Page | 1
PNB 2264 PRACTICAL II 2026
QUESTIONS AND ANSWERS | A+
GRADED | WITH EXPERT SOLUTIONS
What does a force transducer do? - ANSWER-Converts
mechanical force into an electrical signal that can be
interpreted by software to measure muscle tension
Why do we need calibration? - ANSWER-Raw output (millivolts)
needs to be calibrated to give us the more meaningful force unit
of milli-Newtons (mN), gain precise measurements, remove
tension that is not a result of muscle contraction, zero force
transducer
What is a threshold stimulus? - ANSWER-Voltage at which we
first see a twitch response
What is a maximal stimulus? - ANSWER-The stimulus voltage
at which the response amplitude no longer increases
, Page | 2
What is a supramaximal excitation stimulus? - ANSWER-1.5
times the maximal stimulus; recruitment of all muscle fibers
What kind of response does a single muscle fiber have? -
ANSWER-All or none
What kind of response do muscles (with many muscle fibers)
have? - ANSWER-Graded
What is a motor unit? - ANSWER-One motor neuron and all the
muscle fibers it innervates
What causes increased contraction of a muscle? - ANSWER-
Increase in voltage
What is changed to achieve tetanus? - ANSWER-Frequency of
stimulus
Prolonged contraction of a muscle that results from rapidly
repeating stimuli; Occurs because the stimulus frequency is so
, Page | 3
high that the relaxation stage goes away completely leading to
a sustained contraction - ANSWER-Tetanus
What has to be changed to achieve maximal contraction? -
ANSWER-Increased stimulus amplitude
What are the causes of fatigue in muscles? - ANSWER-Build
up of ADP, Pi, Mg2+, H+ (lactic acid); H+ competes with Ca2+
in binding to troponin; Conduction failure (lack of power stroke)
What is the optimal physiological length? - ANSWER-C
What is the range of physiological lengths? - ANSWER-B, D
Which are outside of physiological range? - ANSWER-A, E
Relates the strength of an isometric contraction to the length of
the muscle at which the contraction occurs - ANSWER-Length-
Tension Relationship
, Page | 4
In a state of rigor mortis, the muscles are highly contracted and
difficult to manipulate. Why does this phenomenon occur? -
ANSWER-Lack of ATP
Why does rigor mortis go away? - ANSWER-Decomposition of
tissue (release of enzymes over time)
- ANSWER-Know twitch, summation, tetanus recordings and
explanations
Has pyramidal cells - ANSWER-Cerebral Cortex
Has purkinje fibers - ANSWER-Cerebellum
What happens to Vrest if the internal Na+ concentration
decreases? - ANSWER-It becomes more positive.
PNB 2264 PRACTICAL II 2026
QUESTIONS AND ANSWERS | A+
GRADED | WITH EXPERT SOLUTIONS
What does a force transducer do? - ANSWER-Converts
mechanical force into an electrical signal that can be
interpreted by software to measure muscle tension
Why do we need calibration? - ANSWER-Raw output (millivolts)
needs to be calibrated to give us the more meaningful force unit
of milli-Newtons (mN), gain precise measurements, remove
tension that is not a result of muscle contraction, zero force
transducer
What is a threshold stimulus? - ANSWER-Voltage at which we
first see a twitch response
What is a maximal stimulus? - ANSWER-The stimulus voltage
at which the response amplitude no longer increases
, Page | 2
What is a supramaximal excitation stimulus? - ANSWER-1.5
times the maximal stimulus; recruitment of all muscle fibers
What kind of response does a single muscle fiber have? -
ANSWER-All or none
What kind of response do muscles (with many muscle fibers)
have? - ANSWER-Graded
What is a motor unit? - ANSWER-One motor neuron and all the
muscle fibers it innervates
What causes increased contraction of a muscle? - ANSWER-
Increase in voltage
What is changed to achieve tetanus? - ANSWER-Frequency of
stimulus
Prolonged contraction of a muscle that results from rapidly
repeating stimuli; Occurs because the stimulus frequency is so
, Page | 3
high that the relaxation stage goes away completely leading to
a sustained contraction - ANSWER-Tetanus
What has to be changed to achieve maximal contraction? -
ANSWER-Increased stimulus amplitude
What are the causes of fatigue in muscles? - ANSWER-Build
up of ADP, Pi, Mg2+, H+ (lactic acid); H+ competes with Ca2+
in binding to troponin; Conduction failure (lack of power stroke)
What is the optimal physiological length? - ANSWER-C
What is the range of physiological lengths? - ANSWER-B, D
Which are outside of physiological range? - ANSWER-A, E
Relates the strength of an isometric contraction to the length of
the muscle at which the contraction occurs - ANSWER-Length-
Tension Relationship
, Page | 4
In a state of rigor mortis, the muscles are highly contracted and
difficult to manipulate. Why does this phenomenon occur? -
ANSWER-Lack of ATP
Why does rigor mortis go away? - ANSWER-Decomposition of
tissue (release of enzymes over time)
- ANSWER-Know twitch, summation, tetanus recordings and
explanations
Has pyramidal cells - ANSWER-Cerebral Cortex
Has purkinje fibers - ANSWER-Cerebellum
What happens to Vrest if the internal Na+ concentration
decreases? - ANSWER-It becomes more positive.
