Practical Notes Flashcards
Osmosis Hypothesis
It is hypothesised that the sheep’s blood cells will have a lower Packed Cell Volume (PCV) percentage when placed in a hypertonic solution containing de-ionised water and sodium chloride (NaCl).
Osmosis Materials and Method
- 1M NaCl stock solution was prepared
- Series of dilutions were carried out from the stock solution to create six NaCl concentrations: 0, 100, 150, 200, 300, and 400 mM
- Of these, the negative control was 150 mM and the positive control was 0 mM
- Human patient blood was pipetted into each of the solutions in a 1:3 ratio – one part blood and three parts NaCl
- Mixture containing patient blood and NaCl were transformed to haematocrit tubes
- Each of the tubes were placed into haematocrit centrifuge for 3 minutes at 10,000 rpm
- Critocap reader was used to measure the Packed Cell Volume (%) in each tube
- Above procedure was carried out until three repeated trials were obtained for each concentration
Osmosis positive and negative controls
Neg = 150 mM
Pos = 0 mM
Action Potential Hypothesis 1: stimulus
It is hypothesised that increasing the electrical current as a stimulus on the sciatic nerve of a cane toad (Bufo marinus) will result in an increase in the peak of compound action potential formed, as opposed to no difference with no change in electrical current.
Action Potential Hypothesis 2: Temperature
As the temperature increases, the CAP increases
Action Potential Hypothesis 3: Anaesthetic
It is hypothesised that after the addition of anaesthetic to the sciatic nerve of the cane toad (Bufo marinus), the peak CAP formed will decrease over time, as opposed to remaining the same under the presence of no anaesthetic.
Action Potential Anaesthetic Method
- The sciatic nerve was removed from the leg of the cane toad (Bufo Marinus) and placed onto the spanning electrodes of the nerve bath
- 6 drops of a local anaesthetic were poured onto the nerve and a stimulus strength of 260mV was run through the nerve for five minutes
- 260mV was the lowest stimulus strength that produced a near-maximum peak CAP in the results from part 1; the negative control. The timer was set immediately, and the peak CAP was recorded every minute by the Powerlab.
- The measurement of compound action potential at 0 mins served as the negative control for this experiment, as it provided the peak CAP of the nerve before any anaesthetic has affected it.
Action Potential Temperature Method
Skeletal Muscle Hypothesis 1: Stimulus Strength
Increasing stimulus strength will increase force generated by the gastrocnemius muscle.
Skeletal Muscle Hypothesis 2: Stimulus frequency
As stimulus frequency applied to the cane toad’s (B. marinus) sciatic nerve increases, the peak contractile force generated by the B. marinus gastrocnemius muscle also increases, as opposed to no increase at all.
Skeletal Muscle Method
- The sciatic nerve, attached to the gastrocnemius muscle from a cane toad (Bufo marinus), was placed along the spanning electrodes of the nerve bath, and the muscle was held taught by a string tied to a clamp.
- Stimulus frequencies ranging from 1Hz (negative control) to 25Hz were applied to the nerve, and the peak contractile force generated from the gastrocnemius muscle was recorded.
- The force was measured by the force transducer and the passive force was set as a constant at 250mN.
- The maximum stimulus strength used constantly throughout the experiment was 0.1V (result from experiment 1). The number of pulses as a constant was 5.
- The negative control was the peak contractile force values at a frequency of 1Hz.
Define Positive Control
a control group that is not exposed to the experimental treatment but that is exposed to some other treatment that is known to produce the expected effect. These sorts of controls are particularly useful for validating the experimental procedure.
Define Negative Control
