Sense

Structural receptor types

Functional receptor types

A third classification of receptors is by how the receptor transduces stimuli into membrane potential changes. Stimuli are of three general types. Some stimuli are ions and macromolecules that affect transmembrane receptor proteins when these chemicals diffuse across the cell membrane. Some stimuli are physical variations in the environment that affect receptor cell membrane potentials. Other stimuli include the electromagnetic radiation from visible light. For humans, the only electromagnetic energy that is perceived by our eyes is visible light. 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.^[18]

Receptor cells can be further categorized on the basis of the type of stimuli they transduce. The different types of functional receptor cell types are mechanoreceptors, photoreceptors, chemoreceptors (osmoreceptor), thermoreceptors, electroreceptors (in certain mammals and fish), and nociceptors. Physical stimuli, such as pressure and vibration, as well as the sensation of sound and body position (balance), are interpreted through a mechanoreceptor. Photoreceptors convert light (visible electromagnetic radiation) into signals. Chemical stimuli can be interpreted by a chemoreceptor that interprets chemical stimuli, such as an object's taste or smell, while osmoreceptors respond to a chemical solute concentrations of body fluids. Nociception (pain) interprets the presence of tissue damage, from sensory information from mechano-, chemo-, and thermoreceptors.^[20] Another physical stimulus that has its own type of receptor is temperature, which is sensed through a thermoreceptor that is either sensitive to temperatures above (heat) or below (cold) normal body temperature.^[18]

Absolute threshold

Each sense organ (eyes or nose, for instance) requires a minimal amount of stimulation in order to detect a stimulus. This minimum amount of stimulus is called the absolute threshold.^[7] The absolute threshold is defined as the minimum amount of stimulation necessary for the detection of a stimulus 50% of the time.^[8] Absolute threshold is measured by using a method called signal detection. This process involves presenting stimuli of varying intensities to a subject in order to determine the level at which the subject can reliably detect stimulation in a given sense.^[7]

Differential threshold

Differential threshold or just noticeable difference (JDS) is the smallest detectable difference between two stimuli, or the smallest difference in stimuli that can be judged to be different from each other.^[8] Weber's Law is an empirical law that states that the difference threshold is a constant fraction of the comparison stimulus.^[8] According to Weber's Law, bigger stimuli require larger differences to be noticed.^[7]

Magnitude estimation is a psychophysical method in which subjects assign perceived values of given stimuli. The relationship between stimulus intensity and perceptive intensity is described by Steven's power law.^[8]

Sensory nervous system

All stimuli received by the receptors are transduced to an action potential, which is carried along one or more afferent neurons towards a specific area (cortex) of the brain. Just as different nerves are dedicated to sensory and motors tasks, different areas of the brain (cortices) are similarly dedicated to different sensory and perceptual tasks. More complex processing is accomplished across primary cortical regions that spread beyond the primary cortices. Every nerve, sensory or motor, has its own signal transmission speed. For example, nerves in the frog's legs have a 90 ft/s (99 km/h) signal transmission speed, while sensory nerves in humans, transmit sensory information at speeds between 165 ft/s (181 km/h) and 330 ft/s (362 km/h).^[8]

Absolute threshold

Some examples of human absolute thresholds for the nine to 21 external senses.^[23]

Multimodal perception

Humans respond more strongly to multimodal stimuli compared to the sum of each single modality together, an effect called the superadditive effect of multisensory integration.^[7] Neurons that respond to both visual and auditory stimuli have been identified in the superior temporal sulcus.^[22] Additionally, multimodal "what" and "where" pathways have been proposed for auditory and tactile stimuli.^[24]

Visual system (vision)

The visual system, or sense of sight, is based on the transduction of light stimuli received through the eyes and contributes to visual perception. The visual system detects light on photoreceptors in the retina of each eye that generates electrical nerve impulses for the perception of varying colors and brightness. There are two types of photoreceptors: rods and cones. Rods are very sensitive to light but do not distinguish colors. Cones distinguish colors but are less sensitive to dim light.^[18]

At the molecular level, visual stimuli cause changes in the photopigment molecule that lead to changes in membrane potential of the photoreceptor cell. 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. The energy of a photon is represented by its wavelength, with each wavelength of visible light corresponding to a particular color. Visible light is electromagnetic radiation with a wavelength between 380 and 720 nm. Wavelengths of electromagnetic radiation longer than 720 nm fall into the infrared range, whereas wavelengths shorter than 380 nm fall into the ultraviolet range. Light with a wavelength of 380 nm is blue whereas light with a wavelength of 720 nm is dark red. All other colors fall between red and blue at various points along the wavelength scale.^[18]

