COM S6

Question 1

Outline and compare the detection of vibrations by insects, fish and mammals

Answer 1

Hearing  ability to detect sound waves by changing the vibrations of sound to electrical energy of nerves

Question 2

Outline and compare the detection of vibrations by insects, fish and mammals (Insect)

Answer 2

• Only some can hear  Crickets, grasshoppers, cicadas, butterflies, moths & flies
• Body hairs may vibrate in response to sound waves
• Male mosquitos  hairs on antennae that vibrate in response to wing vibrations of flying female mosquitos  brings together for mating
• Tympanic organ (some insects)  detects vibrations
 Tympanic membrane stretched across internal chamber
 Sound waves vibrate membrane  stimulates receptor cells on inside membrane or within chamber
• Crickets  ears on legs
• Grasshoppers & cicadas  ears on abdomens

Question 3

Outline and compare the detection of vibrations by insects, fish and mammals (Fish)

Answer 3

• Lateral line system on side of body – detects:
 Fish’s movement in water
 Direction and speed of current
 Vibrations from surrounding objects
 Low-frequency sound waves
• Receptor cells  detect movement  water flowing through bends hair cells  produces nervous impulses  sent to brain
• Inner ears near the brain
 Vibrations conducted through skeleton and bladder
 Receptors respond to higher frequencies

Question 4

Outline and compare the detection of vibrations by insects, fish and mammals (Mammals)

Answer 4

• Ears  main organ to detect vibrations
• Vibrations detected by hair cells in internal structures  due to vibrations of membranes & amplification from outside to inner ear
• Used for communication
• Echolocation:
 Detect size, position & movement of close objects
 Used in sperm whales, bats and dolphins

Question 5

Structures of the outer ear?

Answer 5

Pinna, Tympanic Membrane

Question 6

Pinna, its anatomy and function

Answer 6

• Large fleshy external part

• Collects sound waves from wide area (environment)
• Directs sound into ear
• Waves = vibration of air molecules
• Waves continue along canal known as external auditory meatus

Question 7

Tympanic membrane, its anatomy and function

Answer 7

• Ear drum
• Stretches tightly across end of auditory canal
• Sound waves cause it to vibrate  vibrations travel to oval window by ear ossicles
• Separates outer and middle ear

Question 8

Name the structures of the middle ear.

Answer 8

Ear ossicles, Oval window, Round window

Question 9

Ear ossicles, its anatomy

Answer 9

• Three tiny bones

* Malleus (hammer), incus (anvil) and stapes (stirrups)

Question 10

Oval window, its anatomy

Answer 10

• Small, thin membrane between middle and inner ear

* Links ossicles with cochlea

Question 11

Round window, its anatomy

Answer 11

• Located below oval window

* Membrane between middle ear and cochlea

Question 12

Ear ossicles, its function

Answer 12

• Transmit sound waves to inner ear (vibrations travel well through bone)
• Tympanic membrane kept tense by malleus  sound vibrating through membrane transmitted to malleus  into inner ear
• Eardrum vibrates  ossicles vibrate  amplifying the sound and transmitting to oval window
• Stapes connects with oval window  movement of inner ear fluid

Question 13

Oval Window, its function

Answer 13

• Receives vibration from tympanic membrane via ossicles  much greater force
• Passes vibrations onto fluid in cochlea
• Amplifies pressure of sound

Question 14

Round window, its function

Answer 14

• Bulges outward to allow pressure release in cochlea

Question 15

Name the structures of the inner ear.

Answer 15

Cochlea, Organ of Corti, Auditory nerve

Question 16

Cochlea, its anatomy

Answer 16

• Fluid-filled chamber
• Snail-like spiral coiled tube
• Three tubular chambers
• 35mm long
• 1st & 2nd chambers  separated by Reissner’s membrane
• 2nd & 3rd chambers  separated by basilar membrane

Question 17

Cochlea, its function.

Answer 17

• Contains receptors for sound
• Vestibular apparatus  balance
• Round window bulging outwards  fluid in cochlear vibrates
• Changes mechanical energy into electrochemical energy

Question 18

Organ of Corti, its anatomy

Answer 18

• On basilar membrane in cochlea

* Contains auditory receptor cells

Question 19

Organ of Corti, its function

Answer 19

• Hair cells  receptor cells – detect vibrations & generate nerve impulses  travel via auditory nerve to brain
• Transfer vibrations into electrochemical signals

Question 20

Auditory Nerve, its anatomy

Answer 20

• Nerve travelling from ear to brain

Question 21

Auditory nerve, its function

Answer 21

• Transmits electrochemical signals to brain

Question 22

Outline the role of the Eustachian tube

Answer 22

• Connects the middle ear to the pharynx (chamber at nose and throat)
• Usually closed  can be opened by yawning or swallowing
• Connects to air-filled space  Equalise the pressure on either side of tympanic membrane (ear drum)

Question 23

Outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur

Answer 23

• Sound waves collected by the pinna  auditory canal  tympanic membrane (vibrates at same frequency as sound)
• First ossicle (malleus) attached to tympanic membrane  bone vibrates, amplifies vibration  passes onto two other ossicles, amplify vibration
• Last ossicle (stapes) attached to oval window  vibrates  fluid in cochlea vibrates
• Sound energy converted to mechanical energy
• As oval window bulges into inner ear  causes waves in fluid  bends hair cells 
• Hair cells of organ of Corti detect vibration  stimulate nerve impulses
• Mechanical energy converted into electrochemical energy  pass message to cerebrum in brain via auditory nerve

Question 24

Whats the organ of corti?

