Transcript Chapter 15 - Marion ISD

Somatic and special senses
Ch. 15
Introduction
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Sensory receptors - make it possible for the body
to respond to stimuli caused by changes occurring in
the internal or external environment
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Different types of receptors respond to different stimuli
General function—responds to stimuli by converting them
to nerve impulses
Sensations
Sensory adaptation - receptor potential decreases
over time in response to a continuous stimulus
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Receptors for special senses of smell, taste,
vision, hearing, and equilibrium are grouped into
localized areas or into complex organs
Receptors and sensations
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Types of receptors
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Chemoreceptors activated by amount or changing concentration
of certain chemicals; e.g., taste and smell
Pain receptors - Nociceptors—activated by intense stimuli that
may damage tissue; the sensation produced is pain
Thermoreceptors — activated by changes in temperature
Mechanoreceptors activated when “deformed” to generate
receptor potential
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Proprioceptors -Location limited to skeletal muscle, joint capsules,
and tendons
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Provide information on body movement, orientation in space, and
muscle stretch
Photoreceptor— found only in the eye; respond to light stimuli if
the intensity is great enough to generate a receptor potential
Somatic senses
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Touch and pressure
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Free ends of dendrites
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Meissner’s corpuscles
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sense touch
large and superficial
Pacinian corpuscles
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Called nociceptors
Receptors for pain
Respond to deep
pressure/stretch
Deep dermis and joint capsules
Stretch receptors
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Found in tendons and muscles
Once stretched, the muscle
shortens
Temperature senses
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Organs of Ruffini - also called Ruffini’s
corpuscles
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Deep in dermis
Sense heat - 85 - 120 degrees
Bulbs of Krause - sense cold
Sense of pain
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Free nerve endings
Visceral pain
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Referred pain
Pain nerve fibers Chronic/acute
Regulation of pain impulse awareness of pain - thalamus.
Impulse conducted to cerebral
cortex - judges intensity and
location of pain.
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Endorphins provide natural pain
control.
Serotonin inhibits release of pain
impulses in spinal cord.
Special senses - receptors are
in specialized organs
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Smell - olfactory sense
Taste - gustatory sense
Hearing - auditory sense
Static equilibrium - balance when
stationary
Dynamic equilibrium - balance when
moving
Sight - sense of vision
Sense of smell
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Sense of smell
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Olfactory receptors
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Cilia in nasal cavity
chemoreceptors
Olfactory organs epithelial supporting
tissue
Nerve pathways
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Action potential to
olfactory nerves in
olfactory bulb
Thalamic and olfactory
centers in brain
Sense of taste
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Sense of taste
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Taste receptors chemoreceptors
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Taste sensations
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Taste hairs portrude from taste
pores
Chemicals dissolved in saliva
Sweet
Sour
Salt
Bitter
Nerve pathways
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Facial, glossopharyngeal, vagus
nerves to medulla oblongata to
gustatory cortex in cerebrum.
Sense of hearing
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Sense of hearing
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External ear
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Auricle or pinna - visible - collects sound
External auditory meatus - tube
Middle ear
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in temporal bone- contains ossicles
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Malleus - attached to tympanic
membrane
Incus - attached to malleus and stapes
Stapes - attached to chochlea
Inner ear 
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semicircular canals - equilibrium
Cochlea - hearing
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Organ of corti - located in the cochlear
duct. Contains supporting cells and hair
cells
Sense of hearing
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Nerve pathways - sound waves move
tympanic membrane
Movement of membrane moves ossicles
which move oval window which create
waves which bend hairs.
Hearing - stimulation of auditory area in
cerebral cortex.
Causes and types of hearing
loss
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Sense of equilibrium - two types
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Static equilibrium—ability
to sense the position of
the head relative to
gravity or to sense
acceleration or
deceleration
Dynamic equilibrium—
needed to maintain
balance when head or
body is rotated or
suddenly moved; able to
detect changes both in
direction and rate at
which movement occurs
Static Equilibrium
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Stability of head when body is
motionless
Utricle and Saccule - location
for static equilibrium sense
Macula - movement provides
information about head
position
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Otoliths located in macula, gravity
shifts them, bending hair cells.
Nerve fibers send message to
brain
Body is restored to normal
position.
Dynamic equilibrium
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Cristae ampullaris, located in
semicircular canal
Cupula - gelatinous cap in
which hairs are embedded,
moves with flow of endolymph
(fluid)
Semicircular canals placed at
right angles - detect motion in
all directions
When cupula moves, hair cells
are bent, sending action
potential to medulla oblongata
and then other areas for
interpretation.
Sense of balance and
equilibrium
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Visual accessory organs
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Eyelid - palpebrae
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voluntary muscle and
skin, lined with mucous
membrane called
conjunctiva.
Eyelashes and
eyebrows - give some
protection agains
foreign objects
entering eye
Lacrimal gland -secret
tears. Tears are
drained from surface
of eyeball.
Extrinsic muscles of the eye
Attach to outside
of eyeball and
bones of the orbit
Structure of the eye
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Outer tunic
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Middle tunic
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Cornea - transparent portion
that lies over the iris.
Sclera - tough outer coat
Choroid coat - vascular and
pigmented
Ciliary body - attaches to iris
Iris - colored part of the eye
Lens - held in place by
suspensory ligaments and
ciliary muscles. Has
elasticity - shape is
adjustable.
Inner tunic and
cavities/chambers
Retina - innermost coat of eyeball
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Macula lutea
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Contains receptors
Fovea centralis
Optic disk
Cavities - anterior and posterior
chamber
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Anterior cavity contains
anterior/posterior chambers
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Filled with aqueous humor - watery
fluid - involved in bending light
Posterior cavity - right behind lens.
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Filed with Vitreous humor - semisolid,
maintains intraocular pressure.
Overview of the eye
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Light refraction and the process
of seeing
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Refraction - Light waves bent
Accomplished by cornea, lens, aqueous
humor
Accomodation of the lens - increase in
curvature for near vision.
Pupil constricts controlling the entering of
light
Visual receptors - undergo changes that
generate nerve impulses
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Rods - black and
white vision
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Rhodopsin - photo
pigment
Breaks down into opsin
and retinal
Energy is required to
reform rhodopsin
Cones - color vision
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Three types
Visual Pigments
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Rhodopsin
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Opsin, retinal
Isodopsin
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Erythrolabe red
Chlorolabe green
Cyanolabe blue
Visual nerve pathways
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Optic nerves
Optic
chiasma
cross over
Thalamus
Visual cortex
of occipital
lobe