Week 6 – Spinal Region & Motor System Vocabulary

A set of vocabulary flashcards covering anatomical structures, physiological mechanisms, and clinical terminology related to the spinal region and motor systems discussed in Week 6 lecture notes.

Spinal Region

All neural structures located within the vertebrae: spinal cord, dorsal and ventral roots, spinal nerves, and meninges.

Spinal Cord

Central nervous system structure extending from the medulla to roughly the L1–L2 vertebral level.

Dorsal Root

Bundle of sensory axons that conveys information into the posterior spinal cord.

Ventral Root

Bundle of motor axons that exit the anterior spinal cord to supply muscles.

Spinal Nerve

Mixed nerve formed by the union of a dorsal and a ventral root; carries motor, sensory, and autonomic axons.

Cauda Equina

Long lumbar and sacral nerve roots descending below L1 inside the vertebral canal before exiting.

White Matter (Spinal Cord)

Myelinated axons that interconnect cord levels and link the spinal cord with the brain.

Gray Matter (Spinal Cord)

Neuronal cell bodies, dendrites, and interneurons arranged in dorsal, lateral, and ventral horns.

Anterior (Ventral) Horn

Gray-matter area containing motor neuron cell bodies whose axons leave via the ventral root.

Posterior (Dorsal) Horn

Gray-matter area receiving sensory axons that enter via the dorsal root.

Meninges

Three connective-tissue layers (dura, arachnoid, pia) that surround and protect the CNS.

Pia Mater

Innermost meningeal layer that adheres directly to the spinal cord surface.

Arachnoid Mater

Middle meningeal layer; separated from pia by the cerebrospinal-fluid–filled subarachnoid space.

Dura Mater

Tough, outer meningeal layer located just deep to the epidural space.

Epidural Space

Fat-filled space between the dura mater and the vertebrae.

Sarcomere

Basic contractile unit of striated muscle located between two Z-lines.

Muscle Contraction (Sliding-Filament)

Myosin heads bind to actin and pull it toward the sarcomere center, shortening the fiber.

Passive Range of Motion (PROM)

Clinical maneuver used to assess muscle tone by moving a limb without patient effort.

Hypotonicity

Abnormally low resistance to passive stretch during PROM.

Hypertonicity

Abnormally high resistance to passive stretch during PROM.

Motor Unit

One alpha motor neuron and all the muscle fibers it innervates.

Reciprocal Inhibition

Spinal cord mechanism that inhibits antagonist muscles during agonist contraction.

Cocontraction

Simultaneous contraction of agonist and antagonist muscles for joint stability and precision.

Lower Motor Neuron (LMN)

Final common pathway neurons that directly innervate extrafusal or intrafusal muscle fibers.

Alpha Motor Neuron

LMN whose axons synapse on extrafusal (force-producing) muscle fibers.

Gamma Motor Neuron

LMN whose axons innervate intrafusal fibers inside the muscle spindle.

Extrafusal Muscle Fiber

Typical skeletal muscle fiber that attaches to tendons and generates force.

Intrafusal Muscle Fiber

Specialized fiber inside a muscle spindle that senses stretch.

Myotome

Group of muscles innervated by a single spinal nerve; UE myotomes arise from C5–C8.

Golgi Tendon Organ (GTO)

Proprioceptive receptor in tendons that senses muscle tension and modulates contraction.

Deep Tendon Reflex

Quick involuntary muscle contraction triggered by tendon stretch and mediated within the spinal cord.

Muscle Cramp

Sudden, painful, sustained involuntary contraction of muscle.

Fasciculation

Visible or palpable brief twitch of a small group of muscle fibers supplied by one motor unit.

Myoclonus

Sudden, brief, shock-like involuntary jerk of a muscle or muscle group.

Fibrillation

Spontaneous contraction of single muscle fibers disconnected from their motor neuron; not visible to the eye.

Resting Tremor

Rhythmic shaking that occurs when the body part is relaxed and supported.

Intention Tremor

Tremor that increases during purposeful movement and intensifies near the target.

Electromyography (EMG)

Diagnostic test that records electrical activity of muscles to assess muscle and nerve health.

Orthopedic Level (Vertebral Level)

Classification of spinal injury based on the damaged vertebra as used by orthopedists.

Neurologic Level (Segmental Level)

Classification of spinal injury based on the lowest intact spinal cord segment as used by neurologists.