The three types of cone opsins, being sensitive to different wavelengths of light, provide us with color vision. By comparing the activity of the three different cones, the brain can extract color information from visual stimuli. For example, a bright blue light that has a wavelength of approximately 450 nm would activate the "red" cones minimally, the "green" cones marginally, and the "blue" cones predominantly. The relative activation of the three different cones is calculated by the brain, which perceives the color as blue. However, cones cannot react to low-intensity light, and rods do not sense the color of light. Therefore, our low-light vision is—in essence—in grayscale. In other words, in a dark room, everything appears as a shade of gray. If you think that you can see colors in the dark, it is most likely because your brain knows what color something is and is relying on that memory.^[18]

There is some disagreement as to whether the visual system consists of one, two, or three submodalities. Neuroanatomists generally regard it as two submodalities, given that different receptors are responsible for the perception of color and brightness. Some argue^{[citation needed]} that stereopsis, the perception of depth using both eyes, also constitutes a sense, but it is generally regarded as a cognitive (that is, post-sensory) function of the visual cortex of the brain where patterns and objects in images are recognized and interpreted based on previously learned information. This is called visual memory.

The inability to see is called blindness. Blindness may result from damage to the eyeball, especially to the retina, damage to the optic nerve that connects each eye to the brain, and/or from stroke (infarcts in the brain). Temporary or permanent blindness can be caused by poisons or medications. People who are blind from degradation or damage to the visual cortex, but still have functional eyes, are actually capable of some level of vision and reaction to visual stimuli but not a conscious perception; this is known as blindsight. People with blindsight are usually not aware that they are reacting to visual sources, and instead just unconsciously adapt their behavior to the stimulus.

On February 14, 2013, researchers developed a neural implant that gives rats the ability to sense infrared light which for the first time provides living creatures with new abilities, instead of simply replacing or augmenting existing abilities.^[25]

Auditory system (hearing)

Hearing, or audition, is the transduction of sound waves into a neural signal that is made possible by the structures of the ear. The large, fleshy structure on the lateral aspect of the head is known as the auricle. At the end of the auditory canal is the tympanic membrane, or ear drum, which vibrates after it is struck by sound waves. The auricle, ear canal, and tympanic membrane are often referred to as the external ear. The middle ear consists of a space spanned by three small bones called the ossicles. The three ossicles are the malleus, incus, and stapes, which are Latin names that roughly translate to hammer, anvil, and stirrup. The malleus is attached to the tympanic membrane and articulates with the incus. The incus, in turn, articulates with the stapes. The stapes is then attached to the inner ear, where the sound waves will be transduced into a neural signal. The middle ear is connected to the pharynx through the Eustachian tube, which helps equilibrate air pressure across the tympanic membrane. The tube is normally closed but will pop open when the muscles of the pharynx contract during swallowing or yawning.^[18]

Mechanoreceptors turn motion into electrical nerve pulses, which are located in the inner ear. Since sound is vibration, propagating through a medium such as air, the detection of these vibrations, that is the sense of the hearing, is a mechanical sense because these vibrations are mechanically conducted from the eardrum through a series of tiny bones to hair-like fibers in the inner ear, which detect mechanical motion of the fibers within a range of about 20 to 20,000 hertz,^[29] with substantial variation between individuals. Hearing at high frequencies declines with an increase in age. Inability to hear is called deafness or hearing impairment. Sound can also be detected as vibrations conducted through the body. Lower frequencies that can be heard are detected this way. Some deaf people are able to determine the direction and location of vibrations picked up through the feet.^[30]

Studies pertaining to audition started to increase in number towards the latter end of the nineteenth century. During this time, many laboratories in the United States began to create new models, diagrams, and instruments that all pertained to the ear.^[31]

Auditory cognitive psychology is a branch of cognitive psychology that is dedicated to the auditory system. The main point is to understand why humans are able to use sound in thinking outside of actually saying it.^[32]

Relating to auditory cognitive psychology is psychoacoustics. Psychoacoustics is more directed at people interested in music.^[33] Haptics, a word used to refer to both taction and kinesthesia, has many parallels with psychoacoustics.^[33] Most research around these two are focused on the instrument, the listener, and the player of the instrument.^[33]

