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Transcript
SPECIAL
SENSES
1
Special Senses
General Senses
• receptors that are widely distributed throughout the
body
• skin, various organs, and joints
• receive stimulation of touch, temperature, pain
Special Senses
• specialized receptors confined to structures in the
head
• eyes and ears
•Allow vision, hearing, equilibrium, taste, and smell
2
Senses
Sensory Receptors
• specialized cells or multicellular structures that collect
information from the environment
• stimulate neurons to send impulses along sensory fibers to
the brain
Sensation
• a feeling that occurs when brain becomes aware of sensory
impulse
Perception
• a person’s view of the stimulus; the way the brain
interprets the information
3
Receptor Types
Chemoreceptors
• respond to changes in chemical concentrations
Pain receptors (Nociceptors)
• respond to tissue damage
• respond to intense stimuli of any kind
Thermoreceptors
• respond to changes in temperature
Mechanoreceptors
• respond to mechanical forces
• touch/pressure
Photoreceptors
• respond to light
4
Referred Pain
• May occur due to sensory impulses from two regions
following a common nerve pathway to brain
5
Special Senses
• Sensory receptors are within large, complex sensory
organs in the head
• smell in olfactory organs
• taste in taste buds
• hearing and equilibrium in ears
• sight in eyes
6
Sense of Smell
Olfactory Receptors
• chemoreceptors
• respond to chemicals dissolved in liquids
Olfactory Organs
• contain olfactory receptors and supporting epithelial
cells
• cover parts of nasal cavity, superior nasal conchae,
and a portion of the nasal septum
Sensory Adaptation
• when an odor seems to fade away after you have
been exposed to it
7
Olfactory Receptors
8
Sense of Taste-Gustatory Senses
Taste Buds
• organs of taste
• located on papillae of tongue, roof of mouth, linings of
cheeks, and walls of pharynx
Taste Receptors
• chemoreceptors
• taste cells – modified epithelial cells that function
as receptors
• taste hairs – microvilli that protrude from taste
cells; sensitive parts of taste cells
9
Gustatory Sense Organs
10
Tongue Map
11
Taste Receptors
12
Taste Sensations
Four Primary Taste Sensations
• sweet – stimulated by carbohydrates
• sour – stimulated by acids
• salty – stimulated by salts
• bitter – stimulated by many organic compounds
Spicy foods activate pain receptors
13
Hearing
Ear – organ of hearing
Three Sections
• External
• Middle
• Inner
14
External Ear
• Auricle
• Collects sounds waves
• Flap on the side of the head
• External auditory meatus
• Ear canal
• Carries sound to tympanic
membrane
• Terminates with tympanic
membrane
• Tympanic membrane
• Ear drum
• Vibrates in response to sound
waves
• Separates external from
middle ear
15
Middle Ear
• Tympanic cavity
• Air-filled space in
temporal bone
• Three auditory ossicles
• Vibrate in response to
tympanic membrane
• Malleus, incus, and stapes
• Oval window
• Opening in wall of
tympanic cavity
• Stapes vibrates against it
to move fluids in inner ear
16
Auditory Tube
• Eustachian tube
• Connects middle ear to
throat
• Helps maintain equal
pressure on both sides of
tympanic membrane
• Usually closed by valvelike flaps in throat
• Pathway for infection
17
Inner Ear
Three Parts of Labyrinths
• Cochlea
• Functions in hearing
• Semicircular canals
• Functions in equilibrium
• Vestibule
• Functions in equilibrium
Range of Human Hearing
• 20 – 20,000 vibrations per
second
18
Sight
Visual Accessory Organs
• Eyelids
• Lacrimal apparatus
• Extrinsic eye muscles
19
Eyelid
• Palpebra
• Composed of four layers
• skin
• muscle
• connective tissue
• conjunctiva
• Orbicularis oculi - closes
• Levator palperbrae superioris –
opens
• Tarsal glands – secrete oil onto
eyelashes
• Conjunctiva – mucous
membrane; lines eyelid and
covers portion of eyeball
20
Lacrimal Apparatus
• Lacrimal gland
• lateral to eye
• secretes tears
• Canaliculi
• collect tears
• Lacrimal sac
• collects from canaliculi
• Nasolacrimal duct
• collects from lacrimal
sac
• empties tears into nasal
cavity
21
Coats of the Eyeball - Outer Tunic
Cornea
• anterior portion
• transparent
• No blood vessels
Sclera
• posterior portion
• opaque
• protection
22
Middle Tunic
Iris
• anterior portion
• pigmented
• controls light intensity
Ciliary body
• anterior portion
• pigmented
• holds lens
• moves lens for focusing
Choroid coat
• provides blood supply
• pigments absorb extra light
23
Anterior Portion of Eye
• Filled with aqueous humor (thick watery substance)
24
Lens
• transparent
• biconvex
• lies behind iris
• largely composed of
lens fibers
• elastic
• held in place by
suspensory ligaments
of ciliary body
25
Accommodation
• changing of lens shape to view objects
26
Iris
• composed of connective
tissue and smooth muscle
• pupil is hole in iris
• dim light stimulates
radial muscles and pupil
dilates
• bright light stimulates
circular muscles and
pupil constricts
27
Inner Tunic
• Retina
• contains visual receptors - Rods and Cones
• continuous with optic nerve
• ends just behind margin of the ciliary body
• composed of several layers
28
Posterior Cavity
• Contains vitreous humor – thick gel that holds retina
flat against choroid coat
29
Layers of the Eye
30
Visual Receptors
Rods
• long, thin projections
• contain light sensitive
pigment called rhodopsin
• hundred times more
sensitive to light than cones
• provide vision in dim light
• produce colorless vision
• produce outlines of objects
Cones
• short, blunt projections
• contain light sensitive
pigments called
erythrolabe, chlorolabe,
and cyanolabe
• provide vision in bright
light
• produce sharp images
• produce color vision
31
Rods and Cones
32