PSL- CNS (Part 5, 6, 7, 8 ) Flashcards
why does colour depend on wavelength of light
that is because light has a wavelength and a wavelength is a distance from one wave peak to another and different wavelengths correspond to different colours and wavelengths we normally see ranges from 400 nm for violet to 700 nm for red
is our ability to see light restricted between 400nm and 700 nm
for most yes, but we can also see powerful infrared light and people with their lenses removed, they cna see ultraviolet
why did evolution give us eyes that cna see 400-700 nm
because of the power in the sunlight peaks there and earth’s atmosphere is most transparent to these wavelengths
what are the three types of cones that allow us to sense color
the three types are called based on the light they sense and they are red, green,and blue and amount of each in people vary but is is around 63% for red cones, 31% for green and only 6% for blue
what is the reason that allow each cone type to sense different wavelengths
that is because each type has its own visual pigment just like rhodopsin for rods and each pigment will absorb different amount of light at each wavelength
what is evolution behind the cones
blue cones evolved first and can be due to blue light penetrating sea water better than longer wavelengths while red and green evolved from common ancestor
what is the light that each cone type prefer
red and green cone pigments prefer yellow and yellow-green light while blue prefer blue light and melanopsin pigments prefer blue as well
how does brain infer colour from these three cones
it does so by comparing data from the three,
yellow light affect both red and green cones but not blue ones, so yellow light will hyperpolarize the red and green cones but not the blue cones so brain will interpert that activity as yellow
but brain cna be fooled that is why green and red lights will produce same activity so brain gets tricked and u see yellow even if there is no yellow light
does that mean we can produce any colour just by mixing the 3 wavelengths
yes, because any colour we see correspond to pattern of activity in these 3 types of cones
what is difference between spectal and extraspectal colours
spectal colours are the ones that can be evoked by light of a single wavelength, they are the rainbow colours
extraspectal are ones like purpule or white where they can be evoked only by mix of wavelengths
what is example of ganglion cells that are combinations of cone signals
the R+G cells or yellow channels, are ganglion cells excited by red light and by green light
the R-G cells are ganglion cells excited by red light and inhibited by green, others can be G-R cells where they are inhibited by red and excited by green, and these two types are the red-green opponenet channels
some get excited by blue light and inhibited by green and red so they are the B-R-G cells which is same as B-(R+G) where R+G=yellow, and otehr are the yellow minus blue so R+G-B and these two types make the blue-yellow opponent channels
what is the theory behind the opponent channels and after images
it is thought taht as you stare at something green, the G-R cells will gradually fatigue and when u look away, those fatigued lines will be less active than the R-G ones so you end up seeing red and similiar case for blue vs. yellow
however, the responsible cells aren’t sure if they are in retina, LGN or visual cortex
what is teh common type of colour blindness
that would be the red-green colour blindness also known as daltonism as people have trouble distinguishing between those two colours
how is colour blindness linked to chromosomes
it was the first human trait linked to chromosomes where the inheritance pattern for daltonism is that colour blind fathers will have colour blind sons and colour normal daughters as the genes for red and green cones visula pigment lie in X-chromosome and problem in these loci are cause of 95% of all variations in colour vision
what is meant by reflectance for colour constancy
that intrinsic colour of surface is its reflectance as reflectance of surface is its tendancy to reflect certain wavelengths of light and absorb others and this reflectance carries information of teh object
what is meant by colour constancy
that our brains usually infer reflectance so we see ripe banana as yellow even in green light
what are the two main functions of our ear
hearinga nd equilibrium
what is teh structural components of teh ear
external ear consist of pinna and ear cannal, it is sealed at its end by tympanic membrane(eardrum)
after eardrum comes the middle ear which is air filled space connected to pharynx by eustachian tube
the inner ear is the one that contain teh sensores: cholera is for hearing and vestibular apparatus is for equilibirum
what is it that our ear preceive as sound
that is teh pressure waves where at peaks of teh waves, moelcules are crowded together and pressure is high and at the troughs the molecules are far apart and pressure is low
what is frequency
