions 

  1. Reduce excitability of nerves and muscles.

  2. Increase excitability of nerves and muscles.

  3. Conduct nerve impulses.

  4. Both B and C.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

High calcium and magnesium ion concentration decrease the excitability of the muscle fiber membrane by raising the threshold to stimulation, while a low level of the calcium and magnesium ions increase the excitability of muscles fibers. 
So, the correct answer is A.
Multiple choice biology locomotion and movement locomotion in animals bones and movements muscle contraction types of muscles muscles

ATP-ase needed for muscle contraction is present over

  1. Aetinin

  2. Troponin

  3. Myosin

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

ATPase needed for muscle contraction is present over the myosin. Myosin binds to actin at a binding site. Myosin has another binding site for ATP at which enzymatic activity of myosin ATPase hydrolyzes ATP to ADP which releases an inorganic phosphate molecule and energy. The energy released during ATP hydrolysis changes the angle of the myosin head into a cocked position. The myosin head is then in a position for further movement possessing potential energy. The enzyme myosin ATPase catalyses the reaction in the presence of Ca$^{2+}$ and Mg$^{2+}$. So, the correct answer is 'Myosin'.

Multiple choice biology locomotion and movement locomotion in animals bones and movements muscle contraction types of muscles muscles

Which of these ions are involved in muscle contraction? 

  1. $Ca^{2+}$ and $Mg^{2+}$
  2. $Ca^{2+}$ and $Na^+$
  3. $Na^+$ and $K^+$
  4. $Mg^{2+}$ and $K^+$
Reveal answer Fill a bubble to check yourself
A 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.
  • Magnesium also plays a role in regulating muscle contractions. Magnesium acts as a natural calcium blocker to help muscles relax. Hence Ca++ and Mg++ ions are involved in muscle contractions.
  • So, the correct answer is 'Ca$^{2+}$ and Mg$^{2+}$'.
Multiple choice biology locomotion and movement locomotion in animals bones and movements muscle contraction types of muscles muscles

Which one is required for muscle contraction and nerve impulse transmission?

  1. $Ca^{2+}$
  2. $Mg^{2+}$
  3. $Fe^{2+}$

  4. Both A and B
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  •  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
  • Active sites for myosin 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 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. The myosin, releasing the ADP and P1 goes back to its relaxed state. Hence Ca$^{2+}$ is required for muscle contraction and nerve impulse transmission.
  • So, the correct answer is 'Ca 2+'.
Multiple choice biology locomotion and movement locomotion in animals bones and movements muscle contraction types of muscles muscles

Which among the following is not involved in the muscular contraction?

  1. Ca ion

  2. Troponin

  3. Actin

  4. Mg ion
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.
  • magnesium acts as a natural calcium blocker to help muscles relax. Hence Mg ion is not involved in the muscular contraction but it is involved in muscle relaxation by blocking calcium ions.
  • So, the correct answer is 'Mg'
Multiple choice biology locomotion and movement locomotion in animals bones and movements muscle contraction types of muscles muscles

Ion connected with forming cross bridges is

  1. $Na^+$
  2. $Ca^{2+}$
  3. $K^+$

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

Cross bridge cycling forms the basis for movements and force production in the muscle cells. The myosin heads are known as cross bridges because they can bind and move along actin filament. Sarcomere is a stretch of myofibril between two z lines where myosin is in center and actin at periphery, slightly overlapping myosin. Nerve impulse causes release of calcium ions from sarcoplasmic reticulum and binds to troponin which changes configuration of tropomyosin and exposes cross bridge heads on myosin allowing actin myosin binding. This causes contraction of muscle fibre. ATP is required for myosin to dissociate from actin. The calcium ions released from sarcoplasmic reticulum regulate when cross bridging cycle can occur. 

Therefore option B is correct

Multiple choice biology locomotion and movement locomotion in animals bones and movements muscle contraction types of muscles muscles

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

  1. Calcium

  2. Magneisum

  3. Sodium

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

Calcium is the ion released into the sarcoplasma from sarcoplasmic reticulum during the polarisation.  Ca++ attaches to the Troponin-C. This brings a confirmational change in the tropomyosin. As a result unmasking of active sites on actin for myosin takes place. Cross bridges are formed between actin and myosin. This results in muscle contraction.

Magnesium is used in phosphorylation reactions involving ATP.
Sodium and potassium help in maintaining the membrane potential.
So the correct option is A.

Multiple choice biology locomotion and movement locomotion in animals bones and movements muscle contraction types of muscles muscles

Calcium ions bring about muscle contraction through

  1. Activation of myosin ATP-ase

  2. Exposing active sites of actin filaments

  3. Mobilisation of food reserve

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

  • The muscle contraction cycle is triggered by calcium ions binding to the protein complex troponin, exposing the active-binding sites on the actin. 
  • ATP can then attach to myosin, which allows the cross-bridge cycle to start again; further muscle contraction can occur. 
  • Cardiac myosin activators stimulate myosin ATPase, thereby increasing force generation. Hence, Calcium ions bring about muscle contraction
  • through Activation of myosin ATP-ase.
 So, the correct answer is 'Activation of myosin ATP-ase'.