Spinal Cord Glossary

These terms relate to the anatomyThe study of the structure of the human body. and function of the spinal cordThe central nervous system structure that relays signals between the brain and body., including its tractsBundles of nerve fibers in the CNS that carry signals between brain regions., nerves, and meninges(singular: meninx) – Protective membranes surrounding the spinal cord and brain..

• Anterior funiculus – The front portion of the white matterThe outer portion of the spinal cord made of myelinated nerve fibers that transmit signals. in the spinal cord, containing ascending and descending tractsPathways that carry motor signals from the brain to the spinal cord..
• Anterior horn – The front section A cut or slice of the body or an organ for study. of the spinal cord’s gray matterThe inner portion of the spinal cord composed mostly of neuron cell bodies and synapses., housing motor neuronsNeurons that carry outgoing information from the CNS to effector organs..
• Anterior median fissureA deep groove in the brain’s surface. – A deepAway from the surface of the body. groove along the front of the spinal cord that divides it into two halves.
• Anterior root – The portion of a spinal nerve that carries motor signals out of the spinal cord.
• Arachnoid mater – The middle layer of the meninges, located between the dura and pia materThe thin, innermost layer of the meninges that closely adheres to the spinal cord..
• Ascending tracts – Bundles of axons that carry sensory information from the spinal cord to the brain.
• Cauda equina – A bundle of nerve roots extending from the lower spinal cord, resembling a horse’s tail.
• Central canal – A small canal in the spinal cord that contains cerebrospinal fluid(CSF) – A fluid that cushions and nourishes the brain and spinal cord. (CSF).
• Cerebrospinal fluid (CSF) – A fluid that cushions and nourishes the brain and spinal cord.
• Cervical enlargement – A widened area of the spinal cord where nerves for the upper limbs arise.
• Dura mater – The thick, outermost layer of the meninges that protects the spinal cord.
• Epidural space – The space between the dura materThe thick, outermost layer of the meninges that protects the spinal cord. and vertebrae, filled with fat and blood vessels.
• Gray commissure – The bridge of gray matter connecting the left and right sides of the spinal cord.
• Gray matter – The inner portion of the spinal cord composed mostly of neuron cell bodies and synapses.
• Lateral horn – A part of the spinal cord’s gray matter, containing autonomic motor neuronsThe functional cells of the nervous system that transmit signals..
• Lumbosacral enlargement – A widened section of the spinal cord where nerves for the lower limbs arise.
• Medullary cone – The tapered, lower end of the spinal cord.
• Meninges (singular: meninx) – Protective membranes surrounding the spinal cord and brain.
• Pia mater – The thin, innermost layer of the meninges that closely adheres to the spinal cord.
• Posterior horn – The back section of the spinal cord’s gray matter, where sensory neuronsNeurons that carry information from sensory receptors to the CNS. synapseThe junction between two neurons where communication occurs..
• Posterior median sulcus – A shallow groove along the back of the spinal cord.
• Spinal cord – The central nervous systemComposed of the brain and spinal cord; integrates and processes information.  structure that relays signals between the brain and body.
• Spinal tap – A procedure to collect cerebrospinal fluid from the subarachnoid space.
• White matter – The outer portion of the spinal cord made of myelinated nerve fibers that transmit signals.

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2. Nerves & Plexuses

These terms relate to the nerve structures extending from the spinal cord, including their organizationThe structured arrangement of biological systems. and function.

