The Nervous System: HEARING

Question 1

describe HEARING + EQUILIBRIUM

Answer 1

sense of SOUND VIBRATIONS:
- The transduction of such vibrations are very fast–over 1000 times faster than light response!

important for balance and equilibrium - specific receptors

Question 2

what are the EAR’S REGIONS?

Answer 2

REGIONS:
- external ear
- middle ear
- internal ear

Question 3

describe the EXTERNAL (OUTER) EAR - four structures

Answer 3

contains STRUCTURES:

AURICLE (PINNA)
- helps capture sound

EXTERNAL AUDITORY CANAL
- transmits the sound to the eardrum

TYMPANIC MEMBRANE (EARDRUM)
- sound waves vibrate eardrum
- causes malleus bone to vibrate

CERUMINOUS GLANDS
- secretes cerumen (earwax) to protect the canal and eardrum

Question 4

describe the MIDDLE EAR–two structures

Answer 4

contains STRUCTURES:

AUDITORY OSSICLES
(smallest bones in the body)
- malleus
- incus
- stapes
transmits sound vibrations to the OVAL WINDOW

AUDITORY TUBE (pharyngotympanic tube/eustachian tube)
- helps with the regulation of AIR PRESSURE
- travels into the NASOPHARYNX

Question 5

describe the INTERNAL (INNER) EAR (LABYRINTH) - two structures

Answer 5

contains STRUCTURES:

COCHLEA
- transmits vibrations into NEURAL IMPULSES for brain interpretation of sound

SEMICIRCULAR CANALS
works with the cerebellum of the brain to regulate BALANCE + EQUILIBRIUM

Question 6

describe the PATHWAY OF VIBRATIONS

Answer 6

PATHWAY:
(1) STAPES then to the (2) OVAL WINDOW followed to the (3) COCHLEA

FLUID PRESSURE WAVES:
sent to the (1) PREILYMPH OF THE SCALA VESTIBULI then to the (2) SCALA TYMPANI then lastly to the (3) ROUND WINDOW, ending in the MIDDLE EAR

**BASILAR MEMBRANE begins to VIBRATE–moving the HAIR CELLS of the SPIRAL ORGAN (ORGAN OF CORTI) against the TECTORIAL MEMBRANE–generation of NERVE IMPULSES of COCHLEAR NERVE FIBERS

Question 7

describe the COCHLEAR BRANCH and pathway to brain

Answer 7

COCHLEAR BRANCH:
- consists of various cochlear nerve fibers –makes up vestibulocochlear (VIII) nerve

PATHWAY:
1. cochlear nuclei neurons will synapse with axons in MEDULLA OBLONGATA
2. goes to MEDIAL GENICULATE nucleus (thalamus)
3. goes to PRIMARY AUDITORY AREA (cerebral cortex - temporal lobe)**

Question 8

describe the different FORMS of EQUILIBRIUM

Answer 8

STATIC EQUILIBRIUM:
- maintenance of the body’s position relate to the FORCE of GRAVITY

DYNAMIC EQUILIBRIUM:
- maintains of the body’s position in response to SUDDEN MOVEMENTS

VESTIBULAR APPARATUS:
- specific organs that help MAINTAIN EQUILIBRIUM

Question 9

describe the VESTIBULAR APPARATUS

Answer 9

again, specific ORGANS that help MAINTAIN EQUILIBRIUM

OTOLITHIC ORGANS:
- SACCULE
- UTRICLE
contains specific **CALCIUM CARBONATE CRYSTALS (small ear stones–registers specific orientations & gravity)
contains **MACULA (receptors for specifically STATIC EQUILIBRIUM)

OTOLITHIC MEMBRANE
- on top of the macula
- membrane moves down over HAIR CELLS (due to changes in GRAVITY)

HAIR CELLS
- will begin to synapse with the vestibular branch of the VIII nerve

SEMICIRCULAR CANALS
- important for DYNAMIC EQUILIBRIUM
- has a RIGHT ANGLE STRUCTURE; for ROTATIONAL ACCELERATION + DECELERATION
- contains **AMPULLA–affects endolymph and hair cells
- nerve impulses travel down the VESTIBULAR BRANCH

Question 10

describe the DEVELOPMENT OF EARS

Answer 10

EAR DEVELOPMENT
- after over 22 days after fertilization
ectoderm thickens (1) otic placodes [can be seen on either side of hindbrain aka rhombencephalon]*
- then form into (2) otic pits,which then turn into (3) otic vesicles

Question 11

describe clinical condition; PRESBYCUSIS

Answer 11

age-associated loss of hearing (typical around age 60s, 25%)

Question 12

describe clinical condition; TINNITUS

Answer 12

ringing in the ears + greater vestibular imbalance