Bio 201 chapter 17 lecture

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BIO 156
Chapter 11
Chapter 17: The Special Senses
The special senses include:
Taste
Smell
Vision
Hearing
Balance
The Special Senses
Taste

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Taste buds respond to chemicals
dissolved in food.
 Taste buds respond
to five flavors: salty,
bitter, sweet, sour,
and umami.
 Taste buds are
preferentially
responsive to
one flavor.
 Located principally on the upper surface of the tongue.
 Food molecules dissolve in the saliva and bind to the
membranes of the microvilli of the receptor cells.
Smell
The olfactory epithelium is a patch of
receptor cells that detects odors.
 The molecules bind
to membrane
receptors on the
olfactory hairs,
stimulating nerve
impulses that are
transmitted to the
brain via the
olfactory nerve.
 Located in the roof of the nasal cavities.
 The receptor cells respond to thousands of different molecules.

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Vision
The Visual Sense: The Eye
 The middle layer
consists of the
choroid, the
ciliary body, and
the iris.
 The innermost
layer is the retina,
the light-sensitive
layer,
Human eye consists of three distinct layers. The
 The outermost layer consists of the sclera and the cornea.
The retina contains two types of
photoreceptors: rods and cones.
Rods function in dim light and provide black-and-white
vision
Cones operate in
bright light and provide
color vision.
Cones are also
responsible for visual
acuity.

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 The lens and cornea
focus light on the
retina.
 Alterations in the shape
of the lens and eyeball
cause the most
common visual
problems.
 Overlapping visual fields
give us depth
perception.
Figure11-8
Accommodation
Extrinsic Eye Muscles

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Hearing and Balance: The Cochlea and
Middle Ear
The ear consists of three anatomically separate
portions: the outer, middle, and inner ears.
The inner
ear contains
the cochlea
where the
receptors for
sound are
located
The outer ear consists of the auricle and external auditory
canal, both of which direct sound to the eardrum.
The middle ear consists of the eardrum and three small
bones, the ossicles, which transmit vibrations to the inner ear.
The Structures of the Ear

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Hearing requires the participation of
several structures.
The vestibular apparatus houses receptors
that detect body position and movement.
 The utricle
and saccule
contain
receptors that
respond to
linear
acceleration
and tilting of
the head.
 The semicircular canals, utricle, and saccule.
 Fluid movement inside the semicircular canals deflects the
cupula lying over the receptor cells, alerting the brain to
head movements.
End of Chapter 17

Bio 201 chapter 17 lecture

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Bio 201 chapter 17 lecture