special senses n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
SPECIAL SENSES PowerPoint Presentation
Download Presentation
SPECIAL SENSES

Loading in 2 Seconds...

play fullscreen
1 / 93

SPECIAL SENSES - PowerPoint PPT Presentation


  • 129 Views
  • Uploaded on

SPECIAL SENSES. Making Sense of The World. Sensation. relationship between physical energies in the environment & psychological experience of those energies to perceive & detect physical energies & encode them into neural signals. Basic Senses. Sight Hearing Touch Smell Taste also

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'SPECIAL SENSES' - misae


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
special senses

SPECIAL SENSES

Making Sense of The World

sensation
Sensation
  • relationship between physical energies in the environment & psychological experience of those energies
  • to perceive & detect physical energies & encode them into neural signals
basic senses
Basic Senses
  • Sight
  • Hearing
  • Touch
  • Smell
  • Taste
  • also
  • Pain
  • Pressure
  • Temperature
  • Joint position
  • Muscle sense
  • Movement
senses
SENSES
  • systems that translate outside information into activity in nervous system
  • gather information by detecting energies
  • environment contains many different forms of energies
receptors
Receptors
  • detect only the energies have receptor for
  • restricted awareness
  • receptor cells transduce or change physical energy into a signal brain can understand
transduction
Transduction
  • conversion of physical energies into language of brain
  • receptor cells convert physical energies into neural impulses which travel to cerebral cortex to be decoded
  • all sense signals except smell go to relay station-thalamus
  • from there to primary sensory areas in cerebrum-different for each sense
  • here they are modified and sent on to higher regions of brain
olfaction
Olfaction
  • sense of smell
  • chemical sense
  • air borne chemicals detected
  • oldest sense
  • all organisms have some type of chemical sense
  • major senses in most animals
  • help locate food, recognize trails & territories identify kin & find receptive mates
  • social insects send & receive intricate chemical signals which tell themwhere to go and how to behave
  • social behavior of most animals is controlled by chemical signals
  • olfactory receptor area in German Shepherd-72X bigger than in humans
olfactory system
Olfactory System
  • humans are able to distinguish 10,000 smells
  • detected in paired olfactory organs in nasal cavity by specialized receptor cells found in olfactory epithelium-olfactory receptor neurons
olfactory system1
Olfactory System
  • olfactory organs posses 2 layers
  • olfactory epithelium
  • lamina propria
  • olfactory epithelium covers inferior cribifrom plate, superior perpendicular plate & superior nasal conchae of ethmoid bone
  • covered by mucus which contains olfactory receptors
  • lamina propria-comprised of areolar tissue, blood vessels, nerves & olfactory or Bowman’s glands
    • produce secretions that bathe surface of olfactory receptors
olfactory system2
Olfactory System
  • 10 – 100 million olfactory receptors
  • modified bipolar neurons
  • have terminal enlargements or knobs whichproject above epithelial surface
  • from each 8-20 olfactory cilia extend into mucus
  • contain smell receptors
  • cilia project from knob & lie parallel to epithelia surface
  • exposes considerable surface area to dissolved compounds
  • at other end of receptor cell, axons project to olfactory bulb
  • 10-100 axons form into bundles, penetrate cribriform plate terminate in olfactory bulb
  • stem cells allow neurons to regenerate
olfaction1
Olfaction
  • refers to breathing in chemicals
  • Inhaletake in chemicals or odorants
    • chemicals that stimulate olfactory receptors
  • must be smallenough to be volatile to vaporize, reach the nose & dissolve in mucus to stimulate olfactory receptors
  • at olfactory organswater & lipid soluble materials diffuse into mucus
olfaction2
OLFACTION
  • dissolved chemicals interact with receptors- odorant binding proteins
