ANAT41 – Lecture Outline
SENSE ORGANS
General Senses = widespread throughout the body
Sensory Receptors – dendrites specialized to detect certain types of stimuli
2 types:
o Exteroceptors : respond to stimuli that originate outside the body
o Interoceptors: respond to stimuli that originate within the body
Categories of sensory receptors associated with somatic senses:
1. Chemoreceptors – detect chemical stimuli
e.g. pH, oxygen levels, hormones
2. Photoreceptors – detect light stimuli
e.g. only found in the retina of the eye
3. Mechanoreceptors – detect physical stimuli
e.g. pressure, tickle, touch, vibration, proprioceptors
4. Thermoreceptors – detect temperature
5. Pain Receptors (nociceptors)- specific type of chemical receptor that detect
stimuli from damaged tissue
Which of the above receptors are classified as exteroceptors and/or interceptors?
Structurally sensory receptors can be:
 Free nerve endings
 Encapsulated nerve endings
 Specialized cells associated with neurons
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ANAT41 – Lecture Outline
SENSE ORGANS
What happens when a stimulus binds to a sensory receptor?
Awareness of a sensation
Sensation = occurs when nerve impulses arrive at your cerebral cortex
Perception = occurs when the cerebral cortex interprets the meaning
What is sensory adaptation? What type of receptors undergo sensory
adaptation?
What is referred pain?
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ANAT41 – Lecture Outline
SENSE ORGANS
Special senses = localized to one area and include sight, hearing, taste, and smell
 Sense of Taste
Taste buds – sensitive to tastants
Taste cells – sensory receptors for sense of taste located on a taste bud.
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ANAT41 – Lecture Outline
SENSE ORGANS
Where are taste buds located?
We have 5 primary tastes:
1. Sweet
2. Sour
3. Salty
4. Bitter
5. Umami
Taste Nerve Pathway:
What cranial nerves send this information to the cerebrum?
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ANAT41 – Lecture Outline
SENSE ORGANS
 Sense of Smell (olfaction)
Olfactory epithelium- lies in the roof of the nasal cavity; 10-20 million
olfactory cells
Odorant = chemical stimulus that binds to olfactory cells to initiate nerve
impulses
What is the pathway of olfaction beginning at the olfactory cell?
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ANAT41 – Lecture Outline
SENSE ORGANS
Eye
Coats of the eye (tunics): from superficial to deep
1. Outer tunic
a. Cornea
b. Sclera
2. Middle tunic
a. Choroid
b. Ciliary body
c. Iris = regulates the size of the pupil
3. Retina (inner tunic)
a. Rods (shaped like a rod)




Black/white vision
Contains pigment rhodopsin
Allows visibility in dim lighting
Vision is blurry
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ANAT41 – Lecture Outline
SENSE ORGANS
 More numerous in number than cones and more widely
dispersed
b. Cones (shaped like cones)
 Gives us color vision: Includes red, green, and blue
 Best visual acuity – clear and crisp
 Need to have bright light
Fovea centralis = concentrated area of cones that lies in the most posterior
aspect of the eye
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ANAT41 – Lecture Outline
SENSE ORGANS
Optic disc (blind spot) = where the axons of the optic nerve leave the posterior
part of the eye; there are not photoreceptors located here
Visual pathway
optic chiasma
C. Refracting media – structures that bend light
1. Cornea
2. Aqueous humor
Location: anterior cavity
3. Lens – divides the eye into anterior and posterior cavities
4. Vitreous humor – gelatinous like fluid that nourishes the retina
(We will look at this structure in the sheep eye.)
Location: posterior cavity
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ANAT41 – Lecture Outline
SENSE ORGANS
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ANAT41 – Lecture Outline
SENSE ORGANS
Ear
External ear
1. Auricle (pinna)
2. External auditory meatus or canal
3. Tympanic membrane (eardrum)
Middle ear
1. Location: inside temporal bone
2. Auditory ossicles
a. Malleus
b. Incus
c. Stapes
3. Oval window
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ANAT41 – Lecture Outline
SENSE ORGANS
4. Eustachian tube (auditory tube)
Inner ear
1. Location: inside temporal bone
2. General structure
a. Bony or osseous labyrinth
b. Membranous labyrinth
3. Cochlea
Structures of the cochlea
1) scala vestibuli
4) vestibular membrane
2) scala tympani
5) basilar membrane
3) cochlear duct
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ANAT41 – Lecture Outline
SENSE ORGANS
6) organ of Corti (contains
hair cells)
7) tectorial membrane
Tracing the path of the sound waves
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ANAT41 – Lecture Outline
SENSE ORGANS
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ANAT41 – Lecture Outline
SENSE ORGANS
Vestibule – contains receptors for static equilibrium
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ANAT41 – Lecture Outline
SENSE ORGANS
Semicircular canals – contains receptors for dynamic equilibrium
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