11/9 special senses Flashcards
what are the special senses?
they audition/vestibular; olfaction; vision; taste;
What are the basic components of sensory pathways?
receptors to detect changes/ stimuli in environment. mechanism to convert stimulus to electrical signal; transmit info to CNS
what does a Nociceptor sense?
extremes of pressure, temperature, noxious chemicals.
the process by which a stimulus activates a receptor and converts it into electrical energy.
sensory transduction. typically involves openging and closing of ion channels in receptor membrane
the basic path of sensory…
receptor creates a signal that is sent to first order neruons to the spinal cord, to second order neurons to the brain and thrid order to the cortex, and forth order in the cortex to interpret and integrate the signal
what will increase or decrease the likelihood that an action potential will actually be sent on a first order sensory neuron?
the receptor potential (these are graded potentials)
what is the level of sound pressure that would cause pain?
120dB. and damage is at greater than 100dB
what is the external ear?
the Pinna
what is the purpose of the middle ear?
to conduct the sound and impedance matching.
what is the inner ear purpose
to convert mech. to electrical
the small bones of the ears
ossicles
what is impedance matching?
it is how we overcome the loss of sound passing through the air: fluid interface. this is done by generating leverage to concentrate movements to more forceful vibrate the oval window.
the histology of the tympanic membrane
external, thin epidermis, inner simple cuboidal epithelium that sandwich a dense CT layer.
the histology of the middle ear
simple squamous epithelium that transistions into ciliatedpseudostratified epith. that sits on a thin LP that attaches to periosteum.
What is the eustachian tube?
the tube that connects the middle ear with nasopharnynx
What is the purpose of the eustachian tube
to equalize pressure between middle ear and environment and to drain mucus
what would repeated cases of otitis media cause (what type?)
conductive hearing loss due to inability to conduct sound through the middle ear, due to ossicle degredation.
otitus media
bacteria of nasopharnyx invade and multiply in the middle ear and you get a middle ear infection.
what is the result of otitus media repeated?
can cause hearing loss! and causes lots of expense and antibiotic use!
why fewer otitis media in adults?
adults have improved angle and size of the eustachian tube.
what can be done for lots of ear infection
ear tubes that will just fall out by themselves
The three chambers of the inner ear cochlea
scala vestibula, scala media, scala tympani
the membranes that seperate the scala vestibula and the scala media
Reissner’s membrane
the membrane that seperates the sala tympani and the scala media
basilar membrane
the structures of the scala media
these are the structures that facilitate hearing, they are the tectorial membrane lying on the organ or corti that has the three rows on inner and one row of outer hair cells, then the stria vascularis that helps to recycle the potasium back into the scala media
where is the actual site of auditory transduction?
the organ of corti that lies in the scala media on top of the basilar membrane contain the afferent fiber origins!
how can we initiate the auditory transduction of the ear?
deflect the auditory bundles of the inner and outer hair cells with the tectorial membrane. this causes the opening of mechanically coupled ion channels that allow K+ in to depolarize the cell and this will then cause opening of calcium chanels in the basal side and this will lead to a release of neurotransmitters and an action potential in the neural afferent fibers.
the type of cilia on the hair cells of the ear:
stereocilia
what is the tissue that is actually vibrating down the length of the chochlia to cause the binding of the hair cells?
the Basilar membrane upon witch the organ of corti sits. is vibrated by the opposite movements of the oval and round window.
describe the fluid of the cochlear and how it is critical for transduction
the scala vestibuli and the scala tympani are filed with peerilymph that is similar to CSF ionically. however teh scala media where the hair cells are is filled with endolymph that has a very high potasium concentration to allow influx of potasium into cells and depolarization.
what are the cells taht make the potasium conc. of the endolmph
the stria vascularis.
what cellular structures would prevent the endolymph and perilymph from mixing?
the tight junctions of course!
why would a defect in connexin 26 cause hereditary deafness?
it would lead to an inability to build gap junctions properly that could then lead to an inhability to conduct potassium from the hair cells where it come in at the organ or corti around through the supporting epithelia cells and back into the scala media, therefore can’t build the potasium conc. necessary for the function of the hair cells!
what is the neurotransmitter release by cochlear hair cells?
glutamate.
what if the membrane upon which the corti organ sits was uniform all the way through the cholea?
then we would lose the ability to analyze different frequencies of sounds. the tapering width of the basilar membrane gives it the ability to selectively vibrate to different frequencies.
deafness due to loss of the bones of the middle ear or loss of the membrane
conductive hearing loss
what types of lesions would be considered sensorineural hearing loss?
congenital and traumatic leasions of CN VIII, congenital/traumatic (anti-biotic/loud noise etc.) loss of hair cells. and connexin loss!
the cranial nerve to the cochlea
CN VIII
how do we achieve head orientation and balance information?
membraneous labyrinth or the semicircular canals and otolith organs.
how do the semi-circular canals and otoliths work in summary
they have a gelatinus mass or crystals that move to move accross the hair cells and either activate or inhibit the cells, causing a unique pattern of signals.
the tissue that is very important to the stimulation of cranial nerve I
the olfactory epithelium in the upper nasal cavity.
what are the types of cells in the OE?
basal cells, sustentacular cells, olfactory receptor neurons.
what is the site of odarant binding?
the olfactory receptor neurons.
act as a baffle in the nasal canal to cause air flow to become turbulent and reach the OE?
the Turbinates
The three types of cells in the olfactory epithelium
basal cells (at the basal membrane), sustentacular cells, olfactory receptor neurons.
unique properties of the olfactory neurons
they only live about a month and then they are replaced, they are the only neurons exposed to the environment.
purpose of the basal cells in ofactory epithelium
stem cells in olfactory epithelium, replace olfactory neurons
the basics of the olfactory transduction system
each olfactory neurons has just one type of 1000s of different genetically coded olfactory receptors, ordorants will bind a specific “code” of different olfactory receptor proteins to give a combinatoral code.
The molecular signal due to an ordorant binding
the olfactory receptors are all G-protien coupled receptors. they will activate adenylyl cylase, lead to cAMP that will open a cation channel that will open a Ca+ induced Cl- channel and the cell will de-polarize.
the path of the action potential of olfacotry neurons
olfactory neurons depolarize and AP sent up through the cribiform plate and synapse in glomerulus in the olfactory bulb. each glomerulus can synapse with thousands of different neurons of the same type to create an odor map for each scent. then mitral (glomerulus) cells project to higher centers in the CNS
absences of sense of smell
anosmia
impaired sense of smell
hyposmia
distorted sense of smell
dysosmia
