Transcript The Special Senses

Quizzes this week
• Thursday (tomorrow!): Cranial Nerves
and Autonomic Nervous System
• Friday: Terminology
Worksheet on back of notes
Review Youtube
• https://www.youtube.com/watch?v=71pCilo8k
4M
The General & Special Senses
Chapter 8
What are the 5 senses?
What are the 5 senses?
•
•
•
•
•
Hearing (technical name = Audition)
Sight (technical name = Vision)
Smell (technical name = Olfaction)
Taste (technical name = Gustation)
?
What are the 5 senses?
•
•
•
•
•
Hearing (technical name = Audition)
Sight (technical name = Vision)
Smell (technical name = Olfaction)
Taste (technical name = Gustation)
NOT Touch?
What are the 5 senses?
•
•
•
•
•
Hearing (technical name = Audition)
Sight (technical name = Vision)
Smell (technical name = Olfaction)
Taste (technical name = Gustation)
Balance (technical name = Equilibrium)
Introduction
Senses – our perception of what is “out there”
• 2 groups
– General senses
• Includes senses that are not specific
• Receptors not specialized or free nerve endings
• Pass information through spinal nerves
– Special senses
• Highly specialized receptors
• Found within complex sense organs
• Pass information through cranial nerves to cerebral
cortex
Receptors
• Sensory receptors are transducers
– Change stimuli into electro-chemical impulses
– Specific receptors can transduce only certain
types of stimuli
Receptors
Figure 18-01
Interpretation of Sensory Information
• Occurs in cerebral cortex
• Depends on the area of the cerebral cortex
that receives the information
Central Processing and Sensory Adaptation
• Sensory adaptation – the loss of sensitivity
after continuous stimulation
– Occurs in some types of receptors
• Role – prevents brain from being
overloaded with unimportant information
Receptors of the General Senses
• Pain
– Referred pain – adjacent nerve sensations such as left
arm pain in heart attack
– Phantom pain - adjacent nerve sensations such as left
arm sensation when left arm has been amputated
• Thermoreceptors detect changes in temperature
• Mechanoreceptors respond to pressure & touch
• Chemoreceptors detect chemicals in solution
– Blood composition
– (Smell)
– (Taste)
Figure 18-02
Referred Pain
The Special Senses
Olfaction (the nose)
• Olfactory receptors
– Can detect at least 50 different primary smells
– Located in the roof of nasal cavity
– Molecules dissolve in the mucus or lipids of the
epithelium
– Olfactory neurons pass through the roof of the
nasal cavity and synapse in the olfactory nerve
– Olfactory tracts go directly to the cerebral
cortex
Olfactory Receptors
Figure 18-06a
Human Anatomy, 3rd edition
Prentice Hall, © 2001
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Olfactory
Receptors
Figure 18-06b
http://www.youtube.com/watch?v=
pM7H0Wud_Y0
Taste (the tongue)
• Taste receptors are in the taste buds
– Can detect 5 primary tastes
• Sweet, sour, salty, bitter, umami
–
–
–
–
Located in papillae on the surface of the tongue
Taste buds contain the taste receptors
Molecules dissolve in saliva
Cranial nerves relay sensory impulses to the
cerebral cortex
Taste Areas of the Tongue – traditional but “wrong”
Figure 18-07a
http://www.youtube.com/
watch?v=FSHGucgnvLU
&feature=PlayList&p=56
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http://www.youtube.com/
watch?v=lyXA4aNnR3w
&feature=PlayList&p=56
D05189EFBACBB1&ind
ex=1
http://www.youtube.com/
watch?v=RIXtM2u-H8&feature=PlayList&p=
56D05189EFBACBB1&i
ndex=3
Modern concept of a taste map
• Taste researchers have known for many years
that these tongue maps are wrong. The maps
arose early in the 20th century as a result of a
misinterpretation of research reported in the late
1800s, and they have been almost impossible to
purge from the literature. In reality, all qualities
of taste can be elicited from all the regions of the
tongue that contain taste buds. At present, we
have no evidence that any kind of spatial
segregation of sensitivities contributes to the
neural representation of taste quality, although
there are some slight differences in sensitivity
across the tongue and palate, especially in
rodents.
Figure 18-07b
Taste Buds
Figure 18-07c
Taste Bud
Equilibrium & Hearing (the ear)
• External ear
– The auricle directs sound waves into the
external auditory meatus to the tympanic
membrane
• Middle ear
– Contains the auditory ossicles
• Malleus, incus, stapes
– Connected to throat by the eustachian tube
• Inner ear
Figure 18-09
The Ear
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Figure 18-10b
The Middle Ear
The Inner Ear
• Separated from the middle ear by the oval
window
• Consists of a series of canals filled with
fluid
The Inner Ear
– Semicircular canals
• Contains receptors for head position
– Cochlea
• Contains the organ of Corti, the organ of hearing
Figure 18-12b
The Inner Ear
The Semicircular Canals
• Detects balance
• Arranged at right angles to each other
• Contain hair cells are embedded in
gelatinous material with fluid over it
• Detect movement of the head
– Bends the hairs, creating nerve impulses
Hair Cells in the Semicircular
Figure 18-12c
Canals
The Organ of Corti
• Detects sound waves
• Consists of hair cells on a basement
membrane
• Tips of hairs touch the tectorial membrane
• When the basement membrane vibrates, the
hair cells are bent, sending a nerve impulse
Figure 18-16d
Organ of Corti
Figure 18-16e
Organ of Corti
Summary of Hearing
1.
