Spinal cord, spinal nerves and reflexes - Vocabulary flashcards

Vocabulary flashcards covering major terms from the lecture notes on the spinal cord, meninges, matter, roots, nerves, and reflexes.

Spinal cord

Part of the CNS that conducts signals to/from the brain and houses major reflex centers.

Dura mater

Outer fibrous membrane of the spinal meninges.

Arachnoid mater

Middle membrane of the spinal meninges.

Pia mater

Inner membrane bound to the spinal cord; provides support to blood vessels.

Spinal meninges

The three protective membranes surrounding the spinal cord: dura mater, arachnoid mater, and pia mater.

Epidural space

Space between the dura mater and vertebrae containing connective tissue, blood vessels and adipose tissue; site for epidural anesthesia.

Subarachnoid space

Space between the arachnoid and pia maters containing cerebrospinal fluid (CSF); site for spinal anesthesia.

Cerebrospinal fluid (CSF)

Fluid that acts as a shock absorber and diffusion medium for gases and nutrients in the CNS.

Grey matter

CNS tissue organized into horns (dorsal, ventral, lateral) containing interneuron and motor neuron cell bodies.

Dorsal (posterior) horn

Cell bodies of interneurons receiving sensory information.

Ventral (anterior) horn

Cell bodies of somatic motor neurons.

Lateral horn

Cell bodies of autonomic motor neurons (present at T1-L2 and S2-S4).

White matter

Tracts in the CNS; bundles of axons responsible for ascending (sensory) and descending (motor) information.

Ascending tracts

Nerve pathways that carry sensory information toward the brain.

Descending tracts

Nerve pathways that carry motor commands from the brain to the spinal cord.

Dorsal root

Sensory (afferent) axons entering the spinal cord.

Dorsal root ganglion

Cluster of sensory neuron cell bodies in the dorsal root.

Ventral root

Motor (efferent) axons leaving the spinal cord.

Spinal nerve

Fusion of dorsal and ventral roots; a mixed nerve (sensory & motor); typically 1–2 cm long with 31 pairs.

Intervertebral foramen

Openings between vertebrae where spinal nerve roots exit the spinal canal.

Peripheral nerves

Nerves formed by branching spinal nerves (rami) that may converge into a nerve plexus; example: ulnar nerve.

Cauda equina

Bundle of spinal nerve roots extending below the end of the spinal cord ('horse tail').

Spinal reflex

Rapid, automatic responses that can be processed in the spinal cord; may be monosynaptic or polysynaptic.

Reflex arc

The neural pathway of a reflex: receptor, sensory neuron, integration center, motor neuron, effector.

Monosynaptic

A reflex with a single synapse between afferent and efferent neurons.

Polysynaptic

A reflex involving one or more interneurons and multiple synapses.

Interneuron

Neuron within the CNS that forms part of a reflex pathway (involves in polysynaptic reflexes).

Stretch reflex

Monosynaptic reflex that adjusts posture in response to muscle stretch (e.g., patellar reflex).

Muscle spindle

Sensory receptor for stretch; proprioceptors with intrafusal fibers wrapped by sensory neurons; lie among extrafusal fibers.

Proprioceptor

Sensory receptor that monitors position and movement of skeletal muscles and joints.

Reciprocal inhibition

Simultaneous stimulation of one muscle and inhibition of its antagonistic muscle during a reflex.

Withdrawal reflex

Protective reflex that moves a limb away from a painful stimulus; involves excitation of flexors and inhibition of extensors.

Crossed extensor reflex

Contralateral reflex where withdrawal of one limb is accompanied by extension of the opposite limb to maintain balance.

Monosynaptic vs polysynaptic comparisons

Monosynaptic: one synapse; Polysynaptic: involves interneurons and multiple synapses.

Dorsal root ganglia

Sensory neuron cell bodies located in the dorsal root ganglia.

Nerve plexus

Networks formed when ventral rami branch and rejoin to form peripheral nerves.