Sensory Pathways and the Somatic Nervous System Flashcards

A set of vocabulary flashcards covering sensory pathways, general and special senses, receptor classifications, tactile acuity, mechanoreceptors, chemoreceptors, baroreceptors, nociceptors, and cortical homunculi.

Sensory pathways

A series of neurons that relay sensory information from sensory receptors to the C N S.

Sensory receptors

Specialized cells or neuron processes that monitor specific conditions in the body or the external environment.

Afferent pathways

Pathways carrying somatic and visceral sensory information that arrives at the C N S.

Efferent pathways

Somatic motor pathways that exit the C N S and control skeletal muscles.

Sensation

Sensory information arriving in the C N S.

Perception

Conscious awareness of a sensation that assigns meaning to arriving information.

General senses

Sensations including temperature, pain, touch, pressure, vibration, and proprioception.

Special senses

Sensations provided by special sensory receptors, including olfaction, gustation, vision, equilibrium, and hearing.

Receptor specificity

The characteristic sensitivity of each receptor to a specific stimulus.

Receptive field

The physical area monitored by a single sensory receptor cell or sensory unit.

Sensory unit

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

Two-point touch threshold

The distance at which a person can perceive two separate points of touch, used to measure tactile acuity.

Receptor potential

A graded change in membrane potential generated in a receptor cell when acted upon by a stimulus.

Sensory adaptation

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

Phasic receptors

Fast-adapting receptors that are normally inactive and respond with a burst of activity when a stimulus is first applied, but quickly adapt.

Tonic receptors

Slow-adapting receptors that are always active and maintain a high firing rate as long as a stimulus is applied.

Exteroceptors

Sensory receptors classified by location that provide information about the external environment.

Proprioceptors

Sensory receptors that monitor the position of joints and skeletal muscles to provide information about body position.

Interoceptors

Sensory receptors classified by location that provide information about visceral organs and functions.

Thermoreceptors

Phasic free nerve endings located in the dermis, skeletal muscles, liver, and hypothalamus that detect changes in temperature.

Chemoreceptors

Phasic sensory receptors that detect changes in chemical concentration, such as blood gases and pH in body fluids.

Carotid bodies

Chemoreceptors located in the internal carotid arteries that monitor blood pH, carbon dioxide, and oxygen levels via Cranial nerve IX.

Aortic bodies

Chemoreceptors located in branches of the aortic arch that monitor blood pH, carbon dioxide, and oxygen levels via Cranial nerve X.

Mechanoreceptors

Receptors containing mechanically-gated ion channels that detect physical distortion such as stretching, compression, twisting, and touch.

Fine touch and pressure receptors

Extremely sensitive tactile receptors with narrow receptive fields that provide detailed information about stimulus shape or texture.

Crude touch and pressure receptors

Tactile receptors with large receptive fields that provide poor localization and little information about a stimulus.

Root hair plexus

Phasic free nerve endings near hair follicles that detect movement.

Tactile discs (Merkel discs)

Sensitive tonic receptors with small receptive fields that detect fine touch and sustained pressure.

Bulbous corpuscles (Ruffini corpuscles)

Tonic receptors located in the reticular dermis sensitive to deep pressure and distortion.

Lamellar corpuscles (Pacinian corpuscles)

Fast-adapting receptors sensitive to deep pressure and pulsing vibrations, composed of a single dendrite within concentric layers of collagen.

Tactile corpuscles (Meissner corpuscles)

Phasic receptors sensitive to fine touch, pressure, and low-frequency vibration.

Baroreceptors

Free nerve endings branching within elastic tissues of distensible organ walls that detect pressure changes in blood vessels and parts of the digestive, respiratory, and urinary tracts.

Nociceptors

Tonic free nerve endings with large receptive fields that depolarize when tissues are damaged to detect pain.

Muscle spindles

Proprioceptors that monitor skeletal muscle length and trigger stretch reflexes.

Golgi tendon organs

Proprioceptors located at the junction between skeletal muscle and its tendon that monitor tension during muscle contraction.

Sensory homunculus

A functional map of the primary somatosensory cortex where the area devoted to a body region is proportional to the density of sensory neurons in that region.

Motor homunculus

A functional map of the primary motor cortex where the size of each represented region corresponds to the degree of fine motor control available.

Homunculus mapping

Cortical maps of the primary motor and somatosensory cortices corresponding to specific anatomical regions of the body.