1. Special Senses Taste & Smell

2. Chemical Senses: Taste & Smell Chemoreceptors:  Respond to chemicals in a solution. Olfactory receptors are much more sensitive to chemicals than taste but they work together to respond to stimuli

3. Olfactory Receptors and Sense of Smell Olfactory Receptors:  Receptors for sense of smell  Found in an area of the nasal roof in each nasal cavity  Air entering the passageway must pass by them in order to enter the respiratory tract. Olfactory Receptor Cells:  Neurons equipped with olfactory hairs which protrude from the nasal epithelium  They are continually bathed in nasal mucus from the underlying glands.

4. Olfactory Receptors and Sense of Smell Olfactory Nerve:  Impulses come from the olfactory receptor cells and send them to the olfactory cortex in the brain Anosmias:  Olfactory disorder resulting from head/brain damage.  Can also be the after affects of nasal cavity inflammation or aging Olfactory Auras:  Type of hallucination experienced before some epileptics go into seizures.

5. Taste Buds and Sense of taste Taste Buds:  Specific receptors for the sense of taste  Scattered all over the oral cavity  Most of our taste buds are located on the tongue and a few are found on the soft palate and the inner surface of the cheek

6. Taste Buds and Sense of taste Papillae:  Small peg-like formation on the tongues surface.  They are categorized in three ways: Filiform: Sharp Fungiform: rounded Circumvallate: Most common place for taste buds. Circular

7. Taste Buds and Sense of taste Gustatory Cells:  Specific cells which respond to chemicals dissolved in saliva.  They are surrounded by supporting cells in the taste bud Gustatory Hairs: Long microvillae which protrude through the taste pore and when stimulated depolarize sending impulses which are transmitted to the brain. Facial Nerve:  Serves the anterior portion of the tongue

8. 4 Basic Taste Sensations Each taste sensation responds to stimulation of one type of taste bud:  Sweet Receptors: respond to substances like sugar, saccharine and some amino acids.  Sour Receptors: respond to the hydrogen group or the acidity of a solution  Bitter Receptors: respond to alkaloids  Salty Receptors: responds to metal ions in a solution.

9. Developmental Aspects of the Special Senses

10. Developmental Aspects of The Special Senses All special sense organs are complete by birth. Vision is the only sense not fully functional because it takes years of learning.

11. Special Sense Disorders Strabismus:  Cross Eyes  Results from unequal pulls by the external eye muscles preventing the infant from coordinating movement of the two eyes.  Exercises may sometimes fix the problem but surgery may also be necessary Rubella:  Maternal infection that occurs during early pregnancy  Can lead to congenital blindness or cataracts

12. Special Sense Disorders Gonorrhea:  If the mother is infected with Gonorrhea when giving birth the baby will have conjunctivitis at birth Conjunctivitis/Opthalmia Neonatorium:  If the mother is infected with a sexually transmitted disease the baby will be born with red, swollen eyelids which will produce a pus that escapes through the tear ducts.

13. Special Sense Disorders Presbyopia:  “old vision”  Results from decreasing lens elasticity that occurs with age  It is difficult to focus on close objects and as aging progresses the lacrimal glands become less active and eyes are dry and vulnerable to infection. Presbycusis:  Type of sensorinural deafness.  Ear ossicles may fuse and make the hearing condition worse.