Adequate stimulus

Last updated March 06, 2019

The adequate stimulus is a property of a sensory receptor that determines the type of energy^{[ citation needed ]} to which a sensory receptor responds with the initiation of sensory transduction. Sensory receptor are specialized to respond to certain types of stimuli. The adequate stimulus is the amount and type of energy required to stimulate a specific sensory organ.^[1]

Many of the sensory stimuli are categorized by the mechanics by which they are able to function and their purpose. Sensory receptors that are present within the body typically are made to respond to a single stimulus. Sensory receptors are present all throughout the body, and they take a certain amount of a stimulus to trigger these receptors. The use of these sensory receptors allows the brain to interpret the signals to the body which allow a person to respond to the stimulus if the stimulus reaches a minimum threshold to signal the brain. The sensory receptors will activate the sensory transduction system which will in turn send an electrical or chemical stimulus to a cell, and the cell will then respond with electrical signals to the brain which were produced from action potentials.^[1] The minuscule signals, which result from the stimuli, enter the cells must be amplified and turned into an sufficient signal that will be sent to the brain.^[2] A sensory receptor's adequate stimulus is determined by the signal transduction mechanisms and ion channels incorporated in the sensory receptor's plasma membrane. Adequate stimulus are often used in relation with sensory thresholds and absolute thresholds to describe the smallest amount of a stimulus needed to activate a feeling within the sensory organ.

In psychophysics, sensory threshold is the weakest stimulus that an organism can detect. Unless otherwise indicated, it is usually defined as the weakest stimulus that can be detected half the time, for example, as indicated by a point on a probability curve. Methods have been developed to measure thresholds in any of the senses.

In neuroscience and psychophysics, an absolute threshold was originally defined as the lowest level of a stimulus – light, sound, touch, etc. – that an organism could detect. Under the influence of signal detection theory, absolute threshold has been redefined as the level at which a stimulus will be detected a specified percentage of the time. The absolute threshold can be influenced by several different factors, such as the subject's motivations and expectations, cognitive processes, and whether the subject is adapted to the stimulus.
The absolute threshold can be compared to the difference threshold, which is the measure of how different two stimuli must be for the subject to notice that they are not the same.

Categorizations of receptors

They are categorized through the stimuli to which they respond. Adequate stimulus are also often categorized based on their purpose and locations within the body. The following are the categorizations of receptors within the body:

Visual – These are found in the visual organs of species and are responsive to stimuli such as light and often consist of light sensitive molecules that enable certain species to have the ability to see the world in with they live.^[3]
Olfaction – These types of receptor sense are activated in order to sense the external molecules that enter the nasal organ and attach to the receptors which will interpret the stimuli and send the signal containing information about the stimuli to the brain.^[4]
Auditory – These types of receptors are often found within the organs used to hear and are responsive to vibrations within the surrounding areas, and they often allow their owners to understand information about sound waves traveling through the aid.^[5]
Vestibular – These types of receptors are usually found within organs used to hear, and they aid in the detection of movement that surrounds the creature using it.^[5]
Gustatory – These sensory receptors are present within the mouth and are responsive to the molecular stimuli that enter the mouth.^[6] The receptors in the mouth typically fall into two of the following categories: receptors that are responsive to specific chemicals and receptors that are responsive to particles such as hydrogen ions, which are charged.^[7]
Tactile – These types of receptors are normally present within the skin and are able to respond to stimulation such as heat, pressure, and movement ^[8]

Olfaction is a chemoreception that forms the sense of smell. Olfaction has many purposes, such as the detection of hazards, pheromones, and food. It integrates with other senses to form the sense of flavor. Olfaction occurs when odorants bind to specific sites on olfactory receptors located in the nasal cavity. Glomeruli aggregate signals from these receptors and transmit them to the olfactory bulb, where the sensory input will start to interact with parts of the brain responsible for smell identification, memory, and emotion. Often, land organisms will have separate olfaction systems for smell and taste, but water-dwelling organisms usually have only one system.

