PSYC304 Week 7 Notes

docx

School

American Public University *

*We aren’t endorsed by this school

Course

304

Subject

Psychology

Date

Oct 30, 2023

Type

docx

Pages

Uploaded by Hotboy4Life24

PSYC300 | LESSON 7 Chemical Senses; Touch, Vestibular, Proprioception, and Kinesthesia Introduction Topics to be covered include:  Taste  Smell  Touch  Proprioception  Kinesthesia  Vestibular sense In this lesson you will learn about the chemical senses taste and smell, learning the path from chemical receptors in your mouth and nose to the parts of the brain that create a taste or smell experience. You will also study touch and the senses related to our balance and movement: vestibular, proprioception, and kinesthesia. Gatekeeper Senses: Taste and Smell Taste and smell are our chemical senses. Our sense of smell is often called olfaction . Have you ever been walking past a bakery and smelled bread baking? You do not have to see the bread to know you are smelling fresh-baked bread. Molecules from the bread escape into the air through the oven vents. The molecules spread out until they reach your nose. The chemical receptors in your nose transmit a signal to your brain. Your brain uses the signal and past experiences to produce an ‘I smell bread baking’ experience. Is this true for everyone? Would every adult know how baking bread smells? Would every adult even be able to detect the molecules in the air that come from the baking bread? The first part of our lesson will explore how we recognize smells and tastes. Taste and smell serve as gatekeepers for our bodies because they help us discriminate between what would and would not be beneficial for us to consume. Most of us are repelled by the taste and smell of sour milk or rotten meat. Most of us are attracted to foods with a high-caloric density, which in a hunter/gatherer primitive society can be an important survival mechanism. We receive nutrition from eating nuts and berries, but not as much from chewing on grass and acorn shells. As you may recall from the study of neurotransmission, sodium is very important in the transfer of signals from our receptors to our brain. Being attracted to salty food helps us provide our body with the sodium needed by the neurons, and also is part of the regulation of blood pressure. While you may have seen commercials suggest lowering the salt intake for those suffering from high blood pressure, you need some sodium – just not too much. Very bitter substances elicit a negative response. Many common poisons such as arsenic and cyanide taste bitter. Taste and smell can also have an emotional component, such as when a particular smell or food triggers a memory. Our senses of smell and taste do not always influence us to eat the right

foods, as the rising numbers of overweight and obese individuals demonstrate (Goldstein & Brockmole, 2017). Taste Qualities You probably learned in elementary school that the basic tastes qualities are sweet, salty, sour, and bitter, with each strongest in different parts of the tongue. It turns out that the tongue map concept was a fallacy that arose due to a misinterpretation of test results. Scientists also widely accept a fifth taste, umami , “which has been described as meaty, brothy, or savory, and is often associated with flavour-enhancing properties of MSG, monosodium glutamate” (Goldstein & Brockmore, 2017, p. 362). When we taste a substance, we might experience more than one quality to different degrees. These foods come the closest to having a single taste quality:  Salty: sodium chloride, also known as table salt  Sugar: sucrose, common table sugar  Sour: hydrochloric acid  Bitter: quinine, a plant substance that is used to treat malaria. Because of its bitter taste, some people have rubbed quinine on fingertips to prevent nail biting.  Umami: MSG As you will see later, some scientists oppose this view of four (or five) basic taste qualities. Our Taste Perceptual System 1/2  The beginning of our perception of taste occurs when chemical compounds in the foods we eat or liquids we drink come in contact with the tongue. Look at your tongue in a mirror and you will see a very rough surface, with peaks and valleys. The peaks are lingua papillae (plural of papilla), of which there are four basic types (Goldstein & Brochmole, 2017):  Filiform papillae, which are cone-like and spread all over the tongue. Most of what you are looked at in the mirror are filiform papillae. Filiform papilla do not contain taste buds. They are involved in how our tongue helps us chew and swallow food.  Fungiform papillae, squat, mushroom shaped papilla found all over the tongue, but mostly found at the edges and tip. If you rub your fingertip along the edges and tip of your tongue, they feel smoother than the center where you find more filiform papilla. They “not only detect taste, but they also contain sensory cells for touch and temperature” (Lingua papillae, n.d.).  Foliate papillae, folds along the back edges, also contain taste buds.  Circumvallate papilla, flat mounds seen towards the middle of the back edge of the tongue. A single papilla contains multiple taste buds , which has an opening at the top, a taste pore , where chemicals enter to reach our taste receptor cells. A single taste bud may have up to 100 taste receptor cells. When light strikes the rods and cones in the retina of the eye, neurons transmit information to the brain carrying information about the wavelength and intensity of the light. When chemicals enter through the taste pore, the taste receptor cells detect the chemical. Some of the taste receptor cells are most sensitive to bitter tastes, some to sour, some to salty,

