Transcript The ear
Bell Ringer 1. How would your life be effected if you suddenly lost your hearing? 2. How would your life be different if you were never able to hear? How does hearing effect behavior? Section 3.3 p 77-80 Objective Students will be able to: - Define sound and how it is measured - Name the major parts of the ear - Trace the path of a sound from the outer ear to the auditory cortex of the brain - Discuss the dangers of excessive noise Key Terms Auditory nerve: carries impulses form the cochlea to the auditory cortex of the brain Cochlea: snail shaped; filled with fluid and hair cells; converts sound energy into electrical impulse CPS: cycles per second, measure of a sound wave Decibel scale: used to measure the range of sound to which the ear can respond Eardrum: thin, flexible layer of tissue that stretches across the end of the auditory canal; vibrates when sound waves strike it Frequency: # of vibrations/sec. Sound: a form of energy consisting of air waves of changing pressure Three-bone lever: magnifies the vibrations transmitted by the eardrum What is sound? If a tree falls in the woods and no one is there to hear it, does it make a sound? An object produces sound when it vibrates air particles. Waves are divided into: Compression Rarefaction How is sound defined? Frequency (λ) = Pitch Amplitude = Volume What are the major parts of the ear? Pinna (pl. pinnae), the outer part of the ear Functions: - Determines direction of sound - Increases amount of sound caught What are the different ways we determine direction of sound? Single Pinna: cues of direction: up/down/turn-around Two Pinnae: Horizontal position of a sound by comparing the information coming from your two ears. Ex. If the sound is to your left, it will arrive at your left ear a little bit sooner than it arrives at your right ear. -Pinnae face forward: front > behind. Articulated pinnae: focus on sounds from a particular direction. Human pinnae lay fairly flat against the head No muscles for significant What are the major parts of the ear? Eardrum = tympanic membrane 10 millimeters (0.4 inches) wide. The middle ear is connected to the throat via the Eustachian tube. Air pressure on both sides of the eardrum remains equal. The eardrum is rigid, and very sensitive. Even the slightest airpressure fluctuations will move it back and forth. It is attached to the tensor tympani muscle, which constantly pulls it inward. How does the structure of the ear protect us from loud sound? When the brain receives a signal that indicates loud noise. The tensor tympani muscle suddenly contract. This pulls the eardrum/bone How is sound wave turned into neural impulse? Cochlea in the inner ear conducts sound through a fluid, instead of through air. This fluid has a much higher inertia than air Force felt at the eardrum would not move fluid. Before the sound passes on to the inner ear, the total pressure (force per unit of area) must be amplified. Ossicles bones of middle ear. the smallest bones in your body. They What are the ossicles? Malleus hammer Incus anvil Stapes stirrup How do ossicles amplify force? Ossicles move so that the faceplate. Size difference between the eardrum and the stirrup. Eardrum SA 55 mm, Faceplate SA 3.2 square millimeters. When you concentrate this energy over a smaller surface area, the pressure (force per unit of volume) is much greater 22 times the pressure felt at the eardrum. Think High heels… How does the cochlea function? Most complex part of the ear physical vibrations electrical information How does the cochlea function? The basilar membra ne has a peculiar structure . It's made of 20,000 to 30,000 reed-like fibers that extend across the Hearing Review The basic concepts at work in human and animal ears are fairly simple, but the specific structures are extremely complex. Label the Parts of the Ear