6.3 Sense of Smell and Taste PDF

 RNB10702 ANATOMY AND PHYSIOLOGY 2 THE SPECIAL SENSE 1. Receptor & Sensation 2. General Sense 3. Gustatory Sense 4. Sense of Smell  LEARNING OUTCOMES At the end of the session, the students should be able to: distinguish between general sense and special...

 RNB10702 ANATOMY AND PHYSIOLOGY 2 THE SPECIAL SENSE 1. Receptor & Sensation 2. General Sense 3. Gustatory Sense 4. Sense of Smell  LEARNING OUTCOMES At the end of the session, the students should be able to: distinguish between general sense and special sense classify five group of sense receptors briefly describe the anatomy of taste buds and locate the four different taste sensation describe the pathway of gustation (taste) from stimulus to cerebral cortex locate the sense receptors for smell and trace the pathway to the cerebral cortex  INTRODUCTION Sense perception depends on sensory receptors that respond to various stimuli General sense are widely distributed all over the body such as pain, touch, pressure, temperature & proprioception Special sense such as taste, smell, hearing & sight are special as their receptors are localized in a particular area  RECEPTORS & SENSATION There are 5 types of receptors – Chemoreceptors Mechanoreceptors Nociceptors Thermoreceptors Photoreceptors Perceived sensation occurs only after impulses are interpret by the brain  RECEPTORS & SENSATION (cont..) Step involved in sensory perception: There must be a stimulus A receptor must detect the stimulus and create an action potential The action potential (impulse) must be conducted to the CNS Within the CNS, the impulse must be translated into information Information must be interpreted in the CNS into an awareness or perception of the stimulus.  TYPE OF SENSE RECEPTORS Receptors Stimulus Example Chemoreceptors Changes in Taste & smell chemical concentration of substance Mechanoreceptors Changes in Proprioceptors in pressure or joint, receptors for movement in fluids hearing & equilibrium Nociceptors Tissue damage Pain receptors Thermoreceptors Changes in Heat & cold temperature Photoreceptors Light energy Vision  GENERAL SENSE General sense or somatic sense are those that are found throughout the body Associated with the visceral organ as well as skin, muscle & joints & include the following:  Touch  Pressure  Proprioception  Temperature  Pain  1. TOUCH & PRESSURE The receptors for touch & pressure are mechanoreceptors Widely distributed in the skin Receptors involved in touch & pressure are free nerve endings, Meissner’s corpuscles & pacinian corpuscles  2. PROPRIOCEPTION It is the sense of position or orientation Allow us to sense the location & rate of movement of one body part to another The receptors are mechanoreceptors  Golgi tendon organs – found at junction of a tendon with muscle  Muscle spindles – located in skeletal muscle  3. TEMPERATURE Temperature changes are detected by thermoreceptor which are free nerve endings. Thermoreceptors located immediately under the skin - It is sensitive to heat, cold Extreme temperature also stimulate pain receptors  4. PAIN Receptors for pain is called nociceptors It is free nerve endings that are stimulated by tissue damage GUSTATORY SENSE  GUSTATORY SENSE (cont..) Organ of taste is taste buds – located on the wall of papillae on the surface of the tongue Receptors for taste are chemoreceptors that located in the taste bud – sensitive to chemical in the food we eat  GUSTATORY SENSE (cont..) Taste bud contain the taste cells & supporting cell Taste hair on the taste cells (gustatory cell)act as the receptors 4 taste sensation - sour, sweet, bitter, and salty THE PHYSIOLOGY OF GUSTATION 3 cranial nerves involved in gustation The facial (VII) nerve serves taste buds in the anterior 2/3 of the tongue The glossopharyngeal (IX) nerve serves taste buds in the posterior 1/3 of the tongue The vagus (X) nerve serves taste buds in the throat and epiglottis  THE PHYSIOLOGY OF GUSTATION (cont..) When the microvilli (taste hair) are stimulated by chemical in the food we eat (dissolve in the saliva), an impulse is triggered on a nearby nerve fiber Impulse from the anterior 2/3 of the tongue travel along the facial nerve (cranial nerve Vll) & those from the posterior 1/3 travel along the glossopharyngeal nerve (CN lX) to the medulla oblongata From medulla oblongata they travel to the thalamus, the sensory cortex on the parietal lobe of the brain Vagus (x) nerve  RECAP/QUIZ Name the 4 primary taste sensations. Sour, sweet, bitter and salty Name the 3 cranial nerves related to taste buds. Facial (VII) nerve, glossopharyngeal (IX) nerve, vagus (X) nerve Name the cranial nerve that detect the taste in the throat and epiglottis? Vagus (X) nerve THE SENSE OF SMELL  THE SENSE OF SMELL (cont..) The sense of smell is called olfaction The receptors for sense of smell are chemoreceptor The receptor are located in the olfactory epithelium of the nasal cavity  PHYSIOLOGY OF OLFACTORY SENSE Olfactory receptors are stimulated by chemicals dissolve in liquid Air bone molecules responsible for odors dissolve in liquid on the surface of olfactory epithelium & then bind to receptors & trigger impulses  PHYSIOLOGY OF OLFACTORY SENSE (cont..) The olfactory neuron enter the olfactory bulb Impulses are transmitted along the olfactory tracts to the olfactory cortex in the temporal lobe The sense of smell and taste are closely related & complement each other THE OLFACTION PATHWAY