Special Senses
A. Taste (gustation)
1. Taste buds – contain the taste receptors
A) Most are located within the papillae of the tongue
B) A few are located in soft palate, cheeks, pharynx, and epiglottis
C) Contain 3 cell types
1) Gustatory cells – receptor cells; have long microvilli projections
a) Bind to chemical particles dissolved in saliva to stimulate taste sensation
2) Supporting cells – most abundant; insulate the receptors cells from each other
3) Basal cells – at the base of the taste bud
2. Papillae
A) Raised bumps on the tongue that house the taste buds & aid in the handling of food
B) 3 types
1) Circumvallate papillae
a) 7 to 12 large, round papillae found on the back of the tongue in a V pattern
b) Taste buds along the sides of each papillae
2) Fungiform papillae
a) Mushroom-shaped papillae scattered over the surface of the tongue
b) Primarily have taste buds on the tops of each papillae
3) Filiform papillae – most common
a) Cone-shaped papillae scattered over the entire tongue surface
b) Have touch receptors rather than taste buds
3. Taste sensations
A) Salty
1) Stimulated by NaCl and other inorganic salts
B) Sweet
1) Stimulated by sugars, alcohols, saccharin, and some amino acids
C) Sour
1) Stimulated by acids
D) Bitter
1) Stimulated by alkaloids such as nicotine and caffeine
E) Umami
1) Responsible for the “beef taste” of steak, tang in aging cheese, and the flavor of
MSG
2) Stimulated by the chemical glutamate
4. Impulse pathway
A) Taste bud (gustatory receptor cell)
1) Gustatory hair
a) Binds to chemical particles dissolved in saliva
b) Generates impulse
B) Facial (VII), glossopharyngeal (IX) or vagus (X) nerves
C) Medulla oblongata
D) Thalamus
, E) Primary gustatory area in parietal lobe
5. Taste is 80% smell; inhibited by blocked olfactory receptors
B. Smell (olfaction)
1. Olfactory epithelium – patch of receptors located on the superior portion of the nasal
cavity; 3 cell types
A) Olfactory receptor cells
1) Bowling-pin shaped cells
2) 10-100 million
3) Contain olfactory cilia that detect chemical particles dissolved in air
4) Synapse with olfactory nerves (I)
B) Supporting cells – surround & insulate the receptor cells
C) Basal cells – line base of olfactory epithelium
2. Impulse pathway
A) Olfactory receptors
1) Olfactory cilia – on dendritic end of receptor cells
a) Binds with chemical particles dissolved in air
b) Generates impulse
B) Olfactory nerves (I)
1) Olfactory bulbs
a) Cell bodies & dendrites of olfactory neurons
2) Olfactory tracts
a) Axons of olfactory neurons
C) Thalamus
D) Lateral olfactory area – temporal lobe
1) Conscious awareness of smell
E) Orbitofrontal area – frontal lobe
1) Identification & discrimination
C. Eye
1. About 2.5cm (1 inch) in diameter; lies in the orbit surrounded by protective fat layer
2. External wall is made up of 3 tunics (layers)
A) Fibrous tunic – outermost layer made up of dense CT; 2 regions
1) Sclera – posterior portion; white portion of the eye
a) Protects & shapes eyeball; provides sturdy anchoring site for extrinsic eye
muscles
2) Cornea – anterior portion
a) Translucent to allow light to pass through
B) Vascular tunic – middle layer of the eyeball; 3 regions
1) Choroid – highly vascular region
2) Ciliary body – thickened ring of tissue surrounding the lens
a) Ciliary muscle – alters shape of the lens to focus light
3) Iris – visible, colored portion of the eye
a) Controls amount of light entering the eye
b) Pupil – opening in the iris
A. Taste (gustation)
1. Taste buds – contain the taste receptors
A) Most are located within the papillae of the tongue
B) A few are located in soft palate, cheeks, pharynx, and epiglottis
C) Contain 3 cell types
1) Gustatory cells – receptor cells; have long microvilli projections
a) Bind to chemical particles dissolved in saliva to stimulate taste sensation
2) Supporting cells – most abundant; insulate the receptors cells from each other
3) Basal cells – at the base of the taste bud
2. Papillae
A) Raised bumps on the tongue that house the taste buds & aid in the handling of food
B) 3 types
1) Circumvallate papillae
a) 7 to 12 large, round papillae found on the back of the tongue in a V pattern
b) Taste buds along the sides of each papillae
2) Fungiform papillae
a) Mushroom-shaped papillae scattered over the surface of the tongue
b) Primarily have taste buds on the tops of each papillae
3) Filiform papillae – most common
a) Cone-shaped papillae scattered over the entire tongue surface
b) Have touch receptors rather than taste buds
3. Taste sensations
A) Salty
1) Stimulated by NaCl and other inorganic salts
B) Sweet
1) Stimulated by sugars, alcohols, saccharin, and some amino acids
C) Sour
1) Stimulated by acids
D) Bitter
1) Stimulated by alkaloids such as nicotine and caffeine
E) Umami
1) Responsible for the “beef taste” of steak, tang in aging cheese, and the flavor of
MSG
2) Stimulated by the chemical glutamate
4. Impulse pathway
A) Taste bud (gustatory receptor cell)
1) Gustatory hair
a) Binds to chemical particles dissolved in saliva
b) Generates impulse
B) Facial (VII), glossopharyngeal (IX) or vagus (X) nerves
C) Medulla oblongata
D) Thalamus
, E) Primary gustatory area in parietal lobe
5. Taste is 80% smell; inhibited by blocked olfactory receptors
B. Smell (olfaction)
1. Olfactory epithelium – patch of receptors located on the superior portion of the nasal
cavity; 3 cell types
A) Olfactory receptor cells
1) Bowling-pin shaped cells
2) 10-100 million
3) Contain olfactory cilia that detect chemical particles dissolved in air
4) Synapse with olfactory nerves (I)
B) Supporting cells – surround & insulate the receptor cells
C) Basal cells – line base of olfactory epithelium
2. Impulse pathway
A) Olfactory receptors
1) Olfactory cilia – on dendritic end of receptor cells
a) Binds with chemical particles dissolved in air
b) Generates impulse
B) Olfactory nerves (I)
1) Olfactory bulbs
a) Cell bodies & dendrites of olfactory neurons
2) Olfactory tracts
a) Axons of olfactory neurons
C) Thalamus
D) Lateral olfactory area – temporal lobe
1) Conscious awareness of smell
E) Orbitofrontal area – frontal lobe
1) Identification & discrimination
C. Eye
1. About 2.5cm (1 inch) in diameter; lies in the orbit surrounded by protective fat layer
2. External wall is made up of 3 tunics (layers)
A) Fibrous tunic – outermost layer made up of dense CT; 2 regions
1) Sclera – posterior portion; white portion of the eye
a) Protects & shapes eyeball; provides sturdy anchoring site for extrinsic eye
muscles
2) Cornea – anterior portion
a) Translucent to allow light to pass through
B) Vascular tunic – middle layer of the eyeball; 3 regions
1) Choroid – highly vascular region
2) Ciliary body – thickened ring of tissue surrounding the lens
a) Ciliary muscle – alters shape of the lens to focus light
3) Iris – visible, colored portion of the eye
a) Controls amount of light entering the eye
b) Pupil – opening in the iris
