Biology classes preceding my time in psychology looked at the functions of the human eye and how vision worked, but Psychology 101 has delved deeper into the brain processes that occur to represent the visual stimuli that we receive at nearly every moment, and has also revealed more about the role that the retina plays in vision.
The retina is the membrane at the back of the eye that converts light into neural activity. In this membrane there are two types of sensory receptor cells, known as rods and cones. The rod receptors, long, narrow and quite plentiful, enable us to see basic shapes and forms. We also rely on them to see in low levels of light, a process that occurs with “dark adaptation”, the time that it takes for rods to be light sensitive again after being immersed in darkness.
In contrast, the cone receptors are few in number and they give us color vision, as well as being sensitive to fine details. Light passes through the rest of the eye to these sensory receptor cells where they are absorbed by the molecules contained within them. The rods and cones pass the signal onto the bipolar cells, and then onto the ganglion cells. The axons of the ganglion cells are bundled together and depart the eye as the optic nerve, which splits into two different routes.
The primary route transmits the signal through the thalamus to the primary visual cortex, and the remaining axons are connected to the midbrain, both of which are areas that process sensory stimuli.
All previous information I had regarding substance abuse and dependence has been reinforced by the material that was discussed in Psychology 101. Substance abuse is defined as the condition where a person is experiencing recurrent problems that are associated with a certain drug.
This can include problems with the law, other users or dealers. A more serious problem is substance dependence, a consistent pattern of use that leads to impairment, distress or harm. There can be both physical dependence and psychological dependence. Physical dependence is when a user keeps taking a drug to avoid withdrawal symptoms, a set of unpleasant effects resulting from reducing drug use, which may include insomnia, anxiety, sweating, confusion, and hallucinations.
Tolerance, or the reduction of effects of a drug as a result of repeated use can increase the physical dependence of a user. Psychological dependence is continued use that is motivated by intense cravings and deep emotional desire, especially when drugs are used to cope with stressful situations. Drug usage and abuse can be explained by multiple sources of influence, including, but not limited to, sociocultural influences, addictive personality traits, genetic influences, and any expectancies or learned behaviors that a user may have.
For example, any societies that are typically Muslim, which prohibits drinking, have a very low percentage of alcoholism (0.2% in Egypt) compared to typically “wet societies”, such as France or Italy, which see drinking as a healthy part of life (11.2% in Poland).
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