[Music] [Music] so stimuli and responses in humans so what is Kim Uline so constant changes in the surrounding that is what is not a stimuli so what is stimulus stimulus is actually the simpler form of stimuli so examples of stimuli includes our light sound and chemical substances so human use the sensory organs to detect stimuli and the five sensory organs that we have will be the eyes ears nose skin and tongue so each sensory organs have care one sense for example ice has the sense of sight yes sense of hearing no sense of smell tongue sense of taste and skin sense of touch so first let's look at the eyes this will be the external structures of the eyes which is flavor iris and the pupil and this is actually the anatomy of the eyes as well as the functions of the ice I think this will be self-explanatory so I think I'll skip this part the main structure of the eyes that actually converts the light into nerve impulses will be the retina so first let's take deeper look at the retina so the retina has two types of photoreceptors which are the god cells and also the cone cells so thought cells persons are actually sensitive to different light in intensity which includes faint light but they are not sensitive to colors of light not sensitive to colors of light so we have the cone cells which actually sensitive to the color of lights but only under bright conditions and there are three different types of cone cells which are sensitive to red light green and do like so as you can see here this little bit enemy of the retina where the rod cells and also cone cells so the member dot cells detect a light intensities while cone cells are sensitive to the colors of the light so let's just jump forward do the mechanism of sight so yes we can see this an object and the light rays from the object will enter the eyes first through the cornea the eye the aqueous humor the islands and then the vitreous humor and finally hit the retina so the function of all these structures to focus the light so it hits the retina so the object is formed in the retina is actually inverted and also smaller than the object size so what happens when it hits the retina the Lightwoods stimulates the photoreceptors to produce nerve impulses that are later sent to the brain and then in the brain the object will be interpreted to be upright and the necessary responses can be by today so let's look at years so the years is primarily divided into three sections which will be the outer year the middle year and also the inner you so the outer year consists of the yellow and the year cannon while the middle consists of the eardrum ossicles oval window and also the eustachian tube as for the inner ear it consists of the semicircular canals Altera nerves and also talked here so let's jump forward these are actually the functions of the gyro structures but I think this is self-explanatory so I'll jump forward to the mechanism of hearing so the mechanism of hearing is actually kind of simple so what happens is the yellow collects the sound and is channeled into the Year kennel so the year kennel channel's it to the year drum where the sound is transformed into vibrations so these vibrations travels through the ossicles where it is amplified and sends the vibration to the oval window the oval window transfers the vibration to the cochlea where the cochlea converts the sound vibrations to nerve impulses so these nerve impulses will be carried to the brain by the auditory nerves so in the brain the the impulse will be interpreted and necessary actions will be taken the next century opened the Dragon take a look at will be there soon so the skin is actually the largest sensory organ in the human body and it is divided into three layers which will be the epidermis dermis and the fat layer and also has five types of receptor which will be the coldest after pain receptor heat receptor touch receptor and tertiary sector and it is actually very important to know the location of the disatrous such as the painless utter is located in the epidermis while he is up to the touch a certain Co receptors are located on the top region of the dermis and - elicit a dislocated deep in the dermis so when the discipline the skin is simulated nerve impulses are produced and thank you the nervous system to the brain to be interpreted and produce an appropriate response now let's just take a look at the sensitivity of skin on different parts of the body towards teaming up so the sensitivity of the scheme depends on two main factors which will be the number of receptors present and also the thickness of the skin epidermis so for example the of the finger it's really sensitive to its touch because the tip of the finger has large number of touch receptors and the epidermis is thin this is the same case for the tongue nose and the lips as for the elbow the sole of the food and the back of the body this less sensitive to touch this is because it has a thicker skin epidermis as well as a smaller number of touch receptors at that region so let's take a look at the nose as a sensory receptor so the nose is a sensory organ of smell smells are chemical substances present in the end and about 10 million sensory cells for smell are located in the roof of the nasal cavity as you can see in this figure these are the sensory cells of smell and this is the layer of mucous technology and the importance of the mucous which I'll explain in a while so what happens is the chemical substances in the end will dissolve in this layer of mucous and this emulates the cells to produce nothing pulses so without the presence of mucous the chemical substances will not be able to dissolve and this will not reduce any nerve impulses then these nerve impulses are sent to play to be interpreted and to determine the type of smell now let's talk about the tongue so tongue is the sensory organ of taste so when you look at tongue in my a pure flat but it actually has many papillae on the tongue so the papillae consists of hundreds of teeth spots and each tastebuds consist of 10 to 15 cases actors so these taste actors are able to detect five different types of tests which we'll be sweet salty sour bitter and umami so the function of the tastebuds pretty similar