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chemical senses
(smell & taste)
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Olfaction:
- i. Uses chemoreceptors * found in olfactory epithelium consists of 3 cell types:
- 1. supporting cells
- 2. * ofactory cells (bipolar neurons w/ 6-8 cilia)
- 3. basal cells (give rise to new supporting & olfactory cells)
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smells must
- be volatile
- be able to dissolve in mucus of epithelium
- be able to cross membrane of olfactory cells & interact w/receptors
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2 aspects to smell
- 1.acuity – concentration perceived
- 2.discrimination- number of scents distinguished
- Threshold for smell- very low
- Adaptation time- very rapid
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Gustatory
- i.Uses chemoreceptors * located in taste buds; consist of 3 cell types:
- 1.supporting cells
- 2. gustatory cells- bipolar neurons w/ gustatory hair
- 3.basal cells- give rise to the supporting & gustatory cells
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tastes must:
- go into solution
- enter taste porecross membrane & interact with receptors
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There are 5 basic tastes
- a. Salty
- b. Sweet
- c. Sour
- d. Bitter
- e. Umani
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refraction
bending of light rays as they travel through transparent media of differing densities (occurs 4X in our eyes)
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Myopia
(correction- concave lens)
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Hyperopia
(correction – convex lens)
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Astigmatism
(correction- cylindrical lens)
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accommodation
changing lens shape for near & far vision
- distant: flatten lens, relax ciliary muscle
- close: bulge lens, contract ciliary muscle
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presbyopia-
old eyes, lack of ability to change lens shape as well
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constriction of pupils
concentrate light on retina
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convergence of eyeballs
both eyes directed to object being viewed
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chemical
- conversion of light into an electrochemical impulse (nerve impulse) by stimulation of photoreceptors
- involves a photopigment in the receptor changing shape when light hits it
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rhodopsin
scotopsin (a protein) + retinal (vit A derivative)
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retinal bound to scotopsin (bent shaped)
11- cis isomer
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all-trans isomer
- struck by light it changes shape
- shape change>chain of events>vision
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freed opsin sets of a chain reaction that hyperpolarizes photoreceptor
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bipolar neurons have two different types of receptors for the photoreceptors' neurotransmitters (turning them "off" and "on")
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the 2 diff responses of bipolar neurons also affect ganglion cells differently (excitation or inhibition)
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cones
- -use the same basic process, but different photopigments (no rhopsodin)
- - require brighter light to destabilize
- - reform much more quickly
- - 3 types red, green, blue
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rods
up to 100 may converge on a single ganglion cell (providing fuzzy diffuse vision)
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cones vision
each converges into its own ganglion cell (providing sharp detailed vision)
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movement senses
hearing & equilibrium
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hearing
concerned with the movement of sound waves
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sounds
come from vibrations, we perceive their effects as sound
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pitch
frequency of vibrations
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most sensitive
1500-4000 hz
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hearing range
20-20,000 cycles per second
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volume
- amplitude of vibrations
- measured in decibals
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damage to hair cells
120 db
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review parts of ear and functions
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review structure of the cochlea
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route of sound waves through ear
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cochlea
devoted to hearing
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3 major parts of ear
outter, middle, inner
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outter
- pinna
- external auditory canal
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function of outer ear
- channel sound
- pinpoint location
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middle ear
- main function: amplification of sound/vibration
- equalization of pressure
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middle ear structures
- tympanic membrane
- auditory ossicle: malleous, incus, stapes
- oval window
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pharyngotympanic tube
- eustachian tube
- pressure needs to be equal on both sides
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static equilibrium
- handled by structures in vestibule
- saccule & utricle
- perpendicular to one another
- sense body orientation, esp head, relative to ground
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sensory cells static equilibrium
- located in the macula
- covered by the otolithic membrane
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dynamic
- handled by semi circular canals
- maintains body position, esp head, sudden movements
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dynamic sensory cells
- located in cristae (w/in ampullae)
- at base of semicircular canals,
- coverd by cupula
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