  • 4 odorant molecules will activate an olfactory receptoractivates adenylate cyclaseconverts ATPcAMPopens Na channels in membrane local depolarizationdepolarization large enough action potential in axon conveyed to CNS
olfactory pathways
Olfactory Pathways
  • axons of receptors extend through olfactory foramina in cribiform plate to form right & left olfactory nerves
  • terminate in brain in the olfactory bulbsaxons of bulbs extend posteriorlyform olfactory tract projects to primary olfactory cortex located at inferior & medial surface of the temporal lobe
  • projects to hypothalamus & amygdala
  • parts of limbic system
  • amygdale associate experiences with smellsproducing emotion
  • projections are sent to thalamus and to frontal cortex-recognition
olfactory discrimination
Olfactory Discrimination
  • can recognize 2000-4000 chemical stimuli
  • several primary smells for which thousands of receptors are needed
  • 1) ethereal2) camphoraceous3) musky4) floral5) minty6) pungent7) putrid
  • 1% of genes are needed to make receptor proteins to recognize smells
  • no distinct receptor for each detectable odor
gustation
Gustation
  • chemical sense
  • chemicals are taken into the body & dissolved in oral cavity
  • drives appetite
  • protects from poisons
    • bitter & sour tastes produce aversive, avoidance reactions
    • most poisons are bitter
    • off food goes sour or has an acidic taste
taste discrimination
Taste Discrimination
  • 5 primary sensations
  • Sweet
  • Salty
  • Sour
  • Bitter
  • Umami
    • MSG
    • taste of beef, chicken broth & parmesan cheese
  • taste combined with smell gives flavor
    • when nose is blocked foods seem bland or tasteless
anatomy of gustation
Anatomy of Gustation
  • receptor-taste bud
  • 10,000
  • tongue, soft palate, pharynx & epiglottis
  • survives about 10 days
  • Consists of:
  • taste receptors or gustatory cells
  • basal or stem cells
  • supporting cells
anatomy of gustation1
Anatomy of Gustation
  • Supporting cells
  • surrounds about 50 gustatory receptors cells in each taste bud
  • one single long micovillus (gustatory hair) projects from each gustatory receptor cell to surface through taste pore
  • Basal cells
    • stem cells
    • found in periphery of taste buds
anatomy of gustation2
Anatomy of Gustation
  • gustatory receptors
    • embedded in specializations of surrounding epithelium called papillae
  • three types contain taste buds
  • vallate
  • fungiform papillae
  • folliate
papillaetypes
PapillaeTypes
  • Vallate or circumvallate papillae
    • have100 taste buds
    • back of tongue
  • Fungiform papillae
    • possess5 tastebuds
    • over entire tongue
  • Folliate
    • lateral margins
    • taste buds degenerate in early childhoog
  • Filiform papillae
    • no taste buds
    • Tactile receptors
    • provide friction sensations
gustatory transduction
Gustatory Transduction
  • dissolved chemicals contact taste hairs
  • bind to receptor proteins on gustatory cell
  • causes series of chemical reactions producingaction potential
gustatory transduction1
Gustatory Transduction
  • different tastes involve different receptor mechanisms
  • salt receptorsdepolarize after Na channels open
  • sweet receptors depolarize after K channels open
gustatory pathways
Gustatory Pathways
  • Taste is monitored by cranial nerves VII-facial
    • picks up sensation from anterior 2/3rds of tongue
  • IX-glossopharyngeal
    • covers posterior 1/3rd of tongue
  • X-vagus
    • receives information from epiglottis
  • axons from these nerves synapse on nucleus solitarius in medulla oblongata
  • axons of postsynaptic neurons enter medial lemniscus & synapse in thalamus
  • then project to gustatory cortex conscious perception
  • here information is correlated with other sensory data such as texture, peppery, hot
vision
Vision
  • primary sense in humans
  • sensory organs-eyes
accessory eye structures
Accessory Eye Structures
  • Eyelids or palpebrae
    • continuations of skin
    • blink continually to keep surfaces lubricated & things out of eyes
  • Palpebral fissure
    • gap separating free margins of upper & lower eyelids
  • Medial & Lateral canthus
    • where eyelids are connected
  • Eyelashes
    • keep foreign materials out

