Introduction to the Central Nervous System and Spinal Cord

These flashcards provide essential vocabulary definitions for Central Nervous System anatomy, spinal tracts, and reflex mechanisms based on the Chapter 1-8 lecture notes.

Meninges

The three layers of protective tissue surrounding the brain and spinal cord, ordered from superficial to deep as dura, arachnoid, and pia mater.

Subarachnoid Space

The space between the arachnoid and pia mater where cerebrospinal fluid is located.

Cerebrospinal Fluid (CSF)

A fluid that cushions the brain and spinal cord and creates a chemically neutral environment for conducting electricity.

Conus Medullaris

The tapered end of the spinal cord, located approximately at the level of $L2$ to $L3$.

Cauda Equina

A bundle of nerves continuing through the vertebral foramen below the conus medullaris that resembles a horse's tail.

Phylum Terminale

A tether or string made of meninges that attaches to the bottom of the coccyx to hold the meninges in place.

Gray Matter

The internal area of the spinal cord cross-section containing neuronal cell bodies.

White Matter

The outer area of the spinal cord cross-section containing bundles of axons called tracts.

Dorsal Horn

The posterior section of gray matter where sensory or afferent nerves are found.

Dorsal Root Ganglion

A swelling on the dorsal root outside the central nervous system that contains the cell bodies of sensory neurons.

Ventral Horn

The anterior section of gray matter where motor or efferent neurons are found.

Gray Commissure

The area of gray matter that connects the left and right sides of the spinal cord.

Central Canal

A small hole in the center of the gray commissure that contains cerebrospinal fluid.

Lateral Horn

A unique structure found only in the thoracic and upper lumbar spinal cord that houses neurons for the autonomic nervous system.

Cervical Nerves

A set of $8$ pairs of spinal nerves originating from the cervical region.

Thoracic Nerves

A set of $12$ pairs of spinal nerves originating from the thoracic region.

Lumbar Nerves

A set of $5$ pairs of spinal nerves originating from the lumbar region.

Rami

The split in a spinal nerve after the mixing of sensory and motor fibers; includes anterior rami (innervating the chest/abdomen) and posterior rami (innervating the back).

Cervical Plexus

Nerves from $C1$ through $C4$ that innervate the head, neck, and diaphragm.

Brachial Plexus

Nerves from $C5$ through $T1$ that innervate the skin and muscles of the arms.

Lumbar Plexus

Nerves from $L1$ through $L4$ that innervate the abdomen and abdominal organs.

Sacral Plexus

Nerves from $L4$ through $S4$ that go into the leg and glute, including the sciatic nerve.

Dermatomes

Specific areas of skin that receive sensory innervation from a single spinal nerve.

Ascending Tracts

Nerve pathways that carry sensory information up from the body toward the brain using first, second, and third-order neurons.

Spinothalamic Tracts

Ascending pathways that carry information about pain, temperature, pressure, and light touch from the spine to the thalamus.

Spinocerebellar Tracts

Ascending pathways that carry information about proprioception from the spine to the cerebellum.

Proprioception

Information regarding the movements and position of joints and muscles in space.

Fasciculus Bracilis

A part of the DCML pathway that carries touch and vibration information from the lower extremity to the brain.

Fasciculus Cuneatus

A part of the DCML pathway that carries touch and vibration information from the upper extremity to the brain.

DCML Pathways

Standing for dorsal column medial lemniscal pathways, these include the fasciculus bracilis and fasciculus cuneatus.

Descending Tracts

Nerve pathways that carry motor information down from the brain to the body using upper and lower motor neurons.

Upper Motor Neuron

A neuron that travels from the brain down into the spinal cord or brainstem.

Lower Motor Neuron

A neuron that travels from the spinal cord to a muscle.

Spastic Paralysis

A symptom of upper motor neuron damage where a person is paralyzed but the muscles are tense and spasming.

Babinski Sign

A pathological reflex where scraping the bottom of the foot causes the toes to extend and spread; indicates upper motor neuron damage in adults.

Flaccid Paralysis

A symptom of lower motor neuron damage where muscles are limp and cannot move.

Fasciculations

Involuntary muscle twitching, often associated with lower motor neuron lesions.

Corticospinal Tract

A descending tract from the brain's cortex to the spine responsible for voluntary movement.

Reticulospinal Tract

A descending tract from the brainstem to the spine that carries information about posture.

Tectospinal Tract

A descending tract from the brainstem to the spine responsible for head and neck movements in response to sight or sound.

Vestibulospinal Tract

A descending tract from the cerebellum to the spine responsible for balance and coordination.

Rubrospinal Tract

A descending tract from the brainstem to the spine that controls muscle tone in flexor muscle groups.

Extrapyramidal System

A system of tracts that go to and from the brainstem, allowing certain functions like posture and muscle tone to bypass the brain.

Monosynaptic Reflex

A simple reflex involving only one synapse where a sensory neuron attaches directly to a motor neuron with no interneuron.

Polysynaptic Reflex

A reflex involving multiple synapses and at least one interneuron connecting sensory and motor neurons.

Stretch Reflex

An automatic contraction of a muscle in response to it being stretched too far to prevent tearing.

Golgi Tendon Reflex

A reflex that monitors muscle tension and causes the muscle to relax if the tension is too high.

Flexor / Withdrawal Reflex

A reflex triggered by pain that causes the contraction of flexor muscles to move a limb away from a stimulus.

Crossed Extensor Reflex

A reflex that occurs with the withdrawal reflex, tensing the contralateral limb to maintain balance.