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93-452: The traditional theory of EDA holds that skin resistance varies with the state of sweat glands in the skin. Sweating is controlled by the sympathetic nervous system , and skin conductance is an indication of psychological or physiological arousal . If the sympathetic branch of the autonomic nervous system is highly aroused, then sweat gland activity also increases, which in turn increases skin conductance. In this way, skin conductance can be

186-460: A 1:20 ratio of follicles with apocrine glands versus follicles without. They have eccrine glands between hairs over most of their body (while humans have them between the hairs on their scalp ). The overall distribution of sweat glands varies among primates: the rhesus and patas monkeys have them on the chest; the squirrel monkey has them only on the palms and soles; and the stump-tailed macaque , Japanese monkey , and baboon have them over

279-400: A cell in terms of movement, secretion, enzyme production, or gene expression. Receptors on cell surfaces are sensing components that monitor stimuli and respond to changes in the environment by relaying the signal to a control center for further processing and response. Stimuli are always converted into electrical signals via transduction . This electrical signal, or receptor potential , takes

372-443: A device that displays the change in electrical conductance between two points over time. The two current paths are along the surface of the skin and through the body. Active measuring involves sending a small amount of current through the body. Some studies include the human skin's response to alternating current, including recently deceased bodies. There is a relationship between emotional arousal and sympathetic activity, although

465-436: A fast enough frequency, the depolarization is able to spread across the cell body to the axon hillock . From the axon hillock, an action potential can be generated and propagated down the neuron's axon , causing sodium ion channels in the axon to open as the impulse travels. Once the signal begins to travel down the axon, the membrane potential has already passed threshold , which means that it cannot be stopped. This phenomenon

558-421: A hormone which causes the retention of water in the kidneys. This process also increases an individual's thirst. By fluid retention or by consuming fluids, if an individual's blood pressure returns to normal, vasopressin release slows and less fluid is retained by the kidneys. Hypovolemia , or low fluid levels in the body, can also act as a stimulus to cause this response. Epinephrine , also known as adrenaline,

651-406: A large response and cause neurological changes in the body. Pain also causes a behavioral change in the body, which is proportional to the intensity of the pain. The feeling is recorded by sensory receptors on the skin and travels to the central nervous system , where it is integrated and a decision on how to respond is made; if it is decided that a response must be made, a signal is sent back down to

744-440: A large role in axillary sweating. Apoeccrine glands are sensitive to cholinergic activity, though they can also be activated via adrenergic stimulation. Like eccrine glands, they continuously secrete a thin, watery sweat. Specialized sweat glands, including the ceruminous glands , mammary glands , ciliary glands of the eyelids, and sweat glands of the nasal vestibulum , are modified apocrine glands. Ceruminous glands are near

837-485: A measure of emotional and sympathetic responses. More recent research and additional phenomena ( resistance , potential , impedance , electrochemical skin conductance, and admittance , sometimes responsive and sometimes apparently spontaneous) suggest that EDA is more complex than it seems, and research continues into the source and significance of EDA. In 1849, Dubois-Reymond in Germany first observed that human skin

930-616: A muscle, which behaves appropriately according to the stimulus. The postcentral gyrus is the location of the primary somatosensory area , the main sensory receptive area for the sense of touch . Pain receptors are known as nociceptors . Two main types of nociceptors exist, A-fiber nociceptors and C-fiber nociceptors. A-fiber receptors are myelinated and conduct currents rapidly. They are mainly used to conduct fast and sharp types of pain. Conversely, C-fiber receptors are unmyelinated and slowly transmit. These receptors conduct slow, burning, diffuse pain. The absolute threshold for touch

1023-439: A narrow portion similar to secretory coils in eccrine glands as well as a wide section reminiscent of apocrine glands. Apoeccrine glands, found in the armpits and perianal region, have ducts opening onto the skin surface. They are presumed to have developed in puberty from the eccrine glands, and can comprise up to 50% of all axillary glands. Apoeccrine glands secrete more sweat than both eccrine and apocrine glands, thus playing

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1116-407: A proxy of psychological stress. EDA has also been studied as a method of pain assessment in premature born infants. Often, EDA monitoring is combined with the recording of heart rate, respiratory rate, and blood pressure, because they are all autonomically dependent variables. EDA measurement is one component of modern polygraph devices, which are often used as lie detectors. The E-meter used by

