The General and
Special Senses
The General and
Special Senses
The General Senses
Sensory Basics•Sensory receptors—Specialized
cells or cell processes that monitor external or internal conditions. Simplest are free nerve endings.
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The General Senses
More Sensory Basics•Receptive field—The area monitored
by a single receptor cell
•Adaptation—Reduction in sensitivity at a receptor or along a sensory pathway in the presence of a constant stimulus.
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The General Senses
General versus Special Senses•General senses—Temperature, pain,
touch, pressure, vibration, and proprioception. Receptors throughout the body
•Special senses—Smell, taste, vision, balance, and hearing. Receptors located in sense organs (e.g., ear, eye).
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The General Senses Receptors and Receptive Fields
Figure 9-1
Key Note
Stimulation of a receptor produces action potentials that propagate along the axon of a sensory neuron. The frequency or pattern of action potentials contains information about the stimulus. A person’s perception of the nature of that stimulus depends on the path it takes inside the CNS.
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The General Senses
The General Senses
Pain Definitions•Nociceptors—Receptors for tissue damage
to lead to the sensation of pain•Referred pain—Perception of pain in a part
of the body not actually stimulated•Fast (prickling) pain—Localized pain carried
quickly to the CNS on myelinated axons•Slow (burning) pain—Generalized pain
carried on slow unmyelinated axons
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The General Senses
Referred Pain
Figure 9-2
The General Senses
Temperature•Thermoreceptors detect temperature
change• Free nerve endings• Found in dermis, skeletal muscle, liver,
hypothalamus• Fast adapting• Cold receptors greatly outnumber warm
receptors
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The General Senses
Touch, Pressure, and Position•Mechanoreceptors—Receptors that respond
to physical distortion of their cell membranes.• Tactile receptors—Sense touch, pressure, or
vibration• Baroreceptors—Sense pressure changes in
walls of blood vessels, digestive organs, bladder, lungs
• Proprioceptors—Respond to positions of joints and muscle
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The General Senses
Tactile Receptors•Fine touch or pressure receptors
• Highly detailed information about a stimulus
•Crude touch or pressure receptors• Poorly localized information about a
stimulus• Important types: root hair plexus, tactile
disks, tactile corpuscles, lamellated corpuscles, Ruffini corpuscles
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The General Senses
Tactile Receptors in the Skin
Figure 9-3
The General Senses
Baroreceptors•Provide pressure information essential
for autonomic regulation• Arterial blood pressure• Lung inflation• Digestive coordination• Bladder fullness
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The General Senses Baroreceptors and the Regulation of
Autonomic Functions
Figure 9-4
The General Senses
Proprioceptors•Monitor joint angle, tension in
tendons and ligaments, state of muscular contraction
• Include:• Muscle spindles• Golgi tendon organs
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The General Senses
Chemical Detection•Chemoreceptors respond to chemicals
dissolved in body fluids that surround them and monitor the chemical composition of blood and tissues
•Chemicals that can be sensed include:• Carbon dioxide• Oxygen• Hydrogen ion
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The General Senses
Locations and Functions of Chemoreceptors
Figure 9-5
The Special Senses—Smell
Olfactory Organs•Olfactory epithelium
• Olfactory receptor cells•Neurons sensitive to odorants
• Supporting cells• Basal (stem) cells
•Olfactory glands• Mucus-secreting cells
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The Special Senses—Smell
Figure 9-6(a)
The Olfactory Organs
The Special Senses—Smell
The Olfactory Organs
Figure 9-6(b)
The Special Senses—Smell
The Olfactory Pathways•Axons from olfactory receptors
penetrate cribriform plate of ethmoid bone
•Synapse in olfactory bulb•Olfactory tract projects to:
• Olfactory cerebral cortex• Hypothalamus• Limbic System
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The Special Senses—Taste
Taste (Gustatory) Receptors•Taste buds
• Found within papillae on tongue, pharynx, larynx
• Contain gustatory cells, supportive cells
• Taste hairs (cilia) extend into taste pores
• Sense salt, sweet, sour, bitter•Also sense umami, water
• Synapse in medulla oblongata
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The Special Senses—TasteGustatory Receptors
Figure 9-7(a)
The Special Senses—Taste
Figure 9-7(b)
Gustatory Receptors
The Special Senses—TasteGustatory Receptors
Figure 9-7(c)
The Special Senses
Key Note
Olfactory information is routed directly to the cerebrum, and olfactory stimuli have powerful effects on mood and behavior. Gustatory sensations are strongest and clearest when integrated with olfactory sensations.
