Q: Which of the following equations correctly represents the net gain of ATP during anaerobic glycolysis of one molecule of glucose?

$$\text{Glucose} \rightarrow 2 \text{Pyruvate} + 2 \text{ATP} + 2 \text{NADH}$$

Question 1

Which of the following best describes the structural and functional differences between skeletal, cardiac, and smooth muscle tissue?

Accepted Answer

Skeletal muscle is striated, multinucleated, and voluntary; cardiac muscle is striated, has intercalated discs, and is involuntary; smooth muscle is non-striated, single-nucleated, and involuntary.

Question 2

During muscle contraction, which sequence correctly describes the events from the arrival of a nerve impulse at the neuromuscular junction to the release of calcium ions?

Accepted Answer

Nerve impulse → ACh release → ACh binds to receptors → Na+ influx → Muscle action potential → T-tubule depolarization → Sarcoplasmic reticulum releases Ca2+

Question 3

Which enzyme is responsible for breaking down acetylcholine in the synaptic cleft, and what is the physiological significance of this process?

Accepted Answer

Acetylcholinesterase; it terminates the signal transmission, allowing the muscle to relax.

Question 4

A patient is exposed to botulinum toxin. What is the most likely effect on their skeletal muscle function?

Accepted Answer

Paralysis due to inhibition of acetylcholine release at the neuromuscular junction.

Question 5

Which of the following correctly matches the muscle attachment terms with their definitions?

Accepted Answer

Origin: attachment to stationary bone; Insertion: attachment to movable bone.

Question 6

Which of the following best describes the role of ATP in the cross-bridge cycle during muscle contraction?

Accepted Answer

ATP binds to myosin, causing it to release from actin; hydrolysis of ATP re-cocks the myosin head.

Question 7

If a muscle fiber is unable to pump calcium back into the sarcoplasmic reticulum, what would be the most likely consequence?

Accepted Answer

Prolonged muscle contraction due to sustained exposure of myosin-binding sites on actin.

Question 8

Which of the following equations correctly represents the net gain of ATP during anaerobic glycolysis of one molecule of glucose?

Accepted Answer

$$	ext{Glucose} ightarrow 2 	ext{Pyruvate} + 2 	ext{ATP} + 2 	ext{NADH}$$

Question 9

Which part of the sarcomere shortens during muscle contraction?

Accepted Answer

The I band

Question 10

A toxin blocks voltage-gated sodium channels in the sarcolemma. What is the most immediate effect on muscle contraction?

Accepted Answer

Prevention of muscle action potential propagation, leading to paralysis.

Question 11

Which of the following best explains why skeletal muscle fibers are multinucleated?

Accepted Answer

They are formed by the fusion of multiple myoblasts during embryonic development.

Question 12

Which lever class is represented by the biceps brachii flexing the forearm at the elbow?

Accepted Answer

Third-class lever

Question 13

Which of the following correctly describes the function of T-tubules in skeletal muscle fibers?

Accepted Answer

They conduct action potentials deep into the muscle fiber, triggering calcium release from the sarcoplasmic reticulum.

Question 14

Which of the following is the correct sequence of events in the cross-bridge cycle?

Accepted Answer

Myosin binds to actin → Power stroke → ATP binds to myosin → Myosin releases from actin → ATP hydrolysis re-cocks myosin head

Question 15

Which of the following muscle pathologies is characterized by enlargement of existing muscle cells?

Accepted Answer

Hypertrophy

Question 16

Which molecule covers the myosin-binding sites on actin in a relaxed muscle fiber?

Accepted Answer

Tropomyosin

Question 17

Which process is responsible for the removal of acetylcholine from the synaptic cleft after muscle stimulation?

Accepted Answer

Diffusion away, breakdown by acetylcholinesterase, and reuptake by the neuron using a choline pump.

Question 18

Which of the following best describes the function of the sarcoplasmic reticulum in muscle contraction?

Accepted Answer

It stores and releases calcium ions necessary for contraction.

Question 19

A patient presents with spastic paralysis after exposure to tetanus toxin. What is the underlying mechanism?

Accepted Answer

Inhibition of inhibitory neurotransmitter release in the spinal cord, leading to overstimulation of muscles.

Muscular System: Structure, Function, and Physiology

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