Spinal Cord Anatomy and Reflexes

Flashcards for Chapter 13 - The Spinal Cord

Peripheral nervous system

Cranial and spinal nerves, sensory input, and motor response.

Reflexes

Quick, automatic nerve responses triggered by specific stimuli.

Spinal reflexes

Controlled by the spinal cord alone without input from the brain.

Spinal cord

From the brain to vertebrae L1 and L2, containing 4 regions and 31 segments, giving rise to spinal nerves.

Central canal

Contains cerebrospinal fluid (CSF).

Cervical enlargement

Supplies the shoulder and upper limb.

Lumbosacral enlargement

Supplies the pelvis and lower limb.

Conus medullaris

Tapered, conical end of the spinal cord below the lumbar enlargement.

Cauda equina

Nerve roots extending below the conus medullaris.

Filum terminale

Thin thread of fibrous tissue at the end of the conus medullaris.

Anterior root (ventral root)

Axons of motor neurons.

Posterior root (dorsal root)

Axons of sensory neurons.

Spinal ganglia (dorsal root ganglia)

Contain cell bodies of sensory neurons that form the posterior root.

Spinal nerves

Formed by the union of posterior and anterior roots; contain both afferent (sensory) and efferent (motor) fibers.

Dura mater

Outermost meningeal layer.

Epidural space

Between vertebrae and dura mater.

Arachnoid mater

Middle meningeal layer.

Subarachnoid space

Filled with cerebrospinal fluid (CSF).

Pia mater

Innermost meningeal layer, firmly attached to underlying neural structures.

Denticulate ligaments

Anchor pia to dura mater, preventing lateral movement.

Gray matter

Cell bodies of neurons, neuroglia, and unmyelinated axons.

White matter

Myelinated and unmyelinated axons.

Posterior horns

Somatic and visceral sensory nuclei.

Anterior horns

Somatic motor nuclei.

Lateral horns

Visceral motor nuclei.

Dermatome

Specific bilateral region of skin supplied by a single pair of spinal nerves.

Monosynaptic reflex

Single synapse, simplest reflex arc; sensory neuron synapses directly with a motor neuron.

Polysynaptic reflex

At least one interneuron between sensory and motor neuron; slower response.

Stretch reflex

Regulates skeletal muscle length throughout the body.

Muscle spindle

Receptors in stretch reflexes.

Golgi tendon reflex

Prevents too much tension, tearing, or breaking tendons.

Withdrawal reflexes

Move body part away from stimulus (pain or pressure).

Reciprocal inhibition

When flexors contract, extensors relax.

Crossed extensor reflexes

Step on something sharp; before flexor reflex can lift injured foot, crossed extensor reflex straightens opposite limb to receive body weight.

Babinski reflex

Normal in infants; may indicate CNS damage in adults.