Spinal Cord and Nerves Practice Flashcards

A comprehensive set of vocabulary flashcards covering the anatomy, functions, pathways, and reflexes of the spinal cord and nerves based on the lecture transcript.

Conduction

The function of the spinal cord involving bundles of fibers passing information up and down the cord.

Central pattern generators

Pools of neurons providing control of flexors and extensors during locomotion, such as walking.

Conus medullaris

The tapered inferior end of the spinal cord.

Cauda equina

The origins of spinal nerves extending inferiorly from the lumbosacral enlargement and conus medullaris, spanning $L2$ to $S5$ nerve roots.

Dura mater

The outermost fibrous layer of the meninges; the space between this sheath and bone is the epidural space.

Arachnoid mater

A layer of simple squamous epithelium lining the dura mater with a loose mesh of fibers filled with CSF, creating the subarachnoid space.

Pia mater

The delicate membrane adherent to the spinal cord that continues beyond the conus medullaris as the filum terminale.

Denticulate ligaments

Ligaments that anchor the spinal cord to the dura and limit side-to-side movements for stability.

Dorsal horns

The posterior sections of the spinal cord gray matter that contain totally sensory fibers.

Ventral horns

The anterior sections of the spinal cord gray matter that contain totally motor fibers.

Gray commissure

The part of the spinal cord that connects the right and left sides of the central gray matter core.

Dorsal root ganglion

Collections of cell bodies of unipolar sensory neurons forming the dorsal roots.

Neural pool

A group consisting of thousands of interneurons connected with a specific shared body function.

Discharge zone

An area where a single cell can induce an action potential in a postsynaptic cell via spatial summation.

Facilitated zone

An area where a single cell makes it easier for a postsynaptic cell to fire but cannot determine the outcome alone.

Reverberating circuits

Neural circuits where neurons stimulate each other in linear sequence, but one cell restimulates the first cell to restart the process.

Parallel after-discharge circuits

Circuits where an input neuron stimulates several pathways that all stimulate the output neuron, causing it to continue firing after the input stops.

Memory trace (engram)

The physical basis of memory consisting of a pathway of modified, formed, or deleted synapses.

Synaptic plasticity

The process of modifying, forming, or deleting synapses to make neural transmission easier.

Tetanic stimulation

Rapid, repetitive signals that cause $Ca^{2+}$ accumulation in the synaptic knob, making cells more likely to fire.

Posttetanic potentiation

A form of short-term memory lasting a few hours where $Ca^{2+}$ levels stay elevated, requiring little stimulation to recover the memory.

Declarative memory

A type of long-term memory involving the retention of facts as text.

Procedural memory

A type of long-term memory involving the retention of motor skills and emotions.

Decussation

The process where nerve fibers cross from one side of the body to the other.

Contralateral

A term meaning the origin of a tract and its destination are on opposite sides of the body.

Ipsilateral

A term meaning the origin and destination of a tract are on the same side of the body.

Gracile fasciculus

A tract carrying signals for vibration, visceral pain, proprioception, and deep touch from the mid-thoracic and lower body.

Cuneate fasciculus

A tract that joins the gracile fasciculus at the $T6$ level, carrying sensory information from the upper body to the cortex.

Spinothalamic Pathway

An ascending pathway carrying signals for pain, temperature, pressure, tickle, itch, and light/crude touch to the contralateral cerebral hemisphere.

Spinoreticular Tract

A pathway carrying pain signals from tissue injury that ends in the reticular formation of the medulla and pons.

Spinocerebellar Pathway

A pathway carrying proprioceptive signals from limbs and trunk to the cerebellum.

Upper motor neurons (UMN)

Neurons that begin with a soma in the cerebral cortex or brainstem and terminate at a lower motor neuron.

Corticospinal Tract

Also known as pyramidal tracts, these carry motor signals from the cortex for precise, finely coordinated limb movements.

Tectospinal tract

A motor tract beginning in the midbrain tectum that mediates the reflex turning of the head in response to sights and sounds.

Reticulospinal tract

Tracts originating in the reticular formation that control limb muscles for posture and balance and contain descending analgesic pathways.

Vestibulospinal tract

A descending tract that receives impulses for balance from the inner ear and controls extensor muscles and head position.

Endoneurium

The connective tissue layer that separates individual nerve fibers within a nerve.

Perineurium

The layer of connective tissue that surrounds a fascicle of nerve fibers.

Epineurium

The outermost covering of a whole nerve.

Ramus

The branch of a spinal nerve after it leaves the spinal column; can be dorsal, ventral, or meningeal.

Plexus

A complex braided network of intersecting nerves formed by ventral rami from different spinal levels.

Dermatome

A specific area of skin that receives sensory input from a single spinal nerve.

Reflex arc

The basic functional unit of the nervous system consisting of a receptor, afferent nerve, integrating center, efferent nerve, and effector.

Muscle spindle

A proprioceptor that informs the brain of a muscle's length and body movements.

Intrafusal fibers

The specialized muscle fibers found within a muscle spindle.

Alpha Motor Neuron

The neuron that supplies the extrafusal (regular) muscle fibers.

Gamma Motor Neuron

The neuron that stimulates the contraction of the muscle spindle to maintain tension and sensitivity.

Reciprocal inhibition

A reflex mechanism that prevents muscles from working against each other by inhibiting antagonists.

Monosynaptic reflex arc

A reflex arc with only one synapse between the afferent and efferent neurons, such as the patellar tendon reflex.

Polysynaptic Reflex

A reflex involving multiple pathways and synapses, leading to a quick but sustained reaction, such as a flexor withdrawal reflex.

Intersegmental reflex arc

A reflex arc where the input and output occur at variable segments of the spinal cord.

Tendon organ

A proprioceptor located in a tendon that provides feedback on muscle tension.