to the nose where it also requires a fluid to dissolve the chemical substances to trigger the tastebuds so when the food is chew part of the chemical substances in the food is dissolved in the saliva so this dissolved chemical substances will diffuse into the tastebuds to get a pause and stimulate the taste receptors and this produces nerve impulses so these nerve impulses are then sent to the brain and interpreted as sweet salty sour bitter umami all combination of all these taste so now let's look at the sensitivity of different parts of the tongue to taste mine so like I said just now there are five different types of tests that your tank and test which will be the sweet salty sour bitter and umami taste so different regions of the tongue are more sensitive to different types of tests so for example the front of your tongue is more sensitive to sweet this while the sides are more sensitive to sour and salty taste and the back of the tongue is more sensitive to bitter taste and the center of the tongue is more sensitive to the marble taste and this is a diagram that shows exactly where the sensitivity the sensitivity of your different taste receptors lies so now let's see why Ches receptor and also the sense of smell is actually a very good friend so here's a fun activity that you can do to actually understand this further but let me just explain to you what happens when you try to taste your food so when you are going to taste your food of the food is actually the combination of your sense of taste and also the sense of smell so the chemical substances from the food travels to the nose and also resolves in the sly burn so you can taste it and also smell it without the sense of smell the food will taste less flavorful these also the reason why when you're having flu and there's a thick layer of mucus the chemical substances are not able to penetrate deep enough to stimulate the nerves in your nose so there are these causes the lag flavor when you eat when you are happening to you so we know that humans have powerful audio visual sensors but as powerful as the senses are we still have the limitation for the sensors so for example for the limitation of sight we cannot see very tiny objects such as microorganisms as well as very distant objects such as the planet Jupiter we also can see objects that are behind an opaque surface and this limitation of sight includes optical illusions and blind spot so these are a few examples of optical illusions so form a image symbol the line is longer for P Q compared to RS but in reality it's actually the same length so from B the spot in the center for X it might seem larger than Y but in reality is actually the same size and the same goes to C this is an optical illusion which shows the sides of the square to seem curved but in reality is actually a straight line the sides has straight lines so these are optical illusions that might trick your brain to thinking into thinking that something is not not as it seems so another sight limitation is the blind spot so the blind spot is the point where all the optic nerve exit from the eye so at this region the retina is not sensitive to the light so we actually an unaware of the presence of the blind spot in the eyes because it's not possible for the image of the same object to follow the blind spot of both eyes simultaneously and you can actually carry out this small experiment to investigate your blind spot but this can be done using your textbook there's actually various devices that can be used to overcome the limitation of sight example the light microscope and the scanning electron microscope can be used to visualize microscopic objects or microorganisms the binoculars as well as telescopes can be used to visualize objects that are too far away but normal naked eyes to detect the ultrasound machine and also the x-ray machine can be used to visualize objects that are behind an object surface defects of sight and ways to contact them so defects of sites include short segments long signals and astigmatism so what is short segments short sightedness is the inability to see distant object clearly this is because the image is focused in front of the retina it can be caused by a lens that is too thick or eyeball that is too Don so easy way to collect this is to use all concave lens so long sadness is inability to see new objects clearly this is because the images focus behind the retina so the difference is caused by islands and islands that is too thin or a ball that is too short so an easy way to correct this is by using a condom wex lens okay so what estimate ISM it is seeing part of an object clear clearer than the rest of the object this defect is caused by the uneven curvature of the cornea of islands so an easy way to correct astigmatism is by using cylindrical lenses so limitation of hitting a limitation the ability of the year to hear sound we can only hear sounds in the frequency of 20 to 20,000 Hertz but this frequency range is actually different for each individual to a person who's a huge meeting although the frequency range for setting mic at narrow is because the electron becomes less elastic so these are a few examples of devices that help to overcome the limitation of hitting for example the set of scopes help us to listen to heart beats while the doubts become help us to amplify the sound so person that is located far away is able to hear the sound the effects of hearing and ways to correct them so that the defects of healing occurs mainly by the damage to the hub this can be due to infection of microorganism injury aging process or continuous exposure to loud sounds so the damage to the outer ear and the middle ear can be easily corrected but the damage to the inner ear is more difficult to be corrected so the this advancement in the hearing aids is an example of how innovation and technology are applied to help solve the defects of healings the thing to keep in mind is the five senses that is given to us is actually a gift from God so try to avoid unhealthy life lifestyles and try to take precautionary measures when working in highly jobs don't forget to Like share and subscribe our channel if you have any question please comment dunking thank [Music]