Chapter 13 - Spinal Cord & Reflexes

Vocabulary flashcards covering spinal cord anatomy, nerve plexuses, meninges, and different types of spinal reflexes based reflexes based on Chapter 13 lecture notes.

Ascending tracts

Nerve tracts that carry sensory information from the Peripheral Nervous System (PNS) to the Central Nervous System (CNS).

Descending tracts

Nerve tracts that carry motor commands from the Central Nervous System (CNS) to the Peripheral Nervous System (PNS).

Reflexes

Involuntary, automatic responses to a stimulus used for the integration of information.

Cervical Plexus

A nerve plexus spanning $C1-5$ that includes the phrenic nerve.

Brachial Plexus

A nerve plexus spanning from $C5$ to $T1$.

Lumbar Plexus

A nerve plexus spanning from $T12$ to $L4$ that includes the femoral nerve.

Sacral Plexus

A nerve plexus spanning from $L4$ to $S4$ that includes the sciatic nerve.

Dermatomes

Specific sections of skin where each spinal nerve is responsible for sensory and motor activities.

Myotomes

Particular muscle regions innervated by specific nerves.

Epineurium

The connective tissue layer that covers the entire peripheral nerve.

Perineurium

The connective tissue layer that surrounds one fascicle within a nerve.

Endoneurium

The innermost connective tissue layer surrounding individual axons.

Mixed nerves

Nerves that contain both sensory and motor fibers.

Dura mater

The outermost meningeal layer that joins the filum terminale to form the coccygeal ligament.

Arachnoid mater

The middle meningeal layer where the subarachnoid space is filled with CSF and serves as a lumbar puncture site.

Pia mater

The innermost meningeal layer that carries blood vessels and is very tightly attached to the spinal cord.

Central canal

A passage in the spinal cord that carries CSF for nutrients, waste, dissolved gases, and chemical messengers.

Dorsal Root Ganglia (DRG)

Structures located at each segment containing the cell bodies of sensory afferent fibers.

Ventral root

The part of the spinal nerve that contains efferent motor neuron fibers going to effectors.

White Matter

The superficial region of the spinal cord divided into columns and subdivided into sensory or motor tracts.

Posterior Grey Horns

Deep regions of the spinal cord containing somatic and visceral sensory nuclei.

Anterior Grey Horns

Deep regions of the spinal cord containing somatic motor nuclei.

Lateral Grey Horns

Regions found only in thoracic ($T$) and lumbar ($L$) segments containing visceral motor nuclei.

Grey Commissure

The region of the spinal cord where axons cross between the right and left sides.

Rami communicantes

Communicating branches, including white and gray rami, that carry visceral motor fibers to and from sympathetic ganglia.

White rami

Myelinated preganglionic axons found only between $T1$ and $L2$ that carry visceral motor fibers to sympathetic ganglia.

Gray rami

Unmyelinated postganglionic fibers associated with each spinal nerve that innervate glands and smooth muscles.

Reflex Arc

The wiring of a single reflex consisting of a receptor, control center, and effector, generally operating as a negative feedback loop.

Step 1 of Reflex Arc

Arrival of a stimulus and the activation of a receptor.

Innate Reflexes

Genetically determined reflexes.

Somatic Reflexes

Reflexes that control skeletal muscle contractions, including superficial and stretch reflexes.

Monosynaptic Reflex

A reflex circuit involving only one synapse.

Polysynaptic Reflex

A reflex circuit involving multiple synapses, ranging from $2$ to several hundred.

Muscle Spindle

Specialized skeletal muscle structures that monitor stretch and maintain resting tone.

Reciprocal inhibition

A process in polysynaptic reflexes where certain muscle groups are inhibited while others are excited.

Golgi Tendon Apparatus

A sensory structure that increases inhibition on motor neurons when a tendon is stretched to prevent muscle damage.

Crossed Extensor Reflex

A contralateral reflex arc that increases excitation to the extensor motor neuron pool in the opposite limb.

Babinski Reflex

A reflex where an upgoing toe is normal until approximately $2$ years of age, but indicates CNS damage in adults.