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1. Seeley’s
ESSENTIALS OF
Anatomy &
Physiology
Tenth Edition
Cinnamon Vanputte
Jennifer Regan
Andrew Russo
See separate PowerPoint slides for all figures and tables
pre-inserted into PowerPoint without notes.
© 2019 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.

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Chapter 9
Senses
Lecture Outline

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Senses
 Are the means by which the brain receives
information about the environment and the body.
Sensation
 The process initiated by stimulating sensory
receptors.
PERCEPTION
 conscious awareness of stimuli received by
sensory neurons

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Characteristic of Sensation
PROJECTION
 The sensation seems to come from the area
where the receptors were stimulated, even
though it is the brain that truly feels the
sensation
INTENSITY
 The degree to which the sensation is felt; a
strong stimulus affects more receptors and
more impulses are sent to the brain

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Characteristic of Sensation
CONTRAST
 The effect of a previous or simultaneous
sensation on a current sensation as the brain
compares them.
ADAPTATION
 Becoming aware of continuing stimulus
 If the stimulus remains constant, there is no
change for the receptors to detect.

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Characteristic of Sensation
AFTER IMAGE
 The sensation remains in the consciousness
after the stimulus has stopped.

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Classification of Senses
Figure 9.1

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Types of Senses
General senses
• receptors over large part of body that sense touch,
pressure, pain, temperature, and itch
• somatic provide information about body and
environment
• visceral provide information about internal organs
Special senses
• smell, taste, sight, hearing, and balance

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Sensory receptors
 are sensory nerve endings or specialized cells
respond to stimuli by developing action
potentials

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Types of Receptors1
Mechanoreceptors:
• detect movement
• Example, touch, pressure, vibration
Chemoreceptors:
• detect chemicals
• Example, Odors
Photoreceptors:
• detect light

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Types of Receptors2
Thermoreceptors:
• detect temp. changes
Nociceptors:
• detect pain

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Types of Touch Receptors1
Merkel’s disk:
• detect light touch and pressure
Hair follicle receptors:
• detect light touch
Meissner corpuscle:
• deep in epidermis
• localizing tactile sensations

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Types of Touch Receptors2
Ruffini corpuscle
 deep tactile receptors
 detects continuous pressure in skin
Pacinian corpuscle
 deepest receptors
 associated with tendons and joints
 detect deep pressure, vibration, position

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Sensory Receptors in the Skin
Figure 9.2

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Pain
 an unpleasant perceptual and emotional
experience
 can be localized or diffuse.
Localized
 sharp, pricking, cutting pain
 rapid action potential
Diffuse
 burning, aching pain
 slower action potentials

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Pain Control
Local anesthesia:
• action potentials suppressed from pain receptors in
local areas of the body
• chemicals are injected near sensory nerve
General anesthesia:
• loss of consciousness
• chemicals affect reticular formation

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Referred Pain
 A visceral pain that is felt as a cutaneous pain
 originates in a region that is not source of
pain stimulus
 felt when internal organs are damaged or
inflamed
 sensory neurons from superficial area and
neurons of source pain converge onto same
ascending neurons of spinal cord

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Areas of Referred Pain
Figure 9.3

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Olfaction
Olfaction
• sense of smell
• occurs in response to
odorants
• receptors are located in
nasal cavity and hard
palate
• we can detected 10,000
different smells
Figure 9.4a

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Olfaction Process
1. Nasal cavity contains a thin film of mucous
where odors become dissolved.
2. Olfactory neurons are located in mucous.
Dendrites of olfactory neurons are enlarged
and contain cilia.
3. Dendrites pick up odor, depolarize, and carry
odor to axons in olfactory bulb (cranial nerve I).
4. Frontal and temporal lobes process odor.

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Olfactory Epithelium and Olfactory Bulb
Figure 9.4b

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Taste
Taste buds
 sensory structures that detect taste
 located on papillae on tongue, hard palate,
throat
 Inside each taste bud are 40 taste cells
 Each taste cell has taste hairs that
extend into taste pores

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The Tongue
Figure 9.5

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Taste Process
1. Taste buds pick up taste and send it to taste
cells.
2. Taste cells send taste to taste hairs.
3. Taste hairs contain receptors that initiate an
action potential which is carried to parietal
lobe.
4. Brain processes taste.

