00:02 Hello there, I'm your biology teacher,

00:15 Mrs. Akande

00:16 Today we are continuing with our topic,

00:18 Sense Organs.

00:20 At the end of the lesson today,

00:22 we should be able to explain the function

00:24 of the tongue as a sense organ,

00:26 explain the mechanism of testing,

00:28 describe the nose as a sense organ

00:31 and explain the mechanism of smelling,

00:33 list various parts of the ear

00:35 and explain the mechanism of hearing and balance.

00:39 We have been able to describe

00:43 what a sense organ is before now,

00:47 and we have said that the five senses

00:50 we have in our body carry out different functions.

00:54 The sense of test is carried out by the tongue.

00:59 The tongue test only three, four types of substances

01:05 and the stimulus for the tongue is chemicals.

01:12 So when we talk about the tongue,

01:14 I want to explain that when you drink your tea,

01:20 what we call tea,

01:22 and some people make a couple of coco,

01:25 like milo, vitalo or whatever,

01:28 and they drink it.

01:29 Another person puts a tea bag like lip tint in water and drink.

01:33 We always say we are drinking tea,

01:35 but you realize that the person drinking coco

01:38 is having a different taste experience

01:40 from the person drinking lip tint.

01:42 If it is only the tongue that is walking,

01:47 that difference will not be there,

01:48 because the tongue does not determine which one is coco

01:52 and which one is lip tint.

01:53 But the tongue only determine what is sweet,

01:58 what is salty, what is sour, and what is bitter.

02:03 These are the only thing the tongue can determine.

02:07 Is this sour, is this sweet?

02:09 Is this salty or is it bitter?

02:11 So it cannot differentiate between coco and lip tint.

02:15 So the tongue only responds to four chemicals.

02:19 Now, these four tests are enhanced,

02:25 yes, the whole tongue can test almost everything,

02:28 but they are enhanced in setting areas

02:30 of the tongue more than other areas.

02:33 Like when we are talking about a sweet,

02:35 sweet is better at the tip.

02:40 Why salty is closer here and sour is all?

02:47 Bitter is at the back of the tongue.

02:50 So we have a sour, we have a sweet, we have our salty.

02:55 Now, if you take a bitter thing,

02:59 if you just touch it with the tip of your tongue,

03:01 I want to know if this thing is bitter,

03:02 I just touch it like this.

03:03 You may not have that bitter sensation very well to say,

03:06 oh, this thing is very bitter.

03:08 But if you put it in your mouth and you chew it,

03:10 and you turn it around,

03:11 by the time you get to the back of the tongue,

03:13 the bitter taste will eat you more,

03:15 because more of the taste buds that are sensitive

03:19 to bitter are concentrated at the back,

03:23 though we can feel it everywhere.

03:25 Now, why did I say they are concentrated at the back?

03:28 Because the tongue tests by using what we call the taste buds,

03:33 the process of taste.

03:34 This is a taste buds, it's flagship.

03:37 And then we said sensitivity is to chemical.

03:40 So we have the taste poor that opens into the taste buds.

03:45 We have the bazaar cell,

03:46 then we have the sensory neurons

03:49 that runs from the taste buds

03:52 to go to the taste center of the brain.

03:54 So when you eat anything,

03:56 if it does not dissolve,

03:59 you may not be able to taste like if you chew dry bread,

04:01 you may not feel the taste.

04:03 But it is when you chew it for some time,

04:05 and mixes it with saliva and it dissolve,

04:08 then it goes, the chemical flows in,

04:11 and it is when it flows in,

04:12 that you are able to taste what you are eating.

04:16 So like I said,

04:19 taste buds are sensitive to different chemical,

04:24 sweet salt, sour, and bitter.

04:26 So if this one is more sensitive to bitter taste,

04:29 you discover that once you chew a bit of it and it goes in,

04:32 you will feel the bitter taste

04:34 because the information will be passed to the brain.

04:36 So that is how we taste substances.

04:39 Organ of smell, the news.

04:42 We use our nose to smell.

04:45 Inside the Nabak cavity,

04:46 if you open your nose very well and look inside in a mirror,

04:49 you see that the front here is darker

04:52 and you have his, no more his.

04:55 But when you look inside,

04:56 there's the pinkish place inside,

04:59 which is always moist.

05:01 That is the nasal chamber.

05:05 And the head we have in front is to,

05:07 as we've written, as we take in a,

05:09 is to filter dust and other particles from the air

05:13 before it gets inside.

