has all the content of hear physiology

2. OKORI FEDDRICK 2015 – DCM – FT - 003
NAKIBULE RHODA 2015 – DCM – FT - 016
NUME SAMUEL 2015 – DCM – FT - 019
OUMA ANNET 2015 – DCM – FT – 030
TUGUME FAITH 2016 – DCM – FT – FEB - 002
WAHIDA JULIET 2015 – DCM – FT - 033

3.  The auricle directs sound waves into the
external auditory canal
 Waves strike the ear drum and the
compression and decompression of air causes
the ear drum to vibrate back and forth.
 The central area of the ear drum connects to
the malleus therefore it also starts to
vibrate.

4.  The vibration is transmitted from the malleus
to the incus and then to the stapes.
 The stapes push the membrane of the oval
window in and out and it vibrates 20 times
more than the ear drum
 Movement of the oval window sets up fluid
pressure waves in the perilymph of the
cochlea

5.  When the oval window bulges inward,it
pushes the on the perilymph of the scala
vestibuli and pressure waves are transmitted
from the scala vestibuli to the scala tympani
causing the round window to burge outward
into the middle ear

6.  The pressure waves deform walls of the scala
vestibuli and scala tympani and they also
push the vestibular membrane back and forth
and as a result the pressure of the
endolymph inside the cochlear duct increases
and decreases.
 Pressure flactuations of the endolymph move
to the basilar membrane and when it
vibrates the hair cells of the spiral organ
move against the tectorial membrane.

7.  The bending of the microvilli produces
receptor potentials that lead to the
generation of nerve impulses in cochlear
nerve fibres

8. Cochlea (= snail ) and organ of Corti
Vibrations of the stapes against the oval
window produce pressure waves in the
perilymph of the cochlea.
Waves inside the cochlea cause the
basilar membrane to vibrate and the
hair cells in the organ of Corti hit the
tectorial membrane.
The hair cells that make up the organ of
Corti produce electrical signals and
these nervous impulses travel down the
auditory nerve to the temporal lobe of
the cerebrum.
Basilar membrane
with the
organ
of Corti
Tectorial membrane

9.  There are two types of equilibrium i.e static
and dynamic equilibrium
 Static equilibrium which is the maintenance
of body position mainly the head relative to
the force of gravity
 Dynamic equilibrium which is the
maintenance of the body position mainly the
head in response to sudden movements such
as rotation,acceleration and decceleration

10.  The receptor organs for equilibrium are;
 The vestibular apparatus which includes
otolithic organs i.e the saccule and utricle
 semicircular ducts

12.  The utricle and saccule contain a small
thickened region called macula and these
maculae are receptors for static equilibrium
and contribute to some aspects of dynamic
eqilibrium
 For static equilibrium, they provide sensory
information on the position of the head in
space and are essential for maintaining
appropiate posture and balance.

13.  In dynamic equilibrium i.e. when one is an
elevator that is speeding up or slowing down,
the maculae detect sensations of linear
acceleration and deceleration

15.  The maculae are perpendicular to one
another and consist of hair(receptor) cells
and and in between the hair cells are
supporting cells
 The supporting cells secrete the thick
gelatinous glycoprotein called the otolithic
membrane that rests on hair cells and layer
of calcium carbonate crystals called otoliths
extend over the surface of the otolithic
membrane

17.  If the head is tilted forward, the otolithic
membrane along with the otoliths is pulled
by gravity and slides down over the hair cells
in the direction of the tilt and stimulates the
hair cells.
 Similarly if sitted in a car that suddenly jerks
forward, the otolithic membrane due to its
inertia slides backward and stimulates the
hair cells

19. As the otoliths move, they pull on
the gelatinous layer which pulls on
the stereocilia and makes them
bend
Movement of the stereocilia intiate
depolarising receptor potentials in
the vestibular branch of the
vestibulocochlear (viii) nerve

20. As the head
moves, a shift in
the position of the
cilia within the
thick fluid around
them generates a
nerve impulse
The fluid above
the ciliated cells
contains small
crystals of calcium
carbonate, called
otoliths, which
add drag to the
fluid around the
receptor cells and
increase the
effect of gravity’s
pull
STATIC EQUILIBRIUM

21.  It is maintained by 3 semicircular ducts
together with saccule and utricle. The ducts
lie at right angles to one another in 3 planes
i.e the two vertical ones are the anterior
and posterior semicircular ducts and the
horizontal is the lateral semicircular duct.
 In the ampulla, the dilated portion of each
duct there are crista which contain a group
of hair cells and supporting cells covered by
gelatinous material called cupula.

22.  When the head moves, the endolymph in the
semicircular ducts flows over the hairs and
bends them and this movement of the hair
stimulates sensory neuron and the nerve
impulses which pass along the vestibular
branch of vestibulocochlear nerve

23. Receptors are located at
the bases of the
semicircular canals.
the semicircular canals
go off in different
directions.
Nerve fibers from the
vestibule and from the
semicircular canals form
the vestibular nerve,
which joins the cochlear
nerve to form the
vestibulocochlear
nerve, the eighth
cranial nerve.
DYNAMIC EQUILIBRIUM

24.  Most of the vesitibular branch fibres of the
vestibullocochlear nerve enter the brain
stem and terminate in the vestibular nuclear
complex in the pons, the remaining fibres
enter the cerebellum through the inferior
cerebella peduncle.
 Fibres from all the vestibular nuclei extend
to nuclei of cranial nerves that controll eye
movements i.e. oculomotor(iii),
trochlear(iv) and abducens(vi) and to the
accessory(xi) nerve nucleus that helps
control head and neck movements

25.  Fibres from the lateral vestibula nucleus
form the vestibulospinal tract which conveys
impulses to skeletal muscles that muscle
tone in response to head movement.s

26.  The cerebellum continously receives sensory
information from the utricle and saccule and
using this information, the cerebellum
monitors and makes corrective adjustments
in the motor activities that originate in the
cerebral cortex.

27.  Essentially the cerebellum sends continous
nerve impulses to the motor areas of the
cerebrum in response to input from the
utricle, saccule and semicircular ducts.

29.  Gerrald J. Tortora, Bryan D. Principles of
Anatomy and Physiology 12th edition.
 Guyton and Hall, Text Book of Medical
physiology 12th edition.