General Sensation - Chapter 12

Vocabulary terms and definitions related to general sensation, sensory receptors, and somatosensory pathways based on the Chapter 12 lecture notes.

Perception

The process of assigning meaning to sensation information.

Exteroreceptors

Sensory receptors situated at or near body surfaces that respond to stimuli originating in the external environment.

Visceral Interoreceptors

Receptors that detect changes within internal organs to respond to changes in the body's internal environment.

Somatic Interoreceptors

Receptors found within musculoskeletal structures that detect body interactions with the environment.

Thermoreceptors

Sensory receptors that sense changes in temperature.

Chemoreceptors

Sensory receptors that sense changes in chemicals, such as blood gases and $pH$.

Mechanoreceptors

Receptors that sense mechanical stress and changes in pressure, gravity, cell volume/shape, position, touch, itch, and movement.

Nociceptors

Receptors that sense tissue damage, physical trauma, or thermal injury; they are very slowly or non-adapting.

Sensory Adaptation

The loss of responsiveness at the sensory receptor level in the presence of a constant stimulus.

Sensory Unit

The sensation generated by a single sensory neuron and all of its associated receptors.

Receptive Field

The area of a surface covered by a single sensory unit; a larger field makes it harder to localize a stimulus.

Free Nerve Endings

Unencapsulated mechanoreceptors that penetrate the dermis and end in the stratum granulosum; they detect temperature, touch, pressure, stretch, and cell damage.

Merkel Cells

Slowly-adapting, oval-shaped mechanoreceptors located in the tips of fingers and lips that detect fine touch and texture.

Meissner’s Corpuscles

Encapsulated nerve endings found within dermal papillae in glabrous skin that are sensitive to light touch and vibrations between $10$ and $50\,Hz$.

Ruffini Corpuscles

Capsule-enclosed receptors consisting of free nerve endings intertwined with collagen fibers; they detect skin stretch and joint rotation.

Krause’s Corpuscles

Small round or oval-shaped encapsulated mechanoreceptors found in dry skin and mucous membranes that detect pressure and cold temperatures.

Pacinian Corpuscles

Very rapidly adapting nerve endings enclosed by concentric layers of collagen fibers; located in hairless skin to respond to deep pressure and vibration.

TRP Channels

Transient Receptor Potential Cation channels that open at different temperatures and release $Ca^{2+}$ to detect temperature changes in humans.

Diabetic Neuropathy

A condition involving damage to peripheral nerves, particularly nociceptors (pain receptors).

A$\delta$ Fibers

Nerve fibers that detect painful stimuli and carry signals relating to burning or aching pain.

A$\alpha$ Fibers

Nerve fibers that detect painful stimuli and carry sharp, localized pain signals.

C Fibers

Nerve fibers that respond to intense mechanical, chemical, or thermal stimuli.

Fasciculus Gracilis

The medial portion of the dorsal column pathway that carries sensory information from the lower body and legs to the nucleus gracilis.

Fasciculus Cuneatus

The lateral portion of the dorsal column pathway that carries sensory information from the upper body and arms to the nucleus cuneatus.

Medial Lemniscus

The structure formed by second-order interneurons that decussate in the medulla and ascend to the thalamus in the dorsal column pathway.

Lateral Spinothalamic Tract

Part of the anterolateral pathway that conveys pain and temperature information from the lower body (trunk and legs) to the thalamus.

Anterior (Ventral) Spinothalamic Tract

Part of the anterolateral pathway that conveys pain and temperature information from the upper body to the thalamus.