05:15 Now the nerve endings from the,

05:18 nasal cavity is connected to the,

05:20 of a tree noob of our brain.

05:23 How do we smell?

05:25 If we smell anything,

05:28 the thing is that the particle of that

05:29 is most enter our nose.

05:32 Like I say, oh, this place is very little of a dead rat.

05:35 It means that the particle of the dead rat

05:38 occurred diffused through the air

05:40 and they enter into my nose.

05:42 When they enter, they rob against the sensitive hair up there.

05:48 They first of all dissolve in the moisture in the nose.

05:51 They rob against the sensitive hair

05:53 and then set up an impulse,

05:55 which passes to my brain and say,

05:56 oh, that is a smell.

05:58 It is the smell of a dead rat or somebody fatated here.

06:01 This basically that fatated a rotting egg or whatever.

06:04 All these are things we identify with the help of the brain.

06:09 All the nose doses take in this day.

06:12 It robs against the sensitive hair

06:14 and the formation is passed to the brain.

06:17 So we're going to go to the next organ,

06:18 which is the organ of hearing and balance the air.

06:23 The air is the organ that we use to hear sound.

06:28 So the stimulus for the air is sound.

06:30 But also it controls the balance of our body.

06:34 So it also responds to gravity.

06:37 If you look at the ear, what we see outside

06:40 is just a small section of the ear,

06:43 which we call the peanut.

06:45 The entire ear is inside the skull

06:48 and it's divided into three parts.

06:50 We have the external ear, the middle ear and the inner ear.

06:55 Now, if you look at the diagram of the ear,

06:58 this is the peanut that you see on the outside.

07:01 There is a hole, extended from the peanut into the inside of the head,

07:05 which we call the auditory canal.

07:08 And it gets to a membrane, which we call the tympanic membrane or the ear drum.

07:13 And that is the end of the outer ear.

07:16 So the outer ear, we have three things.

07:18 The peanut, the auditory canal,

07:20 which ends in the tympanic membrane.

07:22 Then we now have the middle ear.

07:25 For the middle ear, we have starch from the tympanic membrane.

07:29 Then we have the three ear ossicule.

07:32 And extended from it, we have the ostation tube

07:37 that helps to keep the balance, a pressure balance

07:41 between the inside of the mouth and the inside of the ear.

07:46 So I said the middle ear is made up of,

07:48 starting from the tympanic membrane.

07:50 We have three ear ossicule, we have the ostation tube.

07:54 And it extends to the boundary in which we have the oval window

08:01 and the round window, finestra, rotunda and finestra ovalis.

08:06 So those two connect us to the inner ear.

08:10 In the inner ear, we have the three semicircular canal.

08:14 We have the utriculus, we have the saculus.

08:18 These three are consigned with balance.

08:21 Why we now have the coid cochlea, which is consigned with hearing?

08:26 So those are the three parts of the ear, the outer ear,

08:30 the middle ear and the inner ear.

08:32 Let's look at the function of each one of these structures.

08:37 The pinna, the pinna is part of the outer ear.

08:41 And its function is to collect sound.

08:44 The auditory canal, also part of the outer ear,

08:47 is a passageway for the sound.

08:49 When the pinna collects the sound,

08:50 it pushes it into the auditory canal to hit the tympanic membrane.

08:56 Then we now have the middle ear, the tympanic membrane,

09:00 or what we call the ear drum.

09:02 When the sound hits the ear drum, no sound travels in waves.

09:06 So once the wave is only hit the ear drum,

09:08 it causes it to vibrate.

09:11 And the vibration of the ear drum will be passed to the three ear ossicules.

09:16 These are small bones that have the ability to vibrate.

09:20 You can name them after the carpenter or after the host rider.

09:24 You can name them after the host rider as Milos, Inc. and Steps,

09:30 what you use to climb a host, or the carpenter,

09:35 the hammer, the envy, and the syrup.

09:39 Please, this name is either you learn the one of the carpenter

09:42 or you learn the one of the host rider.

09:45 Don't mix them up.

09:46 And as I'm going to say, Milos, Amville and Stero, no.

09:51 If you are using Milos, then you must go with Inc. and Steps.

09:55 But if you are using hammer, then you go with Amville and Stero.

10:00 Is it clear?

10:01 Now, the ossicules vibrate and then they pass their vibration

10:06 through the windows to the inner ear.

10:09 The hostician tube, I've said before,

10:11 balances pressure put inside the ear with outside of the ear.