2.
3.
4.
5.
6.
7.
8.
Sound waves enter the external auditory meatus
Tympanic membrane vibrates
Auditory ossicles vibrate
Oval window vibrates
Fluid in inner ear vibrates
Basement membrane moves
Hairs rub against the tectorial membrane
Nerve impulse is sent along the auditory nerve
to the brain
Diseases of Hearing
• External Otitis, the most common disorder of the
outer ear, also know as Swimmer’s ear. The
process develops due to loss of the protective
cerumen (wax) and excessive moisture in the ear
canal.
• Otitis Media is one of the most common diseases
of children, due to chronic middle ear infection.
Treatments: antibiotics, otomyringotomy (surgical
insertion of rigid “ear tubes”).
• Conductive Hearing Loss, usually due to
otosclerosis, progressive fixation of the stapes due
to aging or disease.
Vision (the eye)
• Accessory structures
– Eyelids protect the eye
• Conjunctiva lines the eyelid
• Lacrimal gland produces tears
– Extrinsic muscles move the eyeball
Figure 18-18b
The Eye
Structure of the Eye
• Consists of 3 tunics (layers)
– Outer tunic – outermost layer
• Includes the cornea & sclera
– Middle tunic
• Includes the choroid coat, ciliary body, and lens,
iris & pupil
– Inner tunic (retina) – inner layer
• Contains the rods & cones (photoreceptors)
• Includes the optic disc (blind spot),
Figure 18-20b
The Eye
Figure 18-20a
Tunics of the Eye
Inner
Tunic
through
an
ophthalmoscope
Figure 18-22c
The Cavities of the Eye
• The lens separates the interior of the eye
into 2 cavities
– Anterior cavity in front of the lens
• Contains aqueous humor
– Glaucoma
– Posterior cavity behind the lens
• Contains vitreous humor
Figure 18-23
Cavities of the Eye
The Vascular Tunic
• Contains many blood vessels & nerves
• The iris controls the size of the pupil
• Suspensory ligaments attach the lens to the
ciliary body
– Controls the shape of the lens
• Allows focusing on near & distant objects
• Cataract
Figure 18-20c
The Pupil
The Retina
• Cones allow for sharp color vision in bright
light
– 3 types, each with a different pigment
The Retina
• Rods provide for vision in dim light
– Most dense at the periphery of the retina
– Contain the pigment rhodopsin
Visual Receptors
Figure 18-22a1
http://www.youtu
be.com/watch?v=
f0JpsTgy6ck
Summary of Vision
1. Light rays enters through the pupil
2. Light rays cross in the lens
3. Retina receives reversed & upside down
image
4. Rods & cones are stimulated
5. Optic nerve carries impulse to the brain
Visual fields
Abnormal Vision
• Astigmatism
Occurs when the transparent media of the eye
(includes the cornea, crystalline lens) are
inconsistently or irregularly shaped. Causes blurred
vision at far and near distances.
Abnormal Vision
• Cataracts
A clouding and hardening of all or part of the
transparent lens located inside the eye, most
often caused by the aging process, UV light
exposure, etc.
Abnormal Vision
• Glaucoma
A condition characterized either by increased
intraocular pressure- "high blood pressure
of the eye" -that can result in damage to the
optic nerve and to retinal nerve fibers, or by
significant decreased intraocular pressure.
Abnormal Vision
• Hyperopia
Farsightedness. A condition in which rays of light are
focused behind the retina, so distant objects appear
clearer than near ones.
Abnormal Vision
• Presbyopia
Caused by the loss of elasticity in the lens inside
the eye as part of the aging process, resulting in
a gradual decline in a person’s ability to focus
on close objects or to see small print. Virtually
everyone is affected after the age of 40.
Abnormal Vision
• Myopia
Near sightedness. A condition in which light rays are
focused in front of the retina instead of on it, so near
objects appear more clear than far ones.
Abnormal Vision
• Macular degeration
Common eye age-related disease that causes
deterioration of the macula, the central area of the
retina, the paper-thin tissue at the back of the eye
where light-sensitive cells send visual signals to the
brain. Sharp, clear, “straight ahead” vision is
processed by the macula.
Abnormal Vision
• Retinoblastoma
Malignant tumor of the retina. Inherited form is caused
by a genetic abnormality in the Rb gene.