Medial Canthus

Lateral Canthus

accessory eye structures1
Accessory Eye Structures
  • Tarsal glands
    • sebaceous glands associated with eyelashes at inner margin
    • secrete lipids to keep eyelids from sticking together
  • Lacrimal Caruncle
    • medial canthus
    • makes a thick, gritty secretion often found in eyes after sleeping
accessory structures
ACCESSORY STRUCTURES
  • Palpebral conjunctiva
    • epithelium covers inner surface of eye
  • Ocular conjunctiva
    • covers anterior surface
    • extends to edges of cornea
      • transparent part of outer fibrous layer
accessory structures lacrimal apparatus
ACCESSORY STRUCTURES-Lacrimal Apparatus
  • produces, distributes & removes tears
    • tears reduce friction, remove debris, prevent bacterial infections & provide nutrients and O2 to eye
  • consists of
    • lacrimal gland
    • lacrimal canaliculi
    • lacrimal sac
    • nasolacrimal duct
  • lacrimal gland produces key ingredients and most of volume
  • tears accumulate at medial canthus or lacrimal lake
  • lacrimal puncta drains lakeempties into lacrimal caniliculilacrimal sacnasolacrimal duct nasolacrimal canalnasal cavity
the eye
THE EYE
  • irregular spheroid
  • three layers or tunics
  • outer fibroustunic
  • intermediate vascular tunic
  • inner neuraltunic
  • two hollow cavities
  • posterior, vitreouschamber
    • contains gelatinous vitreousbody
    • helps stabilize shape of eye
  • anterior chamber
    • filled with aqueous humor
    • functions to retain shape of eyeball
fibrous tunic
Fibrous Tunic
  • sclera & cornea
  • Functions:
  • mechanical support
  • physical protection
  • attachment site-extrinsic eye muscles
  • housing of focusing structures
  • Sclera
  • white of eye
  • site for insertion of 6 extrinsic eye muscles
  • contains blood vessels & nerves
  • Cornea-continuous with sclera
  • cornea & lens comprise-refractive system
  • focuseslight on retina
    • where photosensitive pigments are found
vascular tunic uvea
Vascular Tunic-Uvea
  • site of attachment for intrinsic eye muscles
  • provides route for blood & lymph
  • regulates amount of light entering eye
  • secretes & reabsorbs aqueous humor
  • controls shape of lens
  • Parts:
  • iris
  • cilliary body
  • choroid
the iris
THE IRIS
  • consists of pigment cells & 2 layers of smooth muscle
  • contraction of muscle produces change in diameter of pupil
    • central opening in iris
  • controlled by ANS
  • bright light causes constriction via consensuallight reflex
    • parasympathic pathway
  • dim light causes dilatation via pupillary reflex
    • sympathetic pathway
cilliary body
Cilliary Body
  • thicken area at periphery of eye
  • iris is attached to it
  • composed of cilliary muscles
choroid
CHOROID
  • separates fibrous & neural tunics
neural tunic retina
Neural Tunic-Retina
  • light sensitive
  • thin, pigmented outer layer
  • sheet of melanin containing cells
  • thick, inner layer-contains light receptors
  • begins visual pathway
  • consists of three layers
retina layers
Retina Layers
  • Photoreceptor layer
  • Bipolar cell layer
  • Ganglion cell layer
the retina
The Retina
  • Third layer
    • lightenergy converted into neural activity
      • contains specialized photoreceptor cells-rods & cone
      • transduce light wavelengths into information the brain understands
  • Second layer
    • bipolar cells
    • magnifies image
  • First layer
    • ganglion cells
    • further adjust image
    • axons form optic nerve
retina
Retina
  • if eyes simply transferred stimuli from retina to brainimages would be blurry
  • images are sharpened by sending information from photoreceptor cells backthrough first 2 layers ofretina
  • Bipolar cells connect photoreceptors to retinal ganglion cells
  • axons from ganglion cells form optic nerve
third layer
Third Layer
  • lightenergy is converted into neural activity
  • contains specialized photoreceptor cells-rods & cones
  • rods cannot see color
    • more sensitive than cones
    • sensitive enough to respond to a single photon of light
        • basic unit of light
  • create coarse, gray image
  • adequate for seeing in poor or dim light
  • can make out shapes fairly well
  • colors are completely absent
  • no color vision in dim light
rods cones
RODS & CONES
  • 18X more rods than cones
  • approximately 125 million rods
  • 6 million cones
  • arranged to produce best possible combination of night & day vision
cones
Cones
  • color vision
  • operate in bright light
  • Three types
  • Blue
  • Red
  • Green
  • experience of color is due to combination of these three cones
cones1
Cones
  • concentrated in macula leutea
  • center is fovea centralis
  • site of highest visual acuity or resolution
the lens
THE LENS
  • transparent structure located behind pupil in cavity of eyeball
  • consists of concentric layers of cells, filled with crystallins
    • transparent proteins responsible for clarity of lens & for focusing
