Question 1

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

Accepted Answer

It stores and releases Ca$$^{2+}$$ ions necessary for muscle contraction.

Question 2

A patient is diagnosed with myasthenia gravis, an autoimmune disease that targets acetylcholine (ACh) receptors. Which of the following symptoms would most likely be observed?

Accepted Answer

Muscle weakness due to impaired synaptic transmission at the neuromuscular junction.

Question 3

Which connective tissue wrapping surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 4

During the sliding filament model of muscle contraction, which event occurs immediately after Ca$$^{2+}$$ binds to troponin?

Accepted Answer

Tropomyosin shifts, exposing myosin-binding sites on actin.

Question 5

Which of the following is a characteristic unique to cardiac muscle tissue?

Accepted Answer

Presence of intercalated discs

Question 6

A muscle fiber is stimulated by a motor neuron, leading to an influx of Na$$^+$$ ions. What is the immediate result of this influx?

Accepted Answer

Depolarization of the sarcolemma

Question 7

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

Ca$$^{2+}$$ leaks from the sarcoplasmic reticulum, allowing actin and myosin to bind, but ATP is unavailable to release the cross-bridges.

Question 8

Which of the following structures is responsible for transmitting the action potential deep into the muscle fiber?

Accepted Answer

Transverse (T) tubules

Question 9

A muscle is attached to a bone at two points. The attachment to the stationary bone is called the:

Accepted Answer

Origin

Question 10

Which of the following best describes the 'all-or-none' response in muscle fibers?

Accepted Answer

Once an action potential is initiated, the muscle fiber contracts completely.

Question 11

Which protein acts as a 'switch' by binding Ca$$^{2+}$$ and initiating muscle contraction?

Accepted Answer

Troponin

Question 12

During muscle contraction, what is the role of ATP in the cross-bridge cycle?

Accepted Answer

ATP binds to myosin, causing it to detach from actin.

Question 13

Which of the following is true regarding the structure of a sarcomere?

Accepted Answer

The A band contains both thick and thin filaments.

Question 14

A drug that irreversibly blocks acetylcholine receptors at the neuromuscular junction would most likely cause:

Accepted Answer

Paralysis of skeletal muscles

Question 15

Which of the following best explains the function of titin in the sarcomere?

Accepted Answer

It provides elasticity and helps anchor thick filaments to the Z disc.

Question 16

Which of the following is a function of muscle tissue that is critical for maintaining homeostasis in the human body?

Accepted Answer

Thermogenesis

Question 17

Which of the following best describes the process of repolarization in a muscle fiber?

Accepted Answer

Voltage-gated K$$^+$$ channels open, allowing K$$^+ to $$exit the cell, restoring the negative membrane potential.

Question 18

Which of the following is a property shared by all three types of muscle tissue?

Accepted Answer

Excitability

Question 19

A patient is experiencing muscle cramps due to a lack of ATP. Which step in the cross-bridge cycle is directly affected?

Accepted Answer

Detachment of myosin from actin

Question 20

Which of the following best describes the difference between direct and indirect muscle attachments?

Accepted Answer

Direct attachments involve the epimysium fusing to the periosteum, while indirect attachments use tendons or aponeuroses.

Muscles and Muscle Tissue: Structure, Function, and Contraction

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