PHYL2002 : Physiology of Cells

Compound Action Potential 1
INVESTIGATING COMPOUND ACTION POTENTIAL BY EMPLOYING THE FROG
SCIATIC NERVE
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Compound Action Potential 2
Investigating Compound Action Potential by Employing the Frog Sciatic Nerve
Abstract
This paper will examine Compound Action Potential (CAP) as observed in a frog's sciatic
nerve. The firing threshold associated with a single myelinated fibre was carefully assessed and
later recorded as a product of impulsive activity in the frog's sciatic nerve fibres. The threshold
was assessed with regard to five time intervals ranging between 0.01 microseconds and 1
microsecond. The results were then presented in graphical form to demonstrate the differences in
Stimulation. During the refractory period the assessment was directed towards the analysis of the
height of the second action potential thereby providing a comparison parameter. Due to strong
depression caused by extended activity the threshold was unable to replica the baseline figures
that were observed prior to the fibre experiments performed during the refractory
period[ CITATION Joh \l 1033 ].
Introduction
Compound action potential (CAP) can be defined as the combined response that is
derived from numerous individual action potentials. The origin and study of action potential is
primary attributed to special characteristics of the cell membrane. According to researchers, all
cells develop membrane potential (Vm)[ CITATION Par17 \l 1033 ]. This can be examined
through simple tests that require the insertion of a microelectrode with a significantly small tip
into a cell via the cellular membrane. Considerable research has been done in the attempt to
understand the origin of membrane voltage; it is hypothesized that is brought about by separation
of charge ions found on the cell membrane. The reason why these charged ions are not "lost" or
absorbed into the cell is attributed to differences in ion concentration and selective permeability
of the cellular membrane. It is after this happens that the separation of charged ions results in

Compound Action Potential 3
electro-chemical equilibrium; thereby, allowing the cell to achieve membrane potential. It is true
that all cells achieve membrane voltage; however, scientists have only observed significant
change in the potential/voltage amongst nervous and muscular cells. The phenomena of cell
membranes changing Vm rapidly after being subjected to stimuli is referred to as excitability;
while, the response itself is termed as an action potential[ CITATION Nob17 \l 1033 ]. The frog
sciatic nerve is a good experiment prop to use because it is considerably large and easy to
manipulate; making it ideal for use with modern voltage measurement equipment and tools. The
experiment will focus on the stimulation of numerous individual nerve fibers and the results will
be recorded with regard to aggregate electrical activity or simply referred to as compound action
potential. The primary aim of the experiment will be to test nerve viability by stimulating the
proximal end and recording CAP from the distal end of the sciatic nerve. Therefore the
objectives in the stdy will be:
Examine and quantify the characteristics of the CAP associated with a frog's sciatic
nerve.
Construct an elaborate strength versus duration curve for the frog's sciatic nerve
Study the refractory period as well as the stimulus threshold.
Methods
An experimental research approach will be used in the assessment of CAP. The experiment will
employ the examination of CAP in a frog's sciatic nerve that has been recently dissected;
preferably within the past 30 to 50 minutes[ CITATION Lau08 \l 1033 ]. We will take a sciatic
nerve with a length of approximately 10mm an electrically stimulate one end while we record
any fluctuations in membrane potential at the opposing end. The strength of the stimulus will be
varied to ensure that differences in the magnitude of the responses can also be recorded (height).