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The Special Senses—Vision
Accessory Structures of the Eye•Eyelids (palpebra) and glands•Superficial epithelium of eye
• Conjunctiva
•Lacrimal apparatus• Tear production and removal
•Extrinsic eye muscles
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The Special Senses—Vision
The Lacrimal Apparatus•Lacrimal gland produce tears
• Bathe conjunctiva• Contain lysozyme to attack bacteria• Tears drain into nasal cavity
•Pass through lacrimal canals, lacrimal sac, nasolacrimal duct
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The Special Senses—Vision
Figure 9-8(a)
The Accessory Structures of the Eye
The Special Senses—Vision
The Accessory Structures of the Eye
Figure 9-8(b)
The Special Senses—Vision
Extrinsic Eye Muscles•Move the eye•Six muscles cooperate to
control gaze• Superior and inferior rectus• Lateral and medial rectus• Superior and inferior oblique
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The Special Senses—Vision
Figure 9-9(a)
The Extrinsic Eye Muscles
The Special Senses—Vision
Figure 9-9(b)
The Extrinsic Eye Muscles
The Special Senses—Vision
Layers of the Eye•Fibrous tunic
• Outermost layer
•Vascular tunic• Intermediate layer
•Neural tunic• Innermost layer
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The Special Senses—Vision
Figure 9-10(a)
The Sectional Anatomy of the Eye
The Special Senses—Vision
Figure 9-10(b)
The Sectional Anatomy of the Eye
The Special Senses—VisionThe Sectional Anatomy of the Eye
Figure 9-10 (c)
The Special Senses—Vision
Layers of the Eye•Fibrous tunic
• Sclera•Dense fibrous connective
tissue•“White of the eye”
• Cornea•Transparent•Light entrance
The Eye: Light PathCopyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
PLAYPLAY
The Special Senses—Vision
Layers of the Eye•Vascular tunic
• Iris•Boundary between anterior and
posterior chambers• Ciliary body
•Ciliary muscle and ciliary process•Attachment of suspensory ligaments
• Choroid•Highly vascular
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The Special Senses—Vision
Functions of the Vascular Tunic•Provide a route for blood vessels•Control amount of light entering eye
• Adjust diameter of pupil
•Secrete and absorb aqueous humor•Adjust lens shape for focusing
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The Special Senses—VisionThe Pupillary Muscles
Figure 9-11
The Special Senses—Vision
Layers of the Eye•Neural tunic (Retina)
• Outer pigmented part•Absorbs stray light
• Inner neural part•Detects light•Processes image•Communicates with brain
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The Special Senses—Vision
Organization of the Retina•Photoreceptor layer•Bipolar cells•Amacrine, horizontal cells
modify signals•Ganglion cells•Optic nerve (CN II)
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The Special Senses—Vision
Retinal Organization
Figure 9-12(a)
The Special Senses—Vision
Figure 9-12(b)
Retinal Organization
The Special Senses—Vision
Figure 9-12(c)
Retinal Organization
The Special Senses—Vision
Chambers of the Eye•Two cavities
• Ciliary body, lens between the two• Anterior cavity
•Anterior compartment
Between cornea and iris
•Posterior compartment
Between iris and lens
• Posterior cavity•Vitreous body
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The Special Senses—Vision
The Aqueous Humor•Secreted by ciliary processes into
posterior chamber•Flows into anterior chamber•Maintains eye shape•Carries nutrients and wastes•Reabsorbed into circulation•Leaves at canal of Schlemm•Excess humor leads to glaucoma
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The Special Senses—Vision
Figure 9-14
Eye Chambers and the Circulation of Aqueous Humor
The Special Senses—Vision
The Lens•Supported by suspensory
ligaments•Built from transparent cells•Surrounded by elastic capsule•Lens and cornea focus light on
retina• Bend light (refraction)
•Accommodation changes lens shape
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The Special Senses—Vision
Figure 9-15(a)
Focal Point, Focal Distance, and Visual Accommodation
The Special Senses—Vision
Focal Point, Focal Distance, and Visual Accommodation
Figure 9-15(b)
The Special Senses—Vision
Figure 9-15(c)
Focal Point, Focal Distance, and Visual Accommodation
The Special Senses—Vision
Figure 9-15(d)
Focal Point, Focal Distance, and Visual Accommodation
The Special Senses—Vision
Figure 9-15(e)
Focal Point, Focal Distance, and Visual Accommodation
The Special Senses—Vision
Figure 9-16(a)
Image Formation
The Special Senses—Vision
Figure 9-16(b)
Image Formation
The Special Senses—Vision
Figure 9-17(a)
Visual Abnormalities
The Special Senses—Vision
Figure 9-17(b)
Visual Abnormalities
The Special Senses—Vision
Figure 9-17(c)
Visual Abnormalities
The Special Senses—Vision
Figure 9-17(d)
Visual Abnormalities
The Special Senses—Vision
Figure 9-17(e)
Visual Abnormalities
The Special Senses—Vision
Key NoteLight passes through the cornea, crosses the anterior cavity to the lens, transits the lens, crosses the posterior chamber, and then penetrates the retina to stimulate the photoreceptors. Cones, most abundant at the fovea and macula lutea, provide detailed color vision in bright light. Rods, dominant in the peripheral retina, provide coarse color-free vision in dim light.
