Question 1

Which structure marks the boundary of a sarcomere in skeletal muscle fibers?

Accepted Answer

Z line

Question 2

During muscle contraction, which band of the sarcomere remains unchanged in length?

Accepted Answer

A band

Question 3

What is the primary function of the sarcoplasmic reticulum in skeletal muscle cells?

Accepted Answer

Storing and releasing calcium ions

Question 4

Which protein binds calcium to initiate muscle contraction?

Accepted Answer

Troponin C

Question 5

What is the role of acetylcholinesterase at the neuromuscular junction?

Accepted Answer

Degrades acetylcholine to terminate the signal

Question 6

Which equation best describes the relationship between muscle tension and sarcomere length?

Accepted Answer

$$T = T_{max} \cdot \exp\left(-\frac{(L - L_{opt})^2$}{2\$$sigma^2$$}\right)$$

Question 7

Which of the following is TRUE regarding the nicotinic acetylcholine receptor (nAChR) at the neuromuscular junction?

Accepted Answer

It is composed of five subunits, including alpha, beta, gamma (or epsilon), and delta

Question 8

A patient presents with muscle weakness. Laboratory tests reveal a defect in the release of acetylcholine at the neuromuscular junction. Which step in the process of muscle contraction is most directly affected?

Accepted Answer

Generation of action potential in the muscle fiber

Question 9

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

Accepted Answer

Transmit action potentials deep into the muscle fiber

Question 10

Which of the following nerve fibers conducts action potentials the fastest?

Accepted Answer

A-alpha fibers

Question 11

What is the effect of calcium binding to troponin C during muscle contraction?

Accepted Answer

It causes tropomyosin to move, exposing the myosin binding site on actin

Question 12

Which of the following best explains why muscle tension decreases when the sarcomere is either too short or too long?

Accepted Answer

The number of cross-bridges formed is optimal only at intermediate sarcomere lengths

Question 13

Which of the following is a correct sequence of events at the neuromuscular junction leading to muscle contraction?

Accepted Answer

Action potential in neuron → Acetylcholine release → Acetylcholine binds nAChR → Sodium influx → Muscle action potential

Question 14

Which of the following statements about graded potentials is correct?

Accepted Answer

Graded potentials can be either stimulatory or inhibitory and may not reach threshold

Question 15

Which of the following best describes the molecular structure of actin in muscle fibers?

Accepted Answer

Actin polymerizes to form F-actin filaments

Question 16

Which of the following is the correct formula for the Nernst equation, used to calculate the equilibrium potential for an ion?

Accepted Answer

$$E = \frac{RT}{zF} \ln \left( \frac{[	ext{ion}]_{	ext{outside}}}{[	ext{ion}]_{	ext{inside}}} ight)$$

Question 17

Which of the following is a consequence of blocking voltage-gated sodium channels in the axon terminal of a motor neuron?

Accepted Answer

Action potential propagation is inhibited

Question 18

Which of the following best describes the function of the motor cortex?

Accepted Answer

It initiates and controls voluntary movements

Question 19

Which of the following is TRUE regarding the transmission of signals from the brain to skeletal muscle?

Accepted Answer

Lower motor neurons transmit signals from the spinal cord to muscle fibers

Question 20

Which of the following best explains the effect of myelination on nerve conduction velocity?

Accepted Answer

Myelination increases conduction velocity by allowing saltatory conduction

Skeletal Muscle Structure and Neuromuscular Junction: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards