The absorbance of rhodopsin in the rods is much more sensitive than in the cone opsins; specifically, rods are sensitive to vision in low light conditions, and cones are sensitive to brighter conditions. In addition, two separate clusters of hair cells the saccule and utricle are oriented to detect vertical and horizontal movements. Non-tasters can taste food, but they are not as sensitive to certain tastes, such as bitterness. This spasm is a reflex that is initiated by stretch receptors to avoid muscle tearing. The same is true for the inferior rectus, which is compensated by contraction of the inferior oblique. They provide information about the position or movement of different parts of the body as well as the length and extent of contraction along with muscle tension. The first two tastes (salty and sour) are triggered by the cations Na+ and H+. Other branches will travel a short distance up or down the spine to interact with neurons at other levels of the spinal cord. What is the distance between the fovea and optic disk in your left eye? By comparing the relative movements of both the horizontal and vertical ampullae, the vestibular system can detect the direction of most head movements within three-dimensional (3-D) space. One major group of bitter-tasting molecules are alkaloids. If no axons are in place within the olfactory nerve, then the axons from newly formed olfactory neurons have no guide to lead them to their connections within the olfactory bulb. Tears are produced by the lacrimal gland, located just inside the orbit, superior and lateral to the eyeball. Sensory Systems: Anatomy, Physiology and Pathophysiology provides a comprehensive description of how human sensory systems function, with comparisons of the five senses and detailed descriptions of the functions of each of them. The tendon inserts obliquely into the superior surface of the eye. This will help to underscore the relationships between the different components. The moving otolithic membrane, in turn, bends the sterocilia, causing some hair cells to depolarize as others hyperpolarize. Chemical stimuli can be interpreted by a chemoreceptor that interprets chemical stimuli, such as an objects taste or smell. This explains why some elderly people salt their food more than younger people do. The video makes the statement (at 0:45) that specialized cells in the retina called ganglion cells convert the light rays into electrical signals. What aspect of retinal processing is simplified by that statement? Within the structure of the papillae are taste buds that contain specialized gustatory receptor cells for the transduction of taste stimuli. Learning Objectives. The oval window is located at the beginning of a fluid-filled tube within the cochlea called the scala vestibuli. Possible cuts include: To be able to best see the eyes structures, you should work very carefully. Sensory Systems: Anatomy, Physiology and Pathophysiology provides a comprehensive description of how human sensory systems function, with comparisons of the five senses and detailed descriptions of the functions of each of them. The perceived sensations correspond to common chemicals: Salty (Na+), Sweet (disaccharides, e.g. This page titled Lab 5: Sensory Systems is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Susan Burran and David DesRochers (GALILEO Open Learning Materials) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request. A third classification of receptors is by how the receptor transduces stimuli into membrane potential changes. As the head rotates in a plane parallel to the semicircular canal, the fluid lags, deflecting the cupula in the direction opposite to the head movement. Generally, spinal nerves contain afferent axons from sensory receptors in the periphery, such as from the skin, mixed with efferent axons travelling to the muscles or other effector organs. An individual sensory modality represents the sensation of a specific type of stimulus. The essential component is neurons, the major functional cells in nervous tissue. Increasing hydrogen ion concentrations in the saliva (lowering saliva pH) triggers progressively stronger graded potentials in the gustatory cells. This will depolarize the hair cell membrane, triggering nerve impulses that travel down the afferent nerve fibers attached to the hair cells. The external ear contains the auricle, ear canal, and tympanic membrane. The otolithic membrane moves separately from the macula in response to head movements. The sphere of the eye can be divided into anterior and posterior chambers. (Micrograph provided by the Regents of University of Michigan Medical School 2012). The chemical senses are taste and smell. If you exhibit some degree of colorblindness, what type? Ex. The three major spaces within the cochlea are highlighted. Some other organisms have receptors that humans lack, such as the heat sensors of snakes, the ultraviolet light sensors of bees, or magnetic receptors in migratory birds. Professional fighters often experience anosmia because of repeated trauma to face and head. However, there are a number of different ways in which this can happen because there are a large diversity of bitter-tasting molecules. Of course, it is often sweetened so that the sour taste is masked. One is oriented in the horizontal plane, whereas the other two are oriented in the vertical plane. Similar to the olfaction tests, serial dilutions of basic chemicals can be used to test for variable sensitivity in subjects. Structure of Sensory Receptor Sensations can be produced mainly by very simple kinds of receptors or complex sense organs receptors for General Senses are relatively simple A. Conjunctiva. Each of the hair cell clusters has a small collection of dense connective tissue attached to the hair cell membrane extensions (stereocilia) to add mass to the system. Receptors are the cells or structures that detect sensations. The superior oblique originates at the posterior orbit, near the origin of the four rectus muscles. The auricle, ear canal, and tympanic membrane are often referred to as the external ear. Other transmembrane proteins, which are not accurately called receptors, are sensitive to mechanical or thermal changes. The photoreceptors (rods and cones) change their membrane potential when stimulated by light energy. shape of the eye. As stated above, a given region of the basilar membrane will only move if the incoming sound is at a specific frequency. These cells release neurotransmitters onto a bipolar cell, which then synapses with the optic nerve neurons. The unit of Hertz measures the frequency of sound waves in terms of cycles produced per second. The eye itself is a hollow sphere composed of three layers of tissue. Creative Commons Attribution License Within the realm of physiology, senses can be classified as either general or specific. Find an individual taste bud and draw it in the space provided. If you differ, then provide a possible explanation as to why: This lab has been adapted from Rice University and is licensed under a Creative Commons Attribution License License (3.0). What may be happening with your cone cells within your retinas? This complexity allows you to be aware of your surroundings and take appropriate actions. Physical changes in these proteins increase ion flow across the membrane, and can generate an action potential or a graded potential in the sensory neurons. Describe the arrangement of sensory and motor regions in the spinal cord. Some of the branches will synapse with local neurons in the dorsal root ganglion, posterior (dorsal) horn, or even the anterior (ventral) horn, at the level of the spinal cord where they enter. Have the subject stand and stare straight ahead for 2 minutes, and note the range of movement. A photon interacting with the molecule causes the flexible double-bonded carbons to change to the trans- conformation, forming all-trans-retinal, which has a straight hydrocarbon chain (Figure 14.17). 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The tongue is covered with small bumps, called papillae, which contain taste buds that are sensitive to chemicals in ingested food or drink. Outer ear - from pinna (or auricle) to tympanum (also known as tympaninc membrane or eardrum). Blunt force trauma to the face, such as that common in many car accidents, can lead to the loss of the olfactory nerve, and subsequently, loss of the sense of smell. Visual acuity refers to the sharpness or clarity of vision and is an indication of the focusing capacities of your eyes, especially the lens and cornea. Perception is the central processing of sensory stimuli into a meaningful pattern. There are at least 30 different genes coding for bitter taste receptors. This intimate connection between the olfactory system and the cerebral cortex is one reason why smell can be a potent trigger of memories and emotion. The neural signals from these two regions are relayed to the brain stem through separate fiber bundles. The anterior and posterior vertical canals are oriented at approximately 45 degrees relative to the sagittal plane (Figure 14.12). The middle ear is connected to the pharynx through the Eustachian tube, which helps equilibrate air pressure across the tympanic membrane. The ability of olfactory neurons to replace themselves decreases with age, leading to age-related anosmia. Sensation is the activation of sensory receptor cells at the level of the stimulus. The canal enters the skull through the external auditory meatus of the temporal bone. (Micrograph provided by the Regents of University of Michigan Medical School 2012), (a) The olfactory system begins in the peripheral structures of the nasal cavity. When the pressure waves from the scala move the basilar membrane, the tectorial membrane slides across the stereocilia. The frequency of the fluid waves match the frequencies of the sound waves (Figure 14.6). The cochlea encodes auditory stimuli for frequencies between 20 and 20,000 Hz, which is the range of sound that human ears can detect. Receptor can refer to specific protein molecules which first interact with the matter or energy, the cell(s) that contains those proteins, or an assembly of cells in the larger organ. They alter the lens to aid focusing. Many internal structures are delicate and tear easily such as the retina. The peripheral nerve provides the pathway for motor, sensory and vegetative axons belonging to the peripheral nervous system. Specific organs include: In order to investigate and understand sensory processes, we will investigate their anatomical structures (at macro- and microscopic levels) and physiological functions. A similar mechanoreceptora hair cell with stereociliasenses head position, head movement, and whether our bodies are in motion. This article describes the anatomy and physiology of the sensory systems, examining structures associated with vision and hearing, equilibrium and sensation. Higher frequency waves move the region of the basilar membrane that is close to the base of the cochlea. General senses often contribute to the sense of touch, as described above, or to proprioception (body movement) and kinesthesia (body movement), or to a visceral sense, which is most important to autonomic functions. The specific response depends on which molecule is binding to the receptor. Sensory neurons can have either (a) free nerve endings or (b) encapsulated endings. The wavelength of visible light determines its color. Note that the photoreceptors in the retina (rods and cones) are located behind the axons, RGCs, bipolar cells, and retinal blood vessels. 3 285-296 doi: 10.1083/jcb.201003144). LM 1600. An important distinction to consider is how humans can functionally separate sensation (activation of the different receptors) as compared to perception (the conscious awareness of the sensation). In humans, from 100-200 different functional receptor proteins have been identified (there are over 1000 in rodents). Therefore, hair cells at the base of the cochlea are activated only by high frequencies, whereas those at the apex of the cochlea are activated only by low frequencies. In a darkened room, there is not enough light to activate cone opsins, and vision is entirely dependent on rods. ________. In other words, in a dark room, everything appears as a shade of gray. Modality refers to the way that information is encoded, which is similar to the idea of transduction. In the video, there is a brief image of a person sticking out their tongue, which has been covered with a colored dye. In normal sunlight, rhodopsin will be constantly bleached while the cones are active. Nociceptive Pain. Mechanoreceptors in the skin, muscles, or the walls of blood vessels are examples of this type. It has two separate regions, the cochlea and the vestibule, which are responsible for hearing and balance, respectively. The sweet taste is the sensitivity of gustatory cells to the presence of glucose dissolved in the saliva. Some sources will also refer to this structure as the pinna, though that term is more appropriate for a structure that can be moved, such as the external ear of a cat. Measure the distance from the image to your eye. What is anchored to this membrane so that they can be activated by movement of the fluids within the cochlea? In this lab, we will explore the anatomy & physiology used for interpreting the environment both within and outside our bodies. If you have missed laboratory or class; complete the makeup work below. The middle layer of the eye is the vascular tunic, which is mostly composed of the choroid, ciliary body, and iris. Receptors can be classified structurally on the basis of cell type and their position in relation to stimuli they sense. A general sense is one that is distributed throughout the body and has receptor cells within the structures of other organs. The tube is normally closed but will pop open when the muscles of the pharynx contract during swallowing or yawning. Smell is the one sensory modality that does not synapse in the thalamus before connecting to the cerebral cortex. An interoceptor is one that interprets stimuli from internal organs and tissues, such as the receptors that sense the increase in blood pressure in the aorta or carotid sinus. Some stimuli are physical variations in the environment that affect receptor cell membrane potentials. Other cranial nerves contain both sensory and motor axons, including the trigeminal, facial, glossopharyngeal, and vagus nerves (however, the vagus nerve is not associated with the somatic nervous system). Opsin pigments are actually transmembrane proteins that contain a cofactor known as retinal. Sucrose and NaCl are common tests for sweet and salty. Stand there and cover one eye without squinting. Nociceptive Pain. Describing sensory function with the term sensation or perception is a deliberate distinction. Without moving your eyes off that word, notice that words at the beginning or end of the paragraph are not in focus. The relative activation of the three different cones is calculated by the brain, which perceives the color as blue. Serial solutions can be applied with cotton swabs to the subject's tongue to test for sensitivity. Finally, a proprioceptor is a receptor located near a moving part of the body, such as a muscle, that interprets the positions of the tissues as they move. For example, a molecule in food can serve as a ligand for taste receptors. You are responsible for identifying these major anatomical structures of the eye: sclera (tough, outer layer), choroid (dark, middle layer), pigmented epithelium, fovea, vitreous humor, aqueous humor, iris, lens, ciliary body, cornea, conjunctiva, optic nerve, blind spot (or optic disc), retina (thin, and pale inner layer). The otoliths essentially make the otolithic membrane top-heavy. See Full PDF Download PDF Related Papers THE SKELETON BONES AND JOINTS From there, the axons split to travel to several brain regions. The utricle and saccule are both largely composed of macula tissue (plural = maculae). Therefore, as the frequency of a sound changes, different hair cells are activated all along the basilar membrane. Other monosaccharides such as