Week 7 ELM 15: Sensory Pathways II - Hearing, Chemical Senses, Touch

Flashcards for reviewing olfaction, gustation, audition, and mechanosensation based on lecture notes.

Olfaction

The sense of smell. Stimulus is received by olfactory receptor neurons (ORNs) in the olfactory epithelium. Information processed through glomeruli in the olfactory bulb.

Gustation

The sense of taste. Receptors are located in taste buds, which are found in papillae.

Audition

The sense of hearing.

Mechanosensation

The sense of touch.

Olfactory bulb

Olfactory sensory neurons converge in this structure.

GPCRs in olfaction

Type of receptors used for smell in humans; odorant binding leads to opening of a cyclic nucleotide-gated channel and depolarization.

Combinatorial coding (smell)

The coding mechanism in smell where each odorant binds to various receptors and activates many neurons, and each neuron is activated by many odorants.

Basic tastes

Bitter - avoid poisons

sweet - indicates sugar and carbohydrates

umami - indicates l-amino acids (monosodium glutamate)

salty - indicates Na+

sour - indicates acids/ H+

(fat may be a sixth)

Circumvallate, foliate, fungiform

Three types of papillae on the tongue that contain taste buds.

OTOP1

Ion channel selective for sour taste.

Sound detection

Detecting variations in air pressure. **Insects use a different mechanism by detecting the speed of moving particles

Normal hearing range for humans

20Hz to 20,000 Hz. **Lower frequency = lower pitch, lower intensity = quieter

Vestibular system

System comprised of semicircular canals (posterior, horizontal, anterior) and otolith organs (utricle, sacculae)

Auditory System

System comprised of the external, middle (bones: malleus, incus, stapes) , and inner ear (cochlea)

Cochlea

Hair cells transduce sound into electrical signals by K+ going in and causing depolarization. Outer hair cells: provide active amplification. Inner hair cells: send signals to auditory nerve.

Sound is represented tonotopically due to properties of this.

Basilar membrane

Otolith organs

Structure that detects force of gravity and acceleration using calcium carbonate crystals.

Semicircular canals

Structure that detects head rotation.

Steady pressure, (skin indentation, texture discrimination) is detected by

Merkel cells and Ruffini endings

Vibration is detected by

Meissner’s and Pacinian corpuscles

Nociceptors

Detect high-threshold stimuli, pain

Piezo2 channels

Protein in Merkel cells involved in touch sensation, mechanotransduction

What type of cells are involved in olfaction

Apical and secondary dendrites, periglomerular cells, mitral cells, and granule cells

Vision

The sense of sight. Stimulus is received by photoreceptor cells in the retina. Information processed through bipolar cells and horizontal cells. Signal sent to central targets

What cells are involved in vision

Bipolar cells, horizontal cells, retinal ganglion cells, amacrine cells

Vision and its sensory structures, receptor molecules, carrier of transduction current, and cortical areas

Sensory structures - Rods and cones

Receptor molecules - Retinal and opsin (GPCR)

Carrier of transduction current - Na+ (hyperpolarization)

Cortical areas - Visual cortex, V1 (occipital lobe)

Olfaction and its sensory structures, receptor molecules, carrier of transduction current, and cortical areas

Sensory structures - Olfactory receptor neurons

Receptor molecules - GPCRs

Carrier of transduction current - Na+, Ca 2+ (depolarization)

Cortical areas - Olfactory cortex (temporal lobe)

Gustation and its sensory structures, receptor molecules, carrier of transduction current, and cortical areas

Sensory structures -Taste receptor cells (neuroepithelial cells)

Receptor molecules - GPCRs, TRP channels, ENaC channel

Carrier of transduction current - Various (depolarization)

Cortical areas - Gustatory cortex (insular lobe and frontal lobe)

Hearing and its sensory structures, receptor molecules, carrier of transduction current, and cortical areas

Sensory structures - Hair cells

Receptor molecules - Unknown

Carrier of transduction current - K+ (depolarization)

Cortical areas - Auditory cortex (temporal lobe)

Touch and its sensory structures, receptor molecules, carrier of transduction current, and cortical areas

Sensory structures - Merkel cells, Ruffini endings, Meissner’s and Pacinian corpuscles

Receptor molecules - Unknown or Piezo

Carrier of transduction current - Probably Na+ and Ca 2+ (depolarization)

Cortical areas - Somatosensory cortex (parietal lobe)