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The Special Senses—Vision
Visual Physiology•Photoreceptors—Cells specialized to
respond to photons, packets of light energy•Two types of photoreceptors
• Rods•Highly sensitive, non-color vision•In peripheral retina
• Cones•Less sensitive, color vision•Mostly in fovea, center of macula lutea
Site of sharpest vision
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The Special Senses—Vision
Photoreceptor Anatomy•Outer segment
• Discs with visual pigments• Light absorption by rhodopsin
•Opsin + retinal
• Inner segment• Synapse with bipolar cell• Control of neurotransmitter release• Effect on bipolar cells
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The Special Senses—VisionThe Structure of Rods and Cones
Figure 9-19
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Figure 9-201 of 7
Retinal andopsin are
reassembledto form
rhodopsin
Photon
Retinal changes shape
Bleaching(separation)enzyme
ADP ATP
Opsin Opsin
Opsininactivated
Regeneration
Retinalrestored
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Figure 9-202 of 7
Retinal andopsin are
reassembledto form
rhodopsin
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Figure 9-203 of 7
Retinal andopsin are
reassembledto form
rhodopsin
Photon
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Figure 9-204 of 7
Retinal andopsin are
reassembledto form
rhodopsin
Photon
Retinal changes shape
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Figure 9-205 of 7
Retinal andopsin are
reassembledto form
rhodopsin
Photon
Retinal changes shape
Bleaching(separation)enzyme
ADP ATP
Retinalrestored
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 9-206 of 7
Retinal andopsin are
reassembledto form
rhodopsin
Photon
Retinal changes shape
Bleaching(separation)enzyme
ADP ATP
Opsin Opsin
Opsininactivated
Retinalrestored
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 9-207 of 7
Retinal andopsin are
reassembledto form
rhodopsin
Photon
Retinal changes shape
RegenerationBleaching
(separation)enzyme
ADP ATP
Retinalrestored
Opsin Opsin
Opsininactivated
The Special Senses—Vision
The Visual Pathway•Ganglion cells axon converge at optic disc•Axons leave as optic nerve (CN II)•Some axons cross at optic chiasm•Synapse in thalamus bilaterally•Thalamic neurons project to visual cortex
• Located in occipital lobes• Contains map of visual field
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The Special Senses—Vision
Figure 9-21
The Visual Pathway
Equilibrium and Hearing
Sensory Functions of the Inner Ear•Dynamic equilibrium•Static equilibrium•Hearing
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Equilibrium and Hearing
Overview of the Ear•Chambers, canals filled with fluid
endolymph•Bony labyrinth
• Surrounds membranous labyrinth• Surrounded by fluid perilymph• Consists of vestibule, semicircular canals,
cochlea
•External, middle ear feed sound to cochlea
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Equilibrium and Hearing
Anatomy of the Ear•External ear
• Pinna (auricle)• External acoustic canal• Tympanic membrane (eardrum)
•Middle ear• Auditory ossicles
•Connect tympanic membrane to inner ear• Auditory tube
•Connection to nasopharynx
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Equilibrium and Hearing
Anatomy of the Inner Ear•Vestibule
• Membranous sacs•Utricle•Saccule
• Receptors for linear acceleration, gravity
•Semicircular canal with ducts• Receptors for rotation
•Cochlea with cochlear duct• Receptors for sound
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Equilibrium and Hearing
Receptors of the Inner Ear•Hair cells
• Mechanoreceptors• Stereocilia on cell surface
•Bending excites/inhibits hair cell•Information on direction and strength
of mechanical stimuli
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Equilibrium and HearingThe Anatomy of the Ear
Figure 9-22
Equilibrium and HearingThe Structure of the Middle Ear
Figure 9-23
Equilibrium and Hearing
Figure 9-24(a,b)
The Anatomy of the Ear
Equilibrium and Hearing
Figure 9-24(c)
The Anatomy of the Ear
The Ear: Ear AnatomyPLAYPLAY
Equilibrium and Hearing
Equilibrium•Semicircular ducts
• Connect to utricle• Contains ampulla with hair cells• Stereocilia contact cupola
•Gelatinous mass distorted by fluid movement
• Detects rotation of head in three planes•Anterior, posterior, lateral ducts
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Equilibrium and Hearing
Equilibrium (continued)•Saccule and utricle
• Hair cells cluster in maculae
• Stereocilia contact otoliths (heavy mineral crystals)
• Gravity pulls otoliths
• Detect tilt of head
•Sensory axons in vestibular branch of CN VIII
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Equilibrium and Hearing
The Vestibular Complex
Figure 9-25(a-c)
Equilibrium and Hearing
The Vestibular Complex
Figure 9-25(a, d)
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Figure 9-25(e)1 of 4
