1.  Sensory Receptors - detect environmental changes and trigger nerve impulses  Somatic Senses  Touch, pressure, temperature, pain  Special Senses  Smell, taste, vision, equilibrium SENSES

2.  Chemoreceptors – respond to chemical stimuli  ex) coratid artery for carbon dioxide  Pain receptors – “nociceptor” usually reacts to tissue injury  Thermoreceptors – different nerve endings for cold & heat; cutaneous & mucosal  Mechanoreceptors – touch, pressure, sound, muscular contraction causing tension  Photoreceptors – rods & cones in the retina – used only in vision Receptors and Sensations

3.  Sensation = feeling that occurs when a brain interprets a sensory impulse  Projection = a connection between the cerebral cortex and other parts of the nervous system or organs of special sense.  Sensory adaptation = sensory receptors stop sending signals when they are repeatedly stimulated (does not apply to pain receptors) 3 Sensations

4.  Sensory Nerve Fibers  epithelial tissue, pain and pressure  Meissner's corpuscles  hairless areas of skin (lips, fingertips, tongue)  Pacinian corpuscles  deep pressure (tendons, joints)  Temperature Senses  warm and cold receptors  Nociceptors  Sense pain Somatic Senses

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6.  Visceral Pain - occurs in visceral tissues such as heart, lungs, intestine  Referred pain - feels as though it is coming from a different part  Acute Pain - originates from skin, usually stops when stimulus stops  Chronic Pain - dull aching sensation Sense of Pain

7.  Inhibitors of Pain  natural brain chemicals can be mimicked by drugs such as morphine  Serotonin  Endorphins Regulation of Pain

8.  Smell = OLFACTORY ORGANS  Taste = TASTE BUDS  Hearing & Equilibrium = EARS  Sight = EYES 8 Special Senses

9.  Olfactory organs contain olfactory receptors = “chemoreceptors” Pathway  Odor molecule enters nose  Cilia on olfactory receptor cells sense the chemicals  Olfactory bulb – receptor cells synapse with Mitral Cells  Nerve impulse sent through the Olfactory Tract  Limbic system in the brain “associates” or processes the information 9 Pathway of Smell Sensation

11.  “Gustatory” sense  Taste buds contain chemoreceptors  Around 10,000  Four Kinds of Papillae: Fungiform, Filiform, Foliate, Circumvallate  FIVE Tastes: Sweet, Sour, Salty, Bitter, Umami  MISCONCEPTION: different taste areas on the tongue! 11 Sense of Taste

12.  Pathway of Taste Sensation  Taste receptors in the papillae  Sensation sent to cranial (facial) nerves  Medulla Oblongata  Thalamus  Parietal Lobe of Cerebrum makes final association 12 Sense of Taste

14.  External Ear  Auricle (pinna) - outer ear  External Auditory Meatus Sense of Hearing

16.  Middle Ear – Tympanic Cavity  Tympanic membrane  Auditory Ossicles  Malleus  Incus  Stapes  Eustachian (Pharyngotympanic) Tube Sense of Hearing

18.  Inner Ear  Labyrinth - communicating chambers and tubes  Osseous Labyrinth and Membranous Labyrinth  Perilymph and Endolymph  fluids within the labyrinth  Semicircular Canals - sense of equilibrium  Cochlea - sense of hearing  Organ of Corti - contains hearing receptors, hair cells detect vibrations Sense of Hearing

21.  Inside the cochlea are special neurons called HAIR CELLS  The stapes is attached to the OVAL WINDOW  vibrations cause the perilymph to vibrate  the hair cells here transmit this vibration  Therefore the HAIR CELLS in this region are RECEPTORS for hearing. Inner Ear: Cochlea

22. Steps in Hearing  1. Sound waves enter external auditory meatus  2. Eardrum vibrates  3. Auditory ossicles (malleus, incus, stapes) amplify vibrations  4. Stapes hits oval window and transmits vibrations to cochlea  5. Organs of corti contain receptor cells (hair cells) that deform from vibrations  6. Impulses sent to the vestibulocochlear nerve  7. Auditory cortex of the temporal lobe interprets sensory impulses  8. Round window dissipates vibrations within the cochlea

23.  Static Equilibrium  sense the position of the head, maintain stability and posture  Dynamic Equilibrium (semicircular canals)  balance the head during sudden movement  Cerebellum  interprets impulses from the semicircular canals and maintains overall balance and stability Sense of Equilibrium

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