PNB 2264 PRACTICAL 2 EXAM
QUESTIONS AND ANSWERS 2026
VERIFIED.
Converts mechanical force into an electrical signal that can be interpreted by software to
measure muscle tension - ANS What does a force transducer do?
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 - ANS Why do we need calibration?
Voltage at which we first see a twitch response - ANS What is a threshold stimulus?
The stimulus voltage at which the response amplitude no longer increases - ANS What is a
maximal stimulus?
1.5 times the maximal stimulus; recruitment of all muscle fibers - ANS What is a
supramaximal excitation stimulus?
All or none - ANS What kind of response does a single muscle fiber have?
Graded - ANS What kind of response do muscles (with many muscle fibers) have?
One motor neuron and all the muscle fibers it innervates - ANS What is a motor unit?
,Increase in voltage - ANS What causes increased contraction of a muscle?
Frequency of stimulus - ANS What is changed to achieve tetanus?
Tetanus - ANS Prolonged contraction of a muscle that results from rapidly repeating stimuli;
Occurs because the stimulus frequency is so high that the relaxation stage goes away
completely leading to a sustained contraction
Increased stimulus amplitude - ANS What has to be changed to achieve maximal contraction?
Build up of ADP, Pi, Mg2+, H+ (lactic acid); H+ competes with Ca2+ in binding to troponin;
Conduction failure (lack of power stroke) - ANS What are the causes of fatigue in muscles?
C - ANS What is the optimal physiological length?
B, D - ANS What is the range of physiological lengths?
A, E - ANS Which are outside of physiological range?
Length-Tension Relationship - ANS Relates the strength of an isometric contraction to the
length of the muscle at which the contraction occurs
Lack of ATP - ANS In a state of rigor mortis, the muscles are highly contracted and difficult to
manipulate. Why does this phenomenon occur?
Decomposition of tissue (release of enzymes over time) - ANS Why does rigor mortis go
away?
Know twitch, summation, tetanus recordings and explanations - ANS
, Cerebral Cortex - ANS Has pyramidal cells
Cerebellum - ANS Has purkinje fibers
It becomes more positive. - ANS What happens to Vrest if the internal Na+ concentration
decreases?
Nernst Potential - ANS Membrane potential at which the electrical gradient equals the
chemical gradient -- The potential at which there is no net flow of that particular ion from one
side of the membrane to the other.
E[ion]=58log[(ion)o/(ion)i] - ANS What is the Nernst potential formula for a cation?
E[ion]=58log[(ion)i/(ion)o] - ANS What is the Nernst potential formula for an anion?
Temperature (58=RT/zF and all but T are constants) - ANS What factor could influence
membrane potential you measured in lab to differ from predicted?
E=(ENa x GNa + EK x GK + ECl x GCl)/(GNa + GK + GCl) - ANS What is the membrane potential
or parallel conduction equation?
Sodium, potassium, chloride - ANS 1)Which three ions are the primary contributors to Vrest?
Permeability - ANS Chemical concept, measuring the relative likelihood of ions being able to
cross a membrane
Conductance - ANS Electrical concept, relating charge movement to driving force on the
charges
QUESTIONS AND ANSWERS 2026
VERIFIED.
Converts mechanical force into an electrical signal that can be interpreted by software to
measure muscle tension - ANS What does a force transducer do?
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 - ANS Why do we need calibration?
Voltage at which we first see a twitch response - ANS What is a threshold stimulus?
The stimulus voltage at which the response amplitude no longer increases - ANS What is a
maximal stimulus?
1.5 times the maximal stimulus; recruitment of all muscle fibers - ANS What is a
supramaximal excitation stimulus?
All or none - ANS What kind of response does a single muscle fiber have?
Graded - ANS What kind of response do muscles (with many muscle fibers) have?
One motor neuron and all the muscle fibers it innervates - ANS What is a motor unit?
,Increase in voltage - ANS What causes increased contraction of a muscle?
Frequency of stimulus - ANS What is changed to achieve tetanus?
Tetanus - ANS Prolonged contraction of a muscle that results from rapidly repeating stimuli;
Occurs because the stimulus frequency is so high that the relaxation stage goes away
completely leading to a sustained contraction
Increased stimulus amplitude - ANS What has to be changed to achieve maximal contraction?
Build up of ADP, Pi, Mg2+, H+ (lactic acid); H+ competes with Ca2+ in binding to troponin;
Conduction failure (lack of power stroke) - ANS What are the causes of fatigue in muscles?
C - ANS What is the optimal physiological length?
B, D - ANS What is the range of physiological lengths?
A, E - ANS Which are outside of physiological range?
Length-Tension Relationship - ANS Relates the strength of an isometric contraction to the
length of the muscle at which the contraction occurs
Lack of ATP - ANS In a state of rigor mortis, the muscles are highly contracted and difficult to
manipulate. Why does this phenomenon occur?
Decomposition of tissue (release of enzymes over time) - ANS Why does rigor mortis go
away?
Know twitch, summation, tetanus recordings and explanations - ANS
, Cerebral Cortex - ANS Has pyramidal cells
Cerebellum - ANS Has purkinje fibers
It becomes more positive. - ANS What happens to Vrest if the internal Na+ concentration
decreases?
Nernst Potential - ANS Membrane potential at which the electrical gradient equals the
chemical gradient -- The potential at which there is no net flow of that particular ion from one
side of the membrane to the other.
E[ion]=58log[(ion)o/(ion)i] - ANS What is the Nernst potential formula for a cation?
E[ion]=58log[(ion)i/(ion)o] - ANS What is the Nernst potential formula for an anion?
Temperature (58=RT/zF and all but T are constants) - ANS What factor could influence
membrane potential you measured in lab to differ from predicted?
E=(ENa x GNa + EK x GK + ECl x GCl)/(GNa + GK + GCl) - ANS What is the membrane potential
or parallel conduction equation?
Sodium, potassium, chloride - ANS 1)Which three ions are the primary contributors to Vrest?
Permeability - ANS Chemical concept, measuring the relative likelihood of ions being able to
cross a membrane
Conductance - ANS Electrical concept, relating charge movement to driving force on the
charges