1209-425: A response to a distinct stimulus. EDRs can also appear spontaneously without an observable external stimulus. These types of EDRs are referred to as "nonspecific EDR" (NS.EDR). The phasic EDR is useful when investigating multifaceted attentional processes. Tonic changes (EDL) are based on the phasic parameters. The spontaneous fluctuations of nonspecific EDR can be used to evaluate tonic EDA. More specifically by using

1302-676: A signal causes a reaction or not. Homeostatic outbalances are the main driving force for changes of the body. These stimuli are monitored closely by receptors and sensors in different parts of the body. These sensors are mechanoreceptors , chemoreceptors and thermoreceptors that, respectively, respond to pressure or stretching, chemical changes, or temperature changes. Examples of mechanoreceptors include baroreceptors which detect changes in blood pressure, Merkel's discs which can detect sustained touch and pressure, and hair cells which detect sound stimuli. Homeostatic imbalances that can serve as internal stimuli include nutrient and ion levels in

1395-510: A small sample of the air being inhaled. Olfactory receptors extend past the epithelial surface providing a base for many cilia that lie in the surrounding mucus. Odorant-binding proteins interact with these cilia stimulating the receptors. Odorants are generally small organic molecules. Greater water and lipid solubility is related directly to stronger smelling odorants. Odorant binding to G protein coupled receptors activates adenylate cyclase , which converts ATP to camp. cAMP , in turn, promotes

1488-447: A specific pathway through the nervous system to initiate a systematic response. Each type of receptor is specialized to respond preferentially to only one kind of stimulus energy, called the adequate stimulus . Sensory receptors have a well-defined range of stimuli to which they respond, and each is tuned to the particular needs of the organism. Stimuli are relayed throughout the body by mechanotransduction or chemotransduction, depending on

1581-423: A type of exocrine gland , which are glands that produce and secrete substances onto an epithelial surface by way of a duct . There are two main types of sweat glands that differ in their structure, function, secretory product, mechanism of excretion, anatomic distribution, and distribution across species: Ceruminous glands (which produce ear wax), mammary glands (which produce milk ), and ciliary glands in

1674-456: Is a sensitive psychophysiological index of changes in autonomic sympathetic arousal that are integrated with emotional and cognitive states." Many biofeedback therapy devices utilize EDA as an indicator of the user's stress response with the goal of helping the user to control anxiety. EDA is used to assess an individual's neurological status without using traditional, but uncomfortable and expensive, EEG-based monitoring. It has also been used as

1767-563: Is also influenced by the cellular responses to those same applied or endogenously generated forces. Mechanosensitive ion channels are found in many cell types and it has been shown that the permeability of these channels to cations is affected by stretch receptors and mechanical stimuli. This permeability of ion channels is the basis for the conversion of the mechanical stimulus into an electrical signal. Chemical stimuli, such as odorants, are received by cellular receptors that are often coupled to ion channels responsible for chemotransduction. Such

1860-501: Is also used commonly to respond to both internal and external changes. One common cause of the release of this hormone is the Fight-or-flight response . When the body encounters an external stimulus that is potentially dangerous, epinephrine is released from the adrenal glands . Epinephrine causes physiological changes in the body, such as constriction of blood vessels, dilation of pupils, increased heart and respiratory rate, and

1953-416: Is directly controlled by the hypothalamus . Thermal sweating is stimulated by a combination of internal body temperature and mean skin temperature. In eccrine sweat glands, stimulation occurs via activation by acetylcholine , which binds to the gland's muscarinic receptors . Emotional sweating is stimulated by stress, anxiety, fear, and pain; it is independent of ambient temperature. Acetylcholine acts on

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2046-503: Is embarrassed. EDA is highly responsive to emotions in some people. Fear, anger, startled response, orienting response, and sexual feelings are among the reactions that may be reflected in EDA. These responses are utilized as part of the polygraph or lie detector test. EDA in regular subjects differs according to feelings of being treated fairly or unfairly, but psychopaths have been shown to manifest no such differences. This indicates that

2139-479: Is inhibitory, inhibitory neurotransmitters, normally GABA will be released into the synapse. This neurotransmitter causes an inhibitory postsynaptic potential in the postsynaptic neuron. This response will cause the postsynaptic neuron to become permeable to chloride ions, making the membrane potential of the cell negative; a negative membrane potential makes it more difficult for the cell to fire an action potential and prevents any signal from being passed on through

