Sensory Physiology Part I: Touch, Pain, Smell, and Taste

Vocabulary flashcards covering sensory physiology concepts including touch receptors, properties of sensation, pain mechanics, taste bud structure and gustatory pathways, and olfactory cell types and olfactory bulb wiring.

Receptor

A specialized cell able to respond to any internal or external stimulus and transmit a signal to a sensory nerve.

Unencapsulated Receptors

Sensory receptors whose dendrites are not wrapped in connective tissue or glial cells, including free nerve endings, tactile discs, and hair receptors.

Free Nerve Endings

Unencapsulated dendrites located in skin and mucous membranes that detect pain and temperature.

Tactile Discs (Merkel Discs)

Unencapsulated receptors located at the base of the epidermis associated with Merkel cells that respond to light touch and texture.

Hair Receptors

Unencapsulated nerve endings wrapped around the base of hair follicles that monitor the movement of hair.

Encapsulated Receptors

Sensory receptors whose nerve endings are enclosed in a capsule of connective tissue or glial cells.

Meissner Corpuscles

Encapsulated receptors located in the dermal papillae of hairless skin that detect light touch and texture.

Krause End Bulb

Encapsulated tactile receptors located in mucous membranes.

Pacinian Corpuscles

Encapsulated receptors located in the periosteum of bone, deep dermis of skin, and external genitalia that detect deep pressure, stretch, tickle, and vibration.

Ruffini Corpuscles

Encapsulated receptors that detect heavy touch, pressure, joint movements, and skin stretching.

Transduction

The conversion of stimulus energy (such as light, heat, touch, or sound) into nerve signals.

Receptor Potential

The conversion of an initial stimulus into an electrical potential, resulting in neurotransmitter release or a volley of action potentials sent to the CNS.

Modality

The specific type of stimulus or sensation produced (e.g., vision, hearing, taste), encoded by a labeled line code based on the pathway origin.

Receptive Field

The specific area that detects stimuli for a single sensory neuron.

Two-Point Threshold

A measurement of touch receptor density that assesses the ability to discriminate between two points of touch based on activating two distinct neuronal receptive fields.

Sensory Adaptation

The decrease in firing frequency of a sensory neuron over time during prolonged exposure to a stimulus, leading to reduced awareness.

Phasic Receptor

A fast-adapting sensory receptor that responds quickly to a stimulus and rapidly decreases its firing rate.

Tonic Receptor

A slow-adapting sensory receptor that continues to generate nerve signals over long periods of continuous stimulation.

Nociceptors

Specialized sensory receptors that respond to tissue injury and produce pain sensations.

Fast Pain

Sharp, localized, stabbing pain perceived at the moment of injury, transmitted along myelinated nerve fibers.

Slow Pain

Longer-lasting, dull, diffuse pain feeling transmitted along unmyelinated nerve fibers.

Somatic Pain

Pain originating from sensory receptors in the skin, muscles, and joints.

Visceral Pain

Pain originating from sensory receptors located in the internal viscera.

Referred Pain

Visceral pain mistakenly perceived as somatic pain in distant or adjacent skin regions because mixed spinal nerve pathways confuse the source in the brain.

Basal Cells (Taste Bud)

Stem cells in taste buds that divide to replace worn-out gustatory cells every 10 days to 2 weeks.

Taste (Gustatory) Cells

Chemoreceptive cells within taste buds featuring a tuft of taste hairs that act as the receptor surface for taste molecules.

Supporting Cells (Taste Bud)

Cells in taste buds that structurally resemble taste cells but lack taste hairs, synaptic vesicles, and a sensory role.

Primary Taste Sensations

The five basic gustatory qualities: salty (metal ions like $\text{Na}^+$ and $\text{K}^+$), sour (acids), sweet (carbohydrates), bitter (alkaloids like nicotine and caffeine), and umami (amino acids).

Facial Nerve (CN VII)

Cranial nerve responsible for collecting sensory taste information from taste buds on the anterior two-thirds of the tongue.

Glossopharyngeal Nerve (CN IX)

Cranial nerve responsible for collecting sensory taste information from the posterior one-third of the tongue.

Vagus Nerve (CN X)

Cranial nerve that collects sensory taste signals from taste buds located on the palate, pharynx, and epiglottis.

Olfactory Receptor Cells

Bipolar sensory neurons located in the olfactory mucosa that are directly exposed to the external environment and transduce odorants.

Supporting Cells (Olfactory Mucosa)

Epithelial cells in the olfactory mucosa that provide nourishment and help detoxify odorant molecules.

Glomeruli (Olfactory Bulb)

Spherical clusters of dendrites in the olfactory bulb where olfactory receptor cells synapse with mitral and tufted cells, each dedicated to a single specific odor type.