The document discusses the organ of Corti, which contains hair cells that are important receptors for hearing. There are two types of hair cells - inner hair cells that transmit auditory stimuli and are more important for hearing, and outer hair cells that modulate the function of inner hair cells. The hair cells differ in their shape, nerve supply, development, stereocilia, motility, vulnerability and location.

1. Y.TANUSREE
BIO PSYCHOLOGY
UNIT-5
PSYCHOBIOLOGY OF SENSORY
SYSTEM

2. ORGAN OF CORTI :
A SENSORY RIDGE ON THE TOP OF THE BASILAR MEMBRANE
AND HAS NUMEROUS HAIR CELLS ARRANGED IN FOUR ROWS ALONG LENGTH OF
BASILAR MEMBRANE. APTICAL PART OF EACH HAIR CELLS HAS HAIR LIKE
STRUCTURES –STEREOCILIA. CONDUCTION OF SOUND WAVE , STEREOCILIA
MAKES A CONTACT WITH STIFF GEL MEMBRANE TECTORIAL MEMBRANE, A ROOF
LIKE STRUCTURE OVERHANGING ORGAN OF CORTI

5. THEY ARE IMPORTANT RECEPTOR CELLS OF HEARING AND TRANSDUCE SOUND ENERGY INTO
ELECTRICAL ENERGY.
THEY ARE OF TWO TYPES :
1) INNER HAIR CELLS form a single row
2) OUTER HAIR CELLS are arranged in three or four rows

6. INNER HAIR CELLS ARE RICHLY SUPPLIED BY AFFERENT COCHLEAR FIBRES AND
ARE PROBABLY MORE IMPORTANT IN THE TRANSMISSION OF AUDITORY
IMPULSES.
OUTER HAIR CELLS MAINLY RECEIVE EFFERENT INNERVATION FROM THE
OLIVARY COMPLEX AND ARE CONCERNED WITH MODULATING THE FUNCTION
OF INNER HAIR CELLS.
NERVE SUPPLY OF HAIR CELLS:
95% OF AFFERENT FIBRES OF SPIRAL GANGLION SUPPLY THE INNER HAIR CELLS WHILE
ONLY 5% SUPPLY THE OUTER HAIR CELLS.
EFFERENT FIBRES TO THE HAIR CELLS COME FROM THE OLIVOCOCHLEAR BUNDLE.
THEIR CELL BODIES ARE SITUATED IN SUPERIOR OLIVARY COMPLEX. EACH COCHLEA
SENDS INNERVATION TO BOTH SIDES OF THE BRAIN.

7. INNER HAIR CELLS OUTER HAIR CELLS
TOTAL NUMBER 3500 12000
ROWS ONE ROW 3-4 ROWS
SHAPE
NERVE SUPPLY
FLASK SHAPED
PRIMARILY
AFFERENT FIBRES
AND VERY FEW
EFFERENT.
CYLINDRICAL
MAINLY EFFERENT
FIBRES AND VERY
FEW AFFERENT

8. DEVELOPMENT DEVELOP EARLIER DEVELOP LATE
FUNCTION TRANSMIT AUDITORY
STIMULI
MODULATE
FUNCTION OF INNER
HAIR CELLS
STEREOCILIA LENGTH SHORT & FAT LONG & THIN
MOTILITY NON MOTILE MOTILE
VULNERABILITY MORE RESISTANT EARLY DAMAGED BY
OTOTOXIC DRUGS
AND HIGH INTENSITY
NOISE

9. LOCATION FARTHER FROM
MODIOLUS
NEARER
OTO ACOUSTIC
EMISSIONS
DOES NOT
GENERATE
GENERATES