1. Senses: Chapter 10

2. Types of Receptors • Chemoreceptors • 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: • 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 scalavestibuli • 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 • 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 • 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 • 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: • 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 DissectionCow's Eye Dissection