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Senses
Touch
proprioceptors & cutaneous
receptors
Proprioceptors
• In skin, muscles and
tendons. They detect the
amount of stretch and
tension
Cutaneous
• In the skin
–Pain, touch, heat, cold, pressure
–Free nerve ending = pain
–Meissner = touch
–Pacinian = pressure
–Ruffini = heat
–Krause = cold
Vision- Eye
Structures-external:
• Muscle- movement
• Lacrimal- washes, disinfects
• Pupil – the hole formed in
the center of the
pigmented iris. Contracts
or dilates depending on
the amount of light
• Eyelids - protection
• Meibomian gland- lubricates eyelid
(blockage causes a “sty”)
• Canal of Schlemm – drains aqueous
fluid (blockage can increase eye
pressure and lead to glaucoma)
• Conjunctiva- mucus membrane
covering= lubricates (conjunctivitis
=pink eye)
3 internal covers- tunics
• Sclera
• Choroid
• Retina
Sclera
•Outermost, tough
•The anterior is clear=
cornea
Choroid
•Middle layer, nutrition
(blood vessels)
• Contains muscles- iris
and ciliary body
Retina
• Inner layer, sensory
• Contains rods and cones
• Rods – sensitive, respond to dim light
and found in the peripheral; gray
tones
• Cones- need bright light; see color
Blind spot
• Point where optic nerve
leaves eye
• No rods, no cones
• Fovea Centralis – pit with a
concentration of cones; this is
your best vision
• Lens- convex, light bending,
refractory
• Anterior is aqueous humor
provides reinforcement and
nutrition to lens & cornea
• Posterior vitreous fluid
reinforces the eye
Errors of refraction
• Myopia- nearsightedness
• Hyperopia- farsightedness
• Astigmatism- problem in the curvature
of part of the lens or cornea
• Cataract- cloudy lens
• Presbyopia-as you age, lenses become
harder and cannot bend as much
Eye reflexes:
• Photopupillary- protects retina
from bright light
• Accomodation- allows close
reading by bending lens
• Convergence- movement of eye
medially when close
Pathway of Light
• Cornea  aqueous humor
 pupil (hole) lens 
vitreous fluid  retina
Pathway of Nerve Impulse
• Retina  receptors (rods and
cones)  optic nerve  optic
chiasma  optic tract 
thalmus  optic radiation 
visual cortex of the occipital
lobe
Nerve impulse pathway
continued
• Vision from the medial eye is
interpreted on the opposite side
of the brain
• Vision from the peripheral eye is
interpreted on the same side of
the brain
Ear- hearing & balance
3 areas:
• External ear• sound transmission,
• pinna (auricle)
• external auditory canal
• tympanic membrane
Middle Ear
• Sound transmission
• Ossicles
• Auditory tube also called:
(eustachian tube or
pharygotympanic tube)
Internal ear• Equilibrium receptors, hearing
receptors
• bony labyrinth (cochlea,
vestibule, semicircular canals)
contains fluid
• Receptors of the semicircular
canal• Cristae are dynamic equilibrium
receptors- angular/ motion
• Receptors of the vestibule• Maculae- static equilibrium
gravity up or down
Hearing
• Receptors in the cochlea
• Organ of Corti- within the
cochlea is stimulated by sound
vibration- moves hair cells
•Deafness is hearing loss
in any degree
• Conduction deafnesstransmission to inner ear is
disrupted
• Sensineural deafnessdamage to receptors, nerve, or
cortex
•Equilibrium problemsnausea, dizziness,
vertigo
Chemical sensesSmell and Taste
• Smell & taste chemicals must
be dissolved in water to excite
receptors
Smell
• Olfactory receptors are located at
the superior part of each nasal
cavity- closely linked to limbic
systems-memories
• Can stimulate the autonomic
nervous system (salivation)
Taste
• Gustatory cells are located in the
taste buds primarily on the
tongue, 4 sensations:
• Sweet (-OH)
• Sour (H+)
• Salty (metal ions)
• Bitter (alkaloids)
•Taste is influenced by
smell, texture,
temperature