Ch. 12 The Spinal Cord, Spinal Nerves, and Spinal Reflexes

Flashcards covering the spinal cord, spinal nerves, and spinal reflexes.

Spinal reflexes

Controlled in the spinal cord and function without input from the brain.

Reflex

Rapid, automatic response triggered by specific stimuli.

White Matter

Superficial layer of the spinal cord; contains myelinated and unmyelinated axons.

Gray Matter

Deep layer of the spinal cord; forms an H or butterfly shape and contains neuron cell bodies, neuroglia, and unmyelinated axons.

Cauda equina

Extended anterior and posterior roots of spinal segments L2 to S5 and filum terminale; resembles a horse’s tail.

Anterior root

Contains axons of motor neurons.

Posterior root

Contains axons of sensory neurons.

Posterior root ganglion

Contains cell bodies of sensory neurons in the posterior root.

Dura mater

Outermost layer of the spinal meninges; tough and fibrous.

Arachnoid mater

Middle meningeal layer; includes the arachnoid membrane and subarachnoid space.

Pia mater

Innermost meningeal layer; meshwork of elastic and collagen fibers anchored to neural tissue.

Subarachnoid space

Contains arachnoid trabeculae and cerebrospinal fluid (CSF); blood vessels for the spinal cord are located here.

Epidural space

Between the dura mater and vertebrae; contains areolar tissue, blood vessels, and adipose tissue.

Denticulate ligaments

Extend from pia mater through arachnoid mater to dura mater; prevent lateral movement of the spinal cord.

Posterior gray horn

Contains somatic and visceral sensory nuclei.

Lateral gray horn

Only in thoracic and lumbar segments; contains visceral motor nuclei.

Anterior gray horn

Contains somatic motor nuclei.

Sensory nuclei

Receive and relay sensory information.

Motor nuclei

Issue motor commands to effectors.

Posterior white column

Located between the posterior gray horns and posterior median sulcus.

Lateral white column

Located between the anterior and posterior columns.

Anterior white column

Located between the anterior gray horns.

Ascending tracts

Carry sensory information in the posterior columns.

Descending tracts

Carry motor commands in the anterior columns.

Epineurium

Outermost layer of connective tissue surrounding a spinal nerve; dense network of collagen fibers.

Perineurium

Middle layer of connective tissue surrounding a spinal nerve; separates the nerve into fascicles.

Endoneurium

Innermost layer of connective tissue surrounding a spinal nerve; surrounds individual axons.

Posterior ramus

Branch of a spinal nerve that innervates the muscles, joints, and skin of the back.

Anterior ramus

Branch of a spinal nerve that innervates the lateral and anterior trunk and limbs.

Rami communicantes

In spinal nerves T1–L2, carry motor output of the sympathetic division of the ANS.

Dermatome

A specific bilateral area of skin supplied by a pair of spinal nerves.

Nerve plexus

Complex, interwoven nerve network formed by the anterior rami of adjacent spinal nerves.

Cervical plexus

Nerve plexus formed from spinal nerves C1–C5 that innervates the neck and diaphragm.

Brachial plexus

Nerve plexus formed from spinal nerves C5–T1 that innervates the pectoral girdle and upper limb.

Lumbar plexus

Nerve plexus formed from spinal nerves T12–L4 that innervates the pelvic girdle and lower limb.

Sacral plexus

Nerve plexus formed from spinal nerves L4–S4 that innervates the pelvic girdle and lower limb; contains the sciatic nerve.

Phrenic nerve

Formed by C3–C5; provides nerve supply to the diaphragm.

Neuronal pools

Functional groups of interconnected neurons that form neural circuits.

Parallel processing

Neural circuit pattern where several neurons or neuronal pools process the same information simultaneously.

Serial processing

Neural circuit pattern where information is relayed in a stepwise fashion from one neuron to the next.

Reverberation

Neural circuit pattern where collateral branches of axons extend back toward the source of the impulse, creating a positive feedback loop.

Stretch reflex

Monosynaptic reflex that automatically regulates skeletal muscle length.

Muscle spindles

Sensory receptors for the stretch reflex; made of intrafusal muscle fibers.

Gamma motor neuron

Innervates each muscle spindle; alters tension in intrafusal fibers.

Withdrawal reflexes

Move away from a stimulus which are triggered by painful stimuli or touch/pressure receptors.

Flexor reflex

Type of withdrawal reflex that affects the muscles of a limb.

Crossed extensor reflexes

Involve contralateral reflex arcs where an additional motor response occurs on the side opposite the stimulus.

Reinforcement

Facilitation of a spinal reflex by the brain.

Babinski reflex

Extension of the hallux and spreading of other toes when stroking the foot on the lateral side of the sole; normal in infants.

Plantar reflex

Toe curling (plantar flexion) when stroking the foot on the lateral side of the sole; normal in adults.