HUMAN EAR

• 2 sensory modalities housed in the ear

  • Hearing
  • Equilibrium
• Hearing pathway

  external ear -> middle ear -> cochlea of inner ear -> cochlear nerve -> superior temporal gyrus (cortex)
• Equilibrium pathway

  semicircular canal, utricle and saccule -> vestibular nerve -> superior temporal gyrus (cortex)
• Sound is the sensation produced when soundwaves strike the tympanic membrane and cause it to vibrate. This vibration initiates vibrations in the middle and inner ear areas, stimulating the hair cells at the organ of Corti. The impulse produced is transmitted by the auditory nerve to the cortex for interpretation
• Sense of Equilibrium

  Mechanoreceptors in the semicircular canals detect rotational and/or angular movement of the head (rotational equilibrium), while mechanoreceptors in the utricle and saccule detect movement of the head in the vertical or horizontal planes (gravitational equilibrium)
• The ear converts sound waves in the external environment into action potentials in the auditory nerves
• Sound Wave Conductions

  1. Ossicular conduction: conduction of sound waves to the fluid of the inner ear via the tympanic membrane and the auditory ossicles

  2. Air conduction: sound waves initiating vibrations of the secondary tympanic membrane that closes the round window

  3. Bone conduction: the transmission of vibrations of the bones of the skull to the fluid of the inner ear
• Loudness of sound is correlated with the amplitude of the sound wave
• Pitch is correlated with the frequency of sound (number of waves/unit of time); the greater the frequency, the higher the pitch
• Noise is a periodic non-repeating vibration
• Music consists of sound waves that have repeating patterns
• Types of Deafness

  • Conduction Deafness: due to impaired sound transmission in the external or middle ear
  • Nerve Deafness: due to damage to the neural pathways