• Anterior ramus – The larger branch of a spinal nerve that supplies the limbs and anteriorThe front of the body or toward the front when standing in the anatomical position. body.
• Brachial plexus – A network of nerves in the neckNarrow region just below the head; common fracture site. and shoulder that control the upper limbs.
• Cervical plexus – A network of nerves that supplies the neck, shoulders, and diaphragm.
• Cervical region – The upper part of the spinal cord, corresponding to the neck vertebrae.
• Coccygeal plexus – A small network of nerves near the coccyxTailbone; small, fused vertebrae at the end of the sacrum..
• Corticospinal tract – A descending motor pathway controlling voluntary movements.
• Cranial nerves – Nerves that arise from the brain and control headRounded proximal end that fits into the acetabulum of the hip bone. and neck functions.
• Dermatome – A specific area of skinThe body’s largest organ, providing protection and regulation. supplied by a single spinal nerve.
• Dermatome map – A diagram showing which spinal nerves correspond to specific skin regions.
• Descending tracts – Pathways that carry motor signals from the brain to the spinal cord.
• Efferent fibers – Nerve fibers that carry motor signals away from the central nervous systemThe organ system that controls body functions using electrical and chemical signals..
• Endoneurium – The connective tissue layer surrounding an individual nerve fiber.
• Epineurium – The outermost connective tissue covering of a nerve.
• Fascicles – Bundles of nerve fibers within a nerve.
• Femoral nerve – A major nerve of the lumbar plexusA network of nerves supplying the lower back and upper legs. that controlsVariables that remain constant to ensure a fair test. muscles of the thigh.
• First order neuron – The sensory neuron that first detects a stimulus.
• Ganglion – A cluster of neuron cell bodies in the peripheral nervous systemPNS All nervous tissue outside the CNS; includes nerves and ganglia..
• General fibers – Nerve fibers that carry sensory or motor information to and from the body.
• Ipsilateral – Referring to the same side of the body.
• Lateral femoral cutaneous nerve – A nerve that supplies sensation to the outer thigh.
• Lumbar plexus – A network of nerves supplying the lower back and upper legs.
• Lumbar region – The lower part of the spinal cord, corresponding to the lower back vertebrae.
• Mixed nerves – Nerves that contain both sensory and motor fibers.
• Motor nerves – Nerves that carry signals from the CNS to muscles.
• Obturator nerve – A nerve that supplies the medialToward the midline of the body thigh muscles.
• Peripheral nerves – Nerves that extend beyond the brain and spinal cord.
• Phrenic nerve – A nerve from the cervical plexusA network of nerves that supplies the neck, shoulders, and diaphragm. that controls the diaphragm.
• Posterior cutaneous nerve – A nerve that provides sensation to the skin of the back.
• Posterior ramus – The smaller branch of a spinal nerve that supplies the back muscles and skin.
• Posterior root – The portion of a spinal nerve carrying sensory signals into the spinal cord.
• Posterior root ganglionA cluster of neuron cell bodies located in the peripheral nervous system (PNS). – A cluster of sensory neuron cell bodies in the posterior rootThe portion of a spinal nerve carrying sensory signals into the spinal cord..
• Radial nerve – A nerve from the brachial plexusA network of nerves in the neck and shoulder that control the upper limbs. that controls the posterior arm and forearm.
• Sacral plexus – A network of nerves in the lower back that controls the pelvis and lower limbs.
• Sacral region – The part of the spinal cord corresponding to the sacrumTriangular bone formed by fusion of five vertebrae; connects spine to pelvis..
• Sciatic nerve – The largest nerve in the body, arising from the sacral plexusA network of nerves in the lower back that controls the pelvis and lower limbs..
• Second order neuron – A neuron that transmits sensory information from the spinal cord to the brain.
• Sensory nerves – Nerves that carry signals from sensory receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter to the CNS.
• Spinal nerves – Nerves that emerge from the spinal cord and connect it to the body.
• Sympathetic chain ganglia – A series of ganglia along the spinal column involved in autonomic responses.
• Thoracic region – The part of the spinal cord corresponding to the chest.
• Ulnar nerve – A nerve from the brachial plexus that controls hand and forearm muscles.
• Upper motor neuron – A neuron that originates in the brain and synapses on a lower motor neuronA neuron that directly stimulates a muscle..
• Visceral fibers – Nerve fibers that carry signals to and from internal organs.

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3. Reflexes & Neural Pathways

These terms relate to the spinal cord’s role in reflexesAutomatic responses to stimuli., locomotionThe ability to move using coordinated muscle contractions., and sensory-motor processing.

• Afferent fibers – Nerve fibers that carry sensory information to the central nervous system.
• Conduction – The transmission of nerve impulses along neurons.
• Contralateral – Referring to the opposite side of the body.
• Contralateral reflex – A reflex where the response occurs on the opposite side of the stimulus.
• Crossed extensor reflex – A reflex that balances the body by extending the opposite limb.
• Decussation – The crossing of nerve fibers from one side of the CNS to the other.
• Locomotion – The ability to move using coordinated muscle contractions.
• Lower motor neuron – A neuron that directly stimulates a muscle.
• Monosynaptic reflex – A simple reflex with a direct connection between a sensory and motor neuron.
• Neural integration – The processing of information in the nervous system.
• Patellar reflex – The knee-jerk reflex.
• Reciprocal inhibition – A reflex that prevents opposing muscles from contracting simultaneously.
• Reflexes – Automatic responses to stimuliChanges in the environment that are detected by sensory receptors..
• Stretch reflex – A reflex that prevents excessive muscle stretching.
• Tendon reflex – A reflex that protects tendons from excessive force.
• Withdraw reflex – A reflex that moves a limb away from a painful stimulus.