focusing
Focusing
  • requires the cornea & lens
  • light is refracted or bent as it passes from one medium to another with different density
  • greatest amount of refraction occurs as light passes from air to cornea
  • more refraction occurs as light passes from aqueous humor to lens
  • lens provides extrarefraction needed to focus light from object to focal point
    • specific point of interaction in retina
  • distance between center of lens & focal point is focal length or distance
photopathway
PhotoPathway
  • Horizontal cells extend across outer part of retina at level of synapses between photoreceptor & bipolar cells
  • Amacrine cellsfound where ganglion cells synapse with bipolar cells
  • Light energy must pass through both ganglion & bipolar cells to get to photoreceptor cells where light energy is converted into neural signals which activates bipolar cells
  • One cone converges on one bipolar cell
    • preserves precise information, provides high acuity and fine detail
  • 1000 or more rods funnel information onto one bipolar cell
    • increases originalillumination & activates ganglion cells
optic nerve
OPTIC NERVE
  • Axons from 1 X 106 ganglion cells converge on optic disc
    • circular region medial to fovea
    • origin of optic nerve
    • penetrates wall of eye at area known as blind spot
    • no photoreceptors
  • forms optic nerve which partially crosses at optic chiasm
  • continues on to thalamus
  • from there to other areas of cortex all at the same time
refraction
Refraction
  • light rays reflected by object enter eye through cornea
  • light proceeds through pupil
    • size controlled by iris
  • behind pupillens focuses light rays into an invertedimage onto retina at back of eye
refraction1
Refraction
  • lens focuses image on photoreceptors by changing shape
    • accommmoation
  • shape of lens is determined by tone of ciliary muscles
  • shape determined by tone of cilliary muscles
accommodation
Accommodation
  • cilliary muscles relax for far vision
    • zonular fibers are pulled taut lens is under tension & flat
  • cilliary muscle contract for near vision
    • releases zonular fibers from tensionlens assumes a natural, rounder & more refractive state
      • rounder shape increases refractive power of lens
errors of refraction
Errors of Refraction
  • Presbyopia
    • lens thickensbecomes harder won't accommodate
    • seen in almost all people over the age of 40
  • Myopia-near sightedness
    • eyeball is too long
errors of refraction1
Errors of Refraction
  • Hypermetropia-far-sightedness
    • eyeball is too short
  • Astigmatism
    • lens or cornea not smoothly spherical
image formation
Image Formation
  • Final stage- constriction of pupil
  • pupil constricts hole narrows
  • due to the circular muscles of iris
photoreception
Photoreception
  • Photoreceptors detect photons of light
    • basic unit of visible light
  • light is radiant energy or electromagnetic radiation
    • comes in waves
    • referred to by wavelengths
  • wavelengths eyes detect are found in visible part of spectrum
  • can detect these because possess receptors excited by wavelengths between 400-700nm
light
LIGHT
  • 2 physical characteristicsof light determine sensory experience of it
  • Wavelength
    • distance of one wave peak to next
    • each wavelength is sensed as a color
  • Amplitude
    • indicates amount of energy
    • determines intensity of light
      • large amplitude makes for bright color
      • small amplitude makes dull color
photoreceptors
Photoreceptors
  • have outer segment containing discs
  • shape of outer segment provides name of photoreceptor
  • Rods
    • each disc is independent entity
    • outer segment forms elongate cylinder
  • Cones
    • discs are infoldings of cell membrane
    • outer segment tapers to tip
    • outer segment is connected to inner by narrow stalk
  • outer segments of both contain photopigment
    • absorbs light
photopigments
PHOTOPIGMENTS
  • one in rods
  • one in each of 3 cones
  • derivatives of rhodopsin or visual purple
  • consists of
  • protein-opsin-bound to light sensitive chromophore-retinal-made from vitamin A
  • Retinal-common to all photopigments
    • attaches to different opsins in cones
    • opsin determines wavelength of light that can be absorbed by retinal
photoreception1
Photoreception
  • photon strikes part of rhodopsin molecule
  • absorbed by visual pigment
  • retinal has 2 possible configurations
  • cis &trans forms
    • normally retinal is in cis form
  • once light is absorbedcis formtrans formtriggers chain of enzymatic steps
steps in photoreception
Steps in Photoreception
  • Step 1: Isomerization
  • Photon of light absorbed
  • Opsin is activated
  • cis formtrans form
step 2 photoreception
Step 2-Photoreception
  • Bleaching
  • trans retinal separates from opsin
  • Photopigment looks colorless
step 3 photoreception
Step 3-Photoreception