Somatosensory system (touch)

Somatosensation is considered a general sense, as opposed to the special senses discussed in this section. Somatosensation is the group of sensory modalities that are associated with touch and interoception. The modalities of somatosensation include pressure, vibration, light touch, tickle, itch, temperature, pain, kinesthesia.^[18] Somatosensation, also called tactition (adjectival form: tactile) is a perception resulting from activation of neural receptors, generally in the skin including hair follicles, but also in the tongue, throat, and mucosa. A variety of pressure receptors respond to variations in pressure (firm, brushing, sustained, etc.). The touch sense of itching caused by insect bites or allergies involves special itch-specific neurons in the skin and spinal cord.^[34] The loss or impairment of the ability to feel anything touched is called tactile anesthesia. Paresthesia is a sensation of tingling, pricking, or numbness of the skin that may result from nerve damage and may be permanent or temporary.

Two types of somatosensory signals that are transduced by free nerve endings are pain and temperature. These two modalities use thermoreceptors and nociceptors to transduce temperature and pain stimuli, respectively. Temperature receptors are stimulated when local temperatures differ from body temperature. Some thermoreceptors are sensitive to just cold and others to just heat. Nociception is the sensation of potentially damaging stimuli. Mechanical, chemical, or thermal stimuli beyond a set threshold will elicit painful sensations. Stressed or damaged tissues release chemicals that activate receptor proteins in the nociceptors. For example, the sensation of heat associated with spicy foods involves capsaicin, the active molecule in hot peppers.^[18]

Low frequency vibrations are sensed by mechanoreceptors called Merkel cells, also known as type I cutaneous mechanoreceptors. Merkel cells are located in the stratum basale of the epidermis. Deep pressure and vibration is transduced by lamellated (Pacinian) corpuscles, which are receptors with encapsulated endings found deep in the dermis, or subcutaneous tissue. Light touch is transduced by the encapsulated endings known as tactile (Meissner) corpuscles. Follicles are also wrapped in a plexus of nerve endings known as the hair follicle plexus. These nerve endings detect the movement of hair at the surface of the skin, such as when an insect may be walking along the skin. Stretching of the skin is transduced by stretch receptors known as bulbous corpuscles. Bulbous corpuscles are also known as Ruffini corpuscles, or type II cutaneous mechanoreceptors.^[18]

The heat receptors are sensitive to infrared radiation and can occur in specialized organs, for instance in pit vipers. The thermoceptors in the skin are quite different from the homeostatic thermoceptors in the brain (hypothalamus), which provide feedback on internal body temperature.

Gustatory system (taste)

The gustatory system or the sense of taste is the sensory system that is partially responsible for the perception of taste (flavor).^[35] A few recognized submodalities exist within taste: sweet, salty, sour, bitter, and umami. Very recent research has suggested that there may also be a sixth taste submodality for fats, or lipids.^[18] The sense of taste is often confused with the perception of flavor, which is the results of the multimodal integration of gustatory (taste) and olfactory (smell) sensations.^[36]

Within the structure of the lingual papillae are taste buds that contain specialized gustatory receptor cells for the transduction of taste stimuli. These receptor cells are sensitive to the chemicals contained within foods that are ingested, and they release neurotransmitters based on the amount of the chemical in the food. Neurotransmitters from the gustatory cells can activate sensory neurons in the facial, glossopharyngeal, and vagus cranial nerves.^[18]

Salty and sour taste submodalities are triggered by the cations Na⁺ and H⁺, respectively. The other taste modalities result from food molecules binding to a G protein–coupled receptor. A G protein signal transduction system ultimately leads to depolarization of the gustatory cell. The sweet taste is the sensitivity of gustatory cells to the presence of glucose (or sugar substitutes) dissolved in the saliva. Bitter taste is similar to sweet in that food molecules bind to G protein–coupled receptors. The taste known as umami is often referred to as the savory taste. Like sweet and bitter, it is based on the activation of G protein–coupled receptors by a specific molecule.^[18]

Once the gustatory cells are activated by the taste molecules, they release neurotransmitters onto the dendrites of sensory neurons. These neurons are part of the facial and glossopharyngeal cranial nerves, as well as a component within the vagus nerve dedicated to the gag reflex. The facial nerve connects to taste buds in the anterior third of the tongue. The glossopharyngeal nerve connects to taste buds in the posterior two thirds of the tongue. The vagus nerve connects to taste buds in the extreme posterior of the tongue, verging on the pharynx, which are more sensitive to noxious stimuli such as bitterness.^[18]

Flavor depends on odor, texture, and temperature as well as on taste. Humans receive tastes through sensory organs called taste buds, or gustatory calyculi, concentrated on the upper surface of the tongue. Other tastes such as calcium^[37][38] and free fatty acids^[39] may also be basic tastes but have yet to receive widespread acceptance. The inability to taste is called ageusia.

