Chapter 15: Neural Integration

Vocabulary flashcards covering sensory and motor pathways, receptor classifications, touch and proprioceptors, spinal cord tracts, neuron orders, and motor deficits from Chapter 15 Neural Integration.

Sensory pathway

A pathway that begins at a sensory receptor and ends at the postcentral gyrus, containing both PNS (afferent) and CNS (ascending) components.

Somatic motor pathway

A voluntary pathway that begins in the precentral gyrus and ends at skeletal muscle, containing both CNS (descending) and PNS (efferent) components.

Stimulus

A change in the environment that can produce a response.

Receptor

A specialized structure that detects a stimulus and acts as a transducer to initiate an action potential.

Punctate distribution

The unequal distribution of receptors throughout the skin, resulting in higher concentrations in areas such as the fingertips, lips, face, and palms.

Adaptation

Decreased sensitivity to a continuous stimulus over time, causing receptors to eventually cease producing action potentials.

Exteroceptors

Receptors located at or near the body surface that detect changes outside the body, such as photoreceptors, hair cells, and tactile skin receptors.

Interoceptors

Receptors located in internal organs that detect changes inside the body, such as baroreceptors monitoring blood pressure and chemoreceptors monitoring blood pH.

Proprioceptors

Receptors that detect changes in body position, tension, and movement, and do not adapt very well.

Mechanoreceptors

Receptors that initiate an action potential when mechanically deformed by pressure, stretch, or vibration.

Thermoreceptors

Receptors, often with free dendritic endings, that respond to changes in temperature (heat or cold).

Nociceptors

Free dendritic endings located in the skin, internal organs, joints, muscles, and meninges that respond to cell damage and tissue injury to produce the sensation of pain.

Chemoreceptors

Receptors that respond to chemicals, such as olfactory receptors in the nasal cavity, taste buds on the tongue, and carotid or aortic bodies in arteries.

Photoreceptors

Visual receptors, such as rods and cones, that respond to light.

Tactile (Merkel) cell/disc

An intraepithelial receptor featuring free dendritic endings located in the deepest epidermal layer (stratum basale) that detects light touch, shape, and texture.

Tactile (Meissner) corpuscle

A rapidly adapting receptor located in the dermal papilla that detects gentle touch and changes in light touch.

Hair root plexus

Rapidly adapting free dendritic endings wrapped around hair follicles that detect movement across the skin.

Lamellated (Pacinian) corpuscle

A sensory receptor located in the dermis that detects deep pressure.

Muscle spindle

Specialized intrafusal muscle fibers that detect changes in muscle length (stretch), supplying information used by the cerebellum to maintain balance.

Golgi tendon organ

A proprioceptor located at the muscle/tendon junction that detects skeletal muscle contraction and signals the muscle to relax to prevent overcontraction and damage.

Joint receptors

Proprioceptors located within the capsules of synovial joints that detect joint position.

Tract

A bundle of axons located entirely within the Central Nervous System (CNS), named according to origin and destination.

Nucleus

A cluster of neuron cell bodies located within the Central Nervous System (CNS), such as the red nucleus of the midbrain.

Nerve

A bundle of axons located in the Peripheral Nervous System (PNS) that can carry both sensory and motor impulses.

Ganglion

A cluster of neuron cell bodies located within the Peripheral Nervous System (PNS), such as the dorsal root ganglion.

First order neuron (Sensory)

An afferent unipolar sensory neuron whose cell body resides in the dorsal root ganglion.

Second order neuron (Sensory)

An interneuron with a cell body located in the spinal cord or brain stem whose axon decussates (crosses over to the opposite side).

Third order neuron (Sensory)

A sensory neuron whose cell body is located in the thalamus and whose axon terminates in the postcentral gyrus.

Anterior spinothalamic pathway

The ascending somatic sensory pathway responsible for conducting crude touch and pressure impulses to the postcentral gyrus via the anterior spinothalamic tract.

Lateral spinothalamic pathway

The ascending somatic sensory pathway responsible for conducting pain and temperature impulses to the postcentral gyrus via the lateral spinothalamic tract.

Posterior column pathway

An ascending pathway formed by the axons of first order neurons ascending to the medulla, conducting sensory impulses for discriminative touch, proprioception, and vibration.

Discriminative touch

Fine touch sensation that can be precisely and readily localized to the exact part of the body that was touched.

Spinocerebellar pathway

An ascending sensory tract that transmits proprioceptive impulses from proprioceptors to the cerebellum for subconscious proprioception.

Upper motor neuron

A pyramidal neuron with its cell body located in the precentral gyrus whose axon descends through the cerebral peduncles toward the spinal cord.

Lower motor neuron

A motor neuron with its cell body in the anterior gray horn of the spinal cord whose axon exits via the ventral root to innervate skeletal muscle.

Decussation of pyramids

The brainstem region where approximately $85\%$ of upper motor neuron axons cross over to become the lateral corticospinal tract, while roughly $20\%$ do not cross and continue as the anterior corticospinal tract.

Upper motor neuron damage

Damage along the direct motor pathway within the CNS that typically causes spastic paralysis and produces a positive Babinski sign.

Lower motor neuron damage

Damage to the anterior gray horn, ventral root, or peripheral motor nerve that prevents action potentials from reaching skeletal muscle, resulting in flaccid paralysis and the loss of peripheral reflexes.

Indirect motor pathways

Descending extrapyramidal pathways that originate in the brain stem to modify skeletal muscle movements, regulate muscle tone, balance, and posture by acting on lower motor neurons in the anterior gray horn.

Basal nuclei

Cerebral structures that help regulate and control body movements by influencing the upper motor neurons of the direct and indirect motor pathways.

Referred pain

The perception of pain in a body region distinct from the site where the painful stimulus or injury originated, such as feeling heart pain in the arm.