Regeneration

Trans retinal transforms back to the cis form

Cis-retinal can bind to opsin

Photopigment is functional again

color deficiency
Color Deficiency
  • Humans can discriminate 7X106 colors
  • some have difficulty with color perception
  • color deficient
  • 1 out of 50 individuals
  • gene responsible is sex-linked
  • deficiency seen more in males than in females
    • 8% of males & 0.05%
  • color deficient usually lacks either red or green opsin
  • have difficulty distinguishing red from green (both appear the same)
  • can’t color blend
  • Vision is said to be di- instead of tri-chromatic
depth perception
Depth Perception
  • havebinocularvision
  • when looking at an object a representation comes from both retinas
  • foveas are about 5-7.5 cm apart
  • visual fields for each eye slightly different
  • occipital cortex receives both of these images & fuses them into one picture
  • fusing confers perception of depth
  • Convergence
visual processing
Visual Processing
  • axons from all ganglion cellsoptic disc
  • optic nerves reach diencephalon & incompletely cross over at optic chiasm
  • From there ½ the fibers lateral geniculatenucleus on same side of brain
  • ½ the fibers continue to opposite lateral geniculate nucleus
  • From there image proceeds to occipital cortex via projection fibers
the ear
The Ear
  • three anatomical areas
  • External
    • collects sound waves & directs them toward middle ear
  • Middle
    • consists of a chamber in temporal bone
  • Inner
    • contains sensory organs for hearing & equilibrium
external ear
External Ear
  • composed of pinna
    • cartilaginous auricle
    • surrounds
  • external auditory canal
    • channels sound waves through auditory canal to
  • eardrum or tympanic membrane
    • thin, semi transparent membrane separates external from middle ear
  • ceruminous glands
  • secrete cerumen
    • waxy substance
    • neededfor protection
    • helps keep foreign objects out of ear
    • helps slow infections
middle ear
Middle Ear
  • filled with air
  • communicates with nasopharynx through auditory or eustachian tube
    • equalization of pressures
  • contains auditory ossicles
    • 3 tiny bones
  • malleus
  • incus
  • stapes
  • malleus attaches to tympanic membrane
  • stapes is bound to oval window
    • opening in middle ear going to inner ear
  • incus lies between malleus & stapes
inner ear
Inner Ear
  • labyrinth
  • contains receptors for hearing & equilibrium
  • Outer bony labyrinth encloses an inner-membranous labyrinth
  • bony labyrinth consists of vestibule, cochlea & semicircular canals
  • filled with perilymph
  • fluid in membranous part is endolymph
  • vestible comprised of membranous sacs: saccule &utricle
  • house receptors for gravity & linear acceleration perception
  • semicircular canals
    • receptors in canals provide information on head location
  • vestibule + semicircular canals make up vestibular complex
hearing receptors
Hearing Receptors
  • receptors for hearing are in cochlea
    • spiral shaped bony chamber
  • divided into thee channels
  • cochlear duct, scala vestibuli & scala tympani
  • the vestibular membrane separates the cochlear duct from the scala vestibuli
  • the basilar membrane separates cochlear duct form scala tympani
  • Resting on basilar membrane is spiral organ or organ or Corti
hearing receptors1
Hearing Receptors
  • sensory receptors are hair cells
    • on basilar membrane
    • 16 X 106 hair cells found in two groups
