Post on 03-Jan-2016
Organs of EquilibriumEquilibrium receptors of the inner ear are
called the vestibular apparatusVestibular apparatus has two functional
partsStatic equilibriumDynamic equilibrium
Static EquilibriumMaculae—receptors in the vestibule
Report on the position of the headSend information via the vestibular nerve
Anatomy of the maculaeHair cells are embedded in the otolithic
membraneOtoliths (tiny stones) float in a gel around the
hair cellsMovements cause otoliths to bend the hair
cells
Dynamic EquilibriumCrista ampullaris—receptors in the
semicircular canalsTuft of hair cellsCupula (gelatinous cap) covers the hair cells
Dynamic EquilibriumAction of angular head movements
The cupula stimulates the hair cellsAn impulse is sent via the vestibular nerve to
the cerebellum
Organs of HearingOrgan of Corti
Located within the cochleaReceptors = hair cells on the basilar
membraneGel-like tectorial membrane is capable of
bending hair cellsCochlear nerve attached to hair cells
transmits nerve impulses to auditory cortex on temporal lobe
Mechanism of HearingVibrations from sound waves move
tectorial membraneHair cells are bent by the membraneAn action potential starts in the cochlear
nerveContinued stimulation can lead to
adaptation
Olfaction—The Sense of Smell
Olfactory receptors are in the roof of the nasal cavityNeurons with long ciliaChemicals must be dissolved in mucus for
detectionImpulses are transmitted via the olfactory
nerveInterpretation of smells is made in the
cortex
The Sense of TasteTaste buds house the receptor organsLocation of taste buds
Most are on the tongueSoft palateCheeks
The Tongue and TasteThe tongue is covered with projections
called papillaeFiliform papillae—sharp with no taste budsFungifiorm papillae—rounded with taste budsCircumvallate papillae—large papillae with
taste budsTaste buds are found on the sides of
papillae
Structure of Taste BudsGustatory cells are the receptors
Have gustatory hairs (long microvilli)Hairs are stimulated by chemicals dissolved
in saliva
Structure of Taste BudsImpulses are carried to the gustatory
complex by several cranial nerves because taste buds are found in different areasFacial nerveGlossopharyngeal nerveVagus nerve
Taste SensationsSweet receptors(sugars)
SaccharineSome amino acids
Sour receptorsAcids
Bitter receptorsAlkaloids
Salty receptorsMetal ions
Developmental Aspects of the Special SensesFormed early in embryonic developmentEyes are outgrowths of the brainAll special senses are functional at birth
Chemical Senses: Taste and SmellBoth senses use chemoreceptors
Stimulated by chemicals in solutionTaste has four types of receptorsSmell can differentiate a large range of
chemicalsBoth senses complement each other and
respond to many of the same stimuli
Developmental Aspects of the Special SensesEye problems
Strabismus—“crossed eyes” results from unequal pulls by the external eye muscles in babies
Ophthalmia neonatorum—conjunctivitis resulting from mother having gonorrhea. Baby’s eyelids are swollen and pus is produced
Developmental Aspects of the Special SensesEye problems
Presbyopia—“old vision” results from decreasing lens elasticity that accompanies aging