Peripheral Nervous System (PNS): Spinal Cord and Spinal Nerves

These flashcards cover key vocabulary and concepts related to the structure and function of the peripheral nervous system, specifically focusing on the spinal cord, spinal nerves, reflexes, and related anatomical features.

Epidural space

The space between the outermost layer of the meninges and the surrounding vertebrae; commonly used for administering epidural anesthesia.

Dura mater

The outermost and toughest layer of the meninges surrounding the brain and spinal cord.

Arachnoid mater

The middle layer of the meninges, which is web-like and contains cerebrospinal fluid.

Pia mater

The innermost layer of the meninges, closely adhering to the surface of the brain and spinal cord.

Conus medullaris

The tapered end of the spinal cord, typically located at the upper border of the L2 vertebra.

Cauda equina

A bundle of spinal nerves and roots, located at the lower end of the spinal cord.

Dermatome

An area of skin that is mainly supplied by a single spinal nerve root, clinically significant for diagnosing nerve damage.

Spinal nerve plexus

A network of interwoven spinal nerves that innervate specific regions of the body; includes cervical, brachial, lumbar, and sacral plexuses.

Reflex arc

The neural pathway that mediates a reflex action, consisting of a sensory neuron, an interneuron (in some cases), and a motor neuron.

Monosynaptic reflex

A reflex that involves a single synapse between a sensory neuron and a motor neuron.

Polysynaptic reflex

A reflex that involves one or more interneurons in addition to a sensory neuron and a motor neuron.

Decussation

The crossing over of nerve fibers from one side of the central nervous system to the other, often seen in motor pathways.

Ascending pathways

Sensory pathways that carry information from the periphery to the brain.

Descending pathways

Motor pathways that transmit impulses from the brain to effectors like muscles.

Anterior (ventral) root

The pathway for motor impulses as they exit the spinal cord toward muscles.

Posterior (dorsal) root

The pathway for sensory impulses as they enter the spinal cord.

Anterior gray horn

Region of gray matter in the spinal cord containing somatic motor neurons.

Posterior gray horn

Region of gray matter in the spinal cord containing sensory neurons and interneurons.

Lateral gray horn

Region only present in T1 to L2 segments of the spinal cord; contains sympathetic motor neurons.

Intrafusal muscle fibers

Muscle fibers found within muscle spindles that detect stretch.

Stretch reflex

A reflex that occurs when a muscle is stretched, causing it to contract reflexively.