and others to sweet tastes. When a taste receptor cells detects a stimulus, it generates an electrical signal, then neurons transmit the information to the brain. In addition to the taste buds on the tongue, there are also taste buds on the palate and behind your mouth. 2/2 Different parts of your tongue use different nerves (Goldstein & Brockmole, 2017): o The front and sides use the chorda tympani nerve o The back of the tongue uses the glossopharyngeal nerve o The mouth and throat use the vagus nerve o The top of the mouth (the soft palette) uses the superficial petrosal nerve These nerves connect in the brain stem, from which the signal is sent to the thalamus, and onward to the primary taste cortex, the insula and frontal operculum. Individual Differences in Taste Perceptions Are there foods you eat that your friends do not like? Watch this video for an explanation: Why People Taste Things Differently. In addition to the number of taste buds mentioned in the video, there are also genetic factors that determine your ability to taste certain substances. Some genetic differences control the presence or absence of specialized receptors. Do you hate broccoli and Brussel sprouts? If you do, you might have a gene that is related to the presence of TAS2R receptors in your taste buds, which is known to be sensitive to bitter chemicals such as phenylthiocarbamide (PTC). People who can taste PTC often dislike vegetables that contain similar compounds called glucosinolates, found in broccoli, radishes, Brussel sprouts, and other vegetables famous for being hated by children (Pearson, 2006). There are a variety of reasons why you might lose some or all of your sense of taste, such as injury, diabetes, vitamin A deficiency, and others (Hutchins, n.d.). Our Sense of Smell Chemicals in the air enter our nose and mouth. The nose and nearby cavities are lined with olfactory receptors. As with light and taste, different receptors have chemical groups to which they are especially sensitive. In one major way, olfactory receptors are different than vision and taste receptors. Different cones are more receptive to certain wavelengths of light. Taste receptor cells are thought to specialize in one of the five basic tastes: salty, sweet, bitter, sour, and umami. There are over 300 types of olfactory receptors. So if you smell bread baking, the olfactory receptors most sensitive to those types of chemicals fire their signal, telling the brain that it detected those chemicals. The signals are sent to the olfactory bulb in the brain. In fact, the smell of bread is a combination of multiple chemicals. When each type of olfactory receptor sends its