  • one-inner group arranged in a row
  • outer group arranged in three rows
  • free surface of each hair cell contains 40-80 stereocilia
    • similar to long microvilli
  • tectorial membrane covers the hair cells
audition
Audition
  • detection of sound
  • stimulusis sound waves
    • from compression & rarefaction of air-or alternating air pressure
  • distance between pressure peaks is wavelength
  • frequency determines pitch
    • measured in terms of cycles or waves per second called hertz-Hz
    • humans detect sounds in frequency range from 20 to 20,000Hz
  • longer waves produce lower frequencies & lower pitches
  • shorter wavelengths make higher frequencies & higher pitches
  • amplitude determines loudness
  • greater amplitude louder a sound
sound
Sound
  • measured in decibels
  • 0 decibels=absolute threshold
  • 10 decibels indicates 10X increase
  • normal conversation- around 60 decibels
  • passing train-about 100
  • above 80 damages hair cells
  • uncomfortable at 120
  • painful above 140
transduction of sound
Transduction of Sound
  • when we speak vocal cords vibrate molecules of air movebump into one another producing waves of compressed, expanded air
  • ears detect these waves & transduce them into nerve impulsesbrain decodes as sound
  • sound waves enter via external earcontinue on to tympanic membrane
  • air molecules under pressure cause tympanic membrane to vibrate
transduction of sound1
Transduction of Sound
  • movement of tympanic membrane displaces auditory ossicles
  • first malleusvibrates
  • handle of malleus strikes incuscausing it to vibrate
  • vibrating incus moves stapes
  • vibrates oval window
  • total force transferred to oval window
    • because window is much smaller force per unit area increases 15-20X.
  • vibrations of oval window produce pressure waves that vibrate perilymphin vestibular duct
  • these waves distort basilar membrane on way to round window of tympanic duct
  • location of maximum distortion varies with frequency
frequency coding
Frequency Coding
  • basilar membrane is narrow and stiff at window end
  • wide and flexible at apical end
  • topographical difference results in different regions vibrating at different frequencies
  • end near stapes (window end) vibrates at high frequencies
  • apical end vibrates at low frequencies
transduction of sound2
Transduction of Sound
  • pressure waves continue into endolymph inside cochlear duct
  • pressure waves in endolymph cause basilar membrane to vibrate which moves the hair cells of spiral organ against tectorial membrane
  • leads to bending of stereocillia & generation of nerve impulse
auditory pathways
Auditory Pathways
  • bending of hair cells opens potassium channels
  • Produces depolarizing potential
  • opens calcium channels
  • causes neurotransmitter vesicles (probably glutamate) release
  • generates nerve impulse
  • impulses pass along axons of forming cochlear branch of vestibulocochlear nerve (VIII)
  • axons synapse with neurons in cochlear nucleus in medulla
  • some axons cross over & ascend in lateral meniscus & terminate in inferior colliculi in midbrain
  • other axons form cochlear nuclei
  • end in superior olivary nucleus in pons
localization of sounds
Localization of Sounds
  • requires binaural fusion
  • brain compares information received from each ear
  • ears are about 6 inches apart
  • makes for intensity differences & time lags to brain
  • very small but allow for stereophonicor3-dimensionalhearing