There is a rare phenomenon when it comes to the gustatory sense. It is called lexical-gustatory synesthesia. Lexical-gustatory synesthesia is when people can "taste" words.^[40] They have reported having flavor sensations they are not actually eating. When they read words, hear words, or even imagine words. They have reported not only simple flavors, but textures, complex flavors, and temperatures as well.^[41]

Olfactory system (smell)

Like the sense of taste, the sense of smell, or the olfactory system, is also responsive to chemical stimuli.^[18] Unlike taste, there are hundreds of olfactory receptors (388 functional ones according to one 2003 study^[42]), each binding to a particular molecular feature. Odor molecules possess a variety of features and, thus, excite specific receptors more or less strongly. This combination of excitatory signals from different receptors makes up what humans perceive as the molecule's smell.^{[citation needed]}

The olfactory receptor neurons are located in a small region within the superior nasal cavity. This region is referred to as the olfactory epithelium and contains bipolar sensory neurons. Each olfactory sensory neuron has dendrites that extend from the apical surface of the epithelium into the mucus lining the cavity. As airborne molecules are inhaled through the nose, they pass over the olfactory epithelial region and dissolve into the mucus. These odorant molecules bind to proteins that keep them dissolved in the mucus and help transport them to the olfactory dendrites. The odorant–protein complex binds to a receptor protein within the cell membrane of an olfactory dendrite. These receptors are G protein–coupled, and will produce a graded membrane potential in the olfactory neurons.^[18]

In the brain, olfaction is processed by the olfactory cortex. Olfactory receptor neurons in the nose differ from most other neurons in that they die and regenerate on a regular basis. The inability to smell is called anosmia. Some neurons in the nose are specialized to detect pheromones.^[43] Loss of the sense of smell can result in food tasting bland. A person with an impaired sense of smell may require additional spice and seasoning levels for food to be tasted. Anosmia may also be related to some presentations of mild depression, because the loss of enjoyment of food may lead to a general sense of despair. The ability of olfactory neurons to replace themselves decreases with age, leading to age-related anosmia. This explains why some elderly people salt their food more than younger people do.^[18]

Vestibular system (balance)

The vestibular sense, or sense of balance (equilibrium), is the sense that contributes to the perception of balance (equilibrium), spatial orientation, direction, or acceleration (equilibrioception). Along with audition, the inner ear is responsible for encoding information about equilibrium. A similar mechanoreceptor—a hair cell with stereocilia—senses head position, head movement, and whether our bodies are in motion. These cells are located within the vestibule of the inner ear. Head position is sensed by the utricle and saccule, whereas head movement is sensed by the semicircular canals. The neural signals generated in the vestibular ganglion are transmitted through the vestibulocochlear nerve to the brain stem and cerebellum.^[18]

The semicircular canals are three ring-like extensions of the vestibule. One is oriented in the horizontal plane, whereas the other two are oriented in the vertical plane. The anterior and posterior vertical canals are oriented at approximately 45 degrees relative to the sagittal plane. The base of each semicircular canal, where it meets with the vestibule, connects to an enlarged region known as the ampulla. 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. 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. The semicircular canals contain several ampullae, with some oriented horizontally and others oriented vertically. 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 (3D) space.^[18]

The vestibular nerve conducts information from sensory receptors in three ampullae that sense motion of fluid in three semicircular canals caused by three-dimensional rotation of the head. The vestibular nerve also conducts information from the utricle and the saccule, which contain hair-like sensory receptors that bend under the weight of otoliths (which are small crystals of calcium carbonate) that provide the inertia needed to detect head rotation, linear acceleration, and the direction of gravitational force.

