Sensory system receptors

Thus the neurotransmitter role of ATP is well established in the periphary and also in sensory systems but its importance in the CNS remains to be elucidated (see Burnstock 1996). That requires the development of more specific antagonists and methods of mapping its location. The strong linkage of its P2x receptors to calcium currents may also provide a role for ATP in more long-term effects such as plasticity and neuronal development and death. 

Olfaction, once thought to be a primitive sense, is now recognized as an elaborate sensory system that deploys a large family of odorant receptors to analyse the chemical environment. Interactions between these receptors and their diverse natural binding molecules (ligands) translate the world of odors into a neural code. Humans have about 350 odorant receptors. Rodents have more than a thousand. 

The EEG does have some disadvantages, or, more correctly, some limitations. It cannot provide information about the effects of toxicants on the integrity of sensory receptors or of sensory or motor pathways. As a corollary, it cannot provide an assessment of the effects of toxicants on sensory system capacities. Finally, the EEG does not provide specific information at the cellular level and therefore lacks the rigor to provide detailed mechanisms of action. 

Jason Kindrachuk is a postdoctoral fellow at the University of British Columbia (UBC) in the laboratory of Professor R. E. W. Hancock. Jason received his Ph.D. from the University of Saskatchewan in 2007 where his research focused on host and pathogen sensory systems. During his study he specially focused on TLR-9 receptor—ligand interactions and the interactions between host defense peptides and the PhoPQ two-component sensory system of Salmonella typhimurium. In 2008 Jason received the Canadian Cystic Fibrosis Foundation Kin Canada Fellowship for his research in the area of alternative therapies for treatment of antibiotic- and multidrug-resistant bacteria. Currently his research is focused on the investigation of structure-activity relationships amongst natural and synthetic host defense peptides from the perspective of associated immunomodulatory activities and as well as vaccine formulation strategies. 

Bacteria and unicellular eukaryotes have a variety of sensory systems that allow them to sample and respond to their environment. In the two-component system, a receptor His kinase senses the signal and autophosphory-lates a His residue, then phosphorylates the response regulator on an Asp residue. 

Vertebrates possess three primary chemosensory systems gustation ( taste ), trigeminal, and olfaction ( smell ) but only one of these, the olfactory system, mediates responses to pheromones. Chemicals that stimulate the olfactory system are known as odorants and comprise one type of biological cue (any entity that stimulates a sensory system). Bouquets of odorants that can be discriminated as specific entities are termed odors. The olfactory system contains olfactory receptor neurons (ORNs) that comprise cranial nerve I and project directly to the forebrain. ORNs are now known to express only one to a few olfactory receptor proteins ( receptors ), which means that the chemoreceptive range of each neuron can be very narrow. The olfactory system also has several subcomponents including the vomeronasal organ, which is described below. 

Animations in this media module show how 7TM receptors and G proteins are employed in two sensory-system signaling pathways. 

How do our sensory systems work How are the initial stimuli detected How are these initial biochemical events transformed into perceptions and experiences We have previously encountered systems that sense and respond to chemical signals—namely, receptors that bind to growth factors and hormones. Our knowledge of these receptors and their associated signal-transduction pathways provides us with concepts and tools for unraveling some of the workings of sensory systems. For example, 7TM receptors (seven-transmembrane receptors, Section 15.1) play key roles in olfaction,... 

Two ears. Our ability to determine the direction from which a sound is coming is partly based on the difference in time at which our two ears detect the sound. Given the speed of sound (350 meter/second) and the separation between our ears (0.15 meter), what difference is expected in the times at which a sound arrives at our two ears How does this difference compare with the time resolution of the human hearing system Would a sensory system that utilized 7TM receptors and G proteins be capable of adequate time resolution ... 

Butenandt A et al (1959) N-Acetyl tyramine, its isolation from Bombyx cocoons and its chemical and biological properties. Arch Biochem Biophys 83 76-83 Cayirlioglu P et al (2008) Hybrid neurons in a microRNA mutant are putative evolutionary intermediates in insect C02 sensory system. Science 319 1256-1260 Clyne PJ et al (1999) A novel family of divergent seven-transmembrane proteins candidate odorant receptors in Drosophila. Neuron 22 327-338... 

However, the solution of these fundamental problems will not bring a complete understanding of the olfactory code any more than the elucidation of retinal receptor transduction events has been able to clarify the neural mechanisms that underlie visual perception. The ORN is but the first element in a complex neural network. The operations of central olfactory networks are also poorly understood and the anatomical organization of the olfactory system appears in some respects to be fundamentally different from the familiar topographically organized circuits of the other major sensory systems. Thus, much remains to be discovered before we will approach the kind of understanding we currently have of visual, auditory and somatosensory neural network function. 

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