frequency is number of waves peaks per second, we preceive frequency as pitch where low frequencies are low pitched sounds and high frequencies are high pitched
we as humans can hear sounds in range of 16-20000 Hz
what is amplitude
teh pressure difference between peak and trough and it ius the main factor that determines our perception of loudness as larger amplitude mean louder sound
but loudness also depend on frequency because if sound is over the range then it wouldn’t sound loud
what is role of eardrum
they get vibrated by sound waves and are what seperate the outer ear from middle ear
if eardrum is seperating middle and outer ear, how does vibrations of sound waves reach inner ear
there are small bones that convey these vibrations through the middle ear as teh middle ear will vibrate malleu bone first which moves the incus and then the incus moves stapes and stapes push against teh oval window like piston
what are the ossicles bones
they consist of these three small bones: malleus, incus, and stapes and are the smallest bones in the human body but they act as the lever system that carry vibration from eardrum to oval window
where is the oval window
it is membrane between middle and inner ear
where does oval window lead to
to choclea which contains the receptor cells
what are the components of cochlea
it has teh vestibular duct and tympanic duct which contain the perilymph and these two ducts are resposnible for communication at helicotrema
it also contain the endolymph
what happens in cochlea when oval window vibrates
it will setup waves in the perilymph as teh wave energy eneters cochlea and as it is moving through cochlea, it shakes the cochlear duct which contains the receptor cells and that wave will also exit into middle ear through another membrane called round window
what is organ of corti and where is it found
it sits on the basilar membrane and under tectorial membrane
it contains the auditory receptor cells which are mechanoreceptores and they are known as hair cells as tehy aren’t neurons but epitherlial cells
these hair cells also have stiff hairs that are called stereocilia which extends ino tectorial membrane and they bend when waves in perilymph deform basilar and tectorial membrane
how do these hair cells send signals to brain
when the cilias bend toward the lonest cilium, they excite its neuron as the hair cell depolarizes and releases neurotransmitter which activtaes primary snensory neuron and these axons form auditory nerve called cochlear nerve which is branch of cranial nerve eight
what happens when cilia of hair cell bend away
when that happens the hair cell release less transmitter which causes hair cell to hypoerpolarize and release less neurotransmitter so it doesn’t excite the neuron as much
why does basilar membrane respond to different frequencies at different points
because membrane is narrow and stiff near round and oval windows and wider and more flexible at the otehr end
so high frequency waves maximally displace membrane at oval window end, whiel low frequency waves maximally displace the other end
the brain will deduce frequency by notion of which hair cells are most active
how do auditory signals pass to brain
there is one from each ear to both sides of the brain and the primary auditory cortex is A1 in temporal lobe
how does brain localizes sounds
based on the loudness and timing as if teh sound is louder in right ear than left that emans sound is coming from right side of the head and if soudness reach right ear first, that means it is coming from right side
what are teh three kinds of hearing loss
conductive hearing loss- sound can;t be transmitted through external or middle ear
sensorineural hearing loss- damage to hair cells or elsewhere in inner ear
central hearing loss- damage to cortex or pathway from cochlea to cortex
how is conductive hearing loss distinguished from senorineural hearing loss
using Rinne test, hold the tuning fork against mastoid boen and then beside ear and ask when sound is louder as normally it is louder through the ear canal but if it is louder through bone then it is conductive loss
in Weber test, hold the tuning fork to patient’s forehead and in midline and ask which ear is it louder: in senorineural loss=louder in good ear, in conductive loss= louder in bad ear since it doesn’t ahve to compete with sounds heard through the ear canal
how is equilibrium sensed by our ears
different parts of vestibular apparatus sense head position and motion
utricle and saccle contain hair cells that are activated when head tilts relative to gravity
semicircular canals are fluid filled hoops that detect head rotation as when head turns right the fluid in tubes sloshes leftward
where do equilibirum pathways project to
mainly to cerebellum as vestibullar hair cells activate teh primarly sensory neurons of vestoibular nerve which branches of cranial nerve 8
these neurons may pass directly to cerebellum or synapse in medullar and tehn they procced to cerebellum or up through thalamus to cortex
the brain uses vestibullar information to infer position and motion and keeps us upright