2232-411: Is known as an all-or-nothing response. Groups of sodium channels opened by the change in membrane potential strengthen the signal as it travels away from the axon hillock, allowing it to move the length of the axon. As the depolarization reaches the end of the axon, or the axon terminal , the end of the neuron becomes permeable to calcium ions, which enters the cell via calcium ion channels. Calcium causes

2325-455: Is mostly water, but it does contain some electrolytes , since it is derived from blood plasma . The presence of sodium chloride gives sweat a salty taste. The total volume of sweat produced depends on the number of functional glands and the size of the surface opening. The degree of secretory activity is regulated by neural and hormonal mechanisms (men sweat more than women). When all of the eccrine sweat glands are working at maximum capacity,

2418-417: Is not under conscious control. Instead, it is modulated autonomously by sympathetic activity which drives human behavior, cognitive and emotional states on a subconscious level. Skin conductance, therefore, offers direct insights into autonomous emotional regulation. Human extremities, including fingers, palms, and soles of feet display different bio-electrical phenomena. They can be detected with an EDA meter,

2511-404: Is often considered to be a single drop of quinine sulfate in 250 gallons of water. Changes in pressure caused by sound reaching the external ear resonate in the tympanic membrane , which articulates with the auditory ossicles, or the bones of the middle ear. These tiny bones multiply these pressure fluctuations as they pass the disturbance into the cochlea, a spiral-shaped bony structure within

2604-507: Is oily, cloudy, viscous, and originally odorless; it gains odor upon decomposition by bacteria. Because both apocrine glands and sebaceous glands open into the hair follicle, apocrine sweat is mixed with sebum . Both apocrine and eccrine sweat glands use merocrine secretion , where vesicles in the gland release sweat via exocytosis , leaving the entire cell intact. It was originally thought that apocrine sweat glands use apocrine secretion due to histological artifacts resembling "blebs" on

2697-424: Is small enough to make sweat hypotonic at the skin surface. Eccrine sweat is clear, odorless, and is composed of 98–99% water; it also contains NaCl , fatty acids , lactic acid , citric acid , ascorbic acid , urea, and uric acid . Its pH ranges from 4 to 6.8. On the other hand, the apocrine sweat has a pH of 6 to 7.5; it contains water, proteins, carbohydrate waste material, lipids, and steroids . The sweat

2790-448: Is the case in olfactory cells . Depolarization in these cells result from opening of non-selective cation channels upon binding of the odorant to the specific receptor. G protein-coupled receptors in the plasma membrane of these cells can initiate second messenger pathways that cause cation channels to open. In response to stimuli, the sensory receptor initiates sensory transduction by creating graded potentials or action potentials in

2883-424: Is the minimum amount of sensation needed to elicit a response from touch receptors. This amount of sensation has a definable value and is often considered to be the force exerted by dropping the wing of a bee onto a person's cheek from a distance of one centimeter. This value will change based on the body part being touched. Vision provides opportunity for the brain to perceive and respond to changes occurring around

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2976-552: The Church of Scientology as part of its practice of " auditing " and " security checking ", is a custom EDA measurement device. External factors such as temperature and humidity affect EDA measurements, which can lead to inconsistent results. Internal factors such as medications and hydration can also change EDA measurements, demonstrating inconsistency with the same stimulus level. Also, the classic understanding has treated EDA as if it represented one homogeneous change in arousal across

3069-409: The central nervous system down neurons until they reach the motor neuron, which releases the neurotransmitter acetylcholine (ACh) into the neuromuscular junction. ACh binds to nicotinic acetylcholine receptors on the surface of the muscle cell and opens ion channels, allowing sodium ions to flow into the cell and potassium ions to flow out; this ion movement causes a depolarization, which allows for

3162-462: The central nervous system . These impulses inhibit the constriction of blood vessels and lower the heart rate. If these nerves do not detect stretching, the body determines perceives low blood pressure as a dangerous stimulus and signals are not sent, preventing the inhibition CNS action; blood vessels constrict and the heart rate increases, causing an increase in blood pressure in the body. Sensory feelings, especially pain, are stimuli that can elicit

3255-443: The cochlea , can interpret and convey to the brain information about equilibrium by a similar method as the one used for hearing. Hair cells in these parts of the ear protrude kinocilia and stereocilia into a gelatinous material that lines the ducts of this canal. In parts of these semi circular canals, specifically the maculae, calcium carbonate crystals known as statoconia rest on the surface of this gelatinous material. When tilting

