VCLC Module I: Foundations, Neuroanatomy, and the Sacropelvis

Comprehensive vocabulary flashcards covering foundational concepts, spinal biomechanics, joint classifications, pelvic neuroanatomy, equine pathology, neurophysiology, and animal chiropractic technique from VCLC Module I.

Chiropractic

A primary contact health care profession focusing on the relationship between structure—primarily the spine—and function, primarily through the nervous system, as it relates to health, posture, and performance.

Innate Intelligence

An early chiropractic vitalistic concept representing the body's inborn capacity for self-healing, homeostasis, and adaptation, emphasizing that the nervous system governs other bodily systems.

Vertebral Motion Segment (Motion Unit)

The functional unit of the spine, comprising an intervertebral disc (IVD), two posterior/dorsal facet joints, neurological elements within the intervertebral foramina (IVFs), and all supporting ligaments and muscles.

Range of Motion (ROM)

The full movement potential of a joint, measured from starting position to maximum movement in a particular direction across three cardinal planes: flexion/extension, axial rotation, and lateral flexion.

Motion Palpation (MP)

A diagnostic manual technique used to assess the quality, quantity, and characteristics of active and passive segmental joint movement to identify restrictions, fixations, or movement abnormalities.

Joint Play

A discrete, short range of movement within a joint independent of voluntary muscle action, assessed by springing or challenging a vertebra in its neutral resting position based on inherent ligamentous laxity.

End Feel (End Play)

The springiness palpated in the terminal position of passive joint movement; loss of this springiness results in a hard end-feel caused by subatmospheric or negative intra-articular pressure.

Fixation

The temporary immobilization of an articulation in a position it normally occupies during physiological movement when at rest, or in a position of rest when the joint is in motion.

Subluxation (Chiropractic)

A motion segment where alignment, movement integrity, or physiological function are altered while the joint surfaces remain in contact, potentially producing neurological disturbance and musculoskeletal dysfunction.

Segmental Dysfunction

Altered or abnormal function of one or more motion segments emphasizing functional biomechanical impairment, restricted movement, muscle spasm, and local inflammation rather than pure structural displacement.

Facilitation

A sustained state of heightened excitability within spinal cord segments or neural circuits, causing neurons to reach threshold more readily in response to minimal sensory or motor inputs.

Coupled Motion

A consistent association of motion about one axis with motion about a second axis where neither can occur independently, such as axial rotation naturally occurring alongside lateral flexion in the spine.

X-Axis (Quadrupeds)

The medio-lateral horizontal axis running from side to side in quadrupeds, along which flexion and extension of the spine and limbs occur in the sagittal plane.

Y-Axis (Quadrupeds)

The dorso-ventral axis running perpendicular to the spine from back to belly in quadrupeds, corresponding to lateral flexion (side-bending) movements occurring in the coronal plane.

Z-Axis (Quadrupeds)

The longitudinal axis aligned along the length of the quadruped body from head to tail, around which axial twisting or rotation occurs in the transverse plane.

Horizontal Beam Model

The operative biomechanical model for the quadruped spine, wherein the vertebral column experiences dorsal tension and ventral compression as dominant static loads resisted passively by the dorsal longitudinal ligament and body cavities.

Mobilization

A form of slow, non-thrust passive manual therapy applied repetitively in graded oscillations within the physiological range of motion without entering the paraphysiological space.

Adjustment (HVLA Manipulation)

A specific, directional, high-velocity, low-amplitude manual thrust delivered into the paraphysiological space at the end of passive ROM, respecting joint plane anatomy without exceeding anatomical limits.

Tribonucleation

The rapid formation and collapse of vapor-filled cavities or bubbles within synovial fluid caused by tensile forces separating joint surfaces during an adjustment, producing the characteristic cavitation sound.

Clinician Contact Point (CP)

The specific anatomical part of the practitioner's hand (such as pisiform, hypothenar, thenar, or digital pad) placed directly against the patient's segmental contact point to deliver a thrust.

Bone Out Of Place (BOOP)

The early, static chiropractic subluxation model popularized by D.D. Palmer and B.J. Palmer, which posited that a displaced vertebra occluded a neural opening and directly impinged upon spinal nerves.

