Sensory Adaptation

Sensory adaptation is defined in our textbook as “the process by which senses become less responsive to particular stimuli” (Editorial Board, n.d.). It is when our body gets used to the things that are occurring. It happens to all of our five senses. We experience “reduced sensitivity to stimulation that results from repeated presentations of that stimulation” (AlleyDog, 2012). What is happening from a scientific standpoint is the sensory neurons changing their sensitivity level to a constant stimulus over an extended period of time. We need to be able to adjust to our environment around us so that we can receive new sensory input when we need to, regardless of the surroundings. Our receptors are able to automatically adjust to different levels of stimulation so that they are as sensitive as possible but aren’t being overloaded. “As a result, our senses become less sensitive when the overall level of stimulation is high, but more sensitive when the overall level of stimulation is low” (Morris, n.d.).

Experiment 1 displayed the sensory adaptation of the skin. You can feel rubbing your index fingers gently over a piece of very coarse sandpaper thanks to your mechanoreceptors responding to the tactile sensation. The glabrous skin on the hands is part of the somatosensory system of our bodies. This system is responsible for haptic perception. Our fingertips are concentrated with Merkel’s disks and Meissner’s corpuscles. The receptor get signals from stimulation projects them to the somatosensory cortex.

This first time that I rubbed my finger over the coarse sandpaper in experiment 1, it felt very abrasive and rough. I rated it at a 6. It didn’t feel quite as abrasive the second time that I went back and rubbed my finger over the same sandpaper again. I rated it a 4. After rubbing it the first time, my receptors adapted to the feeling of the sandpaper and became less sensitive from the stimulation. Because of the decreased sensitivity, I did not perceive the sandpaper to feel as rough.

Experiment 2 displayed the sensory adaptation of chemical sense taste. The three cranial nerves responsible for detecting taster are the facial nerve, the glossopharyngeal nerve, and the vagus nerve. These three nerves send the information to nuclei in the brainstem which passes it along to the thalamus. The thalamus transfers the information to the cortex.

During experiment 2, tasting the sugar water first significantly changed the way that I thought the fresh water was going to taste. The fresh water had a very salty taste even though it did not have any salt added to it. The sugar water caused my taste buds to be less sensitive to sweetness. Because I didn’t taste as much sweetness and I am generally used to, my other taste buds had a heightened sensitivity comparatively. This caused the fresh water to taste saltier than normal to me.

Experiment 3 displayed the sensory adaptation of vision. The cornea detects light. The lens of the eyes bends that light ray into focus. The ray then travels through the pupil and is gathered by photoreceptors on the back of the retina. The two different types of photoreceptors are rods and cones. They are responsible for sending the information to the nervous system through the optic nerve.

At the beginning of the experiment, I had to remove all but 3 of the index cards to detect the light. As my eyes adjusted, the light seemed to become brighter and brighter. Over the 15 minute period, I was able to add an additional 8 cards to the flashlight for a total of 11. Because my eyes shifted to using rods instead of cones, my eyes were able to become more sensitive to the light.

Experiment 4 displayed the sensory adaptation of the skin, just as experiment 1 did. You can feel temperature thanks to your thermo receptors. The thermo receptors communicate stimulation to the hypothalamus.

 During the experiment, when my hands went into the hot and cold, I felt the temperature change immediately. When my hands went from the cold and hot bowls of water into the lukewarm water, the amount of time it took to feel the change felt delayed. Both of my hands also seemed like they were in two different temperatures of water though they clearly were not. My sense of temperature changed based on the direction of heat flow between the water and my skin.

            Adaptation is important from an evolutionary perspective because it allows us to cope with changes in our environment. “Within a single organism, "adaptation" can encompass morphology, physiology, development (through organizational effects or through differential timing of developmental events), and behavior” (UTK, 2010). If we were unable to adjust to a changing environment, we would has a reduced rate of survival.

References

AlleyDog. (2012). Psychology Glossary. Retrieved from Sensory Adaptation: http://www.alleydog.com/glossary/definition.php?term=Sensory%20Adaptation

Editorial Board. (n.d.). Introduction to Psychology. Words of Wisdom, LLC.

Morris. (n.d.). Prentice Hall. Retrieved from Sensory Adaptation: http://cwx.prenhall.com/bookbind/pubbooks/morris2/chapter3/medialib/demo/1.html

UTK. (2010, August). Deep Ethology: evolution. Retrieved from Adaptation Defined: https://notes.utk.edu/bio/greenberg.nsf/6617131020461f6585256d24005739db/3ee9cccd7c64bffd85256cff0061f4d7?OpenDocument