17 1 Smell Olfaction Olfactory Organs Provide sense

17 -1 Smell (Olfaction) • Olfactory Organs • Provide sense of smell • Located in nasal cavity on either side of nasal septum • Made up of two layers 1. Olfactory epithelium 2. Lamina propria © 2012 Pearson Education, Inc.

Figure 17 -1 a The Olfactory Organs Olfactory Pathway to the Cerebrum Olfactory epithelium nerve bulb fibers (N I) Olfactory tract Central nervous system Cribriform plate Superior nasal concha © 2012 Pearson Education, Inc. The olfactory organ on the left side of the nasal septum

Figure 17 -1 b The Olfactory Organs Basal cell: divides to replace To worn-out olfactory receptor cells Olfactory bulb gland Cribriform plate Lamina propria Olfactory nerve fibers Developing olfactory receptor cell Olfactory epithelium Supporting cell Mucous layer Knob Subsance being smelled © 2012 Pearson Education, Inc. An olfactory receptor is a modified neuron with multiple cilia extending from its free surface. Olfactory cilia: surfaces contain receptor proteins (see Spotlight Fig. 17 3)

17 -1 Smell (Olfaction) • Olfactory Pathways • Axons leaving olfactory epithelium • Collect into 20 or more bundles • Penetrate cribriform plate of ethmoid • Reach olfactory bulbs of cerebrum where first synapse occurs © 2012 Pearson Education, Inc.

17 -1 Smell (Olfaction) • Olfactory Pathways • Axons leaving olfactory bulb: • Travel along olfactory tract to reach olfactory cortex, hypothalamus, and portions of limbic system • Arriving information reaches information centers without first synapsing in thalamus © 2012 Pearson Education, Inc.

17 -1 Smell (Olfaction) • Olfactory Discrimination • Can distinguish thousands of chemical stimuli • CNS interprets smells by the pattern of receptor activity • Olfactory Receptor Population • Considerable turnover • Number of olfactory receptors declines with age © 2012 Pearson Education, Inc.

Smell (Olfaction) • Olfactory Discrimination • Can distinguish thousands of chemical stimuli • CNS interprets smells by the pattern of receptor activity • Odor strength and quality/Smell better in the Fall? • Number of olfactory receptors declines with age • http: //informahealthcare. com/doi/abs/10. 1081/CBI 200025989 © 2012 Pearson Education, Inc.

Smell (Olfaction) • 2000 -4000 chemical stimuli • Odor information is stored in long-term memory and has strong connections to emotional memory • If your nose is at its best, you can tell the difference between 4000 -10, 000 smells! • Dogs have 1 million smell cells per nostril and their smell cells are 100 times larger than humans! © 2012 Pearson Education, Inc.

Smell (Olfaction) • Accessory olfactory system, which detects fluidphase stimuli. Behavioral evidence suggests that these fluid-phase stimuli often function as pheromones • In women, the sense of olfaction is strongest around the time of ovulation © 2012 Pearson Education, Inc.

Smell (Olfaction) • Humans can detect individuals that are blood related kin (mothers and children but not husbands and wives) from olfaction. Mothers can identify by body odor their biological children but not their stepchildren. Preadolescent children can olfactory detect their full siblings but not halfsiblings or step siblings and this might explain incest avoidance and the Westermarck effect. © 2012 Pearson Education, Inc.

17 -2 Taste (Gustation) • Gustation • Provides information about the foods and liquids consumed • Taste Receptors (Gustatory Receptors) • Are distributed on tongue and portions of pharynx and larynx • Clustered into taste buds © 2012 Pearson Education, Inc.

Figure 17 -3 a Gustatory Receptors Water receptors (pharynx) Umami Sour Bitter Salty Sweet Landmarks and receptors on the tongue © 2012 Pearson Education, Inc.

Figure 17 -3 c Gustatory Receptors Taste buds LM 280 Taste bud LM 650 Nucleus of transitional cell Nucleus of gustatory cell Nucleus of basal cell Transitional cell Gustatory cell Basal cell Taste hairs (microvilli) Taste pore © 2012 Pearson Education, Inc. Taste buds in a circumvallate papilla. A diagrammatic view of a taste bud, showing gustatory (receptor) cells and supporting cells.

17 -2 Taste (Gustation) • Gustatory Discrimination • Four primary taste sensations 1. Sweet 2. Salty 3. Sour 4. Bitter © 2012 Pearson Education, Inc.

17 -2 Taste (Gustation) • Additional Human Taste Sensations • Umami • Characteristic of beef/chicken broths and Parmesan cheese • Receptors sensitive to amino acids, small peptides, and nucleotides • Water • Detected by water receptors in the pharynx © 2012 Pearson Education, Inc.

17 -2 Taste (Gustation) • Gustatory Discrimination • Dissolved chemicals contact taste hairs • Bind to receptor proteins of gustatory cell • Salt and sour receptors • Chemically gated ion channels • Stimulation produces depolarization of cell • Sweet, bitter, and umami stimuli • G proteins • Gustducins © 2012 Pearson Education, Inc.

Supertaster • A person whose sense of taste is significantly sharper than average. Women are more likely to be supertasters, as are Asians, Africans, and South Americans. Among individuals of European descent, it is estimated that about 25% of the population are supertasters © 2012 Pearson Education, Inc.

Figure 17 -5 c The Sectional Anatomy of the Eye Visual axis Anterior cavity Cornea Posterior Anterior Edge of pupil chamber Iris Suspensory ligament of lens Nose Corneal limbus Conjunctiva Lacrimal punctum Lacrimal caruncle Lower eyelid Medial canthus Ciliary processes Lateral canthus Lens Ciliary body Ora serrata Sclera Choroid Retina Posterior cavity Ethmoidal labyrinth Lateral rectus muscle Medial rectus muscle Optic disc Fovea Optic nerve Central artery and vein Orbital fat Horizontal dissection of right eye © 2012 Pearson Education, Inc.

17 -3 The Eye • Light Refraction • Bending of light by cornea and lens • Focal point • Specific point of intersection on retina • Focal distance • Distance between center of lens and focal point © 2012 Pearson Education, Inc.

Figure 17 -10 Factors Affecting Focal Distance Focal distance Close source Light from distant source (object) Focal distance Focal point Lens The closer the light source, the longer the focal distance © 2012 Pearson Education, Inc. The rounder the lens, the shorter the focal distance

17 -3 The Eye • Light Refraction of Lens • Accommodation • Shape of lens changes to focus image on retina • Astigmatism • Condition where light passing through cornea and lens is not refracted properly • Visual image is distorted © 2012 Pearson Education, Inc.

Figure 17 -11 Accommodation For Close Vision: Ciliary Muscle Contracted, Lens Rounded Lens rounded Focal point on fovea Ciliary muscle contracted For Distant Vision: Ciliary Muscle Relaxed, Lens Flattened Lens flattened Ciliary muscle relaxed © 2012 Pearson Education, Inc.

The Eye • Light Refraction of Lens • http: //www. allaboutvision. com/eyeexam/refraction. htm • Clarity of vision • “Normal” rating is 20/20 © 2012 Pearson Education, Inc.