Chemoreceptors
Stimulated by chemicals in solutions.
Olfactory receptors
roof of nasal cavity
Olfactory receptor cells
known as olfactory hairs detect chemicals
olfactory
chemicals must be dissolved in mucus for detection by chemoreceptors
olfactory nerve (cranial nerve I)
Impulses are transmitted via the olfactory filaments to the
olfactory cortex
Smells are interpreted in the
Locations of taste buds
-most on tongue -soft palate -cheeks -superior part of the pharynx
papillae
TASTE BUDS, tongue is covered with projections called
Gustatory cells
taste receptors,
Possess gustatory hairs (long microvilli)
Gustatory hairs protrude through a taste pore
Hairs are stimulated by chemicals dissolved in saliva
Impulses are carried to the gustatory complex by several cranial nerves because taste buds are found in different areas
facial nerve
glossopharyngeal nerve
vagus nerve
taste buds
are replaced frequently by basal cells
sweet receptors
sugars, saccharine, some amino acids
sour receptors
respond to H+ ions or acids
Bitter receptors
alkaloids
Salty receptors
metal ions
Umami receptors
respond to the amino acid glutamate or the beefy taste of meat
Special sense organs
formed early in embryonic development
age 8 to 9
eye continue to grow and mature until
presbyopia
-"old vision" results from decreasing lens elasticity that accompanies aging -Causes difficulty to focus for close vision
presbycusis
type of sensorineural deafness
otosclerosis
ear ossicles fuse
Congenital ear problems
usually result from missing pinnas and closed or missing external acoustic meatuses