Biological_Influences_of_Sensory_Adaptation

Psychology: Biological Influences of Sensory Adaptation By: Tabitha Harris American InterContinental Online University June 22, 2012 Abstract The purpose of this research paper is to transmit a mental impression of sensory adaptation into words. A verbal account of three experiments associated with sensory adaptation will be documented and explained. Each experiment will contain an observation and conclusion. A description of the brain’s activity and interaction with the vision, auditory, touch, and taste senses will be given. Evidence of sensory adaptation’s association with each experiment will be illustrated. A comprehensive description of the sensory systems that were included in each experiment will be provided. The experience from each experiment will also be recorded, along with an evolutionary perspective on the importance of adaption in the psychology field. Psychology: Biological Influences of Sensory Adaption The gradual decline in sensitivity to a constant stimulus is what psychologists call sensory adaptation. In other words, it’s when your sensory receptors become less responsive to a constant stimulus. Because of sensory adaptation, we become accustomed to constant stimuli which allow us to quickly notice new or changing stimuli. Vision, hearing, taste, smell and touch are the five senses, each with its own sensory systems and receptor cells. For example, touch perception includes skin receptors separate for warmth, cold and pain, travel from the skin cell receptors to the brain and spinal cord. Theoretically, each sensory system is a channel receiving information from the internal and external world, with sense receptors, which are nerve fibers leading from the receptor to the brain or spinal cord, which relay messages (it is hot) stations and processes to areas within the brain. It is when the sensory channel is stimulated, that we have a sensation that is characteristic of that channel (feeling of cold or hot; hearing a loud of soft tone). So, as things change around us, there is activity in the nervous system, where physical energy is converted into chemical impulses (nervous system activity or receptor potential) referred to as process of transduction that occurs at the "specialized receptor cells that converts physical energy into chemical voltage. Conversely, in some sensory systems, the receptor potential directly triggers the nerve impulses that then travel to receptors in the brain through the spinal cord. In vision, for example, the light enter the eye through the pupil and travels through the cornea, the lens, and the eyeball interior to contact the rod and con cells of the retina at the back of the eyeball that contain photosensitive pigments-where transduction occurs (rods and cons), changing the physical energy into receptor potential. Rods - sensitive and responding to low light and cones - less sensitive and responding to bright light. There are three kinds of cones containing red-, green-, or blue sensitive pigment. Then, nerve impulses are generated in specific cells of the retina, which travel to the brain along the optic nerve, with the pattern signaling the visual event from the environment. The sense of smell involves olfactory receptor cells lie in the olfactory epithelium in upper part of nasal cavity. These cells have several long, non-motile cilia, which contain binding sites for olfactory stimuli. Each cell contains one type of receptor. Axons of olfactory receptor cells of same specificity synapse together. Information is passed into the olfactory cortex in the limbic system (http://www.biology-online.org/9/8_sensory_systems.htm). In hearing, there are many informational signals that strike the receptor cells in the ear, such as the warning of a vehicle horn, the ticking of a clock or the siren from an ambulance. Sound waves are the physical stimuli that produce our sensory experience of sound. Commonly, sound waves are produced by the rhythmic vibration of air molecules, but sound waves can be transmitted through other media, too, such as water. Our perception of sound is directly related to the physical properties of sound waves. Loudness is one of the first things noticed about sounds. Loudness is determined by the intensity, or amplitude, of a sound wave and is measured in units called decibels. Zero decibels represent the loudness of the softest sound that humans can hear, or the absolute threshold for hearing. As decibels increase, perceived loudness increases. The sound or hearing system is the part of our nervous system that must be active when physical energy is converted (transduced) into electrical activity by the auditory receptors in the ear, which include three main parts. The external ear includes the pinna, the ear canal, and the eardrum. The pinna is an oddly shaped flap of skin and cartilage that is attached to each side of your head. It is used to locate sound. The pinna’s primary role is to catch sound waves and funnel them into the ear canal. The sound waves travel down the ear canal, then bounces into the eardrum, which is a tightly stretched membrane. When the sound wave hits the eardrum, the eardrum vibrates, matching the vibrations of the sound wave in intensity and frequency. The eardrum is a thin membrane stretched tightly across the inner end of the canal. It separates the outer ear from the middle ear. It is the alteration in the pressure of the sound wave moves this small membrane back and forth. Energy is transmitted mechanically, and amplification take place through the middle ear, but the inner ear sense organs for hearing are contained in a bony structure known as the (cochlea); a fluid-filled tube that is coiled like a “snail” and no larger than a pea. As the fluid in the cochlea ripples, the vibration in return is transmitted to the basilar membrane which runs the length of the coiled cochlea. Inside of the basilar membrane are sensory receptors for sound. These are called hair cells. These hair cells contain tiny projecting fibers that appear to resemble hairs. Damage to the auditory nerve or these hair cells can cause nerve deafness. As the basilar membrane ripples, the hair cells bend which causes the transduction process to begin. The physical vibrations of the sound waves are converted into neural impulses. As the hair cells bend, they arouse the cells of the auditory nerve, which transport the neural information to the thalamus and the auditory cortex in the brain. This makes up the auditory system or auditory pathway for hearing. The touch sensory system also has a unique sensory process involving the skins senses and skin cell receptors. The skin senses taking in information from the environment. Skin is considered