Biology: Membrane Potential and Action Potential Assignment

This assignment provides a comprehensive overview of membrane potential, a critical concept in biology and cognitive psychology. It explores the variations in membrane potential, measured in millivolts, and contrasts the internal and external environments of a cell. The assignment details the resting membrane potential, determined by ion distribution, and the role of hyperpolarization. It explains the process of action potential initiation, including the threshold level and depolarization, as well as the role of sodium ion channels. The assignment further describes the phases of repolarization and hyperpolarization, including the involvement of potassium ion channels and the undershoot phenomenon. Finally, it summarizes the process of cell stimulation, depolarization, and the subsequent action potential cycle. The references used are from reputable sources like Columbia University and Oxford University Press.

Running head: COGNITIVE PSYCHOLOGY
MEMBRANE POTENTIAL
Name of the Student:
Name of the University:
Author Note:
a)

1MEMBRANE POTENTIAL
Answer a:
The stimulating condition of the cell membrane can have multiple variations.
Therefore, these variations are all in the membrane potential. The distribution of multiple
charges crosswise the cell membrane is referred to as potential. It is generally measured in
millivolts and denoted as mV (Zorova et al., 2018). The pattern is to contrast the inside of the
cell relative to the outside environments. Therefore, it can be concluded that membrane
potential is the representative value of the charge on the membrane with respect to their
surroundings.
Answer b:
The resting membrane potential can be determined by the irregular distribution of ions
(charged particles) between inside as well as outside of the cell. The resting potential is the
inequity of the electrical charge that occurs between the internal of electrically excitable
neurons along with their surroundings. The ranges in resting potential membrane lie within
the ranges of -60 to -80 mv, where the inside cell is negatively charged (Sakamuru, Attene-
Ramos & Xia, 2016). Here the cell is in the resting position. If that cell becomes more
electronegative then the membrane will be called hyperpolarized.
Answer c:
According to Levitan & Kaczmarek (2015), for initiation of an action potential, the
threshold level should be in such a way that membrane potential can be depolarised. In the
threshold level, if the neuron does not reach that critical level then there would not be any
action potential. Therefore, it is crucial for regulation as well as propagating the signals. Both
the resting membrane as well as threshold potential maintained the balances.

2MEMBRANE POTENTIAL
Answer d:
The membrane potential will modify to get the electrical signal started. It can start
with an opening channel for sodium ion in the membrane. The concentration of sodium ion is
larger in the outside and while entering inside the cell, it will rush into it that will result in
driving larger concentration. The sodium ion is positively charged and that is the reason that
the resting potential that is in the voltage of -60 to -80 mV will become less negative (sfu.ca,
2020). This leads to the depolarisation phase that moves in the direction of the zero.
Answer e:
The membrane potential continues to grow even after reaching zero and thus resulting
in positive mV. As soon as the membrane potential arrives at + 30 mV, there are other
channels of voltage-gated are openings. This is a specific approach for the potassium ion, the
potassium ion starts leaving the cell that results in taking the positive charge away from the
cell. Therefore, it leads to moving the membrane potential backward to the resting voltage.
This process is referring to as repolarisation.
Answer f:
The repolarisation will return up to the values of -70 mV that is the value of resting
potential. However, the potassium ion reaches below the equilibrium that is below the resting
potential and occurs the hyperpolarisation. Thus, the potassium ions channels are delayed and
lead in overshoot phenomena. The undershoot phenomenon is more negative compared to
the resting potential. This period generally occurs due to the inactivation of the voltage
sodium channels that arise at the top of the action potential. Even if the membrane potential
goes across or beyond the threshold, the inactivated sodium ions can not open the channels.

3MEMBRANE POTENTIAL
Answer g:
The stimulation of the cell will help in the process of depolarization. The
depolarisation will excite the cell membrane from -60mV to -55Mv (columbia.edu, 2020).
Once the membrane reaches that range of voltage, the sodium ion voltage channel opens.
This situation is known as the threshold. If the depolarization does not reach -55mV then it
will not reach the threshold. Therefore, it is important to reach a particular level of voltage to
reach the threshold. Reaching threshold will start the action potential to run in continual
cycle.

4MEMBRANE POTENTIAL
References
columbia.edu. (2020). Membrane Potential (pp. 1-15). columbia.edu. Retrieved from
http://www.columbia.edu/cu/biology/courses/w3008/2004/Week_03_22/chapter_7_K
S.pdf
Levitan, I. B., & Kaczmarek, L. K. (2015). The neuron: cell and molecular biology. Oxford
University Press, USA.
Sakamuru, S., Attene-Ramos, M. S., & Xia, M. (2016). Mitochondrial membrane potential
assay. In High-Throughput Screening Assays in Toxicology (pp. 17-22). Humana
Press, New York, NY.
sfu.ca. (2020). Membrane potentials & ion channels (pp. 1-24). sfu.ca. Retrieved from
http://www.sfu.ca/~eemberly/phys347/lectures/11_membrane_potential.pdf
Zorova, L. D., Popkov, V. A., Plotnikov, E. Y., Silachev, D. N., Pevzner, I. B., Jankauskas, S.
S., ... & Sollott, S. J. (2018). Mitochondrial membrane potential. Analytical
biochemistry, 552, 50-59.