# Essay Example on An action Potential was Generated the amplitude Value was Between

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Q8 Comment briefly on the amplitude of the action potentials generated in these experiments Within all the experiments when an action potential was generated the amplitude value was between 102 109 mV the values were fairly close in value for most stimulus strength even with the stimulus strength and duration changing This is an element of all or nothing principle The most obtained amplitude value was 106mv for most stimulus duration and strength displaying that action potentials are not graded Higher amplitude was produced for higher stimulus duration for each stimulus strength The frequency of the action potential is determined by the intensity of the stimulus As the intensity of the stimulus increased a greater number of action potentials were achieved The repetition of the action potential is occurs during the relative refractory period Graded potentials in comparison to action potentials last longer and are much larger The factors that can affect the frequency of the action potentials are the facts if during the relative refractory period a graded potential is much more powerful than the threshold at resting it will generate additional action potential and if it last a longer period than the relative refractory period this will also generate an action potential Q9 From Graph 1 describe the effect of increasing stimulus strength on the latency of the action potential

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The first graph demonstrates that as the strength of the stimulus increases the latency decreases For example when the stimulus strength was 5 A cm2 and had duration of 5ms the latency of the action potential was 2 78ms but when the stimulus strength was 10 A cm2 for the same duration of 5ms the latency of the action potential was 1 57 As the strength of the stimulus increases the time taken for an action potential to be generated decreases Q10 From Graph 2 describe the effect of increasing stimulus duration on the latency of the action potential In the second graph it displays the fact that as the stimulus duration increases the latency of the action potential decreases For example as shown on graph 2 the duration of 5ms for stimulus strength of 20 A cm2 the latency was 0 98 ms The same effect is shown for all stimulus strength with increased stimulus duration An increased latency is shown for lower stimulus duration For example the stimulus strength of 20 A cm2 and duration of 0 5ms the latency was 1 51ms Overall as the duration of the stimulus increases the time taken for action potential to be generated is reduced Q11 Draw a simple flow diagram to illustrate the positive feedback cycle that results in the rapid depolarization phase of the action potential Activation gates open Depolarisation of membrane Stimulus inducing to attain threshold Positive feedback Depolarization achieved due increasing charge of cell Flow of sodium into cell rises Q12 What event at the ion channel level terminates the above cycle The above cycle is terminated by the delay response of the depolarisation at around 1ms after the activation channel gate opens and the inactivation gate closes this results in the inability of the opening of the channel until it achieves near resting potential when the inactivation gate opens This results in the sodium channel closing and this prevents the sodium ions from entering the cell In addition to that the opening of potassium channels also aids in terminating the cycle Q13 What physiological mechanism is responsible for the absolute refractory period Opening of sodium channels rapidly causes inactivation of the channels so when the sodium channels are inactivated they cannot open instantly again Inactivation recovery is dependent on time and voltage for the activation to occur again

This is part of the repolarisation and mostly repolarization phase which results in the channel being closed and unable to open so an second action potential cannot be produced by another stimulus during this time Q14 Explain your observations to simulations C and D in the Methods and Results section Stimulation C has a lower second stimulus than D Stimulation D did generate an action potential however stimulus C did not generate an action potential The delay in for both stimulation C and D is 7ms which means the membrane is in relative refractory period this is indicated by the action potential produced in D by the larger value of the stimulus 2 amplitude A larger stimulus means the ability of another action potential to be generated Q15 Briefly summarise two effects that refractory periods impose on the behaviour of neurons N B restatement of the definitions of refractory periods is not what is asked here There are two different refractory period One of the refractory period is absolute and the other relative At the time of the relative refractory period an action potential can only be produced according to intensity of the stimulus therefore a minimum delay is a mandatory before a the generation of a second action potential The reason behind is process is the controlling of the frequency of the action potential generation The relative refractory period also makes sure an action potential can move in one direction On the other hand the process of absolute refractory period no action potential is produced

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