I85PREP
⌘ K
NHPC BASLP study materials
NHPC BASLP study resources

NHPC BASLP: Anatomy and Physiology of the Auditory and Speech Systems

NHPC BASLP · Work through your exam, one topic at a time.

All guide sections

Anatomy and Physiology of the Auditory and Speech Systems

This domain tests structure–function links from the pinna to the auditory cortex and from the respiratory–phonatory–articulatory systems to speech output. Questions often ask you to predict a functional deficit from a lesion or to name the structure that explains an audiometric, voice, or resonance finding.

Auditory system

  • The pinna and concha provide high-frequency gain and directional cues; the adult ear canal resonates near 2–4 kHz.
  • Middle-ear impedance matching depends on the tympanic-membrane-to-stapes-footplate area ratio (about 17:1, roughly 25 dB) and the ossicular lever (about 1.3, roughly 2 dB), totaling about 27 dB.
  • The cochlea is tonotopic: base = high frequencies, apex = low. Outer hair cells provide active amplification; inner hair cells are the main afferent sensors.
  • Auditory nerve fibers project to cochlear nuclei, superior olivary complex, inferior colliculus, medial geniculate body, and auditory cortex.

Speech system

  • Respiration supplies subglottal pressure; the larynx regulates phonation. Cricothyroid raises pitch; thyroarytenoid lowers and relaxes the vocal folds.
  • The velum controls nasality; tongue, lips, and jaw shape vocal-tract resonances (formants).
  • CN X supplies most laryngeal muscles; CN XII controls tongue movement; CN VII controls facial muscles.

Worked example

A 2 kHz tone is boosted about 10–15 dB by ear-canal resonance. If middle-ear transfer adds about 27 dB, the cochlea receives a pressure signal much larger than at the tympanic membrane. Reasoning: canal resonance and impedance matching jointly improve sensitivity in the speech range. A tympanic-membrane perforation removes part of the area-ratio advantage and usually produces a conductive loss with a bone–air gap.

Traps

Do not confuse scala media with scala vestibuli, or outer with inner hair cell roles. Do not attribute all laryngeal supply to the recurrent laryngeal nerve: the external branch of the superior laryngeal nerve supplies cricothyroid. Do not equate pitch with loudness.