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

signals, the brain uses prior experience of that set of signals to recognize that bread is baking somewhere near. If the baker changed to baking apple pies, some of the same olfactory receptors would fire since pie crust shares a lot of ingredients with bread, but some new receptors would fire in response to the apple odors in the air (Goldstein & Brockmole, 2017). “The detection threshold is the lowest concentration at which an odorant can be recognized” (Goldstein & Brockmole, 2017, p. 369). For example, menthol can be detected at concentrations of 870 parts per billion in the air. At 15,000 parts per billion, larger amounts of acetone are required in order for us to detect it. The differences in our olfactory sensitivity are best explained by the number of olfactory receptors. Humans have ten million receptors, compared to 100 times that number for dogs (Dodd & Squirrell, 1980; Moulton, 1977). Dogs also have an advantage in the portion of the brain used for taste and smell. Only around 0.03 percent of the human brain is devoted to our senses of taste and smell. Compare that to dogs who have around 2 percent of their brain devoted to taste, which is why dogs have a much more sensitive sense of taste than humans (Avilla, n.d.). Some animals require a strong sense of smell to survive. They are macrosmatic . While smell is important for humans, it is not critical to survival. We are microsmatic . Nasal Cilia The nasal cavity has cilia, small hairlike structures which sway back and forth to move mucus in the nose to the back of the throat. This is a vital part of how the body removes inhaled debris and microbes (viruses, bacteria, and fungus). The cilia sweep these invaders from the outside world into the throat, where they are swallowed. Once swallowed, the stomach acids destroy the debris- laden mucus. When we intake microbes, how do the cilia detect their presence? The cilia have bitter taste receptors (T2Rs) which are thought to respond to products excreted by the microbes. There are specialized receptors for the different types of secretions (Alt & Cohen, 2015). Flavor and Other Relationships of Taste and Smell Our perception of flavor is not just related to taste, but also to smell, touch, and perceptual expectations. You probably have noticed that when you have a stuffy nose from a head cold, food tastes different to you. You can test this for yourself, especially if you have someone else around to help you. Have the other person blindfold you and then pick out two strong tasting liquids, such as orange juice, coffee, or grape juice. Pinch your nose shut. They will offer you a glass or cup with the chosen beverage. Take a drink and swish it around your mouth without swallowing – swallowing with your nose shut can cause problems with your ears. Take note of the flavor. Then release your nostrils, swallow, and take another drink. Did you notice a flavor difference? When we eat or drink, molecules are released into the air in our mouth and can travel to the nasal cavities. Thus, taste and smell are intertwined. These are also intertwined because the neural pathways from receptor to brain intersect.

Our senses of taste and smell have a very unique feature compared to vision and hearing. Our rods and cones are at the back of the eye. Our auditory receptors are in the inner ear. Both of these are protected by other parts of the body between the receptors and the outside environment. Our taste buds and olfactory receptors are in constant contact with the outside world. You can damage your taste buds or your olfactory receptors by exposure to harsh chemicals, disease pathogens, substances to which you are allergic, mechanical damage due to physical contact with a sharp object, or many other ways. Because of this damage, your taste and olfactory receptors live less than seven weeks and are replaced by new olfactory receptors when the old ones die off. This cycle of death and renewal is called neurogenesis . Olfactory Influences Olfaction influences us unconsciously and consciously. Yuhas (2014) reported that “exposure to body odor can elicit responses in other humans .... , human sweat and secretions can affect the reproductive readiness of other humans.” “Devendra Singh and Matthew Bronstad (2001) demonstrated a connection between men’s ratings of women’s body odors and the women’s menstrual cycle by showing that men rated the smell of T-shirts that women had worn for three consecutive nights during the ovulatory phase of their menstrual cycle to be more pleasant then the smell of shirts worn during their nonovulatory phase” (as cited in Goldstein & Brockmole, 2017). Anosmia , the loss of our sense of smell, demonstrates the importance of smell to human lives. Individuals who experience anosmia report disruptions to their quality of life, as they cannot enjoy the smell or taste of food, and cannot detect alerts in the environment, such as the smell of smoke. Haptic Perception So far, all of the senses we looked at, are associated with a particular part of the body: the eye, ear, nose, and mouth. Haptic perception refers to the process by which we recognize an object by contact with the skin (tactile perception), together with information provided by receptors in our skin, muscles, and joints. As a child did you ever play the game in which someone gave you a sack with an object inside? Your challenge was to identify the object by touch. You would actively explore its surface with your hands, using the sensory receptors in your skin to find clues about the object. Haptic perception usually refers to active exploration. The German psychologist Max Dessoir first used the term Haptik in 1892 to refer to the study of our sense of touch (Audiopedia, 2017). The somatosensory system gives us our “conscious perception of touch, pressure, pain, temperature, position, movement, and vibration, which arise from the muscles, joints, skin, and fascia” (Gleveckas-Martens, 2013). The system has three main components (Goldstein & Brockmole, 2017):

