Describe the five basic taste qualities that humans perceive
Since taste and smell are chemical senses, sensations delivered by them are harder to explain and describe to another person. However, when one describes the way a given thing tastes, he or she can refer to common and widely known gustatory sensations, using such words as sweet or bitter. These are called taste qualities, and most researchers agree today that they are five such basic qualities: sweet, bitter, salty, sour, and umami; the latter can also be called savory. Different substances that people consume generally have one or more of these five types of stimuli.
Taste buds (located on some papillae of the tongue but not in the central area of it) contain taste receptor cells, and these receptors are capable of responding to each of the five qualities. Despite the belief that certain areas of the tongue are responsible for feeling a certain kind of taste, stimuli of all five types can affect a receptor wherever on the tongue the taste bud holding it is located. Certain G-proteins are responsible for the sweet, bitter, and umami qualities, while the salty and sour qualities are encoded using ion channels. In the brain, taste signals from the mouth and throat are received by the thalamus and then transmitted to the taste cortex.
What are pheromones? How do they influence the behavior of animals?
While hormones are means of internal chemical communication (i.e., within organisms), pheromones are means of external chemical communication (i.e., among organisms). Pheromones are chemical substances that are secreted by animals (usually through urine or sweat) and can affect other animals, normally altering their behaviors. These substances are perceived and processed by the olfactory system; whether humans exchange pheromones is a debated question, and this is why claims that certain products, such as perfumes, contain pheromones may not be fully scientifically justified.
However, many examples of how pheromones affect other animals are known. For example, certain species use them to mark territories by either urinating or rubbing against objects; e.g., trees. Another instance of the use of pheromones is alarming: by secreting certain substances, an animal warns other members of its population about danger, thus either prompting them to flee or calling upon them to fight for their territory. Importantly, pheromones play a role in sexual attraction, as these substances can attract partners and enhance their sexual desire. Experiments have shown that the exchange of pheromones can also affect the behavior of pregnant females in some species; e.g., mice.
Identify and describe one of each of the ways to control pain
There are three major categories of approaches to controlling pain: pharmacological, physical, and psychological. An example of a pharmacological way to control pain is the use of analgesic medication; i.e., medicines that alleviate pain. They are associated with risks because they may have negative side effects, and noncompliance with the prescribed dosage can result in additional health problems and complications.
An example of controlling pain by physical means is acupuncture. This is the practice of inserting needles into certain points on the body based on the belief that such stimulation can relieve certain symptoms, including pain. Although the regions of the skin to which needles are applied may be far away from the body parts that are in pain, research has shown that acupuncture can be effective.
Finally, an example of psychological pain control is a placebo. It is a substance that cannot have any effects on a person, but the person does not know it, as it is given to him or her as medication. Moreover, doctors who administer placebos in medical experiments may not know which of the drugs are real and which ones are not. Often, placebos are found to help people because people genuinely believe that they are going to help.
What is the difference between passive touch and active touch?
The feeling of touch can be either passive or active, and it depends on whether the person who experiences the sensation initiates it or not. In a general sense, the distinction refers to the difference between a subject and an object. Active touch is normally carried out by hands and fingers; however, other body parts can participate as well; e.g., when a person rubs his or her nose against a surface or an object. Therefore, passive touch occurs when something is applied to a person’s skin without this person’s trying to reach for it, lean against it, or touch it in any other way.
Interestingly, studies have shown that the results of active and passive touch can be different. This is not only because active touch is normally performed by hands and fingers, and fingertips are remarkably more sensitive than most regions of the skin: experiments were also conducted with passive and active touch by the same regions. A person’s brain processes information about tangible stimuli obtained by touch differently depending on whether the person initiating the sensation or not.
Think about yourself looking at a bright red rose. Describe the processes that are involved, starting from the light waves entering your pupil and finishing with the perception of the vivid red color of the flower
Sensation- and perception-related processes can be explained through a simple example: looking at a bright red rose. Although a rather mundane experience for a sighted person, this is, in fact, a combination of complicated physiological processes that enable the ultimate perception and understanding of the image. To analyze what happens in my visual system when I look at the rose, I need to discuss what happens before the light enters my eyes, describe how it is further processed, and explore those processes in the brain that make the perception possible.
