Fundamentals of Anatomy & Physiology Twelfth Edition: Chapter 15 Flashcards

Comprehensive vocabulary flashcards covering the components of the afferent and efferent divisions, specific sensory receptor types, major sensory pathways (spinothalamic, posterior column, spinocerebellar), and somatic motor pathways as presented in the lecture notes.

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 division

The division of the nervous system comprised of somatic sensory pathways (to the cerebral cortex) and visceral sensory pathways (to the brainstem and diencephalon).

Efferent division

The division of the nervous system consisting of somatic motor pathways that control peripheral effectors, specifically skeletal muscles.

Sensation

Sensory information arriving in the C N S.

Perception

Conscious awareness of a sensation.

Transduction

The conversion of an arriving stimulus into an action potential by a sensory receptor.

Receptive field

The area monitored by a single receptor cell; localization of a stimulus is more difficult as this area increases in size.

Receptor potential

A change in the receptor membrane potential in response to a stimulus; can be depolarizing (generator potential) or hyperpolarizing.

Labeled line

Sensory neurons that link specific peripheral receptors to specific cortical neurons, with each carrying information about one modality or type of stimulus.

Tonic receptors

Sensory receptors that are always active; an increase or decrease in stimulation results in a corresponding change in action potential frequency.

Phasic receptors

Sensory receptors that are normally inactive and provide information about the intensity and rate of change of a stimulus by generating a burst of action potentials.

Adaptation

A reduction of receptor sensitivity in the presence of a constant stimulus.

Central adaptation

Inhibition of nuclei along a sensory pathway in the C N S, which can involve conscious or subconscious changes in sensory awareness.

Exteroceptors

Sensory receptors that provide information about the external environment.

Proprioceptors

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

Interoceptors

Sensory receptors that provide information about visceral organs and functions.

Nociceptors

Pain receptors consisting of free nerve endings with large receptive fields; they are tonic receptors and show little peripheral adaptation.

Fast pain

Prickling pain carried by myelinated Type A fibers that reaches the C N S quickly and trigger somatic reflexes.

Slow pain

Burning and aching pain carried by unmyelinated Type C fibers that causes generalized activation of the reticular formation and thalamus.

Thermoreceptors

Phasic receptors located in the dermis, skeletal muscles, liver, and hypothalamus that detect temperature; they conduct sensations along the same pathways as pain.

Mechanoreceptors

Receptors sensitive to physical stimuli that distort plasma membranes, including tactile receptors, baroreceptors, and proprioceptors.

Tactile discs

Sensitive tonic receptors for fine-touch and pressure that are sensitive to shape and texture and have small receptive fields.

Lamellar corpuscles (Pacinian corpuscles)

Fast-adapting receptors sensitive to deep pressure and high-frequency vibrations, consisting of a dendrite within concentric collagen layers.

Baroreceptors

Free nerve endings that detect pressure changes in the walls of distensible organs such as blood vessels or portions of the digestive tract.

Chemoreceptors

Sensory receptors that monitor concentrations of water-soluble and lipid-soluble substances, such as $p H$, $CO_2$, and $O_2$ in arterial blood.

First-order neuron

A sensory neuron that delivers sensations from the periphery to the C N S, with a cell body located in a spinal or cranial nerve ganglion.

Second-order neuron

An interneuron in the spinal cord or brainstem that receives input from first-order neurons and often undergoes decussation.

Third-order neuron

A neuron in the thalamus that synapses with neurons of the primary somatosensory cortex.

Spinothalamic pathway

A somatic sensory pathway carrying sensations of crude touch, pressure, pain, and temperature.

Referred pain

Visceral pain manifest as body surface pain because the internal organ and body surface are innervated by the same spinal segment.

Posterior column pathway

A sensory pathway carrying sensations of fine touch, vibration, pressure, and proprioception; includes the gracile and cuneate fasciculi.

Sensory homunculus

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

Spinocerebellar pathway

Sensory pathway carrying information about the positions of muscles, tendons, and joints to the cerebellum.

Upper motor neuron

A motor neuron with a cell body in a C N S processing center that synapses on a lower motor neuron.

Lower motor neuron

A motor neuron with a cell body in a nucleus of the brainstem or spinal cord whose axon innervates a single motor unit in a skeletal muscle.

Corticospinal pathway (pyramidal system)

A motor pathway providing voluntary control over skeletal muscles, originating at the pyramidal cells of the primary motor cortex.

Medial pathway

Motor pathway controlling muscle tone and gross movements of the trunk and proximal limb muscles; involves vestibular nuclei and colliculi.

Lateral pathway

Motor pathway controlling muscle tone and movements of the distal limb muscles for precise movements; originates in the red nuclei of the midbrain.

Basal nuclei

Centers that provide background patterns of movement involved in voluntary motor activities and can stimulate or inhibit upper motor neurons.