3348-442: The epidermal ridges . There are no pores between the ridges, though sweat tends to spill into them. The thick epidermis of the palms and soles causes the sweat glands to become spirally coiled. Non-primate mammals have eccrine sweat glands only on the palms and soles. Apocrine glands cover the rest of the body, though they are not as effective as humans' in temperature regulation (with the exception of horses '). Prosimians have

3441-623: The keratin fibrils in the ducts; the ducts then close and form a "horny plug". The main active ingredients in modern antiperspirants are aluminum chloride , aluminum chlorohydrate , aluminum zirconium chlorohydrate, and buffered aluminum sulfate . On apocrine glands, antiperspirants also contain antibacterial agents such as trichlorocarbanilide , hexamethylene tetramine , and zinc ricinoleate . The salts are dissolved in ethanol and mixed with essential oils high in eugenol and thymol (such as thyme and clove oils). Antiperspirants may also contain levomethamphetamine . Some diseases of

3534-454: The occipital lobe of the CNS, specifically in the primary visual cortex . The absolute threshold for vision is the minimum amount of sensation needed to elicit a response from photoreceptors in the eye. This amount of sensation has a definable value and is often considered to be the amount of light present from someone holding up a single candle 30 miles away, if one's eyes were adjusted to

3627-408: The temporal lobe of the CNS, specifically in the primary auditory cortex . The absolute threshold for sound is the minimum amount of sensation needed to elicit a response from receptors in the ears. This amount of sensation has a definable value and is often considered to be a watch ticking in an otherwise soundless environment 20 feet away. Semi circular ducts, which are connected directly to

3720-562: The tongue and through the mouth. Gustatory cells are located on the surface of the tongue and adjacent portions of the pharynx and larynx . Gustatory cells form on taste buds , specialized epithelial cells , and are generally turned over every ten days. From each cell, protrudes microvilli, sometimes called taste hairs, through also the taste pore and into the oral cavity. Dissolved chemicals interact with these receptor cells; different tastes bind to specific receptors. Salt and sour receptors are chemically gated ion channels, which depolarize

3813-419: The EDA record of a polygraph may be deceptive in a criminal investigation. EDA reflects both slow varying tonic sympathetic activity and fast varying phasic sympathetic activity. Tonic activity can be expressed in units of electrodermal level (EDL or SCL), while phasic activity is expressed in units of electrodermal responses (EDR or SCR). Phasic changes (EDR) are short-lasting changes in EDA that appear as

Electrodermal activity - Misplaced Pages Continue

3906-551: The German anatomist Karl Krause. Sweat glands were first separated into kinds by the French histologist Louis-Antoine Ranvier , who separated them in 1887 regarding their type of secretion into holocrine glands ( sebaceous glands ) and the merocrine glands (sweat glands), the latter were then in 1917 divided into apocrine and eccrine sweat glands. In 1987, apoeccrine glands were identified. Eccrine sweat glands are everywhere except

3999-540: The absence of any external stimuli, and he developed a meter to observe the variations as they happened in real time. The scientific study of EDA began in the early 1900s. One of the first references to the use of EDA instruments in psychoanalysis is the book by C. G. Jung entitled Studies in Word Analysis , published in 1906. Jung and his colleagues used the meter to evaluate the emotional sensitivities of patients to lists of words during word association . Jung

4092-584: The acrid odor. Apocrine sweat glands are most active in times of stress and sexual excitement. In mammals (including humans), apocrine sweat contains pheromone -like compounds to attract other organisms within their species. Study of human sweat has revealed differences between men and women in apocrine secretions and bacteria. Some human sweat glands cannot be classified as either apocrine or eccrine, having characteristics of both; such glands are termed apoeccrine . They are larger than eccrine glands, but smaller than apocrine glands. Their secretory portion has

4185-507: The blood, oxygen levels, and water levels. Deviations from the homeostatic ideal may generate a homeostatic emotion , such as pain, thirst or fatigue, that motivates behavior that will restore the body to stasis (such as withdrawal, drinking or resting). Blood pressure, heart rate, and cardiac output are measured by stretch receptors found in the carotid arteries . Nerves embed themselves within these receptors and when they detect stretching, they are stimulated and fire action potentials to

4278-424: 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 . When a stimulus is detected by a sensory receptor, it can elicit a reflex via stimulus transduction . An internal stimulus is often the first component of a homeostatic control system . External stimuli are capable of producing systemic responses throughout

