Sensory Pathways and Somatic Nervous System

Flashcards covering key vocabulary related to sensory pathways and the somatic nervous system (SNS).

General senses

Describe our sensitivity to temperature, pain, touch, pressure, vibration, and proprioception (body position).

Special senses

Require specialized sensory receptors for olfaction (smell), gustation (taste), vision (sight), equilibrium (balance), and hearing.

Transduction

Conversion of stimulus into an action potential along sensory fibers.

Receptive field

Area monitored by a single receptor cell.

Nociceptors

A sensory receptor that detects tissue damage and typically elicits pain.

Thermoreceptors

Sensory receptor sensitive to temperature changes.

Chemoreceptors

Sensory receptor sensitive to chemical concentration changes.

Mechanoreceptors

Sensory receptor sensitive to physical distortion such as touch, vibration, pressure etc.

Tactile receptors

Mechanoreceptors that provide sensations of touch, pressure and vibration.

Baroreceptors

Mechanoreceptors that detect pressure changes in blood vessels and in digestive, respiratory, and urinary tracts

Proprioceptors

Mechanoreceptors that monitor positions of joints and skeletal muscles

Lamellar corpuscles (Pacinian corpuscles)

Sensitive to deep pressure and most sensitive to pulsing or high-frequency vibrating stimuli.

Tactile corpuscles (Meissner corpuscles)

Perceive sensations of fine touch, pressure, and low-frequency vibration and adapt to stimulation within 1 second after contact.

Somatic sensory pathways

Carry sensory information from skin and muscles of body wall, head, neck, and limbs to CNS.

First-order neuron

Sensory neuron that delivers sensations to CNS

Second-order neuron

Interneuron in spinal cord or brainstem that receives information from first-order neuron and crosses to opposite side of CNS (decussation)

Third-order neuron

Interneuron with cell body in thalamus that must receive information from second-order neuron and carry the signal to an area of the cerebrum for the sensation to reach our awareness.

Spinothalamic pathway

Carries sensations of crude touch, pressure, pain, and temperature.

Posterior column pathway

Carries sensations of fine touch, vibration, pressure, (and proprioception).

Spinocerebellar pathway

Conveys information about positions of muscles, tendons, and joints from spinal cord to cerebellum; this information never reach our awareness.

Somatic nervous system (SNS)

Controls contractions of skeletal muscles.

Upper motor neuron

Cell body lies in a CNS processing center and activity may facilitate or inhibit lower motor neuron.

Lower motor neuron

Cell body lies in a nucleus of brainstem or spinal cord; only the axon extends outside CNS and innervates a single motor unit in a skeletal muscle.

Corticospinal pathway (pyramidal system)

Provides voluntary control over skeletal muscles.