LSUE BIO1160 Hamlin Chapter 13 Exam 3 (Spinal Cord)

Conduction

•nerve fibers conduct sensory and motor information up and down the spinal cord

Neural integration

•spinal neurons receive input from multiple sources, integrate it, and execute appropriate output (for example, bladder control)

Locomotion

spinal cord contains central pattern generators: groups of neurons that coordinate repetitive sequences of contractions for walking

Reflexes

involuntary responses to stimuli that are vital to posture, coordination and protection

Spinal cord

cylinder of nervous tissue that arises from the brainstem at the foramen magnum of the skull

•cervical, thoracic, lumbar, and sacral regions

spinal cord is divided into these 4 regions

Cervical enlargement

gives rise to nerves of upper limb

Lumbosacral enlargement

•gives rise to nerves of pelvic region, lower limbs

Medullary cone (conus medullaris)

inferior point of cord

Cauda equina

bundle of nerve roots that occupy the vertebral canal from L2 to S5; resembles a horse tail

Meninges

three fibrous membranes that enclose the brain and spinal cord

First-order neuron

detects stimulus and transmits signal to spinal cord or brainstem

Third-order neuron

carries the signal the rest of the way to the sensory region of the cerebral cortex

Second-order neuron

•continues to the thalamus at the upper end of the brainstem

Gracile fasciculus

•carries signals from midthoracic and lower parts of body

Cuneate fasciculus

•carries signals from chest and upper limbs

spinothalamic tract

part of the anterolateral system that passes up the anterior and lateral funiculi of the spinal cord

Upper motor neuron

originates in cerebral cortex or brainstem and terminates on a lower motor neuron

Lower motor neuron

cell body is in brainstem or spinal cord; axon leads to muscle or other target organ

tectospinal tract

•begins in roof of midbrain (tectum), descends contralateral spinal cord as far as the neck

Nerve

a cord-like organ composed of numerous nerve fibers (axons) bound together by connective tissue

Endoneurium

•loose connective tissue external to neurilemma

Perineurium

•layers of overlapping squamous cells that wrap fascicles: bundles of nerve fibers

Epineurium

dense irregular connective tissue that wraps entire nerve

Sensory nerves

composed only of afferent fibers; carry signals from sensory receptors to the CNS

Motor nerves

composed only of efferent fibers; carry signals from CNS to muscles and glands

Mixed nerves

consist of both afferent and efferent fibers

Ganglion

cluster of nerve cell bodies outside the CNS

Posterior ramus

•innervates the muscles and joints in that region of the spine and the skin of the back

Meningeal branch

reenters the vertebral canal and innervates the meninges, vertebrae, and spinal ligaments

Shingles (herpes zoster)

•localized disease caused by the virus traveling down the sensory nerves by fast axonal transport when immune system is compromised

Cervical plexus

•in the neck, C1 to C5: supplies neck and phrenic nerves to the diaphragm

Brachial plexus

near the shoulder, C5 to T1: supplies upper limb and some of shoulder and neck

Lumbar plexus

•in the lower back, L1 to L4: supplies abdominal wall, anterior thigh, and genitalia

Sacral plexus

•in the pelvis, L4, L5, and S1 to S4: supplies remainder of lower trunk and lower limb, including sciatic nerve

Dermatome

a specific area of skin that conveys sensory input to a spinal nerve