Psychology
The retina is one of most important part of the eye and among the most affected part as the person ages. It is apparent that every measure of visual functionality declines as the age increases (Salvi, Akhbar and Currie 2006). Given the increase in socioeconomic relevance of rapid assimilation information particularly the visually communicated information, visual impairment constitutes severe problem to the person in functioning productively in its environment. By definition, the eye retina is the sensitive layer located at the back of the eye, which covers about 65% of the eye’s interior surface (hyperphysics.phy-astr.gsu.edu, N.D.).
It is composed of rods and cones made up of photosensitive cells that sends signal to the brain through the optic nerves by converting light energy. However, the retinal functions degrade due to several factors including aging.
The adult macula poses significant problem in retaining quality vision due to internal and external factors that affect the rate of cell renewal in the body. Macula is located at the center of the favea where the light reflex is altered. As the person gets older, the epithelum pigment, which is composed of non-dividing cell system significantly loses its net count of cells. The remaining cells along with the reduction of the available ones voids the capability to regenerate causing the lipofuscin particles to degrade (Salvi, Akhbar and Currie 2006). Diseases also contribute to visual loss such as diabetes. Theories also suggest that wear and tear is also a major contributor to the degradation of eye retina (Weismann, 1882 as cited from Salvi, Akhbar and Currie 2006). According to the wear and tear theory, the eye including its very important component the retina are often worn down by constant exposure to toxins and harmful elements from the environment. Excessive consumption of fats, sugar and caffeine contributes to the decline in visual quality of the retina resulting to visual complications leading to blindness as the person’s age increases.
Biological Bases of Reinforcement in Alcohol
Alcohol and overconsumption of such is considered as a major social problem in the world where incidents of intoxication results to injuries and or death. On the other hand, experts believe that reinforcement and its biological bases contribute to alcoholism where the positive reinforcement constitutes a learned behavior induced by providing reward. Meanwhile, negative reinforcement is defined by a learned behavior caused by avoiding discomfort. Reinforcement is defined as the process in which the probability of responses is either decreased or increased due to the result of a certain effect. Such effects are attributed to biological factors as the dopamine theory of addiction suggests (Deehan et al., 2013). The chemicals in the brain activate the reinforcement system in the brain, which under certain conditions are triggered by activities and or substances detrimental to survival such as food and water. It was thought that reinforcements are the perpetrator that increases the effect of dopamine receptors in the mesolimbic system (Johnson, 2004 p. 49).
Acetaldehyde is known as the first metabolite of alcohol that establishes the high levels of ACD, which is associated to adverse symptoms of headaches, flushing, and among others (Deehan et al., 2013). In most recent researches, it was found that the content of dopamine (DA) and serotonin (5-HT) including their acid metabolites are involved in creating the pathways to mediate alcohol-drinking behavior. There are also other neurotransmitter system that constitutes the same effect as the 5-HT and DA that plays an important role in ethanol preference such as opioid peptides and gamma-aminobutyric acid (GABA) (Deehan et al., 2013). The way the aforementioned neurotransmitter system works in producing alcoholism is still currently investigated, but the it can be understood from the evidence of the studies that modalities in treating alcohol-seeking behavior can be addressed by means of biological bases.
Biological Bases of Craving and Relapse in Smoking Tobacco
Tobacco and the habit of smoking it has been around for over 1,000 years, but the study of its psychopharmacological ingredient nicotine became the subject of neuroscience research during the past 200 years (Grunberg, 2007). Arguably, the most prominent ingredient that induces the variation of addiction levels to tobacco is nicotine. Apparently, nicotine is also considered as one of the most difficult substances in the body that is difficult to flush out of the system due to its neurological effect of addiction. Addiction to tobacco when being addressed is expected to result to relapse due to craving. By definition, craving and relapse are symptoms that occur during nicotine withdrawal process where the sight, sound, smell and other cues may lead to cravings particularly for people undergoing the nicotine dependency treatment. The occurrence of cravings presumably leads to relapse as the person gives in to the perceived cues.
There is certain biological basis of nicotine addiction that has direct implications to cessation treatment. The nicotine substance is similar in structure to acetylcholine (Ach) that is responsible in conveying information from one neuron to another (Jiloha, 2010). At the moment the former smoker catches the smell of tobacco smoke or saw someone pulling out a pack from the pocket sends a signal to the brain causing intense craving. This is because when a former smoker quits the habit, the habit cortex remains attached to the idea of smoking. The habit circuitry and the frontal cortex share signal, which can be blamed for craving particularly when exposed to smoking cues. The rush of signaling molecules called glutamate particularly in the nucleus accumbens area is most of the time overwhelmed with cue signals that the habit of quitting becomes less apparent and eventually leads to a relapse. In this process, the nicotine binds with the acetylcholine receptors, which in effect influences the cerebral metabolism by stimulating the aforementioned receptors (Jiloha, 2010).
References
Deehan, G. A., Hauser, S. K., Wilden, J. A., Truiit, W. A., & Rodd, Z. A. (2013). Elucidating the biological basis for the reinforcing actions of alcohol in the mesolimbic dopamine system: the role of active metabolites of alcohol. Frontiers in Behavioral Neuroscience, 7(104), 1-13. doi:10.3389/fnbeh.2013.00104
Grunberg, N. E. (2007). A neurobiological basis for nicotine withdrawal. Current Issue, 104(46), 17901–17902. doi:10.1073/pnas.0708964104
Hyperphysics.phy-astr.gsu.edu (n.d.). The Retina of the Human Eye. Retrieved February 14, 2014, from http://hyperphysics.phy-astr.gsu.edu/hbase/vision/retina.html
Jiloh, R. C. (2010). Biological basis of tobacco addiction: Implications for smoking-cessation treatment. Indian J Psychiatry, 52(4), 301–307. doi:10.4103/0019-5545.74303
Johnson, B. A. (2004). The biologic basis of alcohol dependece. Advanced Studies in Nursing, 2(2), 48-53. Retrieved from http://www.jhasim.com/files/articlefiles/pdf/ASIN_2_2_p48_53.pdf
Salvi, S. M., Akhtar, S., & Currie, Z. (2006). Ageing changes in the eye. Postgraduate Medical Journal, 82(971), 581–587. doi:10.1136/pgmj.2005.040857
