© 2012 Pearson Education, Inc. 17-1 Smell (Olfaction) Olfactory Organs Provide sense of smell...

© 2012 Pearson Education, Inc.

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


Figure 17-1a The Olfactory Organs

Olfactoryepithelium

Olfactory Pathway to the Cerebrum

Olfactorynervefibers (N I)

Olfactorybulb

Olfactorytract

Centralnervoussystem

Superiornasal

concha

Cribriformplate

The olfactory organ onthe left side of the nasal septum


Figure 17-1b The Olfactory Organs

Olfactoryepithelium

Cribriformplate

Laminapropria

Basal cell:divides to replaceworn-out olfactory

receptor cells Olfactorygland

Toolfactory

bulb

Olfactorynerve fibers

Developingolfactoryreceptor cell

Olfactoryreceptor cell

Supporting cell

Mucous layer

Knob

Olfactory cilia:surfaces containreceptor proteins(see SpotlightFig. 173)

Subsance being smelled

An olfactory receptor is a modifiedneuron with multiple cilia extendingfrom its free surface.



• 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



• 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



• 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


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-20

0025989


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!

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings


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


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


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


Figure 17-3a Gustatory Receptors

Water receptors(pharynx) Umami

Sour

Bitter

Salty

Sweet

Landmarks andreceptors on thetongue


Figure 17-3c Gustatory Receptors

Tastebuds

Taste buds

Nucleus oftransitional cell

Nucleus ofgustatory cell

Nucleus ofbasal 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) cellsand supporting cells.



• Gustatory Discrimination

• Four primary taste sensations

1. Sweet

2. Salty

3. Sour

4. Bitter



• 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



• 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


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


Figure 17-5c The Sectional Anatomy of the Eye

Lacrimal punctum

Nose

Lens

Edge ofpupil

Visual axis

Anterior cavity

Posteriorchamber

Anteriorchamber

Lacrimal caruncle

Medial canthus

Ciliaryprocesses

Ciliary body

Ora serrata

Ethmoidallabyrinth

Medial rectusmuscle

Optic disc

Optic nerve

Central arteryand vein

Horizontal dissection of right eye

Orbital fat

Fovea

Lateral rectusmuscle

Posteriorcavity

Retina

Choroid

Sclera

Lateralcanthus

Lower eyelid

Conjunctiva

Corneal limbus

Suspensory ligament of lens

Iris

Cornea


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


Figure 17-10 Factors Affecting Focal Distance

Focal distance

Lightfrom

distantsource(object)

Closesource

The closer the light source,the longer the focal distance

Focal distance

Focalpoint

Lens

The rounder the lens,the shorter the focal distance

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


Figure 17-11 Accommodation

For Close Vision: Ciliary Muscle Contracted, Lens Rounded

Lens rounded

Ciliary musclecontracted

Focal pointon fovea

Lens flattened

Ciliary musclerelaxed

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

• http://www.allaboutvision.com/eye-exam/refraction.htm

• Clarity of vision

• “Normal” rating is 20/20

© 2012 Pearson Education, Inc. 17-1 Smell (Olfaction) Olfactory Organs Provide sense of smell...

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