 The cutaneous senses which give us our sense of touch, pain, temperature, and more. This system receives signals when a stimulus makes contact with the skin.  Proprioception which gives us the perception of our body’s position.  Kinesthesia, which is our perception of how we are moving our body. Not everyone has these senses. There are people with chronic insensitivity to pain with anhidrosis (CIPA) that feel no pain, which can be very dangerous (U.S. National Library of Medicine, n.d.). “Unintentional self-injury is common in people with CIPA, typically by biting the tongue, lips, or fingers, which may lead to spontaneous amputation of the affected area. In addition, people with CIPA heal slowly from skin and bone injuries. Repeated trauma can lead to chronic bone infections (osteomyelitis) or a condition called Charcot joints, in which the bones and tissue surrounding joints are destroyed” (U.S. National Library of Medicine, n.d.). The Cutaneous System The skin is not just part of the cutaneous system, it also keeps our inside bits inside and keeps many outside objects, such as harmful chemicals, disease-causing agents, dirt, and more from entering the body. The outermost layer of skin is the epidermis , the dead cells on the surface of the skin. You can remove some of these epidermal cells by placing a piece of tape on the palm of your hand and removing it. Hold the tape up to a light to see the cells. Below that layer of cells is the dermis . You have different types of receptors in your skin. 1/4  Merkel and Meissner Receptors Mechanical receptors respond to contact with a physical object, stretching, pressure, vibration and are located in the dermis and epidermis. Merkel receptors and Meissner corpuscle in the epidermis and dermis respond to a small area, called the cutaneous receptive field . If the stimulus is continuous (you are sitting in a chair most likely so there is constant contact with the skin below your hips), the Merkel receptor’s associated nerve fiber will fire constantly until the object is moved away from the skin. We call this a slowly adapting (SA) fiber . In contrast, the nerve fiber associated with a Meissner capsule is a rapidly adapting (RA) fiber . It fires once when the stimulus is first detected and then will fire again when the stimulus ceases. Think of what happens in the tips of your fingers when you write an e-mail on your computer. Your feet are probably resting on the floor. Your SA nerve fiber fired when you first put your feet down and is still firing. Your RA fiber fired when you first put your foot down, but will not fire again until you move your foot. Your skin has a vast number of Merkel receptors and Meissner capsules on even a small area of skin, giving your brain information on the current signals status of the skin. As we discussed in Lesson 6, your brain can give selective attention to wherever you want to focus. You can sit there reading without paying attention to your skin at all. You can pause reading and thing about where your right foot is. If you are sitting on a couch reading with

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

a dog in your lap, your dog might lick your arm and bring the brain’s attention to the part of your skin where the dog’s tongue touched. If you consider the skin on the tips of your fingers when you write a paper using your keyboard, which, if any or maybe both, receptors are sending signals? Which nerve fibers are firing? Since your fingers are moving to touch a key and then moving off the key, both receptors are sending signals. Both nerve fibers are continually firing. The Merkel receptor’s SA nerve fiber continually fires because the stimulus constantly is detected and then is removed (Goldstein & Brockmole, 2017). 2/4  Pathway to the Brain Think about the receptors all over the surface of your body. All of those receptors are capable of sending information to your brain. Some skin is close to your brain, such as the skin on your ear. Some skin is far from the brain, such as the skin on your feet. The receptors pass their information to nerve fibers. These signals travel to the spinal column, from which the signals pass through via one of these nerves:  Medial lemniscal pathway made up large fibers that transmit information very fast  Spinothalamic pathway made up of smaller fibers that transmit information relatively slowly Signals with information about the position of the limbs and the detection of contact with an object travel the lemniscal pathway. This faster pathway allows us to move quickly and respond quickly to touch. Think of a soccer player sprinting down the field, deftly passing the ball back and forth between his feet. The slower spinothalamic pathway is used for stimuli related to temperature and pain. Both pathways lead to the thalamus. From there the information is passed to receiving areas in the parietal lobe. These receiving areas have a map-like organization in which different parts of the brain are associated with different parts of the body (Goldstein & Brockmole, 2017). If you know people who have had a significant stroke, different parts of the body are impaired depending on what part of the brain was damaged. If the part of the brain controlling the left hand was damaged, the person will have sensing or moving the left hand. 3/4  Pain Our cutaneous system can detect three kind of pain (Scholz & Woolf, 2002): inflammatory due to damage to tissue, neuropathic pain due to damage to the nervous system, and nocioceptive pain which uses input from specialized nociorecptors in response to heat, cold, chemicals, or heavy pressure. When we are injured, pain receptors send a signal using one of two types of nerve fibers (Deardorff, 2003):

