Question 1

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

Accepted Answer

It stores and releases calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$necessary for muscle contraction.

Question 2

A patient is exposed to a toxin that inhibits acetylcholinesterase at the neuromuscular junction. What is the most likely physiological consequence?

Accepted Answer

Continuous stimulation of the muscle fiber, leading to prolonged contraction.

Question 3

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

Accepted Answer

ATP is needed to pump $$\mathrm{Ca$$^{2+}$$}$$ back into the sarcoplasmic reticulum.

Question 4

During a marathon, which pathway is primarily responsible for regenerating ATP in skeletal muscle after the first few minutes of exercise?

Accepted Answer

Aerobic respiration (oxidative phosphorylation)

Question 5

Which of the following statements about the resting membrane potential (RMP) of a neuron is correct?

Accepted Answer

The inside of the neuron is negatively charged relative to the outside, with higher $$\mathrm{K^+}$$ concentration inside and higher $$\mathrm{Na^+}$$ concentration outside.

Question 6

A muscle fiber is unable to relax after contraction, resulting in rigor mortis. Which step of the cross-bridge cycle is most directly disrupted?

Accepted Answer

Detachment of myosin heads from actin due to lack of ATP.

Question 7

Which type of muscle fiber would be most prevalent in the quadriceps of a sprinter who specializes in short, explosive races?

Accepted Answer

Fast glycolytic fibers

Question 8

Which of the following best describes the difference between isotonic and isometric muscle contractions?

Accepted Answer

Isotonic contractions change muscle length, while isometric contractions do not change muscle length.

Question 9

Which of the following is a function of astrocytes in the central nervous system (CNS)?

Accepted Answer

They help maintain the blood-brain barrier and regulate the extracellular environment.

Question 10

A patient presents with muscle weakness and fatigue. Laboratory tests reveal a defect in the Na$$^+/K$^+$$ ATPase pump. Which of the following best explains the effect of this defect on neuronal function?

Accepted Answer

The neuron cannot restore the resting membrane potential after an action potential.

Question 11

Which of the following best describes the 'all-or-nothing' principle of action potentials?

Accepted Answer

Once threshold is reached, an action potential of fixed size is generated; subthreshold stimuli do not produce action potentials.

Question 12

Which of the following best explains why smooth muscle can sustain contractions for longer periods than skeletal muscle with less energy expenditure?

Accepted Answer

Smooth muscle has slower cross-bridge cycling and uses less ATP per contraction.

Question 13

Which of the following is true regarding the recruitment of motor units during muscle contraction?

Accepted Answer

Smaller motor units are recruited first, followed by larger ones as more force is needed.

Question 14

Which of the following best describes the function of myelin in the nervous system?

Accepted Answer

It increases the speed of action potential conduction along axons.

Question 15

Which of the following scenarios best illustrates temporal summation in a postsynaptic neuron?

Accepted Answer

A single presynaptic neuron fires multiple times in rapid succession, causing the postsynaptic potentials to add together.

Question 16

Which of the following best describes the role of troponin in skeletal muscle contraction?

Accepted Answer

Troponin binds calcium ions, causing a conformational change that moves tropomyosin and exposes binding sites on actin.

Question 17

Which of the following neurotransmitters is correctly matched with its primary effect in the central nervous system?

Accepted Answer

Endorphins – inhibit pain by acting as natural opiates.

Question 18

Which of the following best explains why lactic acid is produced during intense exercise?

Accepted Answer

Anaerobic glycolysis occurs when oxygen is limited, resulting in the conversion of pyruvate to lactic acid.

Question 19

Which of the following best describes the difference between EPSPs and IPSPs?

Accepted Answer

EPSPs depolarize the postsynaptic membrane, while IPSPs hyperpolarize it.

Anatomy & Physiology: Muscles, Muscular System, and Nervous System Study Guide – Step-by-Step Guidance

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