PNB 2274 Final Exam with Guaranteed
Pass Solutions 2026 Updated.
Recruitment refers to:
A) Multiple twitches in one fiber of one motor unit.
B) Twitches in all the fibers of several motor units.
C) One twitch in multiple fibers of one motor unit. - Answer B) Twitches in all the fibers of
several motor units.
One motor unit can respond with multiple twitches per stimulus.
A) True
B) False - Answer B) False
What is the optimal sarcomere length for maximal force generation in muscle?
A) Fully stretched
B) Intermediate length
C) Completely contracted - Answer B) Intermediate length
A single motor neuron innervates one muscle fiber.
A) True
B) False - Answer B) False
Which of the following is NOT a mechanism of fatigue?
A) Conduction failure
B) Lactic acid buildup
C) Inhibition of cross-bridge cycling
D) Neurotransmitter breakdown - Answer D) Neurotransmitter breakdown
In light of the "all or none" law of muscle contraction, how can you explain the graded
response? - Answer Graded responses are the result of a change in the number of motor
units recruited. You can recruit a larger or smaller motor unit, or combine multiple motor units
to generate more force.
Define tetanus (0.5 pt). At which stimulus interval did you observe tetanus? (0.5 pt) Explain the
mechanism behind this phenomenon - Answer Tetanus is when the action potentials are so
close together in time that it looks like a single prolonged contraction of the motor unit. Rough
tetanus was observed at 60ms and complete tetanus was at 20ms. The idea is that the
, contractions are so close together in time that the muscle does not relax, and the contraction
appears to be one smooth sustained contraction.
Provide a possible mechanism for why the muscle was unable to maintain a prolonged
contraction in the fatigue experiment. - Answer Muscle fatigue can be due to a lack of ATP. If
it is not being released from the sarcoplasmic reticulum, the muscle contractions will slowly die
down.
Does your trace roughly match with a typical length tension curve? If not, could you provide
some explanations? - Answer Yes, my graph does roughly match the typical length-tension
curve, showing that force is greatest at "resting" length (around 4mm here) and decreases when
it is stretched too much or too little on either side of that.
What stretch resulted in the highest contraction force? What happens to the muscle at the
highest stretch levels? - Answer A stretch of about 4mm caused the highest contraction force.
When the muscle was stretched to it's longest, the muscle could not generate very much net
active force. This is because the I bands are too long and there is not enough overlap between
the thick and thin filaments to generate a large contraction.
A motor unit includes:
A) Multiple muscle fibers innervated by multiple motor neuron.
B) One muscle fiber innervated by multiple motor neuron.
C) Multiple muscle fibers innervated by one motor neuron.
D) One muscle fiber innervated by one motor neuron. - Answer C) Multiple muscle fibers
innervated by one motor neuron.
Which statement regarding a surface EMG recording is false?
A) Increased amplitude of the EMG recording reflects an increase in the strength of muscle
contraction.
B)Surface EMG is easier to perform than intramuscular EMG, so is more routinely used in
teaching labs.
C) The EMG may represent the electrical activity of thousands of individual fibers.
D) The raw signal reflects the action potentials of nerve fibers active at that time. - Answer D)
The raw signal reflects the action potentials of nerve fibers active at that time.
The EMG is a recording of:
A) The action potential of the motor nerves supplying the muscle fibers.
B) The contraction forces of the innervated muscle fibers.
C) The action potentials of the innervated muscle fibers. - Answer C) The action potentials of
the innervated muscle fibers.
Pass Solutions 2026 Updated.
Recruitment refers to:
A) Multiple twitches in one fiber of one motor unit.
B) Twitches in all the fibers of several motor units.
C) One twitch in multiple fibers of one motor unit. - Answer B) Twitches in all the fibers of
several motor units.
One motor unit can respond with multiple twitches per stimulus.
A) True
B) False - Answer B) False
What is the optimal sarcomere length for maximal force generation in muscle?
A) Fully stretched
B) Intermediate length
C) Completely contracted - Answer B) Intermediate length
A single motor neuron innervates one muscle fiber.
A) True
B) False - Answer B) False
Which of the following is NOT a mechanism of fatigue?
A) Conduction failure
B) Lactic acid buildup
C) Inhibition of cross-bridge cycling
D) Neurotransmitter breakdown - Answer D) Neurotransmitter breakdown
In light of the "all or none" law of muscle contraction, how can you explain the graded
response? - Answer Graded responses are the result of a change in the number of motor
units recruited. You can recruit a larger or smaller motor unit, or combine multiple motor units
to generate more force.
Define tetanus (0.5 pt). At which stimulus interval did you observe tetanus? (0.5 pt) Explain the
mechanism behind this phenomenon - Answer Tetanus is when the action potentials are so
close together in time that it looks like a single prolonged contraction of the motor unit. Rough
tetanus was observed at 60ms and complete tetanus was at 20ms. The idea is that the
, contractions are so close together in time that the muscle does not relax, and the contraction
appears to be one smooth sustained contraction.
Provide a possible mechanism for why the muscle was unable to maintain a prolonged
contraction in the fatigue experiment. - Answer Muscle fatigue can be due to a lack of ATP. If
it is not being released from the sarcoplasmic reticulum, the muscle contractions will slowly die
down.
Does your trace roughly match with a typical length tension curve? If not, could you provide
some explanations? - Answer Yes, my graph does roughly match the typical length-tension
curve, showing that force is greatest at "resting" length (around 4mm here) and decreases when
it is stretched too much or too little on either side of that.
What stretch resulted in the highest contraction force? What happens to the muscle at the
highest stretch levels? - Answer A stretch of about 4mm caused the highest contraction force.
When the muscle was stretched to it's longest, the muscle could not generate very much net
active force. This is because the I bands are too long and there is not enough overlap between
the thick and thin filaments to generate a large contraction.
A motor unit includes:
A) Multiple muscle fibers innervated by multiple motor neuron.
B) One muscle fiber innervated by multiple motor neuron.
C) Multiple muscle fibers innervated by one motor neuron.
D) One muscle fiber innervated by one motor neuron. - Answer C) Multiple muscle fibers
innervated by one motor neuron.
Which statement regarding a surface EMG recording is false?
A) Increased amplitude of the EMG recording reflects an increase in the strength of muscle
contraction.
B)Surface EMG is easier to perform than intramuscular EMG, so is more routinely used in
teaching labs.
C) The EMG may represent the electrical activity of thousands of individual fibers.
D) The raw signal reflects the action potentials of nerve fibers active at that time. - Answer D)
The raw signal reflects the action potentials of nerve fibers active at that time.
The EMG is a recording of:
A) The action potential of the motor nerves supplying the muscle fibers.
B) The contraction forces of the innervated muscle fibers.
C) The action potentials of the innervated muscle fibers. - Answer C) The action potentials of
the innervated muscle fibers.