First of all, it is noteworthy that this is not the rose that I see when looking at it but the light reflected from the rose. The way light is shed on the rose—the source of light can be natural, such as the sun, or artificial, such as a lamp—determines the way I will see the flower. The combination of lit and shaded areas will allow my brain to construct the perception of depth later, and this is how I will imagine seeing the rose in three dimensions.
The characteristics of the rose itself, in turn, determine the color that I will perceive; based on the content of its petals, it will reflect the light of different wavelengths, and the hue will depend on this wavelength (Labrecque & Milne, 2012). If the rose is close to me, my eyes will converge to look at it.
Further, the reflected light enters my pupil; the pupil is a “window” into the eye, and it can change its size depending on the brightness of the light to which the eye is exposed. Interestingly, pupil size depends not only on the physical amount of light entering the eye but also on perceived brightness, as it has been confirmed that bright illusions can reduce the pupil (Laeng & Endestad, 2012). Further, the light goes through the lens, which is capable of changing its shape to focus light on the sensitive area consisting of nerves at the back of my eye called the retina.
Before reaching it, light travels through the eyeball, which is filled with different substances in different sections of it, and extra light if absorbed. Light is electromagnetic radiation, and the retina is capable of transforming it into a signal that can be delivered to the brain and processed in it. In this process of transformation, certain characteristics of the light that initially entered the pupil are preserved; for example, the signal will carry the information on the color of the rose.
Interestingly, the retina is not homogeneous and even; it has the fovea (the area at which vision is sharpest) and the blind spot (the area in which light receptors are absent). Normally, at any moment of looking at something, a person does not see the entire picture because, when the eyes are not moving, something is in the blind spot (Carbon, 2014). However, since the eyes move all the time, the brain constructs the entire picture, and we do not see any empty spots in front of us. If the rose is close to my face, and I stare at its center, I may fail to notice a bug on its petal because the bug can be in my blind spot.
Different cells in the retina are responsible for different aspects of processing light. For example, cones will allow me to see the bright red color of the rose in well-lit conditions; however, if it were dimly lit conditions in which I am looking at the rose, I would see the rose nearly black-and-white due to the functioning of a different type of cells: rods. Well-lit and dimly lit conditions are called photopic and scotopic, respectively (Foley & Matlin, 2015). Connections within the retina are provided by several other types of cells, including bipolar and amacrine cells.
The light reversed by the lens and focused on the retina further goes through another crossover, as the two optic nerves going from the retinas to the brain cross over each other at a structure called a chiasm. In the brain, the information delivered by the optic tracts is first processed by the superior colliculus and the lateral geniculate nucleus; the former is responsible for detecting movement.
Later, the information travels to the primary and the secondary visual cortex, and some portions of it end up in the parietal and temporal lobes. Specific regions of the cortex that play an important role in color perception are called blobs. All this is needed to not only perceive the image but also link it to what my brain has already learned: that the thing I am looking at is called a rose, the color of it is called red, and if I lean closer to it, I can feel a pleasant smell.
From the perspective of mechanisms of sensation and perception, looking at a bright red rose is a complex process. When the light reflected from the rose enters my eye through the pupil, it is focused on the retina, in which it is transformed by various cells into a signal that can be sent to the brain through the optical nerve/tract. The brain processes the signal, and its function is not only to construct an image for me by combining different signals but also to make sense of the image by linking it to my memory and the classifications of objects and characteristics that I have learned and that are stored in my brain.
References
Carbon, C. C. (2014). Understanding human perception by human-made illusions. Frontiers in Human Neuroscience, 8(566), 1-6.
Foley, H. J., & Matlin, M. W. (2015). Sensation and perception (5th ed.).Boston, MA: Allyn & Bacon.
Labrecque, L. I., & Milne, G. R. (2012). Exciting red and competent blue: The importance of color in marketing. Journal of the Academy of Marketing Science, 40(5), 711-727.
Laeng, B., & Endestad, T. (2012). Bright illusions reduce the eye’s pupil. Proceedings of the National Academy of Sciences, 109(6), 2162-2167.