Answer 24

• Organ of Corti  ribbon-like structure in cochlea
• Sound receptor = hair cells
• Includes: Basilar membrane – hair cells – tectorial membrane

Question 25

Whats the Basilar membrane?

Answer 25

 Have hair cells of different lengths  Vibrations from oval window  transmitted through cochlea fluids  hair cells vibrate according to frequency  High frequency sounds cause short hair cells at front of membrane (nearest to oval window) to vibrate  Low frequency sounds stimulate long hair cells at end of membrane (travel to end)

Question 26

Describe the relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of different frequencies

Answer 26

• As basilar membrane vibrates  hair cells of organ of Corti pushed against tectorial membrane  hair cells send electrochemical impulse along auditory nerve to brain • Organ of Corti = distinguishes sounds of different frequencies  sending pattern to brain of vibrations  Sends information on intensity and duration of sound • Round window = vibrations stop  Bulges outwards as waves reach it

Question 27

outline the range of frequencies detected by humans as sound and compare this range with two other mammals, discussing possible reasons for the differences identified

Answer 27

* Human frequency range = 20-23000 Hz * Range of frequencies heard varies from species to species ``` Mammal Lowest frequency detected > Highest frequency detected (Hz) Human 20-23 000 Dog 67-45 000 Whale 1000-123 000 Bats 100 000-120 000 ``` • Reasons for differences:  Very high sounds (used by bats) allow for precise echolocation  Whales need to communicate over large distances  low sounds travel long way underwater

Question 28

Mammal Lowest frequency detected > Highest frequency detected (Hz)

Answer 28

Human 20-23 000 Dog 67-45 000 Whale 1000-123 000 Bats 100 000-120 000

Question 29

Outline the role of the sound shadow cast by the head in the location of sound

Answer 29

* Head casts sonic shadow between sound source and furthest ear away from the sound * One ear receives less sound than the other * Humans usually turn head to locate sound * Sound coming from right reaches right ear  then blocked by head * To reach left ear  sound waves must travel around or through head * Head absorbs high frequencies easily than low ones  creates sound shadow for ear furthest away from sound source * Small difference in perception by each ear  brain can interpret direction * When sound comes from in front or behind  both ears receive same stimulus

Question 30

Hearing aid, where is the device placed?

Answer 30

``` • Fit into hollow outside ear canals  Pinna • Battery-operated • Consists of  Microphone to capture sounds  Amplifier to magnify sounds  Earphone to channel into ear ```

Question 31

Hearing aid, position and type of energy transfer occurring?

Answer 31

* Helps in converting sound energy into electrical energy * Sound waves sent to amplifier  Amplify sounds * Amplified sound waves sent to sensory hair cells in organ of Corti  convert into electrical impulses

Question 32

Hearing aid, Conditions under which the technology will assist hearing?

Answer 32

• People with sensorineural hearing loss  Develops when auditory nerve or hair cells damaged by aging, noise, illness etc • Recipient must have some hearing left  Can only amplify sound • Greatly improve comprehension, speech and low frequency discrimination

Question 33

Hearing aid, Limitations of each technology

Answer 33

* Limited assistance in high frequency ranges * Amplification  Loud noises = annoying * Batteries may run out  BUT most models give adequate warning of dying batteries * Do not assist in nerve deafness caused by damage to inner ear, auditory nerve or auditory centre of the brain

Question 34

Cochlear implant, Where is the device placed?

Answer 34

Surgically placed under the skin behind the ear & Transmitter on outside

Question 35

Cochlear Implant, Position and type of energy transfer occurring

Answer 35

* Sound waves  microphone & speech processor * Transmitter  Receiver  Cochlear  direct to auditory nerve * Energy transfer: Sound energy  electrical energy  radio waves  electrical signals  electrochemical

Question 36

Cochlear Implant, Conditions under which the technology will assist hearing?

Answer 36

• Hair cell damage  causes hearing loss  Hair cells convert sound energy into electrical energy that can stimulate auditory nerve • Deaf people • Works best where people lost their hearing after they learnt to speak

Question 37

Cochlear Implant, Limitations of each technology

Answer 37

* Only 80% effective * Risks involved with surgical insertion of implants * Cost: surgery expensive and on-going costs * Surgery side-effects: droopy face and numb tongue * Adjustment to different lifestyle and sensation of hearing sounds  difficult