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group_3_presentation_1_-_sweating [2018/09/28 17:25] vasavans [Mechanism of Sweating] |
group_3_presentation_1_-_sweating [2018/09/28 22:37] (current) premachu |
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| ====== Sweating ====== | ====== Sweating ====== | ||
| + | <box 60% width centre|> {{ :giphy_1_.gif?nolink |}}</box| Figure 1: Sweating.> | ||
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| - | <box width centre|> {{ :insensible_perspiration.png?nolink&300 |}}</box| Figure #: Insensible perspiration.> | + | <box width centre|> {{ :insensible_perspiration.png?nolink&300 |}}</box| Figure 2: Insensible perspiration.> |
| ==== Thermoregulatory Sweating (Heat/Exercise) ==== | ==== Thermoregulatory Sweating (Heat/Exercise) ==== | ||
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| The reason why some people cannot tolerate spicy food could be because their TRPV1 receptor proteins are more sensitive to capsaicin molecules (Byrnes & Hayes, 2013). Ultimately, they are more likely to feel a burning sensation than those with less sensitive TRPV1 receptors. Another reason could be because individuals are able to build a tolerance to spicy foods/capsaicin molecules. After repeated exposure to capsaicin, individuals would become desensitized and not feel much of a burning sensation compared to those who rarely eat spicy food. | The reason why some people cannot tolerate spicy food could be because their TRPV1 receptor proteins are more sensitive to capsaicin molecules (Byrnes & Hayes, 2013). Ultimately, they are more likely to feel a burning sensation than those with less sensitive TRPV1 receptors. Another reason could be because individuals are able to build a tolerance to spicy foods/capsaicin molecules. After repeated exposure to capsaicin, individuals would become desensitized and not feel much of a burning sensation compared to those who rarely eat spicy food. | ||
| - | <box width centre|> {{ :trpv1.png?nolink&300 |}}</box| Figure #: The stimulation of gustatory sweating due to spicy food.> | + | <box width centre|> {{ :trpv1.png?nolink&300 |}} </box| Figure 3: Stimulation of gustatory sweating due to spicy food.> |
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| First, efferent signals from the pre-optic hypothalamus travel via the tegmentum of the pons and the medullary raphe regions to the intermediolateral cell column of the spinal cord. In the spinal cord, neurons emerge from the ventral horn, pass through the white ramus communicans and then synapse in the sympathetic ganglia. Postganglionic non-myelinated C-fibers pass through the gray ramus communicans, combine with peripheral nerves and travel to sweat glands, with these nerve fibers wrapped around the periglandular tissue of the eccrine sweat gland. | First, efferent signals from the pre-optic hypothalamus travel via the tegmentum of the pons and the medullary raphe regions to the intermediolateral cell column of the spinal cord. In the spinal cord, neurons emerge from the ventral horn, pass through the white ramus communicans and then synapse in the sympathetic ganglia. Postganglionic non-myelinated C-fibers pass through the gray ramus communicans, combine with peripheral nerves and travel to sweat glands, with these nerve fibers wrapped around the periglandular tissue of the eccrine sweat gland. | ||
| The sympathetic nerves distributed to sweat glands consist of large numbers of cholinergic terminals and a few adrenergic terminals. The effect of adrenergic terminals in causing sweating is minimal given that exogenous administration of adrenergic agents will cause only minimal sweating relative to acetylcholine (primary neurotransmitter causing sweating) administration. Administration of atropine (muscarinic cholinergic receptor antagonist) greatly attenuates or eliminates sweating during a resting state or cold temperature environment, confirming the dominance of the cholinergic system and muscarinic receptors in human sweating. | The sympathetic nerves distributed to sweat glands consist of large numbers of cholinergic terminals and a few adrenergic terminals. The effect of adrenergic terminals in causing sweating is minimal given that exogenous administration of adrenergic agents will cause only minimal sweating relative to acetylcholine (primary neurotransmitter causing sweating) administration. Administration of atropine (muscarinic cholinergic receptor antagonist) greatly attenuates or eliminates sweating during a resting state or cold temperature environment, confirming the dominance of the cholinergic system and muscarinic receptors in human sweating. | ||
