NEET Biology Locomotion and Movement MCQs Set 05

Answer: (a) the neuromuscular junction

Explanation:
1. A motor neuron stimulates a muscle fibre at the neuromuscular junction (motor end plate) by releasing acetylcholine.
2. The transverse tubules and sarcoplasmic reticulum act later.

Teacher's Note:
1. Neuromuscular junction: nerve to muscle.
2. Neurotransmitter: acetylcholine.

Answer: (b) Actin and Myosin filaments do not shorten but rather slide pass each other

Explanation:
1. In the sliding filament theory the actin and myosin filaments keep their length and slide past each other.
2. The sarcomere shortens because the filaments overlap more.

Teacher's Note:
1. No filament shortens.
2. Z lines come closer.

Answer: (c) Tetanus

Explanation:
1. Tetanus is a sustained contraction due to lack of relaxation between successive stimuli.
2. Spasm is a sudden involuntary contraction and tonus is slight continuous contraction.

Teacher's Note:
1. Tetanus: fused contraction.
2. Fatigue: loss of response.

Answer: (c) Calcium

Explanation:
1. Calcium ions bind troponin and unmask the active sites on actin for myosin cross-bridge formation.
2. Sodium and potassium help in nerve impulse transmission.

Teacher's Note:
1. Ca2+ triggers contraction.
2. Released from sarcoplasmic reticulum.

Answer: (a) Break down product of creatine phosphate in muscle

Explanation:
1. Creatinine is a breakdown product of creatine phosphate in muscle.
2. It is excreted by the kidney.

Teacher's Note:
1. Creatine phosphate to creatinine.
2. Used as a kidney function marker.

Answer: (a) binds to troponin to remove the masking of active sites on actin for myosin.

Explanation:
1. Calcium binds troponin and removes the masking of active sites on actin so myosin can attach.
2. It does not activate ATPase directly or detach the myosin head.

Teacher's Note:
1. Ca2+ unmasks sites.
2. ATP detaches the head.

Answer: (a) Sarcoplasmic reticulum

Explanation:
1. Calcium ions are stored in the sarcoplasmic reticulum of the muscle fibre.
2. They are released when the fibre is stimulated.

Teacher's Note:
1. SR: calcium store.
2. Sarcolemma: cell membrane.

Answer: (b) Striated, involuntary

Explanation:
1. Cardiac muscles are striated and involuntary.
2. They also have intercalated discs.

Teacher's Note:
1. Heart muscle: involuntary striated.
2. Skeletal: voluntary striated.

Answer: (b) Macrophages, Leucocytes

Explanation:
1. Amoeboid movement occurs in macrophages and leucocytes through pseudopodia.
2. Cilia occur in the trachea and fallopian tube.

Teacher's Note:
1. Pseudopodia: amoeboid movement.
2. Cytoskeleton drives it.

Answer: (c) 'Z' line

Explanation:
1. The I band is bisected by an elastic fibre called the Z line.
2. The M line lies in the middle of the A band.

Teacher's Note:
1. Z line: between sarcomeres.
2. M line: centre of A band.

Answer: (d) All of these

Explanation:
1. The myosin head carries ATPase, an ATP binding site and sites that bind actin.
2. So all statements are true.

Teacher's Note:
1. Head: motor part.
2. Tail forms the thick filament.

Answer: (c) Amount of sarcoplasmic reticulum is high

Explanation:
1. Red muscle fibres have a lot of myoglobin and many mitochondria, and they contract slowly for a long time.
2. They have little sarcoplasmic reticulum, so option 3 is not associated.

Teacher's Note:
1. Red: aerobic.
2. White: anaerobic.

Answer: (d) Both 1 and 2

Explanation:
1. The junction between a motor neuron and the sarcolemma of a muscle fibre is called the neuromuscular junction or motor end plate.
2. Both names are right.

Teacher's Note:
1. NMJ = motor end plate.
2. Acetylcholine crosses the cleft.

Answer: (b) 40-50%

Explanation:
1. Muscles make up about 40 to 50 percent of the body weight of an adult.
2. It is the largest tissue by mass.

Teacher's Note:
1. Muscle: 40 to 50 percent.
2. Bone: about 15 percent.

Answer: (a) Cilia

Explanation:
1. In Paramecium, cilia in the cytopharynx sweep food into the gullet.
2. Flagella and myonemes serve other movements.

Teacher's Note:
1. Paramecium moves by cilia.
2. Cilia also feed.

Answer: (c) Lactic acid

Explanation:
1. Repeated activation of muscle causes anaerobic breakdown of glucose and accumulation of lactic acid.
2. This leads to fatigue.

Teacher's Note:
1. Lactic acid: fatigue.
2. Acetylcholine is a neurotransmitter.

Answer: (c) Myoglobin

Explanation:
1. The red oxygen-storing pigment of muscle is myoglobin.
2. Haemoglobin is in red blood cells.

Teacher's Note:
1. Myoglobin: O2 reserve.
2. It gives red colour.

Answer: (c) H-zone

Explanation:
1. The H zone is the central part of the thick filament not overlapped by thin filaments in resting muscle.
2. The A band is the full length of thick filaments.

Teacher's Note:
1. H zone: only myosin.
2. Lost in full contraction.

Answer: (d) A, C

Explanation:
1. Skeletal muscles are under voluntary control (A) and are mainly involved in locomotion and posture (C).
2. They are not found in visceral organs and they are striated, so B and D are wrong.

Teacher's Note:
1. Skeletal: striped.
2. Visceral: smooth.

Answer: (c) Amount of sarcoplasmic reticulum is low.

Explanation:
1. White muscle fibres have little myoglobin, few mitochondria and rely on anaerobic energy.
2. Their sarcoplasmic reticulum is abundant, so statement 3 is not associated.

Teacher's Note:
1. White: fast, anaerobic.
2. Red: slow, aerobic.

Answer: (c) A-(iv), B-(v), C-(ii), D-(iii), E-(i)

Explanation:
1. Tetany is rapid muscle spasm (iv), osteoporosis is decreased bone mass (v), muscular dystrophy is progressive degeneration of skeletal muscle (ii).
2. Arthritis is joint inflammation (iii) and myasthenia gravis is autoimmune (i).

Teacher's Note:
1. Tetany: low calcium.
2. Myasthenia gravis: autoimmune.