4371-435: The body, as in the fight-or-flight response . In order for a stimulus to be detected with high probability, its level of strength 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

4464-464: The body, but in fact different locations of its measurement can lead to different responses; for example, the responses on the left and right wrists are driven by different regions of the brain, providing multiple sources of arousal; thus, the EDA measured in different places on the body varies not only with different sweat gland density but also with different underlying sources of arousal. Lastly, electrodermal responses are delayed 1–3 seconds. These show

4557-438: The body. Information, or stimuli, in the form of light enters the retina , where it excites a special type of neuron called a photoreceptor cell . A local graded potential begins in the photoreceptor, where it excites the cell enough for the impulse to be passed along through a track of neurons to the central nervous system . As the signal travels from photoreceptors to larger neurons, action potentials must be created for

4650-449: The cell surface, however, recent electron micrographs indicate that the cells use merocrine secretion. In both apocrine and eccrine sweat glands, the sweat is originally produced in the gland's coil, where it is isotonic with the blood plasma there. When the rate of sweating is low, salt is conserved and reabsorbed by the gland's duct; high sweat rates, on the other hand, lead to less salt reabsorption and allow more water to evaporate on

4743-406: The cell. Sweet, bitter, and umami receptors are called gustducins , specialized G protein coupled receptors . Both divisions of receptor cells release neurotransmitters to afferent fibers causing action potential firing. The absolute threshold for taste is the minimum amount of sensation needed to elicit a response from receptors in the mouth. This amount of sensation has a definable value and

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4836-406: The complexity of determining the relationship between EDA and sympathetic activity. The skill of the operator may be a significant factor in the successful application of the tool. Sweat gland Sweat glands , also known as sudoriferous or sudoriparous glands , from Latin sudor  'sweat', are small tubular structures of the skin that produce sweat . Sweat glands are

4929-480: The conductance to vary by several microsiemens . A correctly calibrated device can record and display the subtle changes. The combined changes between electrodermal resistance and electrodermal potential make up electrodermal activity. Galvanic skin resistance (GSR) is an older term that refers to the recorded electrical resistance between two electrodes when a very weak current is steadily passed between them. The electrodes are normally placed about an inch apart, and

5022-509: The dark . Smell allows the body to recognize chemical molecules in the air through inhalation. Olfactory organs located on either side of the nasal septum consist of olfactory epithelium and lamina propria . The olfactory epithelium, which contains olfactory receptor cells, covers the inferior surface of the cribiform plate , the superior portion of the perpendicular plate, the superior nasal concha. Only roughly two percent of airborne compounds inhaled are carried to olfactory organs as

5115-429: The dendrites is known as a local graded potential and causes the membrane voltage to change from a negative resting potential to a more positive voltage, a process known as depolarization . The opening of sodium channels allows nearby sodium channels to open, allowing the change in permeability to spread from the dendrites to the cell body . If a graded potential is strong enough, or if several graded potentials occur in

5208-404: The ear canals, and produce cerumen (earwax) that mixes with the oil secreted from sebaceous glands . Mammary glands use apocrine secretion to produce milk. Sweat glands are used to regulate temperature and remove waste by secreting water, sodium salts , and nitrogenous waste (such as urea) onto the skin surface. The main electrolytes of sweat are sodium and chloride , though the amount

5301-463: The eccrine glands and adrenaline acts on both eccrine and apocrine glands to produce sweat. Emotional sweating can occur anywhere, though it is most evident on the palms, soles of the feet, and axillary regions. Sweating on the palms and soles is thought to have evolved as a fleeing reaction in mammals: it increases friction and prevents slipping when running or climbing in stressful situations. Gustatory sweating refers to thermal sweating induced by

5394-427: The electrical change alone does not identify which specific emotion is being elicited. These autonomic sympathetic changes alter sweat and blood flow, which in turn affects GSR and GSP (Galvanic skin potential). The amount of sweat glands varies across the human body, being highest in hand and foot regions (200–600 sweat glands per cm). The response of the skin and muscle tissue to external and internal stimuli can cause

5487-569: The electrical effect was strongest in the palms of the hands, suggesting that sweat was an important factor. Vigouroux (France, 1879), working with emotionally distressed patients, was the first researcher to relate EDA to psychological activity. In 1888, the French neurologist Féré demonstrated that skin resistance activity could be changed by emotional stimulation and that activity could be inhibited by drugs. In 1889 in Russia, Ivane Tarkhnishvili observed variations in skin electrical potentials in

