Practical Paper Flashcards
The two traces below were recorded over 4 seconds, the top trace with no filter; what filter may have been used to reduce noise on the lower trace?
10Hz low pass
What is the approximate latency between the stimulus and the response in the elctromyogram shown below (the scale on the X axis is in seconds)?
10msec
Text BoxPower Lab was used to measure the voltage across the membrane. The left side of the cell (the reference side) was filled with 100 mM KCl, and the test side was filled with 20 mM KCl. The experiment was conducted at 20°C. The voltage recorded in the experiment was actually found to be further from zero than the correct predicted value. What could potentially explain this?
The reference solution could have contained a higher concentration of KCl than was believed
The graph above shows the relationship between the action potential amplitude vs the stimulus interval as demonstrated in the earthworm. What is the maximum possible frequency of action potential generation in a short-term experiment?
500Hz
During exercise the heart rate increases and the duration of systole decreases a little and that of diastole very much more. Which of the following mechanisms account for these changes?
-β1 stimulation shortens the conduction delay in the AV node
-β1 stimulation decreases the activity of the SERCA pump and hence delays Ca2+ re-uptake
-The increased venous return stretches the heart and activates the tension dependent Na+/Ca2+ exchanger
-β1 stimulation of the SAN increases the rate of K+ efflux from the cells
-All of the above
All of the above
During exercise the heart rate increases and the duration of systole decreases a little and that of diastole very much more. What mechanisms account for these changes?
-β1 stimulation shortens the conduction delay in the AV node
-β1 stimulation decreases the activity of the SERCA pump and hence delays Ca2+ re-uptake
-The increased venous return stretches the heart and activates the tension dependent Na+/Ca2+ exchanger
-β1 stimulation of the SAN increases the rate of K+ efflux from the cells
What is the ideal gas equation?
What is the latent period?
The delay from the point of stimulation to the action potential
What causes the stimulus artefact?
The stimulating current traveling directly to the recording electrodes through the body of the worm, or through any liquid on its surface
What is the relative refractory period?
The time period after an action potential during which a higher stimulating voltage is required for a second action potential to be generated
What is the absolute refractory period?
The time period following an action potential during which a second action potential cannot be generated
What is the role of the earth electrode?
To reduce noise and the stimulus artefact
Where should the earth electrode be placed?
Between the stimulating and recording electrodes
Why should the cathode be closer to the recording electrodes than the anode?
Hyperpolarization produced by the anode might prevent the action potential from passing this point on the nerve (“anode block”)
Which stimulating electrode should be closest to the recording electrodes?
Cathode
Why is the cathode expected to initiate the action potential?
Because a negative electrode placed outside a nerve fibre will reduce the potential difference between the inside and outside of the axon, depolarizing the membrane to the point of threshold
What electrode is expected to initiate the action potential?
Cathode
In order to initiate an action potential what must happen to the nerve fibre?
Must be depolarised
Where are the pins placed in the worm?
Why is the worm is dorsal side up, and pins are placed away from the mid-line?
To avoid damaging the ventral nerve cord
What does a 10Hz high pass filter do?
A 10 Hz high-pass filter will remove most of the signal, leaving the high-frequency noise above 10Hz
What does a 10Hz low pass filter do?
A 10 Hz low-pass filter removes frequencies above 10Hz
What does a 50Hz low pass filter do?
A 50 Hz low-pass filter will allow through only those frequency components in your recording below 50 Hz, but this does not usually make very much difference to the trace: it looks very similar to the raw data
How can the respiratory quotient equation be simplified?
RQ= CO2 production/O2 used
How do you calculate the respiratory quotient?
What is the Fick principal?
The rate of blood flow through an organ is equal to the rate of exchange (i.e. gain or loss) of a particular substance (z) from that organ, divided by the difference in concentration of that substance in the blood entering (x) and leaving (y) the organ
What does STPD stand for?
Standard Temperature and Pressure, Dry
What does ATPS stand for?
Atmospheric Temperature and Pressure, Saturated
How do you use the Fick principal to calculate cardiac output?
How do you find the alveolar partial pressure for any gas that you know the dry percentage of?
VA = alveolar ventilation rate
VECO2 = rate of CO2 production
PACO2 = alveolar partial pressure of CO2
K = conversion constant
What is the alveolar ventilation equation?
What is a more accurate way of calculating max pulse rate?
208 - (0.7 x your age in years)
How do you calculate max pulse rate?
220-(your age in years)
Cardiac output =
Stroke volume x Heart rate
Power =
Force x Velocity
Work =
Force x Distance
How do you calculate pulse pressure?
Systolic - Diastolic
How do you calculate mean arterial blood pressure?
MAP = Diastolic + 1/3pulse pressure
What is a more accurate method for determining conduction velocity?
Compare equivalent action potential peaks on two traces, obtained when recording at two different distances (D1 and D2) from the stimulating electrodes.
To calculate conduction velocity by the “difference method” what equation do you use?
Conduction velocity = (D2 - D1) / (LP2 - LP1)
How do you calculate the conduction velocity?
D/LP
D=distance(mm)
LP=latent period(ms)
What is the time constant (τ) equal to?
τ=RC
time constant = resistance x capacitance
The time at which the voltage has reached 63% of its original value
What is τ?
Time constant
If we were to measure the voltage while the capacitor is charging, we would find a relationship given by the equation:
How do you avoid aliasing?
By setting the sampling rate to greater than twice the frequency of the original signal
Current =
Voltage x Resistance
Conductance =
1/Resistance = Current/Voltage
What are the assumptions of the Nernst equations?
Only one ion permeable
Membrane completely permeable to that ion
Ion at equilibrium
What is the Nernst equation?
What is E?
Nernst equilibrium potential
What is R?
Ideal gas constant
What is T?
Temperature (kelvin)
What is z?
Charge of ion (ie 1, 2, 3)
What is F?
Faraday’s number
What is ln?
Natural log
What is [C]?
Concentration of ion
What is the Nernst equation simplified to at room temperature (20 degrees)?
E = 58/z x log10([Cref]/[Ctest])
How do you alter the Nernst equation for a monovalent anion?
Invert [C] in/out and z=1
What is the Nernst equation for a cation at body temperature (37 degrees)?
E = 61/z x log10([Cout]/[Cin])
What is the Nernst equation for an anion at body temperature (37 degrees)?
E = 61/z x log10([Cin]/[Cout])
What is the equilibrium potential of sodium at body temperature?
+61mV
What is the equilibrium potential of calcium at body temperature?
+120mV
What is the equilibrium potential of potassium at body temperature?
-88mV
What is the length constant?
Distance over which voltage decays to 37% of initial value