a giant organ that covers the body. There are actually four skin senses, including pressure or touch, cold, warmth and pain. Most of these skin senses result in such simple sensation (itching, tingling, and feeling of hot and cold, or painful sensation of injury). However, the skin is not uniformly sensitive-being more sensitive at some points and not so sensitive at others (aka: punctuated sensitivity), and, generally, the spots of greatest sensitivity to touch, cold, warmth, and pain stimulus are different. For pressure or touch-- the sensation a person who is touched lightly on the skin report is called pressure or touch. The skin receptors take in the information, travel to the brain. And as discusses above, theoretically, each sensory system is a channel receiving information from the internal and external world, with sense receptors, which are nerve fibers leading from the receptor to the brain or spinal cord, which relay messages (it is hot) stations and processing areas within the brain. It is when the skin receptor channel is stimulated, that we have a sensation that is characteristic of that channel (feeling of pressure; cold or hot; pain). So, when we touch something, it sets off activity in the nervous system, where physical energy is converted into chemical impulses (nervous system activity or receptor potential) referred to as process of transduction that occurs at the "specialized” skin receptor cells that convert physical energy into chemical voltage. Mechanoreceptors in the skin are of 2 types, rapid and slow adapting ones. For temperature--the thermo receptors are of two types, one that responds to an increase and the other that responds to a decrease in temperature (http:/www.biology-online.org/9/8_sensory_systems.htm). The sensory systems for taste--the receptors for taste are specialized receptors located in the mouth. The stimuli that produce the sensation of taste are chemical substances in whatever you eat or drink. These substances are dissolved by saliva, allowing the chemicals to activate the taste buds. Each taste bud contains about 50 receptor cells that are specialized for taste. The primary taste bud receptors are salty, sour, sweet and bitter. Each group has a distinct transduction system that are organized into independent pathways (to the brain) but a single receptor cell may respond to more than one taste category in various degrees that converts physical energy into chemical voltage, to the brain, which returns an action potential back to the taste buds when we experience the taste of sweetness, bitterness, sourness or saltiness. In experimenting with three tasks sensory adaptation was evident. In the first experiment a cup of regular water and a cup of water with sugar were tasted. The sugar water was first, it was swished around in my mouth for a couple of seconds. As I swished it around I noticed that the taste was losing its sweetness. I then tasted the regular water and it had a “nasty” taste! The water tasted like it was not fresh, it tasted “dingy”, and it tasted like it had sulfur in it. This is a result of the sense known as taste. My taste receptors were stimulated by the chemical substances contained in the water. The second experiment contained 15 index cards and a flashlight. In my bathroom, which was jet black, I placed 15 index cards in front of the flash light. I slowly removed 1 index card at a time. I did this for 15 minutes. The longer I stayed in the bathroom, the more I noticed the light getting increasingly dimmer. I took 7 index cards away and began to detect a little bit of light. I added 2 and the light was completely gone again. I did it a second time and I took 10 cards and could barely see light, I added 1 and the light was gone. The vision sense was used in this experiment. My sensory receptors for vision responded to the very narrow and specific ranged wavelengths in the electromagnetic energy spectrum. Finally, my last task involved my touching sense. My sensory receptors transferred signals to my thalamus onto my cerebral cortex and my touching sense was activated. I filled 3 medium sized bowls with hot, lukewarm, and cold water. I submerged my right hand into the cold water and my left into the hot. I left them submerged for about 3 minutes, and then I quickly removed both hands and submerged them into the lukewarm water. The temperature of the lukewarm water was cold. The texture and density differed from the hot and cold water. It felt lighter and smoother. The Evolutionary theory is based on Charles Darwin's theory that humans are products of evolution, as are any other biological phenomena. Second, human nature is a biological phenomenon in that it adapts over time to the environment and culture (e.g. hunting and gathers began to walk straight up as they adapted to their new ways of gathering food for their families. Thus, the evolution process is also a socio-cultural phenomenon, and, since culture is a product of human nature, culture is also a biological phenomenon. These tenets have been accepted within Evolutionary Psychology (EP) (Cosmides & Tooby, 1990), as cited in (Kennair, 2002).Thus adaptation is essential to an evolutionary perspective because that is how they explain the evolutionary process, the organism adapting to the environment over time in order meet the biological needs of the organism. The theory depends on adaptation as a major tenet of the theory; indeed there would be not theory without the idea of adaptation (http:/www.human nature.com/nibbs/02/ep.html).In other words, adaptations are the evolved solutions to problems encountered consistently through periods of evolutionary history. These adaptations are designed through the natural selection of available genetic variation, which in the process, tend to be reduced. Thus human adaptations make up human nature, and are believed to be universal to almost all humans (Cosmides & Toomby, 1990) as cited in (Kennair, 2002) however; degenerative mutations or non-nurturing environments cause the variations (Kennair, 2002). References: Board, E. (2011). Introduction to Psychology (1 ed.). Words of Wisdom, LLC. Cosmides, L., & Toomby, J. (1990). Evolutionary Psychology and the generation of culture part 1:Theorectical Considerations. "Ethology and Socibiology", 29-49. Deb Anderson, M. (2004-2012). Evolutionary Perspective, Adaptation, Sensory Systems and Brain Receptors. Retrieved from BrainMass Incorporated: www.brainmass.com/student/solution.php'sgr_id=239992 Huckenbury, H. &. (2010). Psychology (5 ed.). New York, New York: Worth Publishers. Kennair, L. E. (2002). Human Nature Review. Evolutionary Psychology: An emerging integrative perspective within the science and practice fields of psychology, pp. 17-61.