Buckling Injury Theory

Spinal biomechanics theory established by Panjabi and White (1978) demonstrating that the spine is an unstable column under compressive load that can fail suddenly (buckle) once physiological thresholds are surpassed.

Sandoz Model of Joint Manipulation

A classic 1976 schematic describing joint movement along a linear continuum: active ROM, passive ROM up to the elastic barrier, the paraphysiological space entered during manipulation, and the anatomical barrier.

Vertebral Subluxation Complex (Faye 5-Component Model)

A dynamic model conceptualized by Dr. L. Faye in 1982 consisting of spinal kinesiopathology, neuropathophysiology, myopathophysiology, histopathology, and biochemical (inflammatory) changes.

Lantz 9-Component VSC Model

An expanded model by Dr. Lantz (1995) organizing subluxation into kinesiopathology, neuropathology, myopathology, connective tissue physiology, vascular pathology, inflammatory response, pathoanatomy, pathophysiology, and pathobiochemistry.

Dysponesis

A reversible physiopathologic state consisting of errors in energy expenditure and action potential output from motor and premotor cortices, resulting in aberrant, wasted muscle activity.

Dysautonomia

Functional imbalance or pathology of the autonomic nervous system associated with spinal subluxation complexes and abnormal sympathetic outflow.

Evans and Breen Joint Model (2006)

An updated biomechanical model redefining the paraphysiological space as physical joint surface separation (gapping) rather than an anatomical 'danger zone', showing that gapping occurs most efficiently in the neutral zone.

Neuroplastic Model of Manipulation (Haavik)

A framework developed by Dr. Heidi Haavik (2014) proposing that abnormal spinal segmental movement degrades sensory afferent input to the CNS, altering cortical sensorimotor integration and motor output.

Cellular Immediate Early Gene Response (CIEGR)

A biochemical mechanism whereby receptor stimulation triggers intracellular second messengers and immediate early genes (transcription factors) to synthesize proteins that perpetuate healthy cellular function and neuroplasticity.

Tonal Model

A clinical chiropractic approach viewing the spine and nervous system as a continuous functional unit and defining subluxation as an aberrancy in normal tone, elasticity, or nerve tension.

Dorsal Plane

An anatomical plane oriented parallel to the back of a quadruped, corresponding conceptually to the coronal or frontal plane in human anatomy.

Rostral

A directional term strictly applied to the head of an animal indicating a location directed toward the tip of the nose or muzzle.

Digitigrade Stance

A posture seen in dogs and cats where the animal bears weight upright exclusively on the digits or phalanges of each manus and pes.

Synarthrosis

An immovable or virtually immovable skeletal articulation lacking a joint cavity, encompassing fibrous syndesmoses, cartilaginous synchondroses, and bony synostoses.

Syndesmosis

An immovable or barely movable fibrous joint in which opposing bones are united by dense fibrous tissue or strong interosseous ligaments, such as the equine metacarpus.

Synchondrosis

A rigid cartilaginous joint joined by hyaline cartilage without a joint cavity, typically temporary during skeletal growth (e.g., epiphyseal growth plates).

Diarthrosis (Synovial Joint)

A freely movable joint characterized by opposing articular bone surfaces lined by hyaline cartilage, encased in a joint capsule lined with synovial membrane, and lubricated with synovial fluid.

Plane Joint

A synovial joint type characterized by flat or slightly curved opposing surfaces that permit translation and sliding motion, such as spinal articular facets and costovertebral joints.

Trochoid Joint (Pivot Joint)

A uniaxial synovial joint in which a bony peg or pivot rotates within an osteoligamentous ring, exemplified by the atlantoaxial joint ($\text{C1-C2}$) and proximal radioulnar joint.

Condylar Joint

A synovial joint in which two knuckle-shaped condyles on one bone articulate with corresponding reciprocal concavities on another, exemplified by the equine and canine femorotibial (stifle) joint.

Spheroidal Joint

A multiaxial ball-and-socket synovial joint providing the greatest movement versatility in multiple planes, exemplified by the coxofemoral (hip) joint.

