Chapter 16 Special Senses

a. fast pain - deep cuts, etc. - referred immediately toprimary sensory cortex, usually trigger reflexesb. slow pain - later, persistent, indistinct source, thalamicc. referred pain - visceral, "incorrect" source perceived2. thermoreceptors - detect heat or absence thereof, phasic,same pathways as pain3. mechanoreceptors - stimulated by anything moving orphysical perturbation.a. tactile receptors - touch, pressure, vibrationi. encapsulated receptorsa) Meissners corpuscles - fine touchb) Pacinian corpuscles - deep pressurec) Ruffini corpuscles - tension, crude touchii. unencapsulated receptorsa) free nerve endings - painb) Merkels discs - fine touchc) root hair plexes - hair movementb. baroreceptors are sensitive to internal pressures bloodpressure, lung stretch, digestive tract tensionc. proprioceptors are kinesthetic monitors of tendon musclestretch.4. chemoreceptors - respond to specific chemicals either insolution (taste) or volatilized (smell) or internally inmonitoring blood composition. Internal chemoreceptors monitorblood composition - Na+, pH, osmolarity, etc.III. Special sensesA. Olfaction (Smell)distant chemical sense, many chemicals can be detected at a distance aslong as they are gaseous.1. receptors -sensory epithelium, olfactory receptors and glands,supporting cells and basal cells - covers superior nasal conchaeand septum.2. olfactory pathways - receptor neurons pass into the craniumthrough the cribiform plate and synapse in the olfactory bulbs.These olfactory neurons are unique in that they are the only onesknown to routinely replace themselves or to reach the cerebrumwithout synapsing in the thalamus.3. olfactory discrimination - Although difficult to describe, thenumber of different odors recognizable is immense.B. Gustation (Taste) - taste is chemical also but requires that thedissolved chemicals make contact with the tongue or mouth.1. gustatory receptors - gustatory chemoreceptors on thesides of taste buds. Taste buds are incorporated in thepapillae which are described by their shapes,a. filiform - thin, thread like projectionsb. fungiform - shaped like mushrooms.2