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Types of Tastes
1. Sweet
2. Sour
3. Salty
4. Bitter
5. Umami/savory

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Pathways for the Sense of Taste
Figure 9.6

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Vision
Accessory Structures
Eyebrow:
 protects from sweat
 shade from sun
Eyelid/Eyelashes:
 protects from foreign objects
 lubricates by blinking

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The Eye and Accessory Structures1
Figure 6.7a
(a) ©Eric Wise

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The Eye and Accessory Structures2
Conjunctiva
 thin membrane that covers inner surface
of eyelid
Lacrimal Gland
 produces tears
Extrinsic eye muscles
 help move eyeball

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Lacrimal Gland Structures
Figure 9.7c

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Extrinsic Eye Muscles
Figure 9.8

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Anatomy of Eye
 Hollow, fluid filled sphere
 Composed of 3 layers (tunics)
 Divided into chambers

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The Eye
Figure 9.9

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LAYERS OF THE EYE
1. Fibrous Tunic layer
 Outermost Tunic
 Sclera:
• firm, white outer part
• helps maintain eye shape, provides attachment
sites, protects internal structures
 Cornea:
• transparent structure that covers iris and pupil
• allows light to enter and focuses light

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2. Vascular Tunic
 Middle tunic that contains blood supply
 Choroid- black part (melanin), delivers O2 and
nutrients to retina
 Ciliary body helps hold lens in place
 Suspensory ligaments help to hold lens in
place

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Vascular Tunic2
Lens
 flexible disk
 focuses light onto retina
Iris
 colored part
 surrounds and regulates pupil

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Vascular Tunic3
Pupil
 regulates amount of light entering
 lots of light = constricted
 little light = dilated

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Lens and Ciliary Body
Figure 9.10

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The Iris
Figure 9.11

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3. Nervous Tunic1
 Innermost tunic and consist of retina.
Retina
 covers posterior 5/6 of eye
 contains 2 layers
Pigmented retina
 outer layer
 keeps light from reflecting back in eye

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Nervous Tunic2
Sensory retina
 contains photoreceptors (Rods and
Cones)
 contains interneurons

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Rods
 photoreceptor sensitive to light
 20 times more rods than cones
 can function in dim light
Cones
 photoreceptor provide color vision
 3 types blue, green, red

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Pigments and Pigment Protein
Rhodopsin:
• photosensitive pigment in rod cells
Opsin:
• colorless protein in rhodopsin
Retinal:
• yellow pigment in rhodopsin
• requires vitamin A

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Effects of Light on Rhodopsin1
1. Light strikes rod cell
2. Retinal changes shape
3. Opsin changes shape
4. Retinal dissociates from opsin
5. Change rhodopsin shape stimulates response in rod
cell which results in vision
6. Retinal detaches from opsin
7. ATP required to reattach retinal to opsin and return
rhodopsin to original shape

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Effects of Light on Rhodopsin2
Figure 9.13

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Posterior Region of Retina3
Macula
• small spot near center of retina
Fovea centralis
 Center of macula
 The light is focused when looking directly at an
object
 Cnly cones
 Ability to discriminate fine images

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Posterior Region of Retina 3
Optic disk
 white spot medial to macula
 blood vessels enter eye and
spread over retina
 no photoreceptors
 called blind spot

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The Retina5
Figure 9.14

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Chambers of the Eye1
Anterior chamber
 located between cornea and lens
 filled with Aqueous Humor (watery)
 Aqueous humor helps maintain pressure,
refracts light, and provide nutrients to inner surface
of eye
Posterior chamber
 located behind anterior chamber
 contains aqueous humor

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Chambers of the Eye2
Vitreous chamber
 located in retina region
 filled with vitreous humor: jelly-like
substance
 vitreous humor helps maintain
pressure, holds lens and retina in place,
refracts light

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Functions of the Eye
 The eye functions much like a camera.
 The iris allows light into the eye, which is
focused by the cornea, lens, and humors
onto the retina.
 The light striking the retina produces action
potentials that are relayed to the brain.
 Light refraction and image focusing are two
important processes in establishing vision.