Type I Joint Mechanoreceptors

Slow-adapting, low-threshold mechanoreceptors (Ruffini-like) located in the superficial joint capsule that monitor posture, tonic muscular stability, and joint oscillations at end ROM.

Type II Joint Mechanoreceptors

Fast-adapting, low-threshold mechanoreceptors (Pacinian-like) located in the deep joint capsule that are inactive at rest but fire dynamically at the onset of movement to monitor phasic motion.

Type III Joint Mechanoreceptors

Slow-adapting, high-threshold protective mechanoreceptors located in joint ligaments that function similarly to Golgi tendon organs by producing reflex inhibition of adjacent musculature.

Type IV Joint Receptors

High-threshold nociceptive free nerve endings distributed throughout most joint tissues that respond to excessive mechanical deformation, tissue injury, and inflammatory mediators.

Tuber Coxae

The cranioventral iliac spine and prominent palpable cranial landmark on the wing of the ilium, colloquially known in equines as the 'point of the hip'.

Tuber Sacrale

The craniodorsal iliac spine of the iliac wing that forms the chiropractic reference landmark for pelvic ilium listings in animals.

Iliopsoas Muscle

The strongest muscle of the pelvic girdle, formed by the fusion of the psoas major and iliacus muscles, which inserts on the lesser trochanter of the femur to flex the coxofemoral joint.

Tensor Fasciae Latae (TFL)

A lateral pelvic muscle originating from the tuber coxae and inserting into the lateral femoral fascia, functioning as a primary knee/stifle stabilizer, hip flexor, and stifle extensor.

Hamstrings

The caudal thigh muscle group consisting of the biceps femoris, semitendinosus, and semimembranosus muscles that extend the hip joint, flex the stifle, and extend the hock.

Sacroiliac Nutation

A reciprocal motion of the pelvis occurring during weight bearing where the sacral base tilts anteriorly/ventrally relative to the ilium while the apex tilts caudodorsally.

Knock-Down Hip

A fracture of the equine tuber coxae typically caused by blunt impact when a horse rushes through a narrow opening or stall doorway, manifesting as marked unilateral asymmetry.

Trochanteric Bursitis (Whorlbone Lameness)

Inflammation of the synovial bursa interposed between the tendon of the middle gluteal muscle and the greater trochanter of the femur, common in racing horses due to repetitive track turning.

Fibrotic and Ossifying Myopathy

The development of scar tissue or bone formation within the equine hamstring or gracilis muscles following trauma (e.g., sliding stops), creating an abrupt slapping-down gait in the walk.

Caudal Aortic Embolism (CAE)

Vascular obstruction occurring at the aortic bifurcation or proximal external iliac arteries in equines, primarily caused by Strongylus vulgaris larva migrations, leading to exercise-induced hindlimb lameness.

Astrocytes

The most abundant glial cells of the central nervous system, responsible for maintaining the blood-brain barrier, regulating extracellular ions and neurotransmitters, and forming scar tissue after injury.

Oligodendrocytes

CNS neuroglial cells that produce the lipid-rich myelin sheath insulating multiple axonal internodes within the brain and spinal cord.

Schwann Cells

Peripheral nervous system neuroglial cells that wrap individually around a single segment of an axon to form myelin and participate in nerve regeneration following trauma.

Retrograde Axonal Transport

The cellular mechanism transporting worn organelles, growth factors, and retrograde signals—as well as neurotropic pathogens like rabies—from the axon terminals back to the neuronal soma.

Sodium-Potassium Pump ($\text{Na}^+/\text{K}^+\text{-ATPase}$)

An electrogenic active transport membrane protein that consumes one molecule of ATP to export $3\,\text{Na}^+$ ions while importing $2\,\text{K}^+$ ions, maintaining the resting membrane potential.

Resting Membrane Potential (RMP)

The electrical charge difference across the neuronal cell membrane at rest, typically measuring approximately $-70\,\text{mV}$, established by selective ion permeability and active pumps.

