1. Senses: Chapter 10

2. Types of Receptors Chemoreceptors Pain receptors Thermoreceptors
Respond to changes in chemical concentrations
Pain receptors
Respond to tissue damage
Thermoreceptors
Respond to temperature changes
Mechanoreceptors
Respond to changes in pressure or movement
Photoreceptors
Respond to light

5. Sensation and Projection
Brain:
Sensations come from here
Impulses are interpreted based on what area of the brain they end up in
Brain 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

6. Somatic senses
Sensors are widely spread throughout body and are fairly simple
Include:
Touch
Pressure
Temperature
Pain

7. 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 hair
3) Pacinian corpuscles
Respond to heavy pressure, located in deeper tissues

9. Temperature Receptors
Warm and cold receptors in skin
Free nerve endings
Receptors adapt very fast
Pain receptors
Extreme temperatures and injury stimulate these

10. 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

11. Special senses Sensations arise from specially adapted sensors
Includes:
Smell
Taste
Hearing
Equilibrium
Sight

12. 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

14. 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 chemoreceptors
Incoming foods must be dissolved in saliva to be tasted

16. Areas of the Tongue Four main taste areas:
Sweet - concentrated on the tip of the tongue
Sour - concentrated along the margins of the tongue
Bitter - concentrated along the back of the tongue
Salty - spread throughout

17. 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

19. 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

22. Inner Ear Includes two labyrinths: Two parts to the labyrinth:
1) Osseous labyrinth - bony canals
2) Membranous labyrinth - membrane-bound tube inside the bony canals
Perilymph separates the two
Endolymph is found inside the membranous labyrinth
Two parts to the labyrinth:
1) Semicircular canals - used in equilibrium
2) Cochlea – organ for hearing

24. 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
Animation

26. 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 otoliths
2) 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

28. Sight Visual receptors located in eye Accessory organs aiding eye:
Eyelids
Lacrimal apparatus
Gland that produces tears to cleanse and protect eye and ducts to carry the tears to the nasal cavity
Muscle
Moves the eye

29. The Eye Posterior portion Sclera Choroid coat Retina Vitreous humor
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 receptors
Vitreous humor
Jelly-like fluid filling internal eye

30. The Eye (cont) Anterior portion Cornea Aqueous humor Iris Lens
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 pupil
Iris
Pigmented layer containing smooth muscle to control size of pupil
Lens
Layer that focuses the image on the retina; can change shape to change focus

31. The Retina Contains two types of receptors: Fovea centralis Optic disc
1) Rods
Black-and-white vision; more indistinct image; pigment is rhodopsin
2) 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 disc
Area of retina with connection to optic nerve; lacks receptors (blindspot)

33. Eye Dissection Cow's Eye Dissection