The General and Special Senses

1. The General and Special Senses Chapter 9

2. Overview I • The 4 general receptor classes are throughout the body and are: • Temperature • Pain • Touch, Pressure, Position • Chemical • Your book lists about 6 different general receptors, then explains them in different categories.

3. Overview II • The 5 special senses are localized and are: • Smell (olfactory) • Taste (gustation) • Vision (optical) • Balance (equilibrium) • Hearing (auditory)

4. Overview III • Sensory receptor • Specialized cell, sends sensation to the CNS • The simplest are free nerve endings • The complex-est are specialized • Each monitors a specific receptor field

5. Overview IV • Sensory info • Relayed via action potentials in a sensory (Afferent) fiber • Larger the stimulus = greater frequency of action potentials • CNS interprets the nature of the arriving info on the basis of the area of the brain stimulated • SENSATION is arriving information • ADAPTATION is a reduction in sensitivity in the presence of a constant stimulus • Done via change in sensitivity or inhibition of sensory pathways

6. THE GENERAL SENSES 1/4 PAIN • NOCICEPTORS • Fast pain • Prickling • Slow pain • Burning (not necessarily temperature-related) and aching • Perception of pain in parts not actually hurting is called referred pain (Also, auxiliary pain) • This is because nociceptors have a large receptive field. • Sensitive to: temperature extremes, mechanical damage, dissolved chemicals (e.g. histamine from mast cells)

7. THE GENERAL SENSES 2/4 TEMPERATURE • Thermoceptors • Respond to changes in temperature • Located in dermis, skeletal muscles, liver, hypothalamus • Coldthermoreceptors • Hotthermoreceptors • No known structural differences between these • 3-4 times as many cold to hot thermoreceptors

8. THE GENERAL SENSES 3/4 MECHANORECEPTORS • Sensitive to stimuli such as: • Stretching • Compression • twisting

9. THE GENERAL SENSES 3a/4 TOUCH • TACTILE RECEPTORS • Distinctions are not as precise • Free nerve endings: touch and pressure • Root hair plexus: distortions and movement on the body surface • Merkel (tactile) discs and Merkel cells: fine touch • Meissner’s (tactile) corpuscle: fine touch and pressure LF vibration • Lamellated (pacinian) corpuscle: pulsing, HF vibration, • Ruffini corpuscle: pressure and distortion of the skin

10. THE GENERAL SENSES 3b/4 PRESSURE • BARORECEPTORS • Sensitive to pressure • Provide info for the autonomic activities • Rapid response • Rapid adaptation

11. THE GENERAL SENSES 3c/4 POSITION • PROPRIOCEPTORS • Sensitive to position • Monitor position of joints, tension in tendons and ligaments, and the state of muscle contraction • Free nerve endings, Golgi tendon organs, muscle spindles • Do not adapt • Primarily subconscious processing and only a minor amount of conscious awareness • Your sense of body position comes from these and the info from the inner ear

12. THE GENERAL SENSES 4/4 CHEMICAL • CHEMORECEPTORS • Respond only to these substances dissolved in the surrounding fluid: • Water-soluble • Lipid-soluble • Primarily measure pH, CO2, and O2

13. THE SPECIAL SENSES – 1/5 • SMELL (olfaction) • OLFACTORY RECEPTOR CELLS • Mucus is formed over the olfactory epithelium to help: • prevent the buildup of potentially dangerous/overpowering stimuli • Keeps the area moist • Keeps are free of debris • Only smell about 2% of inhaled air • Must be water or lipid soluble • Diffuses through mucous before they can stimulate olfactory receptor cells.

14. THE SPECIAL SENSES – 2/5 • TASTE • GUSTATORY RECEPTORS (tastebuds) • Over tongue and adjacent parts of the pharynx and larynx (voicebox). • Cirvumvallate papillae: large clusters of tastebuds, come in contact with DISSOLVED food. • Primary taste sensations: sweet, sour, salty, bitter. • Tastebuds in all parts of the tongue can provide all taste sensations. • Technically, there is a 5th sensation: water. • Most sensitive to extremes of pH.

15. ANATOMY OF THE EAR – • Ear is divided into 3 parts: • External: collects and directs sound waves toward the middle ear. • Middle: collects and amplifies sound waves toward a portion of the inner ear. • Inner: contains the sensory organs for hearing and equilibrium.

16. ANATOMY OF THE EAR – 1/3 • EXTERNAL EAR • Our regular “ear” or the auricle (also, pinna) • Cerumen (Earwax) is important: • Together with outward-facing hairs, helps prevent foreign stuff, including insects from entering. • Tympanum/tympanic membrane (eardrum) • Separates external from middle ear

17. ANATOMY OF THE EAR – 2/3 • MIDDLE EAR • The tympanic cavity, mechanically amplifies audio • Also connects to the nasopharynxvia the Eustachian/pharyngotympanic tube. • Unfortunately, you can get an ear infection (otitis media) from microorganisms going up this passageway. • Auditory ossicles: hammer, anvil, stirrup • Muscles can control the amplification of the audio.

18. ANATOMY OF THE EAR – 3/3 • INTERNAL EAR • 3 primary parts: • Vestibule (equilibrium) • Semicircular canals (equilibrium) • Cochlea (hearing)

19. THE SPECIAL SENSES – 3/5 • EQUILIBRIUM • 2 types: • Dynamic • Static • Semicircular ducts: rotational motion • The vestibule: gravity and linear acceleration

20. THE SPECIAL SENSES – 4/5 • HEARING • The ear senses FREQUENCIES • LF near center, HF at outside, where the cochlea is stiffer. • Movement of basilar membrane is amplified as it goes to the tectorial membrane.

21. THE SPECIAL SENSES – 5/5 • VISION

22. Accessory Structures - • Eyelids and associated exocrine glands • Superficial epithelium of the eye • Structures associated with the production, secretion, and removal of tears • The extrinsic eye muscles (muscles outside of the eye itself)

23. Accessory Structures – • Eyelids/palpebrae – act as lubricating windshield wipers • Connected to the canthuses • Associated diseases: • Sty • Conjuctivitis • Lacrimal apparatus