Q: Which equation correctly represents the hydrolysis of ATP during muscle contraction?

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy}$$

Q: Which equation represents the action of the sodium-potassium pump?

$$3\ \mathrm{Na}^+_{\text{in}} + 2\ \mathrm{K}^+_{\text{out}} + \mathrm{ATP} \rightarrow 3\ \mathrm{Na}^+_{\text{out}} + 2\ \mathrm{K}^+_{\text{in}} + \mathrm{ADP} + \mathrm{P}_i$$

Question 1

Which of the following best describes the sequence of events that occur during muscle contraction within a sarcomere?

Accepted Answer

Actin filaments slide past myosin filaments, shortening the sarcomere as the Z lines move closer together.

Question 2

Which structure is responsible for releasing acetylcholine into the synaptic cleft at the neuromuscular junction?

Accepted Answer

The axon terminal of the motor neuron

Question 3

What is the primary role of acetylcholinesterase at the neuromuscular junction?

Accepted Answer

To break down acetylcholine in the synaptic cleft, terminating the signal transmission

Question 4

Which equation correctly represents the hydrolysis of ATP during muscle contraction?

Accepted Answer

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy}$$

Question 5

Which of the following best explains the difference between a pump and a channel in cellular membranes?

Accepted Answer

A pump uses ATP to actively transport ions against their concentration gradient, while a channel allows passive movement of ions.

Question 6

Which of the following is a ligand-gated ion channel?

Accepted Answer

Acetylcholine receptor at the neuromuscular junction

Question 7

A patient is exposed to a toxin that blocks voltage-gated Na$$^+$$ channels. What is the most likely effect on their neurons?

Accepted Answer

Neurons will be unable to generate action potentials.

Question 8

Which of the following best describes the resting membrane potential of a typical neuron?

Accepted Answer

It is established by the sodium-potassium pump, which moves 3 Na$$^+$$ out and 2 K$$^+ in$$, creating a negative charge inside.

Question 9

Which equation represents the action of the sodium-potassium pump?

Accepted Answer

$$3\ \mathrm{Na}^+_{	ext{in}} + 2\ \mathrm{K}^+_{	ext{out}} + \mathrm{ATP} ightarrow 3\ \mathrm{Na}^+_{	ext{out}} + 2\ \mathrm{K}^+_{	ext{in}} + \mathrm{ADP} + \mathrm{P}_i$$

Question 10

Which of the following is NOT a function of the sarcoplasmic reticulum in skeletal muscle?

Accepted Answer

Synthesizing acetylcholine

Question 11

During an action potential, which event occurs immediately after the membrane potential reaches threshold?

Accepted Answer

Voltage-gated sodium channels open, allowing Na$$^+$$ influx

Question 12

Which of the following best explains why ATP is required for muscle relaxation?

Accepted Answer

ATP is needed to detach myosin heads from actin filaments and to pump calcium ions back into the sarcoplasmic reticulum.

Question 13

Which of the following would most likely result from a mutation that prevents the formation of functional acetylcholine receptors at the neuromuscular junction?

Accepted Answer

Muscle cells would fail to respond to nerve impulses, resulting in paralysis.

Question 14

Which of the following is a direct consequence of the opening of voltage-gated potassium channels during an action potential?

Accepted Answer

Repolarization of the membrane

Question 15

Which of the following best describes the role of calcium ions in muscle contraction?

Accepted Answer

Calcium ions bind to troponin, causing tropomyosin to move and expose binding sites on actin.

Question 16

Which of the following is true regarding the propagation of an action potential along a neuron?

Accepted Answer

The action potential is regenerated at each segment of the axon by the opening of voltage-gated ion channels.

Question 17

Which of the following best explains the difference between graded potentials and action potentials?

Accepted Answer

Graded potentials can summate and vary in amplitude, while action potentials are all-or-none responses.

Question 18

A patient is diagnosed with myasthenia gravis, an autoimmune disorder that destroys acetylcholine receptors. Which symptom would you expect?

Accepted Answer

Muscle weakness and fatigue

Question 19

Which of the following is a correct example of how acetylcholine functions at a neuromuscular junction?

Accepted Answer

Acetylcholine binds to receptors on the muscle cell membrane, causing sodium channels to open and initiating muscle contraction.

Muscle Tissue, Neuromuscular Junctions, and Membrane Physiology: Study Notes

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