10:17 The inner ear now.

10:18 It consists of semicircular canal,

10:21 with triculos, succulose, and the coicler.

10:26 All these constitute the membranous labyrinths.

10:30 And they are surrounded by fluids, which

10:34 we call the perileve, which are held in place

10:37 by the bony labyrinths.

10:40 Now, function of the ear.

10:44 We use the ear for hearing and balance.

10:47 How do we hear?

10:48 Let's look at mechanism of hearing.

10:51 Sound waves are collected by the pinna.

10:53 They are passed through the auditory canal

10:56 to the tympanic membrane, which vibrates,

10:59 passes its vibration to the three ear ossicules.

11:03 The ossicules then vibrates, passes their vibration

11:07 through the overwind to the bony labyrinth.

11:11 Causing the perileve to vibrate.

11:14 And once the perileve is vibrating,

11:16 the fluid inside the conchlear, which

11:18 we call the endolith also starts vibrating.

11:22 And the vibration of the endolith will cause the sensory cells,

11:26 which we call the organ of caughti.

11:29 Present inside the cochlear to set up an impulse.

11:33 This impulse will be passed through the auditory canal to the brain,

11:37 where the sound is interpreted.

11:40 Now, we talk about balance and position.

11:43 How does the ear help us to be balanced?

11:47 The organs, the structures involved in balance

11:50 are the utericules, the cyclos are the three semi-secular canal.

11:56 Inside of them, there are endoliths.

11:58 Now, the three semi-secular canal are placed

12:01 in the three planes of position, standing upright,

12:04 lying sideways, or down.

12:07 So it's either up, down, or sideways.

12:10 So if I tilt my head to a particular side,

12:14 the fluid inside the canal on that plane will also tilt.

12:20 And when they tilt, they rub against some small particles

12:25 inside the canal, which we call the otoliths,

12:30 or ear stoves.

12:32 So those ears don't move, and they rub against the fluid moves them,

12:38 and they rub against the sensitive inside the canal.

12:42 And once this happens, an impulse will be set up.

12:47 This impulse will not be transmitted through the vestibular nerve

12:51 to the balance center of the brain.

12:54 We are the position of the head is interpreted.

12:57 And an appropriate message sent to Mosuz to balance the body.

13:01 If I tilt my head to the right, the tendency is that my left hand

13:07 will stretch out to balance my body.

13:09 So if I tilt it to the left also, the same thing

13:13 will happen my right hand will stretch out.

13:14 And if I move forward, I would want to flame my hands backward

13:18 so that my body will be balanced.

13:20 And it is where we lose this ability that people fall down.

13:26 Now, this is very important that if you spin around for a long time,

13:31 you just keep spinning around, around, around.

13:33 After some time, when you stop, you have this impression

13:36 that the world is moving.

13:38 Why do you have that impression that the world is moving

13:41 because you have stopped?

13:42 It's because the fluid inside this canal,

13:45 when you were spinning around, are moving.

13:46 When you stop, they don't stop immediately.

13:49 So they are sending information to the brain

13:51 that you are moving.

13:52 But the conscious part of your brain

13:54 knows that you have stopped.

13:55 So there is only one explanation for the fluidity moving.

13:59 And that is the explanation you not get from your brain.

14:01 That is why you not feel the world, the buildings,

14:04 everything around you is moving around, around.

14:07 No, whatever you are seeing is just an interpretation

14:10 of your brain because the fluid in the semicircular canal

14:14 is still moving.

14:15 Why the conscious parts of your brain

14:17 knows that you have stopped?

14:19 So it tries to put the two images together

14:23 by making you feel everything around you is moving.

14:26 So this is how the ear is able to maintain our balance.

14:31 What's ever information is always transmitted

14:37 to the brain for interpretation.

14:40 So the brain is the active part of whatever

14:44 we are sensing in our environment.

14:50 Now, why is it important that we have two ears?

14:54 We could have one, I would say here.

14:56 But we have two.

14:57 It's an advantage having two ears.

15:00 What is the advantage?

15:01 It increases the range of the sound wave.

15:04 And it enabled us to detect faster the direction of sound.

15:08 Because if the right ear is more stimulated

15:10 than the left ear, then I know that this sound is coming

15:13 from my right, not from my left.

15:16 So having two ears helps us to know faster

15:20 the direction of sound.

15:23 Now, as important as the ear is, there are diseases

15:26 that are also associated with the ear.