  • auditory system can detect minute differences
  • time difference of 0.000027 seconds is all that is needed to be abletoidentify direction from which 2 sounds are coming
  • localization is quite accurate unless sound is located directly ahead, behind, overhead or beneath ears-equidistant fromboth
hair cells
Hair Cells
  • 16,000 hair cells
  • extremely vulnerable
  • overexposure to loud noises, disease, heredity or aging most humans will lose 40% of hearing by age 65
  • once destroyed hair cells cannot regenerate
equilibrium
Equilibrium
  • vestibular sense
  • sensation provided by vestibular complex
  • Two types
  • Static
  • Dynamic
static dynamic equilibrium
Static & Dynamic Equilibrium
  • Static
    • maintenance of position of body (mainly head) relative to force of gravity
    • know where head is when it is tilted
  • Dynamic
    • maintenance of body position (mainly head) in response to sudden movements, such as rotational deceleration or acceleration
    • know where head is if it moves quickly
vestibular sense receptors
Vestibular Sense Receptors
  • Vestibular apparatus
  • Saccule
  • Utricle
  • Semicircular ducts
saccule utricle
Saccule & Utricle
  • Otolithic organs
  • walls contain macula
  • houses receptors for equilibrium
  • contains two types of cells
  • 1) hair cells-sensory receptors 2) supporting cells
saccule utricle1
Saccule & Utricle
  • hair cells of utricle & saccule have 40-80 stereocillia of grduated height & one kinocillium
  • Longer than longest stereocilia
  • steorcillia are connected by tip inks
  • Together sterocilia and kinocillium are-hair bundle
saccule utricle2
Saccule & Utricle
  • supporting cells secrete a gelatin like glycoprotein layer called otolithic membrane
  • rests on hair cells
  • layer of dense calcium carbonate crystals called otoliths extend over surface of otolithic membrane
equilibrium1
Equilibrium
  • when head is upright statoconia sit on top of macula
    • weight presses down
  • when head is tiltedstatoconia shift to sidedistorting hair cells
  • sends information to CNS that head is no longer level
semicircular ducts
Semicircular Ducts
  • contain receptors which respond to rotational head movements-dynamic equilibrium
  • anterior, posterior & lateral semicircular ducts are continuous with utricle
  • each semicircular duct has an ampulla-expanded region containing hair cells
  • hair cells attached to wall of ampulla form crista
  • each crista consists of hair and supporting cells
  • covering the cells is a gelatinous structure- cupula
vestibular sense
Vestibular Sense
  • when head is rotatedendolymph movespushes cupula distorts processes of receptor
  • gluid movement in one directionstimulates hair cells
  • movement in other directioninhibits hair cells
vestibular sense equilibrium
Vestibular Sense & Equilibrium
  • Hair cells of vestible & semicircular ducts are monitored by sensory neurons-vestibular ganglia
  • Branches form cranial nerve 8- vestibulocochlear nerve
    • innervates vestibular nuclei located between pons & medulla
  • nuclei send information to cranial nerves: III, IV, VI and XI-involved with eye, head and neck movements
  • information is then sent down vestibulospinal tracts of spinal cord  adjusts peripheral muscle tone & complements reflexive movements of head & neck
  • nuclei also connect with cerebellum to coordinate movement
  • one spins very fast & stops abruptly, liquid cannot return to normalfeel dizzy
  • Neural connections are also made with ANSdigestive system partnausea.