Ear

Question 1

Intensity of sound is correlated with…..measured in……

Answer 1

Amplitude
Decibel

Question 2

Define decibel & write its equation

Answer 2

It is a logarithmic ,easure of sound intensity compared to the faintest sound that can be heard.
dB=10log(I/I-0)

Question 3

Pitch is correlated to……measured in…….
In human can be heard in the range……with max sensitivity between…..

Answer 3

Frequency of sound waves
Hertz
20-20,000
1000-2000

Question 4

The pich of male is…..while female is…..
Intensity of both is….., in normal coversation

Answer 4

125 Hz
250 Hz
60 dB

Question 5

Define masking

Answer 5

The presence of one sound dec the individual’s ability to hear other sounds

Question 6

Enumerate functions of EAM

Answer 6

-Conduction of sound waves towards ear durm
-Contains ceruminous glands that secrete wax that is (1)protective (traps forgein particles, contains lysozymes & Ig) (2) lubricative to ear drum

Question 7

Function of tympanic membrane

Answer 7

-Conduction of sound waves: vibrate in response to sound waves conducting them to bony ossicles
-Protection of the middle ear from foreign bodies (acts as a barrier)

Question 8

Function of bony ossicles

Answer 8

-Conduction of tympanic membrane vibrations towards oval window
-Magnification of sound waves by lever system

Question 9

Function of ear muscles

Answer 9

-Tensor tympani tenses tympanic membrane to make it read for virbatiom
-Both muscles attenuate sound for protection (acoustic tympanic reflex)

Question 10

Func of cochlea is…..while that if vestibular apparatus is……

Answer 10

Perception of sound waves
Balance & equilibrium

Question 11

Describe the magnification of sound in middle ear

Answer 11

1. The area of tympanic membrane is 16-17 times that of oval window
2. The ossicles act as a lever system, since the malleus is longer than the incus the force at stapes is inc 1.3 times. Thus middle ear causes 20-22 times magnification.

Question 12

Describe the acostic tympanif refkex & its significance

Answer 12

The middle ear muscles contract reflexly in response to intense sounds. They pull on the malleus & the stapes outwards reducing ossicukar conduction & sound transmission.
Significance:
1. It acts to protect the auditory receptors from damage by high intensity sounds
2. The muscles contract just before chewing & vocalization which may reduce intensity of sound coming from these activities.

Question 13

Mention conditions in which the auditory tube opens

Answer 13

1. Swallowing, chewing, yawning opens tube by action of tensor palati allowing air to enter from nasophatynx to middle ear
2. If pressure in middle ear exceeds that of atmosphere by 15 mmHg

Question 14

What happens if auditory tube is:
1. Opened permenantly
2. Blocked (as in common cold)

Answer 14

1. The noises of breathing will interfere with hearing
2. Tympanic membrane is sucked in (due to gradual absorption of air) leading to great dec in auditory acuity

Question 15

Compare fibers at base & apex of cochlea

Answer 15

At base, they are short & stiff & respond to high frequency sounds
At apex, they are long & lax & respond to low frequency sounds

Question 16

Comapre inner & outer hair cells with respect Site & relation to tectorial membrane

Answer 16

I, inner side of rods of Corti, weak or absent contact with tectorial membrane
O, outer side of rods of Corti, direct contact

Question 17

Inner hair cells mainly have…..fibers while outer mainly have…..

Answer 17

Afferent
Efferent

Question 18

Comapre inner & outer hair cells with respect function

Answer 18

I, transducing mechanical vibration of basilar membrane into action potential
O, amplifying the sound (when depolarized) OR clarifying the sound by blocking background noise (when hyperpolarized)

Question 19

Mention steps of auditory transduction

Answer 19

1. Vibration of basilar membrane cause stereocilia to be deflected towards taller member & sheared under tectorial membrane leading to stetching the tip links & opening cation channels with K+ influx leading to depolarizing potential (cochlear microphonic) from rest (-70 mV)
2. This causes Ca++ influx & release of glutamate that leads to action potential in afferent nerve

Question 20

Describe how the outer hair cells perform their function?

Answer 20

They have electromotility. The outer hair cells shorten when depolarized causing modification of basilar membrane movement which improves stimulation of the inner ear, when hyperpolarized lengthen causing clarification by blocking bachgrounf noise.

Question 21

Efferent neural impulses from brain to ear are carried by…….

Answer 21

Olivocochlear bundle

Question 22

Describe structure & function of olivocochlear bundle

Answer 22

Prominent bundle of fibers present in each auditory n from ipsi&contralateral superior olivary nuclei ends primarily on outer hair cells. It releases Ach which has inhibitory effect that may function to block background noise (clarify sound). Some fibers supply middle ear muscles (attenuation reflex)

Question 23

Mention theories of frequency discrimination

Answer 23

1. Place (Helmholtz) theory: the brain detects impulses arriving from different parts of tge basilar membrane as having different frequencies.
2. Travelling wave theory: the part of membrane which is maximally dispalced is maximally stimulated and excites neurons in auditory cortex

Question 24

Intensity discrimination depends on……

Answer 24

The frequency of action potential which is directly proportional to long of intensity (Weber-Fechner law)
This depends on the degree of bending of stereocilia

Question 25

Mention factors of discrimination of locality

Answer 25

A) intensity diffenece (sound is louder on closer ear)
B) time of arrival difference: sound reaches the nearer ear to source first

Question 26

What is Meniere’s syndrome?

Answer 26

An increased pressure of the endolymph inside the scala media & bulging of its wall.

Question 27

What is Prebycusis

Answer 27

It is decreased auditory acuity by age (old age hearing) due to dec elasticity of different parts of the ear.

Question 28

Mention the hearing tests

Answer 28

Whisper test & watch test
Tuning fork tests
Audiometry

Question 29

Olfactory epithelium contains…….
Mention their unique features

Answer 29

Bipolar nerve cells
1. Developemd from ectoderm not neuroectoderm
2. Degenerated & continuously regenerated by new neurons (every 3 months)

Question 30

The olfactory nerve fibers synapse with……froming……

Answer 30

Mitral & tufted cells
Olfactory tract

Question 31

Describe termination of olfactory tract

Answer 31

Ends in 3 olfactory striae:
Lateral stria: ends in 1ry olfactory cortex
Intermediate stria: ends in olfactory tubercle In anterior perforated
Medial stria: terminates in paraterminal gyrus & parahippocampal gyrus & anterior commissure, this links olfaction & limbic system.

Question 32

Compare 1ry & 2ry olfactory cortex

Answer 32

1ry: uncus, part of amygdala, apex of insula (limen insulae). Recieves lateral olfactory stria & projects to 2ry.
2ry: entorhinal area or area 28 in the ant part of parahippocampal gyrus)

Question 33

Mention causes of ansomia

Answer 33

-Bilateral, frontal lobe tumor
-Unilateral, cribriform plate fracture
-cold/rhinitis

Question 34

With respect to smell, ……are connected to hypothalamus

Answer 34

Corticomedial part of amygdala & septal areas

Question 35

Describe the taste pathway orders of neurons

Answer 35

1st order: pseudounipolar cells of: geniculate ganglion (CN VII, ant 2/3 of tongue & soft palate), inferior ganglion of CN IX (post 1/3 of tongue), inferior ganglion of CN X (epiglottis & most posterior part of tongue)
2nd order: neurons of nucleus solitarius which ascend in the solitariothalamic tract to VPMN
3rd order: neurons of VPMN project to insula