Sensory Systems: Transduction, Coding, and Pathways in Neuroscience

What is sensory transduction?

The conversion of stimulus energy into electrical signals (action potentials).

What are the types of voltage representation in sensory coding?

Rate coding, temporal coding, and adaptation (rapid vs. slow).

What elements define sensory coding?

Modality, location, intensity, and duration.

How is somatosensory information mapped in the CNS?

Topographically, with lateralization and homunculus maps.

What is the difference between pain and nociception?

Nociception is the physiological detection of noxious stimuli; pain is the subjective emotional experience.

What are the types of pain?

Acute, episodic, and chronic.

Describe the pain signal transmission pathway.

Nociceptors → afferent fibers → dorsal horn → 2nd-order neurons → spinothalamic tract → brain.

What cells are affected by SARS-CoV-2 in anosmia?

Sustentacular cells, not olfactory neurons.

Does olfactory information pass through the thalamus?

No, it goes directly to the limbic system and brainstem.

What are the five taste modalities?

Salty, bitter, sour, sweet, umami.

What types of receptors detect taste?

GPCRs (type 1 and 2), ion channels, and transporters.

Which cranial nerves carry taste information?

CN VII (anterior 2/3 tongue), CN IX (posterior 1/3), CN X (epiglottis/throat).

What is the taste pathway?

Cranial nerves → solitary tract → solitary nucleus → thalamus → taste cortex.

What is the function of the lens in vision?

Focuses light so retinal points correspond to single light sources.

What are the four photoreceptor types and their peak wavelengths?

Rods (500 nm), blue cones (420 nm), green cones (530 nm), red cones (560 nm).

What is the dark current mechanism?

In darkness, photoreceptors are depolarized due to open cGMP-gated channels; light closes them causing hyperpolarization.

What is the visual pathway?

Photoreceptors → bipolar cells → ganglion cells → optic nerve.

What are the components of the ear?

External (pinna, canal), middle (tympanic membrane, ossicles), inner (cochlea, semicircular canals).

What fluid in the cochlea has high potassium concentration?

Endolymph.

What is tonotopic mapping?

Encoding of different sound frequencies at specific locations along the cochlea.

What are the types of hearing loss?

Conductive and sensorineural.

How is sound localized in the brainstem?

Delay line coding and amplitude differences processed by the superior olivary nucleus.

How are sound waves converted into fluid waves in auditory transduction?

Sound waves vibrate the tympanic membrane

How do hair cells generate electrical signals in auditory transduction?

Movement of endolymph in the cochlear duct causes the basilar membrane to vibrate

What detects angular acceleration?

Semicircular canals.

What detects linear acceleration?

Utricle (horizontal) and saccule (vertical).

What cranial nerve carries auditory and vestibular information?

CN VIII.

What do contralateral vs. ipsilateral deficits indicate?

Contralateral = opposite side of lesion; ipsilateral = same side.

What do hemianopsia patterns help with?

Localizing visual pathway lesions.

What is the function of Pacinian corpuscles?

Rapid adaptation and edge detection.

Which side of the body does the brain typically control?

The contralateral side.