P.2 Auditory and Somatosensory Physiology & Disorders

20 question-and-answer flashcards covering auditory processing, hearing disorders, somatosensory receptors, pathways, and related concepts.

What is timing theory (phase locking)?

Spiral ganglion cells fire in sync with the phases of a sound wave, supporting pitch perception up to roughly 4–5 kHz.

What is tonotopy in the primary auditory cortex (A1)?

A1 contains an ordered frequency map that mirrors the cochlea’s frequency distribution.

What binaural cues are used for sound localization?

Interaural Time Difference (ITD) for low frequencies and Interaural Level Difference (ILD) for high frequencies, processed in the superior olive.

What are spectral notches and what do they help with?

Frequency-specific reflections shaped by the pinna that aid vertical and front/back sound localization, processed in the cochlear nucleus.

What are the auditory “what” and “where” pathways?

Ventral pathway identifies sound (“what”); dorsal pathway localizes sound (“where”).

What causes cochlear hearing loss?

Hair-cell damage from noise, ototoxic drugs, viral infection, or aging (presbycusis).

What is hidden hearing loss?

Synaptic damage that is not detected by standard audiograms but impairs hearing clarity in noisy environments.

What is retrocochlear hearing loss?

Damage to the auditory nerve or central auditory pathways, often due to tumors or brain injury.

What is tinnitus?

Phantom perception of sound, potentially arising from hair-cell damage and cortical reorganization.

What causes conductive deafness?

Mechanical problems such as ear-wax buildup, stiff ossicles, or tympanic membrane damage.

What are the three components of somatosensation?

Exteroception (external stimuli), interoception (internal organs), and proprioception (body position).

What are the four low-threshold mechanoreceptors (LTMRs)?

Merkel discs (pressure, texture), Meissner corpuscles (grip, low-frequency vibration), Ruffini endings (skin stretch), and Pacinian corpuscles (high-frequency vibration).

Which skin receptors have small versus large receptive fields?

Type I receptors (Merkel, Meissner) have small receptive fields; Type II receptors (Ruffini, Pacinian) have large receptive fields.

What is two-point discrimination?

A measure of tactile acuity; fingertips have the lowest threshold (highest sensitivity), whereas calves have the highest threshold.

What are hair-follicle receptors and their fiber types?

Receptors in hairy skin that detect hair deflection via longitudinal lanceolate endings, using Aδ and C fibers.

What are high-threshold mechanoreceptors (HTMRs)?

Free nerve endings that sense painful or noxious mechanical stimuli and use Aβ, Aδ, and C fibers.

What are the three models for mechanical transduction in touch receptors?

(1) Direct stretch activation, (2) tethered-channel activation, and (3) indirect chemical activation.

Which TRP channels detect temperature?

TRPV1 detects heat and capsaicin (burning), while TRPM8 detects cold and menthol.

What are the two main ascending somatosensory pathways?

Touch: dorsal column–medial lemniscus pathway (crosses in the medulla); Pain/temperature: spinothalamic tract (crosses at the spinal cord level).

What is a dermatome?

A skin region innervated by a single spinal nerve, useful for mapping sensory deficits or spinal lesions.