Transcript Nerve activates contraction - Silver Falls School District

Chapter 8
Special Senses –
Chemoreceptors:
Taste & Smell
Chemical Senses – Taste & Smell
 Both senses use
chemoreceptors
- Stimulated by chemicals in
solution
- Taste - 5 types of receptors
- Smell - large range of
chemicals
 Both senses complement
each other and respond to
many of the same stimuli
Smell
Olfaction – The Sense of Smell
 Olfactory receptors are in roof
of the nasal cavity
- Neurons with long cilia
- Chemicals must be dissolved in
mucus for detection
 Impulses are transmitted via
the olfactory nerve
 Interpretation of smells is made
in the cortex
Olfactory Epithelium
Taste
The Tongue and Taste
 The tongue is covered
with projections called
papillae
- Filiform – pointy with no
taste buds
- Fungifiorm – rounded with
taste buds
- Circumvallate – large with
taste buds
 Taste buds are found on
the sides of papillae
The Sense of Taste
 Taste buds
house the
receptor
organs
 Location of
taste buds
- Most are on
tongue
- Soft palate
- Cheeks
Structure of Taste Buds
 Gustatory cells are the receptors
- Hairs stimulated by chemicals dissolved in saliva
 1 taste bud = cluster of 100 specialized cells few exposed at
a time.
 Taste bud lifespan is about 10 days
Cranial Taste Nerves
Impulses carried to
the gustatory
complex by several
cranial nerves
because taste buds
are found in
different areas
 Facial nerve
 Glossopharyngeal
nerve
 Vagus nerve
Taste Sensations
1. Sweet receptors (-OH groups)
 Sugars
 Saccharine
 Some amino acids
2. Sour receptors
 Acids
3. Bitter receptors
 Alkaloids
4. Salty receptors
 Metal ions
5. Umami receptors (meaty/savory)
 Glutamate
Developmental Aspects
 Formed early in
embryonic development
 All special senses are
functional at birth, but
vision isn’t fully developed.
- Eyes are outgrowths of brain,
born ½ size; grow mostly 1st yr &
until puberty
- Baby’s focal length is ~9”.
- Reaches 20’ by age 3.