| - | <box width centre|> {{ :mechanism1.png?direct&300 |}}</box| Figure#. Mechanism of sweating picture at skin surface.> | + | <box width centre|> {{ :mechanism1.png?direct&300 |}}</box| Figure 4. Neural mechanism of sweating from the brain to sweat glands.> |
| In addition to the central neural drive, sweating can also be initiated by an axon reflex. Exogenous administration of acetylcholine not only directly stimulates muscarinic cholinergic receptors on sweat glands, but also activates an axon reflex via stimulation of axonal nicotinic cholinergic receptors. The neural impulse due to the activated axon terminal travels through nerve terminals, resulting in the release of acetylcholine. Acetylcholine released from cholinergic nerves is rapidly hydrolyzed by acetylcholinesterase. Thus, acetylcholinesterase is capable of modulating sweat rate during low to moderate sweating activity. | In addition to the central neural drive, sweating can also be initiated by an axon reflex. Exogenous administration of acetylcholine not only directly stimulates muscarinic cholinergic receptors on sweat glands, but also activates an axon reflex via stimulation of axonal nicotinic cholinergic receptors. The neural impulse due to the activated axon terminal travels through nerve terminals, resulting in the release of acetylcholine. Acetylcholine released from cholinergic nerves is rapidly hydrolyzed by acetylcholinesterase. Thus, acetylcholinesterase is capable of modulating sweat rate during low to moderate sweating activity. | ||
| - | <box width centre|> {{ :mech2.png?direct&300 |}}</box| Figure#. Release of acetylcholine at the level of the postsynaptic neuron.> | + | <box width centre|> {{ :mech2.png?direct&300 |}}</box| Figure 5. Release of acetylcholine at the level of the sweat gland.> |
| The neurotransmitter(s) responsible for active cutaneous vasodilation has yet to be fully understood. However, neuropeptides such as calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), and substance P as well as nitric oxide (NO) have been implicated. All these neurotransmitters except substance P have been shown to increase sweat secretion. Even though acetylcholine is the primary neurotransmitter responsible for sweat secretion, enhanced sweating due to local administration of VIP, CGRP, or NO suggest that these peptides may contribute to the overall modulation of sweating during a thermal challenge as well. | The neurotransmitter(s) responsible for active cutaneous vasodilation has yet to be fully understood. However, neuropeptides such as calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), and substance P as well as nitric oxide (NO) have been implicated. All these neurotransmitters except substance P have been shown to increase sweat secretion. Even though acetylcholine is the primary neurotransmitter responsible for sweat secretion, enhanced sweating due to local administration of VIP, CGRP, or NO suggest that these peptides may contribute to the overall modulation of sweating during a thermal challenge as well. | ||
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| High sweat production occurs during an active state (exercise) or in a warm temperature environment and results in a strong stimulation of the sweat gland. As a result, cells in the interstitial space do not have enough time to reabsorb all the sodium and chloride from the primary secretion in the straight duct. Therefore, a high volume of sweat that is concentrated in Na+ and Cl- and less concentrated in K+ gets secreted. | High sweat production occurs during an active state (exercise) or in a warm temperature environment and results in a strong stimulation of the sweat gland. As a result, cells in the interstitial space do not have enough time to reabsorb all the sodium and chloride from the primary secretion in the straight duct. Therefore, a high volume of sweat that is concentrated in Na+ and Cl- and less concentrated in K+ gets secreted. | ||
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| + | <box width centre|> {{ :1.gif?nolink&300 |}} </box| Figure 6. Movement of water and ions during the production of sweat.> | ||