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Functions of the Eye2
Light Refraction
• Bending of light
Focal point:
• point where light rays converge
• occurs anterior to retina
• object is inverted

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Focusing by the Eye
Figure 9.15

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Focusing Images on Retina
Accommodation
 Lens becomes less rounded and image can
be focused on retina
 Enables eye to focus on images closer than
20 feet

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Focusing by the Eye
Figure 9.15

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Visual Defects1
Myopia
 nearsightedness
 image is in front
of retina
Hyperopia
 farsightedness
 image is behind
retina

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Presbyopia:
 lens becomes less elastic
 reading glasses required

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Visual Defects
Diplopia
 AKA Double vision
 Misalignment of the two eyes
 Due to weakness of the muscles

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Visual Defects2
Astigmatism
 irregular curvature of lens or cornea
 glasses or contacts required to correct
Color Blindness
 absence or deficient cones
 primarily in males

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Glaucoma
 increased
pressure in eye
 can lead to
blindness

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Visual Defects
CATARACT
 Clouding or
opacity of
crystalline lens
that leads to
blurring of vision
and eventually
loss of sight

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Chart to Determine Color Blindness
Figure 6.16
(a) ©Steve Allen/Getty Images RF; (b) ©Prisma Bildagentur AG/Alamy

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The Ear
The organs of hearing and balance are located in
the ears.
Each ear is divided into three areas:
1. the external ear
2. the middle ear
3. the inner ear

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The External Ear
Auricle/Pinna
 fleshy part on outside
External auditory meatus
 canal that leads to eardrum
Tympanic membrane
 Eardrum
 thin membrane that separates external from the
middle ear
 Sound waves reaching the TM cause it to vibrate

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Structure of the Ear
Figure 9.18

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Middle Ear
 Air filled chamber with ossicles
Malleus (hammer)
 bone attached to tympanic membrane
Incus (anvil)
 bone that connects malleus to stapes
Stapes (stirrup)
 bone located at base of oval window

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The Middle Ear2
Oval window:
• separates middle and inner ear
Eustachian or auditory tube:
• opens into pharynx
• equalizes air pressure between outside air and
middle ear

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Inner Ear
 Set of fluid filled chambers
Bony labyrinth
 tunnels filled with fluid
 3 regions: cochlea, vestibule, semicircular canals
Membranous labyrinth
 inside bony labyrinth
 filled with endolymph

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The Inner Ear2
Endolymph:
• clear fluid in membranous labyrinth
Perilymph:
• fluid between membranous and bony labyrinth

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Cochlea
• snail-shell shaped structure
• where hearing takes place
• Has three channels

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Channels of Cochlea
Scala vestibuli
• Extends from the oval window to the apex of
cochlea; filled with perilymph
Scala tympani
• Extend in parallel; filled with perilymph
Cochlea duct
• Formed by the space between vestibular and basilar
membrane; filled with endolymph

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The Inner Ear5
Vestibular membrane
 wall of membranous labyrinth that lines
scala vestibuli
Basilar membrane
 wall of membranous labyrinth that lines
scala tympani

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The Inner Ear4
Spiral organ/Organ of Corti
• in cochlear duct
• contains hair cells
Tectorial membrane:
• in cochlea
• vibrates against hair cells

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Structure of the Ear
Figure 9.18

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Structure of the Inner Ear
Figure 6.19
(e) Courtesy of A. J. Hudspeth

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Effect of Sound Waves on Middle and
Inner Ear Structures
Figure 9.20

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Balance (Equilibrium)
Static equilibrium
 associated with vestibule
 evaluates position of head relative to gravity
Dynamic equilibrium
 associated with semicircular canals
 evaluates changes in direction and rate of head
movement

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Balance1
Vestibule:
• inner ear
• contains utricle and saccule
Maculae:
• specialized patches of epithelium in utricle and
saccule surround by endolymph
• contain hair cells

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Balance2
Otoliths:
• gelatinous substance that moves in response to
gravity
• attached to hair cell microvilli which initiate action
potentials

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Location and Structure of the Macula
Figure 6.22
(d) ©Susumu Nishinag/Science Source

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Function of the Vestibule in Maintaining
Balance
Figure 6.23
(d) ©Susumu Nishinag/Science Source

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Balance3
Semicircular canals:
• dynamic equilibrium
• sense movement if any direction
Ampulla:
• base of semicircular canal
Crista ampullaris:
• in ampulla

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Balance4
Cupula:
• gelatinous mass
• contains microvilli
• float that is displaced by endolymph movement

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Semicircular Canals
Figure 6.24

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Function of the Crista Ampullaris
Figure 6.25
(a) ©Julie Jacobson/AP Photo