5580-594: The entire body. Domestic animals have apocrine glands at the base of each hair follicle, but eccrine glands only in foot pads and snout. Their apocrine glands, like those in humans, produce an odorless oily milky secretion evolved not to evaporate and cool but rather coat and stick to hair so odor-causing bacteria can grow on it. Eccrine glands on their foot pads, like those on palms and soles of humans, did not evolve to cool either but rather increase friction and enhance grip. Dogs and cats have apocrine glands that are specialized in both structure and function located at

5673-418: The existence of a bio-electrical charge behind his concept of vegetative, pleasurable "streamings". By 1972, more than 1500 articles on electrodermal activity had been published in professional publications, and today EDA is regarded as the most popular method for investigating human psychophysiological phenomena. As of 2013, EDA monitoring was still on the increase in clinical applications. Skin conductance

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5766-526: The eyelids ( Moll's glands ), ears ( ceruminous glands ), anal sac , clitoral hood , and circumanal area . The pores of eccrine sweat pores were first identified by the Italian physiologist Marcello Malpighi . Sweat glands themselves were first discovered by the Czech physiologist, Johannes Purkinjé in 1833. The differing densities of sweat glands in different body regions was first investigated in 1844 by

5859-492: The eyelids are modified apocrine sweat glands. Generally, sweat glands consist of a secretory unit that produces sweat, and a duct that carries the sweat away. The secretory coil or base, is set deep in the lower dermis and hypodermis , and the entire gland is surrounded by adipose tissue . In both sweat gland types, the secretory coils are surrounded by contractile myoepithelial cells that function to facilitate excretion of secretory product. The secretory activities of

5952-406: The fluid medium that surrounds it causes the cupula itself to move. The ampulla communicates to the brain information about the head's horizontal rotation. Neurons of the adjacent vestibular ganglia monitor the hair cells in these ducts. These sensory fibers form the vestibular branch of the cranial nerve VIII . In general, cellular response to stimuli is defined as a change in state or activity of

6045-464: The frequency of "nonspecific EDR" as an index of EDA during a specific time period, e. g. 30–60 seconds. Tonic EDA is considered useful in investigations of general arousal and alertness. EDA is a common measure of autonomic nervous system activity, with a long history of being used in psychological research. Hugo D. Critchley, Chair of Psychiatry at the Brighton and Sussex Medical School states, "EDA

6138-614: The gland cells and the contractions of myoepithelial cells are controlled by both the autonomic nervous system and by the circulating hormones. The distal or apical part of the duct that opens to the skin's surface is known as the acrosyringium . Each sweat gland receives several nerve fibers that branch out into bands of one or more axons and encircle the individual tubules of the secretory coil. Capillaries are also interwoven among sweat tubules. The number of active sweat glands varies greatly among different people, though comparisons between different areas (ex. axillae vs. groin) show

6231-421: The head or when the body undergoes linear acceleration, these crystals move disturbing the cilia of the hair cells and, consequently, affecting the release of neurotransmitter to be taken up by surrounding sensory nerves. In other areas of the semi circular canal, specifically the ampulla, a structure known as the cupula—analogous to the gelatinous material in the maculae—distorts hair cells in a similar fashion when

6324-409: The incoming nutrients; by starting the digestive process before food reaches the stomach, the body is able to more effectively and efficiently metabolize food into necessary nutrients. Once food hits the mouth, taste and information from receptors in the mouth add to the digestive response. Chemoreceptors and mechanorceptors , activated by chewing and swallowing, further increase the enzyme release in

6417-757: The ingestion of food. The increase in metabolism caused by ingestion raises body temperature, leading to thermal sweating. Hot and spicy foods also lead to mild gustatory sweating in the face, scalp and neck: capsaicin (the compound that makes spicy food taste "hot"), binds to receptors in the mouth that detect warmth. The increased stimulation of such receptors induces a thermoregulatory response. Unlike deodorant , which simply reduces axillary odor without affecting body functions, antiperspirant reduces both eccrine and apocrine sweating. Antiperspirants, which are classified as drugs, cause proteins to precipitate and mechanically block eccrine (and sometimes apocrine) sweat ducts. The metal salts found in antiperspirants alters

