A chemosensor, also known as chemoreceptor, is a sensory receptor that transduces a chemical signal into an action potential. In a Sensory system, a sensory receptor is a structure that recognizes a stimulus in the internal or external environment of an Organism. In Physiology, transduction is the conversion of a stimulus from one form to another In Neurophysiology, the action potential is a self-regenerating Wave of Electrochemical activity that allows Nerve cells to carry a signal Or, more generally, a chemosensor detects certain chemical stimuli in the environment.
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Classes
There are two main classes of the chemosensor: direct and distance.
- Examples of distance chemoreceptors are:
- olfactory receptor neurons in the olfactory system
- neurons in the vomeronasal organ that detect pheromones
- Examples of direct chemoreceptors include
- taste buds in the gustatory system
- carotid bodies and aortic bodies that detect changes in pH inside the body. An olfactory receptor neuron also called an olfactory sensory neuron is the primary transduction cell in the Olfactory system. The Olfactory helps and relates sense of smell. The olfactory system is the Sensory system used for Olfaction. The vomeronasal organ ( VNO) or Jacobson's organ, is an auxiliary Olfactory Sense organ that is found in many Animals It was A pheromone (from Greek φέρω phero "to bear" + ‘ορμόνη " Hormone " is a Chemical that triggers a natural Taste buds are small structures on the upper surface of the Tongue, Soft palate, upper Esophagus and Epiglottis that provide information about The gustatory system is the Sensory system for the sense of Taste. The carotid body ( Carotid glomus or Glomus caroticum) is a small cluster of Chemoreceptors and supporting cells located near the fork ( Bifurcation pH is the measure of the acidity or alkalinity of a Solution.
Systems affected
Breathing rate
Chemoreceptors detect the levels of carbon dioxide in the blood. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single To do this, they monitor the concentration of hydrogen ions in the blood, which decreases the pH of the blood. Hydrogen ion is recommended by IUPAC as a general term for all Ions of Hydrogen and its Isotopes Depending on the Charge of the ion pH is the measure of the acidity or alkalinity of a Solution. This is a direct consequence of an increase in carbon dioxide concentration, because carbon dioxide becomes carbonic acid in an aqueous environment.
The response is that the inspiratory centre (in the medulla), sends nervous impulses to the external intercostal muscles and the diaphragm, via the intercostal nerve and the phrenic nerve, respectively, to increase breathing rate and the volume of the lungs during inhalation. In Neurophysiology, the action potential is a self-regenerating Wave of Electrochemical activity that allows Nerve cells to carry a signal Intercostal muscles are several groups of Muscles that run between the Ribs, and help form and move the Chest wall. For other types of diaphragm see Diaphragm. In the Anatomy of Mammals the thoracic diaphragm is a sheet of Muscle The intercostal nerves are the anterior divisions (rami anteriores ventral divisions of the Thoracic spinal nerves from T1 to T11 The phrenic nerve arises from the third fourth and fifth cervical Spinal nerves (C3-C5 in Humans.
Chemoreceptors which affect breathing rate are broken down into two categories.
- central chemoreceptors are located on the ventrolateral surface of medulla oblongata and detect changes in pH of cerebrospinal fluid. Central chemoreceptors of the central nervous system located on the ventrolateral Medullary surface are sensitive to the PH of their environment The medulla oblongata is the lower portion of the Brainstem. It deals with autonomic functions such as breathing and blood pressure They do not respond to a drop in oxygen, and eventually desensitize.
- peripheral chemoreceptors: Aortic body detects changes in blood oxygen and carbon dioxide, but not pH, while carotid body detects all three. Peripheral chemoreceptors act most importantly to detect variation of the Oxygen in the Arterial blood, in addition to detecting arterial Carbon dioxide The carotid body ( Carotid glomus or Glomus caroticum) is a small cluster of Chemoreceptors and supporting cells located near the fork ( Bifurcation They do not desensitize. Their effect on breathing rate is less than that of the central chemoreceptors.