Classes

There are several different types of stimuli to which adequate stimuli respond. The following are examples of stimuli to which receptors may:

Light – When the adequate stimulus of a sensory receptor is light, the sensory receptors contain pigment molecules whose shape is transformed by light, and the changes in these molecules activate ion channels which initiate sensory transduction.^[9]
Sound – When the adequate stimulus of a sensory receptor is sound, the sensory receptors are hair cells (mechanoreceptors). These hair cells contain stereocilia, which when bent, trigger the opening of ion channels. Thus hair cells transform the pressure waves of the sound into receptor potentials to initiate sensory transduction.^[10]

Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to visible light, which is the visible spectrum that is visible to the human eye and is responsible for the sense of sight. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), or 4.00 × 10⁻⁷ to 7.00 × 10⁻⁷ m, between the infrared and the ultraviolet. This wavelength means a frequency range of roughly 430–750 terahertz (THz).

Sound mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing; pressure wave, generated by vibrating structure

In physics, sound is a vibration that typically propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid.

Hair cells are the sensory receptors of both the auditory system and the vestibular system in the ears of all vertebrates. Through mechanotransduction, hair cells detect movement in their environment. In mammals, the auditory hair cells are located within the spiral organ of Corti on the thin basilar membrane in the cochlea of the inner ear. They derive their name from the tufts of stereocilia called hair bundles that protrude from the apical surface of the cell into the fluid-filled cochlear duct. Mammalian cochlear hair cells are of two anatomically and functionally distinct types, known as outer, and inner hair cells. Damage to these hair cells results in decreased hearing sensitivity, and because the inner ear hair cells cannot regenerate, this damage is permanent. However, other organisms, such as the frequently studied zebrafish, and birds have hair cells that can regenerate. The human cochlea contains on the order of 3,500 inner hair cells and 12,000 outer hair cells at birth.

Sensory receptors

Sensory receptors are the ends of nerves within the body that respond to stimuli. There are many different types of sensory receptors that each respond to stimuli that they are uniquely fitted to res Types of sensory receptors include the following:

Nociceptor – These are stimulus that are responsive to the stimuli that signal potential damage to the body. ^[11]
Photoreceptors – These are receptors that are responsive to light that enters the eye and produces the visual stimuli that many animals use to function.^[3]
Mechanoreceptors – These are receptors that are responsive to physical stimulation such as movement, vibration, and stress.^[7]
Thermoreceptors – These are types of receptors that are present within the skin and monitor any changes in the skins temperature^[12]

A nociceptor is a sensory neuron that responds to damaging or potentially damaging stimuli by sending “possible threat” signals to the spinal cord and the brain. If the brain perceives the threat as credible, it creates the sensation of pain to direct attention to the body part, so the threat can hopefully be mitigated; this process is called nociception.

A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential.

Classic examples of absolute threshold

In 1962, Eugene Galanter, a psychologist, tested stimuli till people were able to feel them approximately 50% of the time, then used the following as examples of absolute threshold:^[13]

Visual – On a clear, dark night a candle can be seen from approximately 30 miles away.^[14]
Olfactory – A person can smell a single drop of perfume after it has diffused into 3 rooms.^[14]
Auditory – In a silent area, a person can hear a watch tick from approximately 20 feet.^[14]
Vestibular – A person is able to tell of a tilt that when on a clock face is seen to be less than half a minute.^[14]
Gustatory – A person can taste a single teaspoon of sugar which is diluted in 2 gallons of water.^[14]
Tactile – A person can feel a fly's wing dropped from 3 feet above them falling onto their cheek.^[14]

Through these conditions, Galanter was able to show that human's sensory organs are often more sensitive than originally thought.^[13]

Notes

1 2 Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 7. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.
↑ Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 8. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.
1 2 Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 14. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.
↑ Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. pp. 427–429. ISBN 978-1605352114.
1 2 Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. pp. 10–11. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.
↑ Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. p. 471. ISBN 978-1605352114.
1 2 Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. p. 392. ISBN 978-1605352114.
↑ Walker, Richard (2008). Firefly guide to the human body (Rev. ed.). Buffalo, NY: Firefly Books. p. 46. ISBN 1552978796.
↑ Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 15. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.
↑ Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 11. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.
↑ Walker, Richard (2008). Firefly guide to the human body (Rev. ed.). Buffalo, NY: Firefly Books. p. 47. ISBN 1552978796.
↑ Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. p. 394. ISBN 978-1605352114.
1 2 Hockenbury, Don H; Hockenbury, Sandra E. (2010). Psychology (5th ed.). New York, NY: Worth Publishers. p. 92. ISBN 978-1429201438.
1 2 3 4 5 6 Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. p. 7. ISBN 978-1605352114.

