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SENSES: CHAPTER
10
Types of Receptors
Chemoreceptors Respond to changes in chemical concentrations
Pain receptorsRespond to tissue damage
Thermoreceptors Respond to temperature changes
MechanoreceptorsRespond to changes in pressure or movement
Photoreceptors Respond to light
Sensation and Projection
Brain:Sensations come from hereImpulses are interpreted based on what area of
the brain they end up inBrain projects the sensation back to the sensor so
the person feels the sensation at the sensor Sensory Adaptation:
Ability of the PNS or CNS to block sensory impulses that it deems unimportant or has become used to
Somatic senses Sensors are widely
spread throughout body and are fairly simple
Include:TouchPressureTemperaturePain
Touch and Pressure Three kinds of receptors
1) Free nerve endings○ Sensations of touch and pressure
2) Meissner’s corpuscles○ Provide sensations of light touch, usually
located in regoins of skin without hair3) Pacinian corpuscles○ Respond to heavy pressure, located in
deeper tissues
Temperature Receptors Warm and cold receptors in skin
Free nerve endings Receptors adapt very fast
Pain receptorsExtreme temperatures and injury stimulate
these
Pain Receptors Sensations arise from free nerve ending
throughout body except brain Pain receptors adapt poorly Visceral pain
Refers pain to areas on the skin
Special senses Sensations arise from specially adapted
sensors Includes:
Smell TasteHearingEquilibriumSight
Smell Olfactory receptors are located in small
patches along the roof of the nasal cavity They are chemoreceptors
Incoming gases must dissolve in the mucous covering the nasal cavity
Dissolved particles interact with the cilia and may stimulate an action potential
Taste Taste buds
Located primarily on tongue, although some found on roof of mouth and sides of the throat
Each taste bud has many gustatory receptors and tiny cilia projections
These are chemoreceptorsIncoming foods must be dissolved in saliva to be
tasted
Areas of the Tongue Four main taste areas:
1. Sweet - concentrated on the tip of the tongue2. Sour - concentrated along the margins of the
tongue3. Bitter - concentrated along the back of the
tongue4. Salty - spread throughout
The Outer Ear Sound waves are directed into the ear by
the external auricle They travel down the external acoustic
meatus Bounce against tympanic membrane
(eardrum) and make the eardrum move
The Middle Ear Occurs in the tympanic cavity Has three small auditory ossicles/bones Vibrations at the tympanic membrane cause the
three bones to vibrate The final bone vibrates against the oval window
of the inner ear The bones amplify the sound Eustachian tube
Connects middle ear to throat, equalizes pressure for eardrum, often where earaches occur
Inner Ear Includes two labyrinths:
1) Osseous labyrinth - bony canals2) Membranous labyrinth - membrane-bound tube
inside the bony canalsPerilymph separates the twoEndolymph is found inside the membranous labyrinth
Two parts to the labyrinth:1) Semicircular canals - used in equilibrium 2) Cochlea – organ for hearing
Inner Ear (cont) Vibrations at the oval window cause vibrations in
the perilymph of the scala vestibuli Vibrations pass through vestibular membrane into
endolymph Vibrations than pass through basilar membrane to
perilymph of scala tympani Organ of Corti
Found in basilar membrane, contains hearing sensors with hairs; vibrations cause hairs to move
AnimationAnimation
Equilibrium Two divisions:
1) Static Equilibrium - senses posture while at rest○ Occurs in vestibule○ Position of head is determined by hairs on the
macula, hairs respond to shifting of otoliths2) Dynamic Equilibrium – maintaining balance
during movement○ Occurs in the semicircular canals, in particular
the ampulla○Movements cause the perilymph to stimulate
hairs in the ampulla
Sight Visual receptors located in eye Accessory organs aiding eye:
EyelidsLacrimal apparatus○ Gland that produces tears to cleanse and protect
eye and ducts to carry the tears to the nasal cavityMuscle○ Moves the eye
The Eye Posterior portion
Sclera○ Tough fibrous covering
Choroid coat○ Contains melanocytes to help darker the inside of
the eye Retina ○ Thin complex inner layer that is continuous with the
optic nerve and contains the receptorsVitreous humor○ Jelly-like fluid filling internal eye
The Eye (cont) Anterior portion
Cornea○ Transparent covering
Aqueous humor○ Fluid that is made between the iris and lens but can move
to between the cornea and the iris through the pupilIris○ Pigmented layer containing smooth muscle to control size
of pupilLens○ Layer that focuses the image on the retina; can change
shape to change focus
The Retina Contains two types of receptors:
1) Rods○ Black-and-white vision; more indistinct image; pigment is
rhodopsin2) Cones○ Color vision; refined image; pigments are sensitive to red,
green, and blue hues Fovea centralis
Part of retina containing high concentration of cones; area with sharpest focus
Optic discArea of retina with connection to optic nerve; lacks
receptors (blindspot)
Eye DissectionCow's Eye Dissection