Adequate stimulus

The adequate stimulus is a property of a sensory receptor that determines the type of energy 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.

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]

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]

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]

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. ^ a b Frings, Stephan (2012-01-01). "Sensory cells and sensory organs". In Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter. Sensory Perception. Springer Vienna. pp. 5–21. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.
  2. ^ Frings, Stephan (2012-01-01). "Sensory cells and sensory organs". In Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter. Sensory Perception. Springer Vienna. pp. 5–21. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.
  3. ^ a b Frings, Stephan (2012-01-01). "Sensory cells and sensory organs". In Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter. Sensory Perception. Springer Vienna. pp. 5–21. 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.
  5. ^ a b Frings, Stephan (2012-01-01). "Sensory cells and sensory organs". In Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter. 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.
  7. ^ a b 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 978-1552978795.
  9. ^ Frings, Stephan (2012-01-01). "Sensory cells and sensory organs". In Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter. Sensory Perception. Springer Vienna. pp. 5–21. doi:10.1007/978-3-211-99751-2_1. ISBN 9783211997505.
  10. ^ Frings, Stephan (2012-01-01). "Sensory cells and sensory organs". In Barth, Friedrich G.; Giampieri-Deutsch, Patrizia; Klein, Hans-Dieter. Sensory Perception. Springer Vienna. pp. 5–21. 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 978-1552978795.
  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.
  13. ^ a b Hockenbury, Don H; Hockenbury, Sandra E. (2010). Psychology (5th ed.). New York, NY: Worth Publishers. p. 92. ISBN 978-1429201438.
  14. ^ a b c d e f 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.
All-or-none law

The all-or-none law is the principle that the strength by which a nerve or muscle fibre responds to a stimulus is independent of the strength of the stimulus. If that stimulus exceeds the threshold potential, the nerve or muscle fibre will give a complete response; otherwise, there is no response.

It was first established by the American physiologist Henry Pickering Bowditch in 1871 for the contraction of heart muscle. According to him, describing the relation of response to stimulus,““An induction shock produces a contraction or fails to do so according to its strength; if it does so at all, it produces the greatest contraction that can be produced by any strength of stimulus in the condition of the muscle at the time.”The individual fibres of both skeletal muscle and nerve respond to stimulation according to the all-or-none principle.

Near-sightedness

Near-sightedness, also known as short-sightedness and myopia, is an eye disorder where light focuses in front of, instead of on, the retina. This causes distant objects to be blurry while close objects appear normal. Other symptoms may include headaches and eye strain. Severe near-sightedness increases the risk of retinal detachment, cataracts, and glaucoma.The underlying cause is believed to be a combination of genetic and environmental factors. Risk factors include doing work that involves focusing on close objects, greater time spent indoors, and a family history of the condition. It is also associated with a high socioeconomic class. The underlying mechanism involves the length of the eyeball growing too long or less commonly the lens being too strong. It is a type of refractive error. Diagnosis is by eye examination.Tentative evidence indicates that the risk of near-sightedness can be decreased by having young children spend more time outside. This may be related to natural light exposure. Near-sightedness can be corrected with eyeglasses, contact lenses, or surgery. Eyeglasses are the easiest and safest method of correction. Contact lenses can provide a wider field of vision, but are associated with a risk of infection. Refractive surgery permanently changes the shape of the cornea.Near-sightedness is the most common eye problem and is estimated to affect 1.5 billion people (22% of the population). Rates vary significantly in different areas of the world. Rates among adults are between 15 and 49%. Rates are similar in males and females. Among children, it affects 1% of rural Nepalese, 4% of South Africans, 12% of Americans, and 37% in some large Chinese cities. Rates have increased since the 1950s. Uncorrected near-sightedness is one of the most common causes of vision impairment globally along with cataracts, macular degeneration, and vitamin A deficiency.

Reflex hammer

A reflex hammer is a medical instrument used by practitioners to test deep tendon reflexes. Testing for reflexes is an important part of the neurological physical examination in order to detect abnormalities in the central or peripheral nervous system.

Reflex hammers can also be used for chest percussion.

Sensory neuron

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.This sensory information travels along afferent nerve fibers in an afferent or sensory nerve, to the brain via the spinal cord. The stimulus can come from extoreceptors outside the body, for example light and sound, or from interoreceptors inside the body, for example blood pressure or the sense of body position.

Different types of sensory neurons have different sensory receptors that respond to different kinds of stimuli.

Stimulus (physiology)

In physiology, a stimulus (plural stimuli) 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.

TPC Harding Park

TPC Harding Park, formerly Harding Park Golf Club and commonly known as Harding Park, is a municipal golf course on the West Coast of the United States, located in western San Francisco, California. It is owned by the city and county of San Francisco.

It is now a part of the PGA Tour's Tournament Players Club (TPC) network of courses, following an agreement between the tour and the city that was announced on November 3, 2010. It is located in the southwest area of San Francisco, on the west side of San Francisco State University, and surrounded by Lake Merced on its other three sides. The entrance is at Harding Road, which connects to Skyline Boulevard on the east.

Thermoreceptor

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 (low conduction velocity), while those responding to cold have both C-fibers and thinly myelinated A delta fibers (faster conduction velocity). 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.

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