NUR112: ANATOMY AND PHYSIOLOGYISU Echague – College of NursingModule 14Special SenseOverview/IntroductionEnvironmental changes are necessary to be sensed by the body for it to adjust. The body isequipped with special senses so that we can sense and respond to these changes. This can be doneby the use of our special sense. In this module, we will look into the basic mechanisms how visual,olfactory, tactile, auditory and tastes are sensed and processed by the body.Course objectives.At the end of this module, you are expected to1.Identify the structure of different special senses2.Discuss the process of impulse transmission from a stimuli until it reaches the brain3.Describe how sensory inputs are received and integrated in the brainCourse Contents.The special senses have highly localized receptors that provide specific information about theenvironment. The five special senses are smell, taste, sight. Touch, hearing and balance.OlfactionOlfactionis also known as sense of smell. The olfactory sensesresponds to airborne molecules called odorants, entering the nasal cavity.Olfactory neuronshave very low thresholds and accommodate rapidly.Olfactory neurons in the olfactory epithelium are bipolar neurons. The distalends have olfactory hairs.Olfactory hairshave receptors that respond todissolved substances. Approximately 1000 different odorant receptors.Receptors activate G proteins, which results in ion channels opening anddepolarizationAxons from the olfactory neurons extend as olfactory nerves to theolfactory bulb, where they synapse with interneurons. Axons frominterneurons form the olfactory tracts, which connect to the olfactory cortex.Olfactory bulbs and cortex accommodate to odors.TasteSensory structures that detect taste stimuli aretaste buds. Most tastebuds are located in the epithelium of papillae. Taste buds are found on theTongue, Palate, Lips and Throat.There are four types of papillae. Three contain taste buds. The fourthand most numerous has no taste buds, but gives the tongue its roughnessTaste buds consist of Taste cells (~50), Basilar cells and Supporting cellsReceptors on the hairs detect dissolved substances. Five basic types of tasteexist.Saltyfor Sodium ions,Sourfor Acids,Sweetfor Sugars, some othercarbohydrates, and some proteins,Bitterfor alkaloids (bases) andUmamiElicited by the amino acid glutamate and related compoundsAll taste buds can sense the five primary tastes, but tend to be most sensitive to one.Sensitivity to bitter substances is the highest (Poisons). Taste is strongly influenced by olfactorysensations. Nasal congestion can dampen the taste sensation. Tongue can detect other stimulibesides taste like Temperature and Texture110
NUR112: ANATOMY AND PHYSIOLOGYISU Echague – College of NursingThefacial nervecarries taste sensations from the anterior two-thirds of the tongue. Theglossopharyngeal nervecarries taste sensations from the posterior one-third of the tongue. Thevagus nervecarries taste sensations from the epiglottis. The neural pathways for taste extend fromthe medulla oblongata to the thalamus and to the cerebral cortexVisual SystemConsists of the eyeball and optic nerve. It also includes the accessory Structures like theeyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles. TheEyebrowsPreventperspiration from entering the eyes and help shade the eyes.
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