Smell

An example of smell in non-mammals is that of sharks, which combine their keen sense of smell with timing to determine the direction of a smell. They follow the nostril that first detected the smell.^[53] Insects have olfactory receptors on their antennae. Although it is unknown to the degree and magnitude which non-human mammals can smell better than humans,^[54] humans are known to have far fewer olfactory receptors than mice, and humans have also accumulated more genetic mutations in their olfactory receptors than other primates.^[55]

Vomeronasal organ

Many animals (salamanders, reptiles, mammals) have a vomeronasal organ^[56] that is connected with the mouth cavity. In mammals it is mainly used to detect pheromones of marked territory, trails, and sexual state. Reptiles like snakes and monitor lizards make extensive use of it as a smelling organ by transferring scent molecules to the vomeronasal organ with the tips of the forked tongue. In reptiles, the vomeronasal organ is commonly referred to as Jacobson's organ. In mammals, it is often associated with a special behavior called flehmen characterized by uplifting of the lips. The organ is vestigial in humans, because associated neurons have not been found that give any sensory input in humans.^[57]

Taste

Flies and butterflies have taste organs on their feet, allowing them to taste anything they land on. Catfish have taste organs across their entire bodies, and can taste anything they touch, including chemicals in the water.^[58]

Vision

Cats have the ability to see in low light, which is due to muscles surrounding their irides–which contract and expand their pupils–as well as to the tapetum lucidum, a reflective membrane that optimizes the image. Pit vipers, pythons and some boas have organs that allow them to detect infrared light, such that these snakes are able to sense the body heat of their prey. The common vampire bat may also have an infrared sensor on its nose.^[59] It has been found that birds and some other animals are tetrachromats and have the ability to see in the ultraviolet down to 300 nanometers. Bees and dragonflies^[60] are also able to see in the ultraviolet. Mantis shrimps can perceive both polarized light and multispectral images and have twelve distinct kinds of color receptors, unlike humans which have three kinds and most mammals which have two kinds.^[61]

Cephalopods have the ability to change color using chromatophores in their skin. Researchers believe that opsins in the skin can sense different wavelengths of light and help the creatures choose a coloration that camouflages them, in addition to light input from the eyes.^[62] Other researchers hypothesize that cephalopod eyes in species which only have a single photoreceptor protein may use chromatic aberration to turn monochromatic vision into color vision,^[63] explaining pupils shaped like the letter U, the letter W, or a dumbbell, as well as explaining the need for colorful mating displays.^[64] Some cephalopods can distinguish the polarization of light. ^{[citation needed]}

Spatial orientation

Many invertebrates have a statocyst, which is a sensor for acceleration and orientation that works very differently from the mammalian's semi-circular canals. ^{[citation needed]}

Magnetoception

Magnetoception (or magnetoreception) is the ability to detect the direction one is facing based on the Earth's magnetic field. Directional awareness is most commonly observed in birds, which rely on their magnetic sense to navigate during migration.^{[65][66][67][68]} It has also been observed in insects such as bees. Cattle make use of magnetoception to align themselves in a north–south direction.^[69] Magnetotactic bacteria build miniature magnets inside themselves and use them to determine their orientation relative to the Earth's magnetic field.^[70][71] There has been some recent (tentative) research suggesting that the rhodopsin in the human eye, which responds particularly well to blue light, can facilitate magnetoception in humans.^[72]

Echolocation

Certain animals, including bats and cetaceans, have the ability to determine orientation to other objects through interpretation of reflected sound (like sonar). They most often use this to navigate through poor lighting conditions or to identify and track prey. There is currently an uncertainty whether this is simply an extremely developed post-sensory interpretation of auditory perceptions or it actually constitutes a separate sense. Resolution of the issue will require brain scans of animals while they actually perform echolocation, a task that has proven difficult in practice. ^{[citation needed]}

Blind people report they are able to navigate and in some cases identify an object by interpreting reflected sounds (especially their own footsteps), a phenomenon known as human echolocation. ^{[citation needed]}

Electroreception

Electroreception (or electroception) is the ability to detect electric fields. Several species of fish, sharks, and rays have the capacity to sense changes in electric fields in their immediate vicinity. For cartilaginous fish this occurs through a specialized organ called the ampullae of Lorenzini. Some fish passively sense changing nearby electric fields; some generate their own weak electric fields, and sense the pattern of field potentials over their body surface; and some use these electric field generating and sensing capacities for social communication. The mechanisms by which electroceptive fish construct a spatial representation from very small differences in field potentials involve comparisons of spike latencies from different parts of the fish's body. ^{[citation needed]}

The only orders of mammals that are known to demonstrate electroception are the dolphin and monotreme orders. Among these mammals, the platypus^[73] has the most acute sense of electroception.

