Transcript SensesHHAP

Somatic and Special Senses
The Senses
Somatic Senses are general senses of touch
◦ Temperature
◦ Pressure
◦ Pain
 Special senses are
◦ Smell
◦ Taste
◦ Sight
◦ Hearing
◦ Equilibrium

All of these senses occur when “stimuli”
are received through sensory receptors.
 These stimuli are converted to an
electrical message that is carried to the
brain and interpreted.
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Types of Receptors
Chemoreceptors: detect chemicals;
such as taste and smell
 Mechanoreceptors: detect changes in
pressure; touch pressure, hearing , balance
and blood pressure
 Thermoreceptors: detect changes in
temperature
 Photoreceptors: detect changes in light,
responsible for vision
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Somatic Senses
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Touch and Pressure
◦ Merkel disk: found in the stratum basal and
perceive very light touch ex; lips and fingertips
◦ Meissner corpuscle: found in the dermis of
hairless skin and perceive light touch ex; lips,
fingertips and palms
◦ Pacinian corpuscles: found in the lower
dermis, subcutaneous. Responds to heavy
pressure
Somatic Senses
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Temperature
◦ Cold receptors: located in the stratum
basale; perceive temperatures between 50o and
105oF
◦ Hot receptors: located in the dermis;
perceive temperatures between 90o and 118oF
Somatic Senses
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Pain
◦ Nociceptors are found in every tissue except
the brain
◦ Pain is caused by tissue damage
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Excessive stretching
Prolonged muscular contraction
Inadequate blood flow
Presence of certain chemicals
Somatic Senses: Pain
Tissue injury/irritation  release of
prostaglandins stimulate receptors
 PAIN  prostaglandins are slowly
removed from area
 Pain remains until all prostaglandins
are removed
 Pain serves as a protective function;
it lets you know that tissue damage
is taking place
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Acute vs. Chronic pain
Acute: sharp pain, conducted rapidly
 Chronic: dull pain conducted slowly
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Referred Pain
Tissue damage that takes place in the
organs of the body may cause pain in a
different area.
 This happens because pain impulses travel
along common pathway and the brain
can’t tell where tissue damage is
occurring.
 Ex: tissue damage that takes place in the
heart may be perceived as pain in the arm;
brain misinterprets location of tissue
injury
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The Sense of Taste
Taste buds house
the receptor
organs
 Location of taste
buds

◦ Most are on the
tongue
◦ Soft palate
◦ Cheeks
Figure 8.18a–b
The Tongue and Taste
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The tongue is covered with projections
called papillae
◦ Filiform papillae – sharp with no taste buds
◦ Fungifiorm papillae – rounded with taste buds
◦ Circumvallate papillae – large papillae with taste
buds
Taste buds are found on the sides of papillae
 Impulses are carried to the gustatory
complex by several cranial nerves because
taste buds are found in different areas
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Taste Sensations
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Sweet receptors: Sugars, Saccharine
Sour receptors: Acids
Salty receptors: Metal ions
Bitter receptors Alkaloids
Umami: Amino Acid called glutamate-savory as in meats,
cheese (protein heavy foods)
Taste pores are openings where food falls
into and are tasted
 Gustatory hairs help direct food into the
taste pore
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Anatomy of Taste Buds
Figure 8.18
Chemical Senses – Taste and Smell
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Both senses use chemoreceptors
◦ Stimulated by chemicals in solution
◦ Taste has five types of receptors
◦ Smell can differentiate a large range of
chemicals
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Both senses complement each other and
respond to many of the same stimuli
Olfaction – The Sense of Smell
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Olfactory receptors are in the roof of the
nasal cavity
◦ Chemicals must be dissolved in mucus for
detection
Impulses sensed via the olfactory nerve
 Humans can recognize over10,000 scents
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Olfactory Epithelium
Figure 8.17
The Eye and Vision
Photoreceptors receive stimuli
 70% of all sensory receptors are in the
eyes
 Each eye has over a million nerve fibers
 Protection for the eye