Heart rate
Chemoreceptors in the medulla oblongata, carotid arteries and aortic arch, detect the levels of carbon dioxide in the blood, in the same way as applicable in the Breathing Rate section. The medulla oblongata is the lower portion of the Brainstem. It deals with autonomic functions such as breathing and blood pressure In Human anatomy, the common carotid artery is an Artery that supplies the head and neck with Oxygenated blood; it divides in the neck to form the Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single
In response to this high concentration, a nervous impulse is sent to the cardiovascular centre in the medulla, which will then feedback to the sympathetic ganglia, increasing nervous impulses here, and prompting the sinoatrial node to stimulate more contractions of the myogenic cardiac muscle increasing heart rate by causing the secretion of nor-adrenaline directly on to the sinoatrial node. The cardiovascular centre is a part of the human Brain responsible for the regulation of the rate at which the Heart beats The medulla oblongata is the lower portion of the Brainstem. It deals with autonomic functions such as breathing and blood pressure Sympathetic ganglia are the ganglia of the Sympathetic nervous system. The Sinoatrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker tissue located in the Right atrium The cardiac muscle is a type of involuntary striated Muscle found in the walls of the Heart. The Sinoatrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker tissue located in the Right atrium
Sense organs
In taste sensation, the tongue is composed of 5 different taste buds: salty, sour, sweet, bitter, and savory. Taste (or more formally gustation) is a form of direct Chemoreception and is one of the traditional five Senses is one of the five Basic tastes sensed by specialized receptor cells present on the human Tongue. The salty and sour tastes work directly through the ion channels, the sweet and bitter taste work through G protein-coupled receptors, and the savoury sensation is activated by glutamate. G protein-coupled receptors ( GPCRs) also known as seven transmembrane domain receptors, 7TM receptors, heptahelical receptors, and Glutamic acid (abbreviated as Glu or E) is one of the 20 Alpha Amino acids It is not among the human Essential amino acids Its
Noses in vertebrates and antennae in many invertebrates act as distance chemoreceptors. Anatomically a nose is a protuberance in Vertebrates that houses the Nostrils or nares which admit and expel air for respiration in conjunction with the Antennae (singular antenna) are paired Appendages connected to the front-most segments of Arthropods In Crustaceans they are Molecules diffused through the air and bind to specific receptors on olfactory sensory neurons, activating an opening ion channel via G-proteins.
When inputs from the environment are significant to the survival of the organism the input must be detected. As all life processes are ultimately based on chemistry it is natural that detection and passing on of the external input will involve chemical events. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties The chemistry of the environment is, of course, relevant to survival, and detection of chemical input from the outside may well articulate directly with cell chemicals.
For example: The emissions of a predator's food source, such as odors or pheromones, may be in the air or on a surface where the food source has been. A pheromone (from Greek φέρω phero "to bear" + ‘ορμόνη " Hormone " is a Chemical that triggers a natural Cells in the head, usually the air passages or mouth, have chemical receptors on their surface that change when in contact with the emissions. The change does not stop there. It passes in either chemical or electrochemical form to the central processor, the brain or spinal cord. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain The spinal cord is a long thin tubular bundle of Nerves that is an extension of the Central nervous system from the brain and is enclosed in and protected The resulting output from the CNS (central nervous system) makes body actions that will engage the food and enhance survival. In Vertebrates the central nervous system ( CNS) is the part of the Nervous system which is enclosed in the Meninges.
SAW Chemosensor
SAW Chemosensor [1] (Surface Acoustic Wave Chemosensor) is used to analyse gases.
See also
- Sensory receptor
- Molecular sensor
- Chemosensory clusters
- Diffuse chemosensory system
- Solitary chemosensory cells
References
External links
- MeSH Chemoreceptors
- chemoreceptor at eMedicine Dictionary
- c_25/12231846 at Dorland's Medical Dictionary
- c_25/12231874 at Dorland's Medical Dictionary
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