Learn Science [Form 2]

Chapter 1 - Lesson 5

CHAPTER 1: THE WORLD THROUGH OUR SENSES

1.5 The Sense of Hearing

Structure of the human ear

1 The ear is the sensory organ of hearing and balance.

2 The sense of hearing is sensitive to sound stimuli.

3 The human ear can be divided into three main parts: the outer ear, the middle ear and the inner ear.

4 Figure 1.9 shows a cross section of the human ear.

Figure 1.9 Structure of the human ear

The hearing mechanism

Figure 1.10 How sounds are heard

SCIENCE ALERT!

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Okay. So let's take a recap!

1.5 The Sense of Hearing

Structure of the human ear

Ear ➡ is the sensory organ of hearing and balance.

The sense of hearing is sensitive to sound stimuli.

The human ear can be divided into three main parts: the outer ear, the middle ear and the inner ear.

Parts of the ear and its functions:

◇ Pinna ➡ Collects and directs sound waves (vibrating air) into the auditory ◇ canal.
◇ Auditory canal ➡ Directs sound waves to the eardrum.
◇ Eardrum ➡ Vibrates at the same frequency as the sound waves that hit it and transfers the vibrations to the ossicles.
◇ Ossicles ➡ Amplify the vibrations and transfer them from the eardrum to the oval window.
◇ Oval window ➡ Transfers the vibrations from the ossicles to the inner ear.
◇ Round window ➡ Vibrates in opposition to the oval window lying above it.
◇ Cochlea ➡ Detects vibrations and converts them into nerve impulses.
◇ Auditory nerve ➡ Sends nerve impulses to the brain which interprets the messages as sound.
◇ Semicircular canals ➡ Help the body maintain its balance (not involved in the hearing mechanism).
◇ Eustachian tube ➡ Helps balance the air pressure on both sides of the eardrum (not involved in the hearing mechanism).

The hearing mechanism

1. The pinna gathers sound waves and directs them to the auditory canal.
2. The sound waves travel along the auditory canal and reach the eardrum. It vibrates at the same frequency as the sound waves.
3. The vibrations are transferred to the ossicles. The ossicles amplify the vibrations 20 times in magnitude before passing them to the oval window.
4. Vibrations of the oval window cause the fluid in the cochlea to vibrate.
5. The movement of the fluid stimulates the receptors in the cochlea. Nerve impulses are generated.
6. The auditory nerve sends the nerve impulses to the brain.
7. The brain interprets the messages as sounds.

Sound waves ➡ Pinna ➡ Auditory canal ➡ Eardrum ➡ Ossicles ➡ Oval window ➡ Cochlea ➡ Auditory nerve ➡ Brain

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Can you guys see the picture clearly? Tips: You could zoom in to see it more clearly. Well, sorry if I couldn't type cause it is so hard so yeah. I decided to just capture them and there is it. Hope yah understand. :)

New update! Notes added at the end. 😊

~ CutieKittyMe