| Sweat in apocrine sweat glands is produced in the same way. However, the sweat from apocrine glands also contains the proteins and fatty acids from plasma, which makes the secretion thicker and gives it a milkier or yellowish color. This explains why underarm stains in clothing appear yellowish. Sweat itself has no odor, but when bacteria on the skin and hair metabolize the proteins and fatty acids found in sweat from apocrine sweat glands, they produce an unpleasant odor (Freudenrich, 2010). | Sweat in apocrine sweat glands is produced in the same way. However, the sweat from apocrine glands also contains the proteins and fatty acids from plasma, which makes the secretion thicker and gives it a milkier or yellowish color. This explains why underarm stains in clothing appear yellowish. Sweat itself has no odor, but when bacteria on the skin and hair metabolize the proteins and fatty acids found in sweat from apocrine sweat glands, they produce an unpleasant odor (Freudenrich, 2010). | ||
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| - | {{ :ach.png?nolink&300 |}} | + | <box 35% width centre|> {{ :ach.png?nolink&300 |}} </box| Figure 7: Structure of acetylcholine hormone.> |
| ====== Sweating in Animals ====== | ====== Sweating in Animals ====== | ||
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| Cats and dogs sweat in similar ways. The main source of sweating for dogs is panting and having their tongues stick out. By dogs panting, the water evaporates from their tongues, nasal passages and lungs (Goldbaum, 2016). Ultimately, this lowers their overall body temperature. Another way dogs sweat is through their paws. Likewise, cats also sweat through their paws. Although both these animals have sweat glands in their feet, there is a much larger surface area for panting which makes it more efficient (Goldbaum, 2016). | Cats and dogs sweat in similar ways. The main source of sweating for dogs is panting and having their tongues stick out. By dogs panting, the water evaporates from their tongues, nasal passages and lungs (Goldbaum, 2016). Ultimately, this lowers their overall body temperature. Another way dogs sweat is through their paws. Likewise, cats also sweat through their paws. Although both these animals have sweat glands in their feet, there is a much larger surface area for panting which makes it more efficient (Goldbaum, 2016). | ||
| - | {{ :cat.jpg?nolink&300 |}} | + | <box 35% width centre|> {{ :cat-paw-reading.jpg?nolink&300 |}} </box| Figure 8: Cat paws that contain sweat glands.> |
| - | ==== Horses ==== | + | |
| - | The sweat of horses contain a chemical called latherin. This chemical is a natural detergent and functions to lather the body (Vance et al., 2013). According to researcher Malcolm Kennedy of the University of Gaslow, latherin's original function was found to be protein in saliva that helps with the breakdown of fibrous foods (Vance et al., 2013). However, eventually this chemical evolved to be expired during sweat. When this type of sweat is secreted in a horse, it spreads across the pelt to lower it's body temperature (Vance et al., 2013). | + | |
| - | {{ :horse.jpg?nolink&300 |}} | + | ==== Horses ==== |
| + | The sweat of horses contains a chemical called latherin. This chemical is a natural detergent and functions to lather the body (Vance et al., 2013). According to researcher Malcolm Kennedy of the University of Gaslow, latherin's original function was found to be protein in saliva that helps with the breakdown of fibrous foods (Vance et al., 2013). Eventually, this chemical evolved to be expired during sweat. When this type of sweat is secreted in a horse, it spreads across the pelt to lower its body temperature (Vance et al., 2013). | ||
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| + | <box 35% width centre|> {{ :horse_sweat.jpg?nolink&300 |}} </box| Figure 9: Horse sweat which contains latherin (white substance).> | ||
| ==== Hippos ==== | ==== Hippos ==== | ||
| The sweat of hippos is a red oily substance. This substance prevents damage caused by the sun and helps cool them off (Seeker, 2016). | The sweat of hippos is a red oily substance. This substance prevents damage caused by the sun and helps cool them off (Seeker, 2016). | ||
| - | {{ :hippo-face-web620.jpg?nolink&300 |}} | + | <box 35% width centre|> {{ :hippo_sweat.jpg?nolink&300 |}} </box| Figure 10: The red colour of hippos indicate their sweat.> |
| ====== Treatments for Excessive Sweating ====== | ====== Treatments for Excessive Sweating ====== | ||