◦ Most of the eye is enclosed in a bony orbit
◦ A cushion of fat surrounds most of the eye
Accessory organs of the eye
Eyelid:covers the eye moistens, protects the eye
Conjunctiva: lines the inner surface of the eyelid
and outer surface of eye
Accessory organs of the eye
Lacrimal gland: secretes tears; above eye.
 Lacrimal ducts carry tears into nasal cavity
 Lacrimal sac collects tears, sends to nasal cavity
 Tears keep eye moist but also contain the
enzyme lysozyme which reduces eye infections
Extrinsic Eye Muscles
Muscles attach to outer surface of the eye
 Produce eye movements
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Figure 8.2
Structure of the eye
The eye is a hollow muscular structure about
2.5cm in diameter.
 It is filled with fluid that gives it shape
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Figure 8.3a
Structure of the Eye
Sclera: White covering known as the
“white of the eye”
 Cornea: Transparent, central anterior
portion, covering
◦ Allows for light to pass through
◦ Repairs itself easily
◦ The only human tissue that can be
transplanted without fear of rejection
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Structure of the Eye
Optic nerve: carries visual impulses to the
brain
 Choroid coat: middle layer of the eye;
contains lots of blood vessels to nourish eye
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Structure of the Eye
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Iris: a ring of muscular tissue that forms
the opening that determines how much
light enters the eye
◦ Muscles contract  pupil is small
◦ Muscles relax (dilate)  pupil is large
Structure of the Eye
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Vitreous humor: Gel substance behind lens
◦ Keeps the eye from collapsing
◦ Lasts a lifetime and is not replaced
Aqueous humor: a thin fluid that fills the
anterior chamber of the eye (between the
cornea and lens)
◦ Constantly being formed and drained.
◦ When it doesn’t drain -glaucoma (vision going
gray
Structure of the Eye
Retina: inner lining of the eye
 Macula-center of visual acuity
 Macular degeneration- separation of
retina causes blindness
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Structure of the Eye
Retina:
 Contains receptor cells (photoreceptors)
◦ Rods: dim vision, peripheral vision, gray tones,
found on edge of retina
◦ Cones: blue, red, green cones, each sensitive
to a different wavelength
Cones are densest near the fovea centralis
(center of macula):area of retina with only cones
Structure of the Eye
No photoreceptor cells are at the optic
disk, or blind
 Signals pass from photoreceptors thru the
retina to the optic nerve
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Structure of the Eye
Lens: biconvex crystal-like structure
 Held in place by a suspensory ligament
attached to the ciliary body
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Figure 8.3a
Structure of the Eye
Light must be
focused to a point on
the retina for optimal
vision
 The eye is set for
distance vision
(over 20 ft away)
 The lens must change
shape to focus for
closer objects
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Figure 8.9
Visual Pathway
Photoreceptors of
the retina are
stimulated by an
object
 Stimulates the Optic
nerve
 Message travels
across the optic
chiasma to the brain
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Figure 8.11
Common Disorders of the Eye
Conjunctivitisinflammation of the
membrane that lines the
eye
 Cataract-lens loses its
flexibility and
transparency (cloudy)
 Glaucoma-increased
pressure in the fluid of
the eye-interferes with
optic nerve functioning
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Common Disorders of the Eye
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Myopia-(nearsightedness)objects at a distance are
blurry (CAN see near)
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PresbyopiaFarsightedness due to
age-lens becomes stiff and
yellowish-can’t focus close
up-especially in low light –
usually happens between
40-45 years old
Common Disorders of the Eye
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Amblyopia-”lazy eye”one eye has poor vision
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Strabismus-also called
lazy eye-eyes are not
aligned with ,each other
“crossed eyes”
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Color blindness is the
result of lack of one
cone type
The Ear
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Houses two senses
◦ Hearing
◦ Equilibrium (balance)
Receptors are mechanoreceptors
 Different organs house receptors for each
sense
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Anatomy of the Ear
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Ear is divided into 3 areas: Outer (external)
Middle ear, Inner ear
Figure 8.12
External Ear
Pinna (auricle): Collects sounds with funnel
shape
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External auditory canal: narrow chamber in
the temporal bone,
 Lined with skin & Ceruminous (wax) glands
 Ends at the tympanic membrane (eardrum)
 Carries sound to the middle ear
Figure 8.12
The Middle Ear
Air-filled cavity within the temporal bone
 Only involved in the sense of hearing
 Tympanic membrane: aka eardrum;
cone-shaped, responds to sound waves by
moving back and forth
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Bones of the Middle Ear
◦ Malleus (hammer)
◦ Incus (anvil)
◦ Stapes (stirrip)
• Vibrations
from eardrum
move the
malleus
• These bones
transfer sound
to the inner ear
Figure 8.12
Middle Ear/Tympanic Cavity
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Two tubes associated with the middle ear:
1. The opening from the auditory canal,
covered by the tympanic membrane
2. The Eustachian or auditory tube connecting
the middle ear with the throat
 Allows for equalizing pressure during yawning or
swallowing. This tube is otherwise collapsed
 Site of ear infections; tubes in your ears are plastic
tubes that keep Eustachian tube open
Inner Ear or Bony Labyrinth
Includes organs for hearing and balance
 A labyrinth of bony chambers in temporal
bone includes:
 Cochlea,
 Vestibule
 Semicircular
canals
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Figure 8.12
Inner Ear: Semicircular canals
Loops that extend into each “dimension”
 Full of jello-like fluid and hairs
 As you move the jello pulls on the hairs
which sends a message to the brain about
your position
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Inner Ear: Cochlea
Shell shaped organ that sends sound
vibrations through the round window to
the……
 Organ of corti: contains sensory
receptors that transmit “hearing”
impulses to brain
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Inner Ear:Vestibule
Contains fluid, little stones called otoliths
and hairs
 When head moves fluid with otoliths
move the hairs this sends a message to
the brain on position of the head
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Equilibrium
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Static
◦ Helps you maintain
stability and posture of
the head and body
when not in motion
◦ Occurs in the
vestibule which
contains hairs that
bend according to
position of head
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Vs
Dynamic
◦ Helps you maintain
balance when you are
in motion
◦ Occurs in the
semicircular canals
which are loops of
fluid that move hairs
depending on the
position of the body
Balance
Common Disorders of the Ear
Otitis media: ear
infection
 Labyrinthitisinflammation of the inner
ear causes vertigo
(dizziness)
 Meniere’s (MAIN-eeairz) Disease-chronic
condition that affects the
labyrinth and leads to
progressive hearing loss
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