6510-404: The inner ear. Hair cells in the cochlear duct, specifically the organ of Corti , are deflected as waves of fluid and membrane motion travel through the chambers of the cochlea. Bipolar sensory neurons located in the center of the cochlea monitor the information from these receptor cells and pass it on to the brainstem via the cochlear branch of cranial nerve VIII . Sound information is processed in

6603-410: The lips, ear canal , foreskin , glans penis , labia minora , clitoral hood , and clitoris . They are ten times smaller than apocrine sweat glands, do not extend as deeply into the dermis, and excrete directly onto the surface of the skin. The proportion of eccrine glands decreases with age. The clear secretion produced by eccrine sweat glands is termed sweat or sensible perspiration . Sweat

6696-567: The metabolism of glucose. All of these responses to a single stimuli aid in protecting the individual, whether the decision is made to stay and fight, or run away and avoid danger. The digestive system can respond to external stimuli, such as the sight or smell of food, and cause physiological changes before the food ever enters the body. This reflex is known as the cephalic phase of digestion . The sight and smell of food are strong enough stimuli to cause salivation, gastric and pancreatic enzyme secretion, and endocrine secretion in preparation for

6789-411: The more explicit interpretation of external stimuli. Effectively, these localized graded potentials trigger action potentials that communicate, in their frequency, along nerve axons eventually arriving in specific cortexes of the brain. In these also highly specialized parts of the brain, these signals are coordinated with others to possibly trigger a new response. If a signal from the presynaptic neuron

6882-432: The nature of the stimulus. In response to a mechanical stimulus, cellular sensors of force are proposed to be extracellular matrix molecules, cytoskeleton, transmembrane proteins, proteins at the membrane-phospholipid interface, elements of the nuclear matrix, chromatin, and the lipid bilayer. Response can be twofold: the extracellular matrix, for example, is a conductor of mechanical forces but its structure and composition

6975-535: The neuron. Depending on the type of stimulus, a neuron can be either excitatory or inhibitory. Nerves in the peripheral nervous system spread out to various parts of the body, including muscle fibers . A muscle fiber and the motor neuron to which it is connected. The spot at which the motor neuron attaches to the muscle fiber is known as the neuromuscular junction . When muscles receive information from internal or external stimuli, muscle fibers are stimulated by their respective motor neuron. Impulses are passed from

7068-461: The opening of sodium channels resulting in a localized potential. The absolute threshold for smell is the minimum amount of sensation needed to elicit a response from receptors in the nose. This amount of sensation has a definable value and is often considered to be a single drop of perfume in a six-room house. This value will change depending on what substance is being smelled. Taste records flavoring of food and other materials that pass across

7161-525: The pancreas and liver can be secreted to aid in metabolism and breakdown of food. Intracellular measurements of electrical potential across the membrane can be obtained by microelectrode recording. Patch clamp techniques allow for the manipulation of the intracellular or extracellular ionic or lipid concentration while still recording potential. In this way, the effect of various conditions on threshold and propagation can be assessed. Positron emission tomography (PET) and magnetic resonance imaging (MRI) permit

7254-458: The rate of perspiration for a human being may exceed three liters per hour, and dangerous losses of fluids and electrolytes can occur. Eccrine glands have three primary functions: Apocrine sweat glands are found in the armpit, areola (around the nipples), perineum (between the anus and genitals), in the ear, and the eyelids. The secretory portion is larger than that of eccrine glands (making them larger overall). Rather than opening directly onto

7347-425: The release of calcium ions within the cell. Calcium ions bind to proteins within the muscle cell to allow for muscle contraction; the ultimate consequence of a stimulus. The endocrine system is affected largely by many internal and external stimuli. One internal stimulus that causes hormone release is blood pressure . Hypotension , or low blood pressure, is a large driving force for the release of vasopressin ,

7440-535: The release of neurotransmitters stored in synaptic vesicles , which enter the synapse between two neurons known as the presynaptic and postsynaptic neurons; if the signal from the presynaptic neuron is excitatory, it will cause the release of an excitatory neurotransmitter, causing a similar response in the postsynaptic neuron. These neurons may communicate with thousands of other receptors and target cells through extensive, complex dendritic networks. Communication between receptors in this fashion enables discrimination and

7533-415: The resistance recorded varies according to the emotional state of the subject. Galvanic skin potential (GSP) refers to the voltage measured between two electrodes without any externally applied current. It is measured by connecting the electrodes to a voltage amplifier. This voltage also varies with the emotional state of the subject. A painful stimulus such as a pinprick elicits a sympathetic response by

