Saturday, August 24, 2013
The Properties of Neurons
Brief Description of the Electrical Properties of a Neuron
Neurons, like all living cells, have an electrical charge, which transmits information within the neuron (Breedlove, Watson, & Rosenzweig, 2010). A difference exists between the electrical charge of the inside and the outside of the cell membrane. This keeps the neuron in a state of equilibrium, which is called the resting membrane potential. Ions (electrically charged particles), especially potassium ions, create changes in the polarization and gives neurons the ability to generate electrical signals. These signals are the basis for communication within the neuron, and subsequently, the chemical communication between the neurons.
The Changing Properties of Neurons
In the absence of stimulation, neurons are in a state of resting potential, a state which neurons have the ability to change. Depolarization causes a change in the axons, which causes the axon to become more positive inside than outside for a limited time. This is an action potential - when an electrical signal is generated because of the change in polarization (Breedlove et al., 2010). When a signal is generated, it travels along the axon to the axon terminals. At the axon terminals, the neuron sends either an electrical signal or a chemical (neurotransmitter) signal, depending on the type of synapse. When a signal is sent between the presynaptic and postsynaptic cells, this begins neurotransmission or communication between the neurons (Breedlove et al., 2010). During the action potential, the neuron becomes refractory, meaning it becomes inactivated for a brief time.
Other Changes in the Properties of Neurons
Neurodegenerative diseases such as Alzheimer's disease, Parkinson's and Huntington's disease cause changes in the properties of neurons or the way they function in the brain (Breedlove, Watson, & Rosensweig, 2010). Neurons in the brain are sensitive to oxidative stress and in some neurodegenerative diseases such as Parkinson's, Huntington's, Alzheimer's, ALS, and stroke-related pathologies, oxidative stress leads to dysfunction in the mitochondria and then cell death (Facecchia, Fochesato, Ray, Stohs, & Pandey, 2011). Neurons rely on the functioning of mitochondria for neurotransmission (Kann & Kovacs, 2006).
Ethical Implications of Electrode Implantation
Several ethical and moral implications exist for implanting an electrode to stimulate the brain of a convicted murderer. It has been argued that the alterations generated by neural prostheses profoundly affects an individual's identity, and it can be a change that can have a socially isolating affect (Rosahl, 2007). Implantation surgeries can be lengthy and dangerous, and certainly could not be performed without the informed consent of the individual (Shah et al., 2010). Whether these arguments are the applicable for convicted murderers is another question with moral, ethical, religious, and political implications. The answers might hinge on the weight of the benefit to society and the systems of social justice, as well as the families of the victims. Perhaps when considering replacing time served with the implantation of a device, the former would accompany the latter, rather than being replaced by it. Certainly, the benefits cannot be ignored. Regardless of the benefits and moral or ethical shortcomings of the implantation of such devices, deep brain stimulation is widely accepted for many conditions, although the understanding of their mechanisms are inconclusive (Shah et al., 2010).
Breedlove, S. M., Watson, N. V., & Rosenzweig, M. R. (2010). Biological psychology: An introduction to behavioral, cognitive, and clinical neuroscience. (6th ed.) Sunderland, MA: Sinauer Associates, Inc. Publishers.
Facecchia, K., Fochesato, L., Ray, S. D., Stohs, S. J., & Pandey, S. (2011). Oxidative Toxicity in Neurodegenerative Diseases: Role of Mitochondrial Dysfunction and Therapeutic Strategies. Journal Of Toxicology, 1-12. doi:10.1155/2011/683728
Kann, O., & Kovacs, R. (2006). Mitochondria and neuronal activity. AJP: Cell Physiology, 292(2), C641-C657. doi: 10.1152/ajpcell.00222.2006
Shah, R. S., Chang S. Y., Min, H. K., Cho, Z. H., Blaha, C. D., & Lee, K. H. (2010). Deep brain stimulation: technology at the cutting edge. Journal of Clinical Neurology, 6(4), 167–182. doi: 10.3988/jcn.2010.4.167
Rosahl, S. K. (2007, February). Neuroprosthetics and Neuroenhancement: Can We Draw a Line? American Medical Association Journal of Ethics. Retrieved June 9, 2013, from http://virtualmentor.ama-assn.org/2007/02/msoc2-0702.html