The Ear

Question 1

Divisions of external ear

Answer 1

Pinna (auricle), external auditory canal, tympanic membrane

Question 2

Pinna (auricle)

Answer 2

• Outer ear made up of cartilage
• Collects and transmits sound waves to middle ear

-Causes tympanic membrane to vibrate

Question 3

External Auditory Canal

Answer 3

-Short curved tube in temporal bone

-Filled with ceruminous (wax) gland

-includes hairs & earwax for protection from particles

Question 4

Tympanic membrane (eardrum)

Answer 4

• Thin connective tissue membrane, separates out & middle ear

-Vibrates in response to sound

-Transfers sound energy to middle ear ossicles

Question 5

Divisions of the Middle Ear

Answer 5

-Ear ossicles (malleus, stapes, incus)

-Pharyngotympanic/Eustachian tube

-Mastoid Cavity of temporal bone

-Oval & round windows

Question 6

Difference between Oval & Round window

Answer 6

Oval - phase of compression

Round - phase of rarefaction

Question 7

Pharyngotympanic/Eusrachian Tube

Answer 7

• Equalizes pressures on both sides of tympanic membrane by preventing rupturing

Question 8

How does the middle ear provide protection from large sounds of low frequency

Answer 8

Contracting malleus (tensor tympani) & stapes (stapedius) to reduce motion of ossicles

Question 9

Smallest skeletal muscle in the body

Answer 9

strapdius

Question 10

Why does the middle ear only provide protection for prolonged loud noises and not sudden loud noises?

Answer 10

Because the malleus (tensor tympani) and stapes (stapedius) need time for contract

Question 11

Ear ossicles

Answer 11

• Transits vibrations of eardrum (tympanic membrane) to fluid in cochlea via oval window
• Loud sound protection (malleus & stapes contracting)

Question 12

Divisions of Inner Ear

Answer 12

Bondy Labyrinth - Vestibule, semicircular canals, cochlea

Membranous Labyrinth - Semicircular ducts, cochlear duct

Question 13

Perilymph

Answer 13

• Fluid found in bony labyrinth (inner ear)
• Transmits vibrations to cochlea
• Similar to Cerebrospinal fluid (CSF)

Question 14

Endolymph

Answer 14

• Found in membranous labyrinth
• Stimulates hair cells for hearing, helps detect head movement in semicircular canals

-Potassium rich fluid

• Similar to intracellular fluid

-Helps facilitate movement of hair cells in cochlea

Question 15

What is the cochlea and what does it contain

Answer 15

• Spiral, bondy chamber in inner ear
• Contains cochlear duct & organic of corti l (hearing receptor)

Question 16

Basilar membrane

Answer 16

• Composes bottom of cochlear duct
• Supports the organ of Corti

Question 17

What are the three chambers of the Cochlea

Answer 17

Scala Vestibule & Scala Tympani - filled with perilymph, continues with tympanic via helicotrema

Scala Tympani terminates at round window

Scala Media - filled with endolymph

Question 18

Semicircular canals

Answer 18

Monitors head movement and regulates dynamic equilibrium

Question 19

Vestibule Apparatus

Answer 19

• Maintains orientation & balance

Question 20

Organ of Corti

Answer 20

Hearing receptor

Question 21

Nerve VIII

Answer 21

• Transmits sound & balance from ear to brain
• Runs from organ of Corti to the brain

-Organic of court detect vibrations converts into nerve impulses

Question 22

What happens in the cochlea when sound waves cause the fluid inside it to move?

Answer 22

Fluid (perilymph) movement bends the hair cells in the cochlea, generating neural signals that are sent to the brain

Question 23

Hair cells in sound detection

Answer 23

• Fluid bends hairs cells cilia, ion channels open causing depolarization
• releases of neurotransmitters glutamate sendings signals to brain

Question 24

Basilar membrane Base vs middle vs apex

Answer 24

Base (near oval window) - short stiff fibres that detect high frequency

Middle - detect medium frequency

Apex - long fibres that detect low frequency

Question 25

Organ of Corti

Answer 25

- Includes stereocilia (hairs) in endolymph & touch tectorial membrane - Afferent fibers of cochlear nerve attach to base of hair cells

Question 26

What neurotransmitter is released during depolarization by the stimulation of cilia

Answer 26

Glutamate, stimulates cochlear nerve which sends impulses to the brain

Question 27

How do sound signals travel through auditory pathway

Answer 27

- Cochlear bench of vestibulocochlear nerve (CN VIII) - Medulla -> thalamus -> primary auditory cortex (temporal lobe)

Question 28

What are the two types of balance

Answer 28

Static - head is stationary or moving in a straight line, detects head position Dynamic - head is rotating, detects body position

Question 29

The Vestibule

Answer 29

- Includes two sacs in perilymph (utricle - superior & saccule - inferior) -Houses equilibrium receptors in maculae -responds to gravity & position changes

Question 30

Maculae

Answer 30

- Static balance receptor - in walls of utricle & saccule - stereocilia embedded in otolithic membrane

Question 31

Otolithic membrane

Answer 31

- Jelly-like mass studded with CaCO3 (otoliths) which add weight and sensitivity to movement - sits over hairs in maculae - causes stereocilia to bend when head tilts of moves linearly - detects gravity-related movement

Question 32

Utricular & saccular hair cells

Answer 32

utricular - detect horizontal movement saccular - detect vertical movement

Question 33

Mechanism of static balance when head tilts forward

Answer 33

- otolithic membrane slides forward, bending sterocilia -K channels open, hair cells depolarize, neurotransmitter released -increased action potential frequency

Question 34

Mechanism of static balance when head tilts backwards

Answer 34

- K channels close, reducing neurotransmitter release - fewer action potentials

Question 35

Crista Ampullaris

Answer 35

- receptor for dynamic balance - located in ampulla of each semicircular duct - dendrites of vestibular nerve fibres surround hair cells

Question 36

Summarize mechanism of dynamic balance

Answer 36

head moves -> semicircular ducts & hairs move with it endolymph lags behind causing cupula to bend bending of stereociliar -opens or closes K channels -neurotransmitter release which alters action potential frequency - brain interprets frequency changes from all three canals and determines rotation movement

Question 37

Equilibrium pathway to the brain

Answer 37

1. Impulse Transmission 2. Processing centres 3. Integration 4. no conscious perception

Question 38

Receptor for dynamic balance

Answer 38

Crista Ampullaris

Question 39

Action potential decreases, K+ channels close

Answer 39

Head tilts backward

Question 40

Action potential increases, K+ channels open

Answer 40

Head tilts forward

Question 41

Detects horizontal movement

Answer 41

Utricular hair cells

Question 42

Detects vertical movement

Answer 42

Saccule hair cells

Question 43

How does the brain determine rotational movement?

Answer 43

Head moves - semicircular ducts & hair cells move - endolymph lags behind, cupula bends, bending of stereocilia causing K+ channels to open or close & action potential to increase or decrease from release of neurotransmitter , brain interprets frequency change from all three canals & determines rotational movement

Question 44

Where is the maculae located?

Answer 44

Walls of utricle & saccule

Question 45

Responds to gravity & head position changes

Answer 45

vestibule

Question 46

Detects position of head movement when stationary or moving in a straight line

Answer 46

Static balance

Question 47

Detects body position when head if rotation

Answer 47

Dynamic balance