Action Potential (AP)

An all-or-none, rapid, self-propagating electrical reversal of membrane potential along an axon, initiated at the axon hillock when local depolarization reaches threshold (approximately $-55\,\text{mV}$).

Saltatory Conduction

The rapid and energy-efficient mode of action potential propagation along myelinated nerve fibers where depolarization jumps from one node of Ranvier to the next.

Spatial Summation

The integration of postsynaptic potentials generated simultaneously across multiple distinct synapses converging on the dendrites and soma of a postsynaptic neuron.

Temporal Summation

The cumulative additive effect produced when a single presynaptic terminal discharges action potentials in rapid, repetitive succession onto a postsynaptic membrane.

Substance P

A neuropeptide neuromodulator released by primary unmyelinated nociceptive fibers that enhances slow pain transmission, promotes neurogenic inflammation, and mediates central sensitization.

Neurulation

The embryonic process wherein the neural plate folds inward to create the neural groove and fuses into the neural tube (giving rise to the CNS) while neural crest cells detach to form the PNS.

Central Sensitization

A neurophysiological state within dorsal horn spinal neurons characterized by increased excitability, lowered activation thresholds, and amplified receptive fields following sustained nociceptive bombardment.

Somatic Efferent (SE) Fibers

Motor axons originating from cell bodies in the ventral horn of the spinal cord that directly innervate voluntary skeletal muscles.

Visceral Efferent (VE) Fibers

Autonomic motor fibers composed of a two-neuron relay (preganglionic and postganglionic) that innervate smooth muscle, cardiac muscle, and visceral glands.

General Somatic Afferent (GSA) Fibers

Sensory nerve fibers conveying exteroceptive and proprioceptive sensory input from the skin, skeletal muscles, tendons, and joint capsules to the central nervous system.

Meningeal Branch (Sinuvertebral Nerve)

A recurrent branch of the spinal nerve that re-enters the intervertebral foramen to supply sensory innervation to the meninges, dorsal longitudinal ligament, periosteum, and outer annulus fibrosus.

Ramus Communicans

A primary communicating branch connecting a spinal nerve to the sympathetic trunk, carrying preganglionic visceral efferent fibers and visceral afferents.

Pacinian Corpuscles

Rapidly adapting, onion-like encapsulated mechanoreceptors residing in the deep dermis, subcutaneous tissue, and joint ligaments that detect high-frequency vibration and rapid tissue deformation.

Ruffini Endings

Slowly adapting mechanoreceptors situated in the dermis, joint capsules, and ligaments that respond to skin stretch, sustained mechanical pressure, and joint movement.

Muscle Spindle

An encapsulated stretch receptor arranged in parallel with extrafusal skeletal muscle fibers, containing intrafusal bag and chain fibers innervated by group Ia/II afferents and gamma motor neurons to monitor muscle length and velocity of stretch.

Golgi Tendon Organ (GTO)

A proprioceptor situated in series at the musculotendinous junction, innervated by group Ib afferent fibers that fire under excessive tensile load to trigger the autogenic inhibition reflex.

Trot

A symmetrical, rhythmic two-beat diagonal gait in equines where diagonally opposite limbs (e.g., right hind and left fore) strike the ground simultaneously, separated by a brief suspension phase.

Canter

An asymmetrical three-beat equine gait with suspension, beginning with an outside hind leg, followed by the diagonal pair, and concluding on the leading forelimb.

Cross-Firing (Disunited Canter)

An abnormal equine gait coordination flaw wherein the horse leads with one forelimb in front while cantering on the opposite lead with the hindlimbs.

Forging

A gait fault where the toe of a hindfoot strikes the solar surface or shoe of the forefoot on the ipsilateral side during movement.

Logan Basic Technique

A low-force, tonal chiropractic technique founded by Dr. Hugh B. Logan that utilizes sustained thumb contact against the sacrotuberous ligament to level the sacral base and restore pelvic structural balance.

Apex Contact (Logan Basic)

The primary adjusting contact in Logan Basic Technique, applied with the tip of the thumb against the sacrum where the sacrotuberous ligament attaches to the sacral apex, held for 1–3 minutes.