Related Research Articles

The nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called motor or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory or afferent. Spinal nerves serve both functions and are called mixed nerves. The PNS is divided into three separate subsystems, the somatic, autonomic, and enteric nervous systems. Somatic nerves mediate voluntary movement. The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves.

Perception is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information, or the environment.

Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellular response. Proteins responsible for detecting stimuli are generally termed receptors, although in some cases the term sensor is used. The changes elicited by ligand binding in a receptor give rise to a signaling cascade, which is a chain of biochemical events along a signaling pathway. When signaling pathways interact with one another they form networks, which allow cellular responses to be coordinated, often by combinatorial signaling events. At the molecular level, such responses include changes in the transcription or translation of genes, and post-translational and conformational changes in proteins, as well as changes in their location. These molecular events are the basic mechanisms controlling cell growth, proliferation, metabolism and many other processes. In multicellular organisms, signal transduction pathways have evolved to regulate cell communication in a wide variety of ways.

Sensory nervous system part of the nervous system responsible for processing sensory information

The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons, neural pathways, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, touch, taste, smell, and balance. In short, senses are transducers from the physical world to the realm of the mind where we interpret the information, creating our perception of the world around us.

A taxis is the movement of an organism in response to a stimulus such as light or the presence of food. Taxes are innate behavioural responses. A taxis differs from a tropism in that in the case of taxis, the organism has motility and demonstrates guided movement towards or away from the stimulus source. It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus.

A chemoreceptor, also known as chemosensor, is a specialized sensory receptor cell which transduces (converts) a chemical substance and generates a biological signal. This signal may be in the form of an action potential if the chemoreceptor is a neuron, or in the form of a neurotransmitter that can activate a nearby nerve fiber if the chemosensor is a specialized sensory receptor cell, such as the taste receptor in a taste bud or in an internal peripheral chemoreceptor such as the carotid body. In more general terms, a chemosensor detects toxic or hazardous chemicals in the internal or external environment of the human body and transmits that information to the central nervous system,, in order to expel the biologically active toxins from the blood, and prevent further consumption of alcohol and/or other acutely toxic recreational intoxicants.

A receptor potential, also known as a generator potential, a type of graded potential, is the transmembrane potential difference produced by activation of a sensory receptor.

In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity. When a stimulus is applied to a sensory receptor, it normally elicits or influences a reflex via stimulus transduction. These sensory receptors can receive information from outside the body, as in touch receptors found in the skin or light receptors in the eye, as well as from inside the body, as in chemoreceptors and mechanoreceptors. An internal stimulus is often the first component of a homeostatic control system. External stimuli are capable of producing systemic responses throughout the body, as in the fight-or-flight response. In order for a stimulus to be detected with high probability, its level must exceed the absolute threshold; if a signal does reach threshold, the information is transmitted to the central nervous system (CNS), where it is integrated and a decision on how to react is made. Although stimuli commonly cause the body to respond, it is the CNS that finally determines whether a signal causes a reaction or not.

In physiology, sensory transduction is the conversion of a sensory stimulus from one form to another. Transduction in the nervous system typically refers to stimulus-alerting events wherein a physical stimulus is converted into an action potential, which is transmitted along axons towards the central nervous system for integration. It is a step in the larger process of sensory processing.

Stimulus modality, also called sensory modality, is one aspect of a stimulus or what is perceived after a stimulus. For example, the temperature modality is registered after heat or cold stimulate a receptor. Some sensory modalities include: light, sound, temperature, taste, pressure, and smell. The type and location of the sensory receptor activated by the stimulus plays the primary role in coding the sensation. All sensory modalities work together to heighten stimuli sensation when necessary.

