Special Senses Vision, Hearing, Equilibrium, Small, and Taste

Physiology of Equilibrium Vestibular Apparatus –Vestibule & Semicircular canals – Responds to head movements –Works w/sight, muscles, and tendons to provide info used to control balance in cerebellum Static Equilibrium –Receptors report on position of head w/respect to gravity when body is not moving –Determines which way is up/down –Keeps head upright Dynamic Equilibrium –Receptors in semicircular canals respond to angular or rotary movements of the head –3 canals (one in ea/plane) –Transmits up vestibular nerve to cerebellum –When moving at a constant rate receptors stop sending impulses

Physiology of Hearing Sound waves transmit via vibrations tympanic membrane  auditory ossicles  oval window  fluids of cochlea Fluid bends hair cells which act as hearing receptors in the Organ of Corti (inside the cochlear duct) –High pitched sounds disturb short hair fibers close to the oval window –Low pitch sounds affect the longer hair fibers further along the cochlea Hairs transmit impulse via cochlear nerve to auditory cortex in temporal lobe Sound reaches ea/ear at different times therefore we hear “in-stereo” and detect location of sound When same sounds or tones keep reaching ears the auditory receptors stop responding to the sounds

Deafness Deafness – hearing loss of any degree 2 types: –Conduction Something interferes w/conduction of sound vibrations (i.e. earwax build up) Hearing aids helpful –Sensorineural Damage to receptor cells in organ of Corti, the cochlear nerve, or auditory cortex (i.e. damage due to repeated loud sounds)

Smell Sense of smell – provided by a pair of olfactory organs In nasal cavity on either side of nasal septum Olfactory receptor cells found in olfactory epithelium Underlying olfactory glands secrete mucus (keep nostrils moist and debris free) Tips of receptor cells have cilia that extend into mucus The binding of an odorant changes permeability of receptor membrane producing an action potential Signal sent to olfactory bulbs  olfactory cortex of cerebrum & hypothalamus Smell is the only sensory info that doesn’t synapse with the thalamus first, explains profound emotional and behavioral responses certain smells produce ch?v=H_WFlTtPZmEhttp:// ch?v=H_WFlTtPZmE

Taste Gustatory receptors are distributed on tongue, pharynx, and larynx Taste buds – taste receptors, well protected (from mech. stress), found along sides of epithelial projections called papillae Dissolved chums change the memb. potential of taste cells  action potential of sensory neurons  medulla oblongata  thalamus  primary sensory cortex 4 taste sensations: Sweet, Salty, Sour, Bitter –No difference in structure of taste buds –Extremely sensitive to sour (acids) and bitter (bio toxins) than sweet and salty 2 additional tastes recently discovered: –Umami – pleasant taste (beef & chxn broth, parmesan cheese) –Water – (in pharynx) – water balance and blood volume Sensitivity to tastes increases as olfactory function increases =relatedhttp:// =related