Sensory systems smell

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. 

Central nervous system and neuromuscular junction. A remarkable number of alkaloids interfere with the metabolism and activity of neurotransmitters in the brain and nerve cells, a fact known to man for a thousand years (Table IV). The cellular interactions have been discussed above. Disturbance of neurotransmitter metabolism impairs sensory faculties, smell, vision, or hearing, or they may produce euphoric or hallucinogenic effects. 

Effects observed in humans following neurotoxic exposure include modification of motor and sensory activities, emotional states, integrative capabilities such as learning and memory, adverse effects on sensory systems (including sight, hearing, smell, touch, and pain sensation), behavior modification, sleep loss, speech impairment, delirium, hallucinations, convulsions, and deaths1-4 ... 

Smell, taste, vision, hearing, and touch are based on signal-transduction pathways activated by signals from the environment. These sensory systems function similarly to the signal-transduction pathways for many hormones. "These intercellular signaling pathways appear to have been appropriated and modified to process environmental information. 

In this chapter, we shall focus on the five major sensory systems found in human beings and other mammals olfaction (the sense of smell i.e., the detection of small molecules in the air), taste or gustation (the detection of selected organic compounds and ions by the tongue), vision (the detection of light), hearing (the detection of sound, or... 

Nature uses chemical signalling in sensory systems snch as taste and smell. The most important means for information processing in nature is based on information exchange between DNA and RNA our brain use signals relying on the behaviour of ions, etc. This... 

Schiffman, S. S. Changes in taste and smell with age Psychophysical aspects. In J. M. Ordy K. R. Brizzee, Eds., "Sensory Systems and Communication in the Elderly," (Vol. 6). Raven Press New York, 1979 pp. 227-246. 

Fibers from these olfactory sense cells which are present in the olfactory epithelium, enter the olfactory bulbs. In contrast to the absence of differentiated organs in other sensory systems, the differentiation of the olfactory system at hatching suggests that in monotremes as in marsupials, sense of smell plays a part in location of the maternal teat (Griffiths, 1978). 

Sensory systems Olfaction Zinc nasal sprays can cause loss of the sense of smell in animals and humans, and the FDA has warned consumers and healthcare professionals to stop using zinc-containing nasal products sold over-the-counter as cold remedies (Zicam Nasal Gel and Nasal Swab), because they are associated with long-lasting or permanent loss of the sense of smell [99 ]. The FDA has received over 130 reports of anosmia associated with the use of these products. Many have stated that loss of the sense of smell occurred with the first dose of the product, while others have reported that it happened after later doses. According to the FDA, these products have not been shown to be effective in reducing the duration or severity of cold symptoms. This advice does not relate to oral zinc tablets and lozenges. 

Sensory systems Olfaction Alterations in taste and smell function, which are rare, have been reported for pyrazinamide when combined with other drugs. Reversible olfactory... 

Taste-active chemicals react with receptors on the surface of sensory cells in the papillae causing electrical depolarization, ie, drop in the voltage across the sensory cell membrane. The collection of biochemical events that are involved in this process is called transduction (15,16). Not all the chemical steps involved in transduction are known however, it is clear that different transduction mechanisms are involved in different taste quaUties different transduction mechanisms exist for the same chemical in different species (15). Thus the specificity of chemosensory processes, ie, taste and smell, to different chemicals is caused by differences in the sensory cell membrane, the transduction mechanisms, and the central nervous system (14). 

Motion sickness is caused by stimulation of the vestibular system. This area contains many histaminic (Hj) and muscarinic cholinergic receptors. The higher brain (i.e., cerebral cortex) is affected by sensory input such as sights, smells, or emotions that can lead to vomiting. This area is involved in anticipatory nausea and vomiting associated with chemotherapy. 

Sensations interpreted as pain, including burning, aching, stinging, and soreness, are the most distinctive forms of sensory input to the central nervous system. Pain serves an important protective function because it causes awareness of actual or potential tissue damage. Furthermore, it stimulates an individual to react to remove or withdraw from the source of the pain. Unlike other forms of sensory input, such as vision, hearing, and smell, pain... 

Sensation provides the input to the system. The sources of sensory information can be outside your body through one of the five primary senses sight, sound, taste, smell, and touch. The source of information can also be inside your body. The nervous system receives and monitors information such as your blood pressure, blood sugar, and blood oxygen level. 

The perception of flavor is a fine balance between the sensory input of both desirable and undesirable flavors. It involves a complex series of biochemical and physiological reactions that occur at the cellular and subcellular level (see Chapters 1-3). Final sensory perception or response to the food is regulated by the action and interaction of flavor compounds and their products on two neur networks, the olfactory and gustatory systems or the smell and taste systems, respectively (Figure 1). The major food flavor components involved in the initiation and transduction of the flavor response are the food s lipids, carbohydrates, and proteins, as well as their reaction products. Since proteins and peptides of meat constitute the major chemical components of muscle foods, they will be the major focus of discussion in this chapter. 

T o properly recognize the smell of a particular molecule, each sensory neuron should express a single odorant receptor and respond to an appropriate range of odorants with similar molecular characteristics. This presumption (one receptor-one olfactory neuron rule) was deemed acceptable for quite some time but did not have a firm experimental basis until recently when it was demonstrated in the olfactory system of mice.206... 

Sensory neurons transduce physical stimuli, such as smell, light, or sound, into action potentials, which are then transmitted to the spinal cord or brain. Sensory neurons, which bring information into the central nervous system, are also referred to as afferent neurons. Motor neurons transmit nerve impulses away from the brain and spinal cord to muscles or glands and are also called efferent neurons. Intemeurons transmit nerve impulses between sensory neurons and the motor neurons. Interneurons are responsible for receiving, relaying, integrating, and sending nerve impulses. Intemeurons are found exclusively in the central nervous system and account for almost 99% of all the nerve cells in the body. 

Uses.—It is necessary to distinguish clearly between the local and systemic effects of cocaine. When locally applied cocaine is a paralyzant to the peripheral ends of the sensory nerves, and to a lesser degree to the motor nerves, and stimulating to the muscular coats of the blood vessels. As a result of these actions when painted over mucous membranes it causes blanching of the part and diminished sensation. It produces not only lessened serisibility to pain and touch but also of the acuity of the special senses, thus it diminishes in the mouth the power of taste and in the nose that of smell. 

The nervous system is comprised of the brain, spinal cord, sensory organs, and a vast array of nerves that control thought, movement, heart function, respiration, vision, hearing, speech, smell, touch, and many other physiological functions. The nervous system is readily attacked by toxic chemicals for the following reasons ... 

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