fructose, or artificial sweeteners such as aspartame (NutraSweet), saccharine, or sucralose (Splenda) also activate the sweet receptors. At the uppermost tip of the cochlea, the scala vestibuli curves over the top of the cochlear duct. The difference in inertia between the hair cell stereocilia and the otolithic membrane in which they are embedded leads to a shearing force that causes the stereocilia to bend in the direction of that linear acceleration. A single unit of light is called a photon, which is described in physics as a packet of energy with properties of both a particle and a wave. Use a microscope to explore the cellular aspect of a taste bud. a. 190 no. Umami is a Japanese word that means delicious taste, and is often translated to mean savory. Proprioceptive Sensations- relating to the physical state of the body (position, tendons, muscles, equilibrium) Visceral Sensations- sensations from the internal organs Deep Sensations- come from the deep tissues (fascia, muscles, and bone) 4 Detection and Transmission of Tactile Sensations Interrelaitons Among the Tactile Sensations of Touch, The ampulla contains the hair cells that respond to rotational movement, such as turning the head while saying no. The stereocilia of these hair cells extend into the cupula, a membrane that attaches to the top of the ampulla. Inner ear Cochlea, which contains the hair cells (receptors) within the Organ of Corti. This occurs when a stimulus changes the cell membrane potential of a sensory neuron. (a) All photoreceptors have inner segments containing the nucleus and other important organelles and outer segments with membrane arrays containing the photosensitive opsin molecules. Publication types Review then you must include on every digital page view the following attribution: Use the information below to generate a citation. An exteroceptor is a receptor that is located near a stimulus in the external environment, such as the somatosensory receptors that are located in the skin. Therefore, visual acuity, or the sharpness of vision, is greatest at the fovea. The types of nerve endings, their locations, and the stimuli they transduce are presented in Table 14.1. Osmoreceptors respond to solute concentrations of body fluids. (c) Axons of the olfactory receptor neurons project through the cribriform plate of the ethmoid bone and synapse with the neurons of the olfactory bulb (tissue source: simian). The highest concentration of bitter receptors appear to be in the posterior tongue, where a gag reflex could still spit out poisonous food. HISTORICAL NOTE: The standard map of taste buds common in many lab manuals has been disproved by subsequent research (J. Using a tuning fork, have a subject sit with their eyes closed. The retina is composed of several layers and contains specialized cells for the initial processing of visual stimuli. Read back a little to see if you can figure it out. The eyes are located within either orbit in the skull. Stimuli from varying sources, and of different types, are received and changed into the electrochemical signals of the nervous system. Testing is a simple positive response for bitter taste, while non-tasters will report no taste. Phenylthiocarbamide (PTC), also known as phenylthiourea (PTU), is only detected by ~70% of the population on average. Perception is dependent on sensation, but not all sensations are perceived. The G protein changes the membrane potential of the photoreceptor cell, which then releases less neurotransmitter into the outer synaptic layer of the retina. However, the tendon of the oblique muscles threads through a pulley-like piece of cartilage known as the trochlea. The inner ear is often described as a bony labyrinth, as it is composed of a series of canals embedded within the temporal bone. Such low frequency vibrations are sensed by mechanoreceptors called Merkel cells, also known as type I cutaneous mechanoreceptors. The bony orbits surround the eyeballs, protecting them and anchoring the soft tissues of the eye (Figure 14.13). The humors are fluids filling the anterior and posterior chambers of the eye. The axon of an olfactory neuron extends from the basal surface of the epithelium, through an olfactory foramen in the cribriform plate of the ethmoid bone, and into the brain. Also, taste is often integrated as a perception with olfactory sensory input. Visible light is electromagnetic radiation with a wavelength between 380 and 720 nm. If you drag your finger across a textured surface, the skin of your finger will vibrate. Head position is sensed by the utricle and saccule, whereas head movement is sensed by the semicircular canals. The three types of cone opsins, being sensitive to different wavelengths of light, provide us with color vision. Sensory System f Sensory Organs (Receptors) Monitor the internal and external environment Transmit signals from periphery to CNS for processing Critical for homeostasis f Types of Sensory Receptors Functional Types Based on modality (type of environmental change they sense) 1. Have your partner stand near the chart and tell you which line to read starting from the top. The central integration may then lead to a motor response. Typically, spinal nerve systems that connect to the brain are contralateral, in that the right side of the body is connected to the left side of the brain and the left side of the body to the right side of the brain.