7626-402: The same cell or in an adjacent one. Sensitivity to stimuli is obtained by chemical amplification through second messenger pathways in which enzymatic cascades produce large numbers of intermediate products, increasing the effect of one receptor molecule. Though receptors and stimuli are varied, most extrinsic stimuli first generate localized graded potentials in the neurons associated with

7719-437: The same directional changes (certain areas always have more active sweat glands while others always have fewer). According to Henry Gray 's estimates, the palm has around 370 sweat glands per cm ; the back of the hand has 200 per cm ; the forehead has 175 per cm ; the breast, abdomen, and forearm have 155 per cm ; and the back and legs have 60–80 per cm . In the finger pads, sweat glands pores are somewhat irregularly spaced on

7812-399: The signal to have enough strength to reach the CNS. If the stimulus does not warrant a strong enough response, it is said to not reach absolute threshold , and the body does not react. However, if the stimulus is strong enough to create an action potential in neurons away from the photoreceptor, the body will integrate the information and react appropriately. Visual information is processed in

7905-597: The skin (via osmosis ) to increase evaporative cooling . Secretion of sweat occurs when the myoepithelial cell cells surrounding the secretory glands contract. Eccrine sweat increases the rate of bacterial growth and volatilizes the odor compounds of apocrine sweat, strengthening the latter's acrid smell. Normally, only a certain number of sweat glands are actively producing sweat. When stimuli call for more sweating, more sweat glands are activated, with each then producing more sweat. Both eccrine and apocrine sweat glands participate in thermoregulatory sweating, which

7998-421: The specific sensory organ or tissue. In the nervous system , internal and external stimuli can elicit two different categories of responses: an excitatory response, normally in the form of an action potential , and an inhibitory response. When a neuron is stimulated by an excitatory impulse, neuronal dendrites are bound by neurotransmitters which cause the cell to become permeable to a specific type of ion;

8091-405: The stomach and intestine. The digestive system is also able to respond to internal stimuli. The digestive tract, or enteric nervous system alone contains millions of neurons. These neurons act as sensory receptors that can detect changes, such as food entering the small intestine, in the digestive tract. Depending on what these sensory receptors detect, certain enzymes and digestive juices from

8184-408: The surface of the skin, apocrine glands secrete sweat into the pilary canal of the hair follicle . Before puberty, the apocrine sweat glands are inactive; hormonal changes in puberty cause the glands to increase in size and begin functioning. The substance secreted is thicker than eccrine sweat and provides nutrients for bacteria on the skin: the bacteria's decomposition of sweat is what creates

8277-477: The sweat glands include: Sweat gland tumors include: Adenolipomas are lipomas associated with eccrine sweat glands. Many diseases cause sweat gland dysfunction: Stimulus (physiology) In physiology , a stimulus is a change in a living thing's internal or external environment . This change can be detected by an organism or organ using sensitivity, and leads to a physiological reaction. Sensory receptors can receive stimuli from outside

8370-419: The sweat glands, increasing secretion. Although this increase is generally very small, sweat contains water and electrolytes, which increase electrical conductivity, thus lowering the electrical resistance of the skin. These changes in turn affect GSR. Another common manifestation is the vasodilation (dilation) of blood vessels in the face, referred to as blushing, as well as increased sweating that occurs when one

8463-401: The type of neurotransmitter determines to which ion the neurotransmitter will become permeable. In excitatory postsynaptic potentials , an excitatory response is generated. This is caused by an excitatory neurotransmitter, normally glutamate binding to a neuron's dendrites, causing an influx of sodium ions through channels located near the binding site. This change in membrane permeability in

8556-478: Was electrically active. He immersed the limbs of his subjects in a zinc sulfate solution and found that electric current flowed between a limb with muscles contracted and one that was relaxed. He therefore attributed his EDA observations to muscular phenomena. Thirty years later, in 1878 in Switzerland, Hermann and Luchsinger demonstrated a connection between EDA and sweat glands. Hermann later demonstrated that

8649-638: Was so impressed with EDA monitoring, he allegedly cried, "Aha, a looking glass into the unconscious!" Jung described his use of the device in counseling in his book, Studies in Word Association , and such use has continued with various practitioners. The controversial Austrian psychoanalyst Wilhelm Reich also studied EDA in his experiments at the Psychological Institute at the University of Oslo, in 1935 and 1936, to confirm

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