Special Sense

Special sense

Olfaction

Axons of ORN leave olfactory epithelium

Pass thro cribriform plate

Synapse on neurons in olfactory bulb

Impulse travel via CN 1

Arrive cerebral cortex, hypothalamus, limbic 

Ear

External 

• auricle
• external acoustic meatus (hair, ceruminous gland)

Middle

• eardrum/tympanic membrane 
• auditory ossicles - malleus, incus, stapes
• muscle 
• tensor tympani muscle - connect malleus to temporal bone & contraction stiffen eardrum lower vibration
• stapedius - reduce stapes movement 

Internal

• bony labyrinth - perilymph - dense bone shell
• vestibular system
• semicircular canal 
• duct w endolymph 
• anterior tilt
• posterior no
• lateral yes 
• ampullary crest 
• ampullary cupula - kino (single long), stereocilia 
• vestibule - utricle & saccule - gravity & linear acceleration 
• macula utricle horizontal
• macula saccule vertical
• cochlear duct + cochlea
• vestibular duct
• tympanic duct 
• organ of Corti 

Hearing 

• sound waves arrive eardrum
• eardrum vibrate
• auditory ossicles displace
• stapes push oval window
• establish pressure waves in perilymph thro vestibular duct to tympanic duct
• pressure relieve at round window
• hair cell of organ of Corti on basilar membrane of cochlear duct moved by waves
• press tectorial membrane
• stereocilia distort
• send signals via cochlear branch of CN VIII to CNS 

Physiology

• fx = waves no passing fixed point in given time 
• high fx, short wavelength
• pitch = perception of fx
• intensity = energy in waves (amplitude) - loudness
• greater energy, larger amplitude - louder 

Ds

• motion sickness
• conductive - earwax, infection, perforated tympanic 
• sensorineural - damage to nerve/cochlea 
• aging 
• tympanic membrane not flexible
• articulation between auditory ossicles stiffen
• round window ossify 

Gustation

Taste receptor on superior of tongues, pharynx, larynx 

Taste bud in papillae 

Papillae types

• filiform provide friction to move obj
• fungiform - 5 taste bud
• foliate on lateral of posterior tongue 
• vallate - 100-300 taste bud 

Vision

• receptor
• bipolar on ganglion
• optic nerve
• optic chiasm
• thalamus
• optic radiation - fibers radiate to visual cortex of occipital lobe 

Eye color

• melanocyte density & distribution
• pigmented epithelium density 

Focal point: specific point on retina

Focal distance: distance between center of lens and it's focal point 

Determined by distance from object to lens & lens shape 

Accommodation: focus by changing lens shape 

Far vision

• ciliary muscle relax
• ciliary zonule pulls on lens
• lens flat 
• focus image 

Close/near vision

• ciliary muscle contract
• ciliary body toward lens 
• decrease tension in zonule
• spherical lens 
• increase refraction

Myopia近视

• focal distance too short
• image in front retina
• eye ball too deep
• resting curvature of lens too great 
• concave

Hyperopia远视

• focal distance too long
• image focus beyond retina
• eye ball too shallow
• lens too flat
• convex 

Photoreceptor

• rods - BW
• cones - color, visual acuity
• bipolar cells
• Horizontal - photoreceptor/bipolar synapse
• Amacrine - bipolar & ganglion synapse 

Ds

• color blind - non functional cone
• blind spot - optic disc no receptor
• senile cataract - lens not transparent