Tag: locomotion and movements

Questions Related to locomotion and movements

Muscular and nervous excitability is reduced by

muscle contraction locomotion and movements biology

  1. $Na^+$

  2. $K^+$

  3. $Ca^{2+}$

  4. $Mg^{2+}$

Show answer
Correct Option: B
Explanation:

  • Potassium is an important mineral that functions as an electrolyte. 
  • It helps regulate fluid balance, nerve signals and muscle contractions and nervous excitability. 
  • Increased extracellular potassium levels result in depolarization of the membrane potentials of cells due to the increase in the equilibrium potential of potassium.
  •  This depolarization opens some voltage-gated sodium channels but also increases the inactivation at the same time. Hence, Muscular and nervous excitability is reduced by K+. 
So, the correct answer is 'K+'.

Which one of the following sets of ions is necessary for chemical events for muscle contraction?

muscle contraction locomotion and movements biology

  1. $Ca^+ \, and \, Mg^{++}$

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

  3. $K^+ \, and \, Ca^+$

  4. $Na^+ \, and \, Fe^{+++}$

Show answer
Correct Option: A
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 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 '$Ca _+$ and $Mg++$'.

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

muscle contraction locomotion and movements biology

  1. Actin

  2. ATP

  3. Myosin

  4. Actomyosin

Show answer
Correct Option: B
Explanation:

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

So the correct answer is 'ATP'.

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 ?

muscle contraction locomotion and movements biology

  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)

Show answer
Correct Option: B
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)'.

Which of the following ions help in muscle contraction ?

muscle contraction locomotion and movements biology

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

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

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

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

Show answer
Correct Option: C
Explanation:

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

Which of the following is incorrect regarding muscle contraction ?

muscle contraction locomotion and movements biology

  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

Show answer
Correct Option: D
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).

Active sites on the actin filaments are exposed when the

muscle contraction locomotion and movements biology

  1. $Mg^{+}$ ions bind with troponin

  2. $Ca^{++}$ ions bind with tropomyosin

  3. $Ca^{++}$ ions bind with troponin

  4. $Mg^{++}$ ions bind with troponin

Show answer
Correct Option: C
Explanation:
  • When an electrical signal passes down the motor nerve to the muscle it causes the depolarisation of the muscle membrane.
  • This triggers the release of calcium ions into the muscle interior where they bind to troponin.
  • This causes the tropomyosin to shift from the face of the actin filament to which myosin heads needs to bind to produce contraction.
  • Thus, the active sites on actin filaments are exposed.

The protein whose removal enables myosin to bind actin in smooth muscle is 

muscle contraction locomotion and movements biology

  1. Tropomyosin

  2. Caldesmon

  3. Myosin light chain kinase

  4. Calmodulin

Show answer
Correct Option: D

If a second stimulus is applied to a muscle that is still in contraction phase; a second contraction is added to the first and results in greater muscle shortening than caused by a single stimulation; it is called

muscle contraction locomotion and movements biology

  1. Absolute refraction

  2. Double muscle twitch

  3. Summation

  4. Fatigue

Show answer
Correct Option: C
Explanation:

When a weak signal is sent by the CNS to contract a muscle, the smaller motor units, being more excitable than the larger ones, are stimulated first. As the strength of the signal increases, more motor units are excited in addition to larger ones, with the largest motor units having as much as 50 times the contractile strength as the smaller ones. As more and larger motor units are activated, the force of muscle contraction becomes progressively stronger. This is known as multiple fibre summations.

If a solution of actin is mixed with a solution of myosin, the resulting mixture becomes very viscous. If ATP is added to this viscous mixture, the viscosity is eliminated and ATP is hydrolysed to ADP and inorganic phosphate. The mixture regains viscosity if all the ATP is hydrolysed. These observations suggest that

muscle contraction locomotion and movements biology

  1. Actin and myosin bind together

  2. The complex of actin and myosin (actomyosin)

  3. ATP seems to alter the binding between actin and myosin

  4. All of the above

Show answer
Correct Option: D
Explanation:

Actomyosin is a contractile complex of actin and myosin, that together with ATP, is active during muscular contraction.
Disruption of the myosin-actin interaction requires ATP, while the myosin molecule can hydrolyze ATP into ADP and Pi.
ATP disconnects actin from myosin, after which it is hydrolyzed by the myosin molecule to produce the energy required for muscle contraction.