Locomotion & Movement – Muscle – 2:
1. Which of these constitute a motor unit?
A. Motor neuron + muscle fibres
B. Motor neuron + fascia
C. Motor neuron + muscle
D. Motor neuron + muscle bundle
Answer: A
Explanation: Muscle fibres connected to a motor neuron make up a motor unit. The motor neuron carries an impulse from the CNS or the central nervous system which stimulates the muscle to contract.
2. Which of these is a neurotransmitter?
A. HMM
B. Troponin
C. ATPase
D. Acetylcholine
Answer: D
Explanation: Acetylcholine is a neurotransmitter. It is a chemical compound that helps in the transmission of signals or impulses to and from the CNS or the central nervous system via the neurons.
3. What does acetylcholine generate in the sarcolemma?
A. Resting potential
B. Graded potential
C. Action potential
D. Membrane potential
Answer: C
Explanation: Acetylcholine is a neurotransmitter. It is a chemical compound that helps in the transmission of impulses. Acetylcholine generates action potential in the sarcolemma which spreads through the muscle fibre.
4. ‘F’ actin is a polymer of ‘G’ actins. True or false?
A. True
B. False
Answer: A
Explanation: ‘F’ actin is a polymer of ‘G’ or globular actins which are monomers. Two ‘F’ or filamentous actins are wound together in a helical manner to form the thin filament or the actin filament.
5. Why does the repeated activation of the muscles cause fatigue?
A. Due to the aerobic breakdown of glycogen
B. Due to the breakdown of glucose
C. Due to glycogen formation
D. Due to lactic acid accumulation
Answer: D
Explanation: The repeated activation of the muscles leads to the anaerobic breakdown of glycogen. This takes place due to the unavailability of oxygen. This results in the formation of lactic acid, which accumulates and causes fatigue.
6. Which of these proteins store oxygen?
A. Troponin
B. Tropomyosin
C. Myoglobin
D. ‘G’ actin
Answer: C
Explanation: Myoglobin is present in the muscle fibres. It is red in colour. The function of myoglobin is to store oxygen, so that it is readily available for providing energy in the form of ATP for the proper functioning of muscles.
7. Which organelle is abundant in red fibres of muscles?
A. Sarcoplasmic reticulum
B. Nuclei
C. Mitochondria
D. Peroxisomes
Answer: C
Explanation: Red fibres of muscle are rich in mitochondria as produce energy in the form of ATP. Red fibres are also rich in myoglobin, which is a red coloured protein that has the function of oxygen storage.
8. Which of these statements is false regarding white fibres of muscle?
A. They contain a large number of sarcoplasmic reticula
B. They derive energy from aerobic processes
C. They are not rich in myoglobin
D. They contain fewer mitochondria than red fibres
Answer: B
9. What is present in the centre of each ‘I’ band?
A. ‘H’ line
B. ‘A’ line
C. ‘M’ line
D. ‘Z’ line
Answer: D
Explanation: The ‘I’ band or the isotropic band is also known as the light band. It contains the protein actin. The ‘Z’ line is present in the centre of each ‘I’ band which bisects it. The ‘Z’ line is an elastic fibre.
10. Which of these structures holds myosin filaments together?
A. ‘H’ line
B. ‘A’ line
C. ‘M’ line
D. ‘Z’ line
Answer: C
Explanation: The myosin filaments or the thick filaments are held together by the ‘M’ line. The ‘M’ line is present in the middle of the ‘A’ band or the anisotropic band or the dark band, and is thin and fibrous.
11. Which of these is found at the two ends of a sarcomere?
A. ‘H’ line
B. ‘A’ line
C. ‘M’ line
D. ‘Z’ line
Answer: D
Explanation: The two ends of a sarcomere or a contractile unit of a muscle is marked by the presence of ‘Z’ lines. It contains one whole ‘A’ band or anisotropic band and half of an ‘I’ band or isotropic band.
12. Which of these is not a component of the thin filament?
A. LMM
B. Tropomyosin
C. Troponin
D. ‘F’ actin
Answer: A
Explanation: The thin filament or the actin filament is composed of two filaments of ‘F’ actin wound helically to each other. ‘F’ actin is a polymer of monomeric ‘G’ actins. The proteins troponin and tropomyosin are also present.
13. What is present in the globular head of meromyosin?
A. Troponin
B. ATPase
C. Tropomyosin
D. LMM
Answer: B