15:30 Mainly defect of the middle ear or the inner ear.

15:35 Which can lead to deafness or partial deafness.

15:39 So what are they?

15:40 We have conditions of deafness.

15:43 If you say somebody is deaf, it's inability to hear.

15:46 And that can be a problem of the ear.

15:49 Or say, remember those three small bones

15:51 that I said can vibrate in the middle ear?

15:54 If they become hurting, that they

15:56 can no more vibrate when the ear drum is vibrating,

16:00 then they cannot transmit the sound

16:03 through the ear over windows.

16:05 So the person will become deaf.

16:07 It could also be nerve deafness.

16:08 The ear is working perfectly, but the auditory nerve

16:11 is not functioning.

16:12 So the ossicus vibrate, the perilline vibrate,

16:15 the endally vibrate.

16:16 But nobody to transmit the information to the brain.

16:19 So you will still not hear.

16:21 So these are reason why people could be deaf.

16:25 Also, it could just be too much works in the ear.

16:29 Yes, we are not encouraged to always put cotton ball

16:31 or start cleaning our ear all the time.

16:33 But if the voice accumulates too much,

16:36 it could block the ear that the sound

16:38 I suppose to pass through the auditory canal

16:40 to heat the tmp membrane is not able to travel through

16:44 and the person becomes deaf.

16:46 So in such a case, you see a doctor.

16:48 It could also be due to autosclerosis.

16:51 That is the hardening of the steps, the ear ossicus.

16:59 They become hurting.

17:00 And then the transmission is also impaired.

17:05 Then it could be nerve deafness.

17:06 Like when you go to places where they are

17:08 loud noise, they tell you to wear ear muffler like in the airport.

17:12 If you are walking inside the airfield,

17:14 wear the planes are flying from.

17:16 You are advised to wear all shooting ranges.

17:19 You are advised to wear ear blockers.

17:22 Because if too loud sound enter the ear,

17:26 it could burst the ear drum.

17:28 That be at least to permanent deafness.

17:30 But sometimes it could be so loud that it does not burst it,

17:34 but it hinders its vibration.

17:36 It goes beyond the level.

17:38 So it becomes stiffing.

17:39 And so you hear this ringing sound in the ear.

17:43 And some people may stay like that for three days.

17:45 They are not able to hear anything until it heals itself.

17:48 So to avoid either bursting your ear drum

17:50 or getting a ringing sound in which you cannot hear anything,

17:53 when you are places in loud noise, please wear ear mufflers.

17:58 Then deafness can also be due to autosclerosis.

18:01 When they blow vessels, supply and blow to the ears

18:05 become hard in due to old age.

18:08 Such people would be hard of hearing.

18:10 They may hear some sound, but they may not be able to hear

18:12 doorbell ringing and things like that.

18:15 Then it could also be viral infection.

18:17 Like some people can have infection that can infect the ear drum

18:21 or infect the inner ear.

18:23 If such infection, technically, like missiles

18:25 can make people to be deaf, polio, influenza, deep terror,

18:30 all these, even meningitis can lead to deafness.

18:33 Because it could be conduction deafness or other kind of deafness.

18:38 But all these diseases can be taken care of during childhood

18:43 so that we can prevent such things.

18:45 Even children born to parents with syphilis

18:49 may pick up the syphilis bacteria through the bed canal

18:53 and it may affect the ear and the child may also become deaf.

18:59 So it could be injury, like a heavy slap to the ear

19:04 can boost the ear drum or destroy something inside the ear,

19:08 maybe bleeding and other things which can lead to deafness.

19:13 So with this, we have come to the end of the class.

19:19 We should be able to take care of our ear and show that

19:23 you don't put sharp objects, don't wear earphones all the time.

19:28 Don't show children meningitis against diseases.

19:33 Don't clean your ear with a cotton board all the time.

19:37 Do not introduce hot liquid into your ears.

19:41 This way, you take care of your ears.

19:43 But before we leave the topic for today,

19:46 I believe that we have learned so much.

19:49 Now we should be able to make a diagram of the tongue

19:53 showing the various parts.

19:54 Here, those four senses are most sensitive.

19:58 You should be able to explain the mechanism of a smelling.

20:02 These three structures of the middle ear

20:05 stretch the function of the three semicircular cana

20:08 and explain the mechanism of hearing.

20:12 Thank you for watching.

20:14 I am Ms. Sakunday, your biology teacher.

20:17 See you next time.

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