Fundamentals of Anatomy & Physiology - Chapter 15: Sensory Pathways and the Somatic Nervous System

This set of flashcards covers vocabulary and key concepts from Chapter 15 including sensory receptors, afferent and efferent divisions, specific sensory pathways, and the organization of the somatic motor system.

Sensory Pathways

A series of neurons that relay information from sensory receptors to the CNS.

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 composed of somatic and visceral sensory pathways.

Efferent Division

The division of the nervous system composed of somatic motor pathways that control peripheral effectors like skeletal muscles.

Sensation

The arrival of sensory information in the CNS.

Perception

The conscious awareness of a sensation.

Transduction

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

Receptive Field

The specific 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 caused by a stimulus; can be depolarizing or hyperpolarizing.

Labeled Line

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

Sensory Coding

The pattern and frequency of action potentials that indicate the duration, strength, and variation of a stimulus.

Tonic Receptors

Sensory receptors that are always active and generate action potentials at a frequency reflecting background stimulation levels.

Phasic Receptors

Sensory receptors that are normally inactive but become active for a short time in response to changing conditions.

Peripheral Adaptation

A reduction in receptor sensitivity that occurs in the PNS when receptor activity levels change in the presence of a constant stimulus.

Central Adaptation

A reduction in sensory awareness that occurs in the CNS involving the inhibition of nuclei along a sensory pathway.

Exteroceptors

Receptors that provide information about the external environment.

Proprioceptors

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

Interoceptors

Receptors that provide information about visceral organs and functions.

Nociceptors

General sensory receptors located in the skin, joints, and blood vessel walls that detect pain.

Fast Pain

Prickling pain, such as from an injection, carried to the CNS by myelinated Type A fibers.

Slow Pain

Burning or aching pain carried to the CNS by unmyelinated Type C fibers.

Thermoreceptors

Phasic receptors located in the dermis and hypothalamus that detect temperature.

Mechanoreceptors

Receptors with mechanically-gated ion channels that respond to physical distortions of their plasma membranes.

Tactile Receptors

A class of mechanoreceptors that provide sensations of touch, pressure, and vibration.

Baroreceptors

Free nerve endings that detect pressure changes in distensible organs like blood vessels or the digestive tract.

Muscle Spindles

Proprioceptors that monitor skeletal muscle length and trigger stretch reflexes.

Golgi Tendon Organs

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

Chemoreceptors

Receptors that monitor $pH$, carbon dioxide, and oxygen levels in body fluids and arterial blood.

First-order Neuron

A sensory neuron that delivers sensations from the periphery to the CNS, typically with its cell body in a cranial or spinal nerve ganglion.

Second-order Neuron

An interneuron in the brainstem or spinal cord that receives input from a first-order neuron and typically undergoes decussation.

Third-order Neuron

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

Decussation

The crossing of an axon to the opposite side of the CNS.

Spinothalamic Pathway

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

Posterior Column Pathway

The somatic sensory pathway carrying highly localized sensations of fine touch, pressure, vibration, and proprioception.

Spinocerebellar Pathway

The sensory pathway that delivers proprioceptive information about the position of muscles, tendons, and joints to the cerebellum.

Sensory Homunculus

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

Upper Motor Neuron

A motor neuron with a cell body in a CNS processing center that synapses on a lower motor neuron to control skeletal muscle.

Lower Motor Neuron

A motor neuron with a cell body in the brainstem or spinal cord that innervates a single motor unit in a skeletal muscle.

Corticospinal Pathway

Also known as the pyramidal system, this pathway provides voluntary control over skeletal muscles.

Motor Homunculus

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

Basal Nuclei

Structures that provide background patterns of movement for voluntary motor activities and help coordinate muscle contractions.

Cerebellum

The brain region responsible for monitoring proprioceptive, visual, and vestibular sensations to adjust and coordinate movements.