 A-delta nerve fibers carry the first pain message quickly to the spinal cord, at a speed of approximately 40 miles per hour.  C-fibers, carrying their message at a slower three miles per hour, are associated with continuous pain. Once these fibers pass the signal to the spinal cord, the spinal cord transmits the messages to the brain. The gate control theory of pain suggests that the signals are interrupted in the spinal column by nerve gates that may or may not pass the signal onward to the brain. 4/4  Other Stimuli Our skin also responds to non-painful levels of heat and cold. There are receptors at the base of the hairs of our skin that detect hair movement. What Touching Tells Us Klatsky, Lederman and Metzger (1985) identified six major ways we touch an object. While we can touch objects with any part of our body, these types will be described for touching an object with your hand and the properties associated with that type of touch.  Lateral motion: Rubbing your skin (usually the fingers) along the surface. Lateral motion gives us information about the texture of an object.  Pressure: Tapping or pressing down, which gives us information about the object’s hardness.  Static contact: Placing your skin (usually the fingers or hand) on an object without moving your hand, which tells you the relative temperature of an object – is it warmer or colder than your fingers.  Unsupported holding: Allowing the object to rest in your hand, supporting the object gives you information about the weight of an object.  Enclosure: Placing one or both hands around the outside of an object. If the object is small enough, the object is completely surrounded by your hands. Enclosure gives you information about the shape and size of an object.  Contour following: Tracing the edges (the contours) of the object also gives you information about the size and shape. The information you gain from any kind of touch gives you more than just the information. If you are using unsupported holding, your temperature receptors are also giving your brain information about whether the object is hotter or colder than your fingers. Your sense of touch can detect tiny differences in an object. You have probably heard about Braille, which converts letters and numbers into dot patterns for the blind. While books on tape have largely replaced books in Braille, it is still widely used. There is even a braille smartwatch: Finally, Someone Invented a Smartwatch for the Blind.

Proprioception, Kinesthesia, and the Vestibular System Watch this video that explains your sense of proprioception and kinestheia at: Proprioception and Kinesthesia: Processing the Environment .  Proprioception You were briefly introduced to the vestibular system, proprioception and kinesthesia in Lesson 6. You have sensory receptors inside the muscles and tendons you use to move your body. The receptors detect when the muscle or tendon contracts or relaxes. The brain integrates information from all the muscles currently expanding and contracting to give you a sense of the position of our body, which is called proprioception. Much of our proprioception is a background activity. Most of the time, you are not giving selective attention to the position of your body. Sometimes you do give proprioception your full attention, such as when you try to balance on one foot in yoga class.  Kinesthesia Kinesthesia is our ability to detect movement of the body, both consciously and unconsciously. The sensory organs in our muscles. Training can improve this sense, allowing you to improve your ability to catch a ball, paint a picture, hammer a nail, or whatever tasks you need to do. In common usage, proprioception and kinesthesia are used interchangeably. While they both use input from the receptors in muscles and tendons, proprioception is more concerned with the position and kinesthesia with movement.  Vestibular System Another related part of our senses is the vestibular system . Sensory receptors in the inner ear detect different kinds of motion. “The utricle and saccule detect gravity (information in a vertical orientation) and linear movement. The semicircular canals, which detect rotational movement, are located at right angles to each other and are filled with a fluid called endolymph. When the head rotates in the direction sensed by a particular canal, the endolymphatic fluid within it lags behind because of inertia, and exerts pressure against the canal’s sensory receptor. The receptor then sends impulses to the brain about movement from the specific canal that is stimulated. When the vestibular organs on both sides of the head are functioning properly, they send symmetrical impulses to the brain. (Impulses originating from the right side are consistent with impulses originating from the left side.)” (Vestibular Disorder Association, n.d.).  Balance Our ability to maintain our balance is an integration of the motion detectors of the vestibular system, and the sensory input from muscles and tendons that tell us the position of our body (proprioception) and the way it is moving (kinesthesia). It also uses our vision. You can test that