A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. Normally there are four main types in glabrous, or hairless, mammalian skin: lamellar corpuscles, tactile corpuscles, Merkel nerve endings, and bulbous corpuscles. There are also mechanoreceptors in hairy skin, and the hair cells in thoreceptors of primates like rhesus monkeys and other mammals are similar to those of humans and also studied even in early 20th century anatomically and neurophysiologically.

A thermoreceptor is a non-specialised sense receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature, primarily within the innocuous range. In the mammalian peripheral nervous system, warmth receptors are thought to be unmyelinated C-fibres, while those responding to cold have both C-fibers and thinly myelinated A delta fibers. The adequate stimulus for a warm receptor is warming, which results in an increase in their action potential discharge rate. Cooling results in a decrease in warm receptor discharge rate. For cold receptors their firing rate increases during cooling and decreases during warming. Some cold receptors also respond with a brief action potential discharge to high temperatures, i.e. typically above 45°C, and this is known as a paradoxical response to heat. The mechanism responsible for this behavior has not been determined.

Sensory neurons also known as afferent neurons are neurons that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The cell bodies of the sensory neurons are located in the dorsal ganglia of the spinal cord.

Sensation is an animal's, including humans', detection of external or internal stimulation. It is different from perception, which is about making sense of, or describing, the stimulation.

Neural adaptation or sensory adaptation is a gradual decrease over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus. For example, if a hand is rested on a table, the table's surface is immediately felt on the skin. After a little while though this is no longer felt. The sensory neurons that initially respond are no longer stimulated to respond; this is an example of neural adaptation.

Plant perception or Plant Gnosophysiology is the ability of plants to sense and respond to the environment to adjust their morphology, physiology, and phenotype accordingly. Other disciplines such as plant physiology, ecology and molecular biology are used to assess this ability. Plants react to chemicals, gravity, light, moisture, infections, temperature, oxygen and carbon dioxide concentrations, parasite infestation, disease, physical disruption, sound, and touch.

Group C nerve fibers are one of three classes of nerve fiber in the central nervous system (CNS) and peripheral nervous system (PNS). The C group fibers are unmyelinated and have a small diameter and low conduction velocity, whereas Groups A and B are myelinated. Group C fibers include postganglionic fibers in the autonomic nervous system (ANS), and nerve fibers at the dorsal roots. These fibers carry sensory information.

Stimulus filtering occurs when an animal’s nervous system fails to respond to stimuli that would otherwise cause a reaction to occur. The nervous system has developed the capability to perceive and distinguish between minute differences in stimuli, which allows the animal to only react to significant impetus. This enables the animal to conserve energy as it is not responding to unimportant signals.

References

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[:0-1] 1 2 Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 7. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.

[2] Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 8. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.

[:1-3] 1 2 Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 14. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.

[4] Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. pp. 427–429. ISBN 978-1605352114.

[:2-5] 1 2 Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. pp. 10–11. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.

[6] Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. p. 471. ISBN 978-1605352114.

[:3-7] 1 2 Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. p. 392. ISBN 978-1605352114.

[8] Walker, Richard (2008). Firefly guide to the human body (Rev. ed.). Buffalo, NY: Firefly Books. p. 46. ISBN 1552978796.

[9] Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 15. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.

[10] Frings, Stephan (2012-01-01). Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter, eds. Sensory Perception. Springer Vienna. p. 11. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.

[11] Walker, Richard (2008). Firefly guide to the human body (Rev. ed.). Buffalo, NY: Firefly Books. p. 47. ISBN 1552978796.

[12] Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. p. 394. ISBN 978-1605352114.

[:4-13] 1 2 Hockenbury, Don H; Hockenbury, Sandra E. (2010). Psychology (5th ed.). New York, NY: Worth Publishers. p. 92. ISBN 978-1429201438.

[wolfe7-14] 1 2 3 4 5 6 Wolfe, Jermy M.; Kluender, Keith R.; Levi, Dennis M. (2015). Sensation and Perception (fourth ed.). Sunderland, Massachusetts U.S.A.: Sinauer Associates, Inc. p. 7. ISBN 978-1605352114.