Vestibular apparatus: mechanoreceptors in 2 inner ear structures: semicircular canals; detect angular acceleration otolith organs; detect linear forces or accelerations on head(remember f = ma) Semicircular canals: really are complete circles, not semicircles. Set of 3 on each side of head oriented orthogonally (right angles) to one another so cover all 3 dimensions in space not same as hair follicle receptors in skin hair cell receptors located within enlargement called. Ampulla hair cell stereocilia embedded in the cupula (gelatinous) which forms a flexible barrier across the ampulla. Otolith organs: receptors are also hair cells cilia embedded in matrix containing calcium carbonate crystals. V1) all info proprioceptive in nature of what head is doing at one time info goes to area 3a of s1 vestibular info, stretching muscle spindles head mapping of proprioceptive system otolith organs near utricle and saccule. Olfactory receptors: unique primordial sensory system developed in mammals over 1,000 dif receptor genes; ~350 rec prots expressed in humans.