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

out for yourself. If you are able, stand on one foot. Do this near something you can easily grab like the side of a couch. If you can do that, close your eyes. Did closing your eyes make it harder to stand on one foot? For most of us, it does. Conclusion This lesson began with the study of our chemical senses: taste and smell, which is also called olfaction. We looked at our sense of touch and the different types of sensory receptors beneath the surface of our skin. We also examined the vestibular system, how different parts of the inner ear give us detailed information about changes in the position of the head. Sensory input from muscles and tendons gives us a sense of position of the body (proprioception) and its movement (kinesthesia). Sources Alt, J. A., & Cohen, N. (2015, February 17). Nasal physiology. American Rhinological Society . Retrieved from http://care.american-rhinologic.org/nasal_physiology Audiopedia. (2017, September 19). What is haptic perception? Retrieved from https://www.youtube.com/watch?v=CCXMcWKLdRs Avilla, R. (n.d.). Episode 4: Taste and smell. Psychology VidCast . Retrieved from https://apus.intelluslearning.com/open-access/35238/ Deardorff, W. W. (2003, March 3). The gate control theory of chronic pain. Spine Health . Retrieved from https://www.spine-health.com/conditions/chronic-pain/gate-control-theory- chronic-pain Dodd, G.G., & Squirrell, D.J. (1980) Structure and mechanism in the mammalian olfactory system. Symposium of the Zoology Society of London, 45, 35-56. Gleveckas-Martens, N. (2013, July 12). Somatosensory system anatomy: Overview. Medscape . Retrieved from https://emedicine.medscape.com/article/1948621-overview Goldstein, E. B. & Brockmole, J. R. (2017). Sensation and perception (10th ed.). Boston, MA: Cengage. Hutchins, M. (n.d.). Interactive oral sciences 1507: Chemical sensory system functions (continued). University of Texas Health Science Center at Houston. Retrieved from http://www.uth.tmc.edu/courses/dental/smell-taste/taste.html Klatzky, R. L., Lederman, S. J., & Metzger, V. A. (1985). Identifying objects by touch: An “expert system.” Perception & Psychophysics, 37 (4), 299-302.

Moulton, D. G. (1977) Minimum odorant concentrations detectable by the dog and their implications for olfactory receptor sensitivity. In D. Miller-Schwarze & M. M. Mozell (Eds.), Chemical signs in vertebrates (455-464). New York: Plenum Press. Pearson, H. (2006, September 18). Distaste for sprouts in the genes. Nature . Retrieved from http://www.nature.com/news/2006/060918/full/news060918-1.html U.S. National Library of Medicine. (n.d.) Congenital insensitivity to pain with anhidrosis. Retrieved from https://ghr.nlm.nih.gov/condition/congenital-insensitivity-to-pain-with-anhidrosis Vestibular Disorders Association. (n.d.) The human balance system. Retrieved from http://vestibular.org/understanding-vestibular-disorder/human-balance-system Yuhas, D. (2014, May 1). Are human pheromones real? Scientific American Mind . Retrieved from https://www.scientificamerican.com/article/are-human-pheromones-real/ Image Citations "Freshly baked and sliced break next to some wheat " by 2940905_ML. "The anatomy of the tongue and taste bud" by https://commons.wikimedia.org/wiki/File:1402_The_Tongue.jpg. "A drawing of the parts of the brain" by https://pixabay.com/en/brain-human-anatomy-organ- medicine-148131/. "The transmission from the olfactory receptors " by By The original uploader was Sunshineconnelly at English Wikibooks - Transferred from en.wikibooks to Commons by Adrignola using CommonsHelper., CC BY 3.0, https://commons.wikimedia.org/w/index.php? curid=13676069. "Anatomy of the nose " by 16481968_ML. "Anatomy of the skin" by 33834719_ML. "Hands reading braille " by 47710344_ML. "A woman balanced on one foot" by 14099412.