A dolphin can detect electric fields in water using electroreceptors in vibrissal crypts arrayed in pairs on its snout and which evolved from whisker motion sensors.^[74] These electroreceptors can detect electric fields as weak as 4.6 microvolts per centimeter, such as those generated by contracting muscles and pumping gills of potential prey. This permits the dolphin to locate prey from the seafloor where sediment limits visibility and echolocation.

Spiders have been shown to detect electric fields to determine a suitable time to extend web for 'ballooning'.^[75]

Body modification enthusiasts have experimented with magnetic implants to attempt to replicate this sense.^[76] However, in general humans (and it is presumed other mammals) can detect electric fields only indirectly by detecting the effect they have on hairs. An electrically charged balloon, for instance, will exert a force on human arm hairs, which can be felt through tactition and identified as coming from a static charge (and not from wind or the like). This is not electroreception, as it is a post-sensory cognitive action.

Hygroreception

Hygroreception is the ability to detect changes in the moisture content of the environment.^[11][77]

Infrared sensing

The ability to sense infrared thermal radiation evolved independently in various families of snakes. Essentially, it allows these reptiles to "see" radiant heat at wavelengths between 5 and 30 μm to a degree of accuracy such that a blind rattlesnake can target vulnerable body parts of the prey at which it strikes.^[78] It was previously thought that the organs evolved primarily as prey detectors, but it is now believed that it may also be used in thermoregulatory decision making.^[79] The facial pit underwent parallel evolution in pitvipers and some boas and pythons, having evolved once in pitvipers and multiple times in boas and pythons.^{[80][verification needed]} The electrophysiology of the structure is similar between the two lineages, but they differ in gross structural anatomy. Most superficially, pitvipers possess one large pit organ on either side of the head, between the eye and the nostril (loreal pit), while boas and pythons have three or more comparatively smaller pits lining the upper and sometimes the lower lip, in or between the scales. Those of the pitvipers are the more advanced, having a suspended sensory membrane as opposed to a simple pit structure. Within the family Viperidae, the pit organ is seen only in the subfamily Crotalinae: the pitvipers. The organ is used extensively to detect and target endothermic prey such as rodents and birds, and it was previously assumed that the organ evolved specifically for that purpose. However, recent evidence shows that the pit organ may also be used for thermoregulation. According to Krochmal et al., pitvipers can use their pits for thermoregulatory decision-making while true vipers (vipers who do not contain heat-sensing pits) cannot.

In spite of its detection of IR light, the pits' IR detection mechanism is not similar to photoreceptors – while photoreceptors detect light via photochemical reactions, the protein in the pits of snakes is in fact a temperature-sensitive ion channel. It senses infrared signals through a mechanism involving warming of the pit organ, rather than a chemical reaction to light.^[81] This is consistent with the thin pit membrane, which allows incoming IR radiation to quickly and precisely warm a given ion channel and trigger a nerve impulse, as well as vascularize the pit membrane in order to rapidly cool the ion channel back to its original "resting" or "inactive" temperature.^[81]

Other

This section does not cite any sources. (April 2023)

Pressure detection uses the organ of Weber, a system consisting of three appendages of vertebrae transferring changes in shape of the gas bladder to the middle ear. It can be used to regulate the buoyancy of the fish. Fish like the weather fish and other loaches are also known to respond to low pressure areas but they lack a swim bladder.

Current detection is a detection system of water currents, consisting mostly of vortices, found in the lateral line of fish and aquatic forms of amphibians. The lateral line is also sensitive to low-frequency vibrations. The mechanoreceptors are hair cells, the same mechanoreceptors for vestibular sense and hearing. It is used primarily for navigation, hunting, and schooling. The receptors of the electrical sense are modified hair cells of the lateral line system.

Polarized light direction/detection is used by bees to orient themselves, especially on cloudy days. Cuttlefish, some beetles, and mantis shrimp can also perceive the polarization of light. Most sighted humans can in fact learn to roughly detect large areas of polarization by an effect called Haidinger's brush; however, this is considered an entoptic phenomenon rather than a separate sense.

Slit sensillae of spiders detect mechanical strain in the exoskeleton, providing information on force and vibrations.