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

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

© 2012 Pearson Education, Inc 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 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 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

© 2012 Pearson Education, Inc. Smell (Olfaction) 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 ,000 smells! Dogs have 1 million smell cells per nostril and their smell cells are 100 times larger than humans! Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

© 2012 Pearson Education, Inc. Smell (Olfaction) Accessory olfactory system, which detects fluid- phase 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 half-siblings or step siblings and this might explain incest avoidance and the Westermarck effect. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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

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

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

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

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

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

© 2012 Pearson Education, Inc. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Eye Light Refraction of Lens exam/refraction.htm exam/refraction.htm Clarity of vision “Normal” rating is 20/20