Exam 5 Study Guide Flashcards
external ear
sound waves travel from auricle and are funneled into external acoustic meatus and then to the tympanic membrane.
inner ear
bony labyrinth is filled with fluid called perilymph.
membranous network is filled with endolymph.
sound waves send fluids into motion.
vestibulae
bony labyrinth composed of perilymph.
has two membranous labyrinths, the utricle and the saccule, which have receptors for equilibrium and balance called maculae. maculae respond to linear acceleration and change in head position
semicircular canals
bony labyrinth has membraneous labyrinths called semicircular ducts. has ampulla with receptors cristae ampullaris. responds to angular acceleration and rotation of head
cochlea
membranous labyrinth in each turn of cochlea is cochlear duct. duct contains spiral organ of Corti or receptor of hearing.
each turn of cochlea there are three chambers and bony labyrinths, the cochlear duct (endolymph), Scala vestibuli and Scala tympani (perilymph).
when fluid is set in motion, it activates the spiral organ of Corti which is the receptor for hearing.
spiral organ of Corti
inside cochlear duct and contains a basilar membrane and tectorial membrane, and supporting and hairs cells sandwiched in between.
sound wave path
auricle catches waves, funnels waves into EAM, then vibrates the tympanic membrane, which vibrates ossicles, which pushes on oval window, and that sets perilymph in Scala vestibuli in cochlea in motion.
sounds with frequency below our hearing generates waves in s. vestibuli and they stay in the bony labyrinth and Scala tympani.
sounds within hearing range go into cochlear duct or membranous labynth.
cochlear duct bends, the basilar membrane of organ of Corti also bends, so an action potential will be generated in the cochlear nerve.
sound waves then go to the Scala media and then die out.
Interpretation of sound
sound wave or pressure waves is a pressure disturbance and regions of compressed air molecules and lower pressure air molecules.
sound is interpreted from pitch (frequency of wavelengths) and loudness (amplitude of each wave).
middle ear
membrane vibrates are sounds waves are transferred to ossicle bones (males, incus, stapes). stapes sits in oval window. middle ear connects to throat via eustatian tube, which is why ear infections can occur with sore throat.
determining frequency/pitch
basilar membrane has stuff and floppy fibers, so frequency can be determined by where the membrane is bent or deflected. high pitch/frequency sounds are stronger so the stiff fibers will be bent more.
sound transduction
when there is a deflection of basilar membrane, hair cells (stereocillia are mechanosensitive, so they respond to bending.) are bent and generate action potentials on cochlear nerve, which are sent to the brain for sound interpretation.
bending of stereocillia and generates tension in tip links and opens channels which causes graded depolarization of hair cells. NT is then released at synapse with cochlear nerve, and AP is generated on cochlear nerve.
pitch
basilar membrane allows pitch discrimination
auditory pathway
ascending multi neuronal path. start with neurons innervating spiral organ of Corti. bring AP to two neurons in medulla. then neurons bring info to synapse at inferior colliculi or auditory reflex center. then synapses at thalamus which relays sensory info about sound to primary auditory cortex.
conduction deafness
sound conduction path is impaired from perforated tympanic membrane or otosclerosis (stiffening of ossicles, so they won’t vibrate).
sensorineural deafness
damage to neural structures from loss of hair cells or stroke affecting brain structures that relay sound info
static equilibrium
sensing changes in head position or linear head position
anatomy of maculae
each macula has many hair cells and supporting cells.
has stereocillia (long microvilli) with ion channels
1 kinocillium- an individual cilium, longest protrusion on hair cells and helps with directionality
has otoliths or little rocks that increase mass or inertia in the gel or membrane (otolith membrane)
Utricle
macula is oriented horizontally and responds to head tilt or horizontal acceleration
saccule
macula sits on the side of the membranous labyrinth and the hair cells are horizontal, so the hair cells respond to vertical acceleration
difference between organ of Corti and maculae
In organ or Corti, bending of hair cells causes action potentials.
in maculae, bending of hair cells increases or decreases action potentials
dynamic equilibrium
crista ampullaris senses changes in dynamic equilibrium because hair cells (with stereocillia and a kinocillium) that are embedded in a gel to increase the mass called ampullary cupula.
bending and basal firing
bending in one direction increases firing and bending in opposite direction decreases basal firing because of the endolymph movement.
3 layers of the eye
outer fibrous, middle vascular, and inner layer
outer fibrous layer
dense connective tissue, avascular. composed of the sclera and cornea
cornea
allows light to enter the eye, light bending apparatus
vascular layer/pigmented layer
contains blood vessels and melanocytes for pigment and functions to absorb light that enters the eye
composed of the choroid, the cilliary body, and the iris.
choroid
dense in melanin and blood vessels
cilliary body
has smooth muscle called cilliary muscles and cilliary processes that function for producing aqueous humor, and provides a point of attachment for ligaments
the cilliary zonule or suspensory ligaments hold the lens in place and change the shape of it
iris
composed of an inner smooth muscle layer called sphincter papillae, smooth muscle cells are oriented circularly. parasympathetic input causes pupil to constrict.
outer layer is dilator papillae and cells are oriented radially. contracted pulls on the sphincter papillae. sympathetic input causes pupil to dilate.
inner layer/retina
external pigmented layer
inner neural layer is composed of modified neurons in sequence, the axons of the last neuron become a part of the optic nerve.
neurons from ext. to int. are photoreceptors, bipolar cells, and ganglion cells. axons of ganglion cells become a part of the optic nerve and send sensory info about light to the brain. light passes through bipolar and ganglion cells to activate photoreceptors.
the opening at the back of the retina called the optic disc/blind spot is where optic nerve exits the eye.
anterior limit of neural layer is sawtooth region (name)
rods
very sensitive so used to sense dim light and important for peripheral vision. located more so on the periphery. cannot interpret color and cannot produce sharp images.
cones
are used for bright light and for color and sharp/detailed vision. not distributed uniformly, most concentrated in macula lutea. foveae centralis is the central pit of the macula lutea. good for visual acuity
internal structures
behind the lens to back of eye: posterior segment: filled with virtuous humor developed in the fetus and persists for life. very important for structural support to posterior regions off the eye and keeps layers of eye held together. important for maintaining intraocular pressure.
back of the lens forward: anterior segment: filled with aqueous humor secreted by cilliary processes and provides nutrients to anterior eye structures, and drains into scleral venus sinus. flows from post to anterior chamber and then drains back into venus blood
anterior segment can be divided into chambers. iris to cornea is anterior chamber
