chapter 14 spinal cord

Denticulate ligaments

Extensions of the dura mater that fuse with the arachnoid layer to anchor the spinal cord and prevent displacement.

Conus medullaris

Tapered, cone-shaped inferior end of the spinal cord located near the second lumbar vertebra.

Filum terminale

Extension of the pia mater extending from the conus medullaris to attach the spinal cord to the coccyx.

Cauda equina

Bundle of nerve roots extending inferiorly from the conus medullaris through the lower vertebral canal.

Cervical enlargement

Thickened region in the neck where nerves supplying the upper limbs originate.

Lumbar enlargement

Thickened area in the lower back where nerves supplying the lower limbs emerge.

Central canal

Internal microscopic channel containing cerebrospinal fluid that extends the entire length of the spinal cord.

Gray commissure

Crossbar of gray matter surrounding the central canal that connects the left and right wings.

White commissure

Transverse structure that connects the white matter of the right and left sides of the spinal cord together.

Anterior horn of gray matter

Region of spinal gray matter containing cell bodies of somatic motor neurons supplying skeletal muscles.

Posterior horn of gray matter

Region of spinal gray matter housing motor neurons directed to cardiac muscle, smooth muscle, and glands.

Spinoreticular tracts

Ascending pathways in the spinal cord that conduct impulses for pain from body tissues to the brain.

Gracile fasciculus tracts

Ascending sensory pathways conveying impulses for touch, pressure, vibration, and conscious body position awareness.

Anterior corticospinal tracts

Descending motor pathways carrying voluntary movement signals from the brain to skeletal muscles.

Lateral vestibulospinal tracts

Descending tracts conducting signals from the brain to body receptors to regulate muscle tone, posture, and coordination.

Spinal tap

Diagnostic clinical procedure in which cerebrospinal fluid is removed from the subarachnoid space.

Anterior root of a spinal nerve

Spinal cord attachment point consisting purely of outgoing motor axons.

Posterior root of a spinal nerve

Spinal cord attachment point consisting purely of incoming sensory axons.

Endoneurium

Delicate inner connective tissue layer wrapping around each individual nerve fiber.

Perineurium

Connective tissue sheath that encloses bundles of nerve fibers known as fascicles.

Epineurium

Tough, outermost fibrous connective tissue coat surrounding and protecting an entire nerve.

Somatic reflex

Involuntary motor response specifically producing contraction of skeletal muscles.

Autonomic reflex

Involuntary motor response regulating smooth muscle, cardiac muscle, or glandular activity.

Reflex arc

Neural route of a reflex composed sequentially of receptor, sensory neuron, integration center, motor neuron, and effector.

Patellar reflex

Knee extension stretch response used clinically as an indicator of mid-lumbar spinal cord integrity.

Babinski sign

Abnormal adult response of great toe extension and toe fanning upon sole stimulation, which is normal in infants under two.

Plantar flexion reflex

Normal adult response characterized by downward curling of the toes when the sole of the foot is stimulated.

Flexor reflex

Protective withdrawal response causing rapid limb withdrawal away from an injurious or painful stimulus.

Crossed extension reflex

Contralateral motor response where extensors contract in one limb as flexors contract in the opposite limb to maintain balance.

Tendon reflex

Protective inhibitory mechanism causing muscle relaxation when excessive tension is placed on a tendon.

Paraplegia

Loss of motor function confined to the lower limbs, typically resulting from lumbar spinal cord trauma.

Quadriplegia

Paralysis involving all four limbs, characteristically caused by trauma to the cervical region of the spinal cord.

Hemiplegia

Paralysis confined to one lateral half of the body, usually resulting from brain damage rather than cord injury.

Amyotrophic lateral sclerosis (ALS)

Progressive neurodegenerative disorder marked by destruction of anterior horn motor neurons, impairing speech, swallowing, and respiration.

Guillain-Barré syndrome

Acute demyelinating peripheral nerve condition that can lead to death, frequently triggered by a viral infection.

Paresthesia

Subjective abnormal sensations such as burning, prickling, or tingling felt in the absence of actual stimulation.