Gravity
Gravity
Head in horizontal position
Head tilted posteriorly
Receptoroutput increases
Otolith moves
“downhill,”distorting
hair cell processes
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Figure 9-25(e)2 of 4
Gravity
Head in horizontal position
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Figure 9-25(e)3 of 4
Gravity
Gravity
Head in horizontal position
Head tilted posteriorly
Otolith moves
“downhill,”distorting
hair cell processes
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Figure 9-25(e)4 of 4
Gravity
Gravity
Head in horizontal position
Head tilted posteriorly
Receptoroutput increases
Otolith moves
“downhill,”distorting
hair cell processes
The Ear: BalancePLAYPLAY
Equilibrium and Hearing
Overview of Hearing•Sound waves vibrate tympanic membrane•Ossicles transfer vibration to oval window•Oval window presses on perilymph in
vestibular duct•Pressure wave distorts basilar membrane•Hair cells of organ of Corti press on
tectorial membrane
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Equilibrium and Hearing
The Cochlea and the Organ of Corti
Figure 9-26(a)
Equilibrium and Hearing
Figure 9-26(b)
The Cochlea and the Organ of Corti
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Figure 9-271 of 7
Externalacoustic
canal
Movementof sound
waves
Malleus
Incus
StapesOval
window
Cochlear branch ofcranial nerve VIII
Vestibular duct(perilymph)
Vestibular membrane
Cochlear duct(endolymph)Basilar membraneTympanic duct(perilymph)
Tympanicmembrane
Roundwindow
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
Vibrations of the basilar membrane causes vibration of hair cells against the tectorial membrane.
Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII.
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Figure 9-272 of 7
Externalacoustic
canal
Movementof sound
waves
Sound waves arrive at tympanic membrane.
Tympanicmembrane
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Figure 9-273 of 7
Externalacoustic
canal
Movementof sound
waves
Malleus
Incus
Stapes
Tympanicmembrane
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 9-274 of 7
Externalacoustic
canal
Movementof sound
waves
Malleus
Incus
StapesOval
window
Tympanicmembrane
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 9-275 of 7
Externalacoustic
canal
Movementof sound
waves
Malleus
Incus
StapesOval
window
Tympanicmembrane
Roundwindow
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 9-276 of 7
Externalacoustic
canal
Movementof sound
waves
Malleus
Incus
StapesOval
window
Vestibular duct(perilymph)
Vestibular membrane
Cochlear duct(endolymph)Basilar membraneTympanic duct(perilymph)
Tympanicmembrane
Roundwindow
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
Vibrations of the basilar membrane causes vibration of hair cells against the tectorial membrane.
The Ear: Receptor ComplexesCopyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
PLAYPLAYFigure 9-277 of 7
Externalacoustic
canal
Movementof sound
waves
Malleus
Incus
StapesOval
window
Cochlear branch ofcranial nerve VIII
Vestibular duct(perilymph)
Vestibular membrane
Cochlear duct(endolymph)Basilar membraneTympanic duct(perilymph)
Tympanicmembrane
Roundwindow
Sound waves arrive at tympanic membrane.
Movement of tympanic membrane causes displacement of the auditory ossicles.
Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct.
The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
Vibrations of the basilar membrane causes vibration of hair cells against the tectorial membrane.
Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII.
Equilibrium and Hearing
Auditory Pathways•Hair cells excite sensory neurons•Sensory neurons located in spiral
ganglion•Afferent axons form cochlear branch of
vestibulocochlear nerve (CN VIII)•Synapses in cochlear nucleus in medulla•Neurons relay to midbrain•Midbrain relays to thalamus•Thalamus relays to auditory cortex
(temporal lobe) in a frequency map
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Equilibrium and Hearing
Pathways for Auditory Sensations
Figure 9-28
Equilibrium and Hearing
Key NoteBalance and hearing both rely on hair cells. Which stimulus excites a particular group depends on the structure of the associated sense organ. In the semicircular ducts, fluid movement due to head rotation is sensed. In the utricle and saccule, shifts in the position of otoliths by gravity is sensed. In the cochlea, sound pressure waves distort the basilar membrane.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Aging and the Senses
Impact of Aging on Sensory Ability•Gradual reduction in smell and taste
sensitivity as receptors are lost•Lens changes lead to presbyopia
(loss of near vision)•Chance of cataract increases•Progressive loss of hearing
sensitivity as receptors are lost (presbycusis)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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