60 terms

Chapter 12 Spinal Cord and Spinal nerves

Spinal Cord
primary communication link between the brain and the peripheral nervous system, integration of incoming info, reflex mechanisms, form foramen magnum to L2
Spinal Nerves
31 pairs, exit the vertebral column through the intervertebral and sacral foramina, not uniform in diameter
Cervical and Lumbosacral Enlargements
larger diameter of cord, give rise to the spinal nerves of the limbs
Conus Medullaris
cone like region of the spinal cord inferior to the lumbosacral enlargement, have caudal equina off of it
Cauda Equina
roots of nerves that extend from the end of the spinal cord
connective tissue membranes that surround the brain and spinal cord
Dura Mater
form a thecal sac that surrounds the spinal cord, attaches to the rim of the foramen magnum and ends at the level of the second sacral vertebra, most superior
Arachnoid Mater
thin wispy meningeal layer deep to the dura mater
Pia Mater
deepest meningeal layer that is bound tightly to the surface of the spinal cord
Epidural Space
between the periosteum of the vertebral canal and the dura mater, contains blood vessels, areolar tissue and fat
Subdural space
between the arachnoid mater and the dura mater, serous fluid
Subarachnoid space
between the arachnoid mater and the pia matter, cerebrospinal fluid
Anterior Median Fissure
deep cleft partially separating right and left halves, on anterior side
Posterior Median Sulcus
deep cleft partially separating right and left halves, on posterior side
White Matter
consist of myelinated axons forming tracts, located peripherally, organized into three columns ventral, dorsal, lateral
Funiculi or columns of white matter subdivided into tracts know as ____
Tracts (fasiculi)
composed of axons ascending to the brain or desending from the brain, axons within carry same type of info
Gray Matter
dominated by the cell bodies of neurons, neuroglia, and unmyelinated axons
Dorsal (posterior) Horns
gray matter, contains somatic and visceral sensory nuclei
Ventral (anterior) Horn
gray matter, contains somatic motor nuclei
Lateral Horns
gray matter, contains visceral motor nuclei
Gray and White Commissures
connect each half of the spinal cord
Central Canal
located in the center of the gray commissures
spinal nerves arise as rootlets then combine to form roots, located along the dorsal and ventral surfaces of the spinal cord
Dorsal Root
root containing sensory axons
Dorsal Root Ganglion
collections of cell bodies of the sensory neurons
Ventral Root
contains motor axons
Spinal Nerve
dorsal and ventral root merge laterally to form, contain sensory and motor axons
basic functional unit of the nervous system, simplest portion capable of receiving a stimulus and producing a response, stereotypic, unconscious, and involuntary responses to stimuli, maintains homeostasis
response to stimulus is always the same
no awareness is necessary for the reflex to occur
one cannot will the reflex to happen
Somatic Reflexes
mediated through the somatic motor nervous system, responses; remove for painful stimuli, keep from falling suddenly, cause movement because of external forces
Autonomic Reflexes
mediated through the autonomic nervous system, responsible for maintaining variables within their normal ranges; blood pressure, carbon dioxide levels, water intake
Sensory Receptors
respond to stimuli and produce action potentials in sensory neurons
Sensory Neurons
propagate action potentials to the CNS
Interneurons in the CNS
synapse with sensory neurons and with motor neurons
Motor Neurons
carry acton potentials from the CNS to effector organs
Effector Organs
part of body that responds to the action potentials
Stretch Reflex
muscles contract in response to a stretching force applied to them, innervated by specific motor neurons, sensory neurons innervate the non contractile centers of the muscle spindle cells, synapse with alpha motor neurons, and intern innervate the muscle with spindle
Muscle Spindles
specialized muscle cells that respond to stretch
Gamma Motor Neurons
specific motor neurons that control sensitivity of muscle spindles
Golgi Tendon Reflex
reflex preventing contracting muscles from applying excessive tension to tendons, prevents damage to tendons, produces sudden relaxation of muscles
Golgi Tendon Organ
encapsulated nerve endings that have at their ends numerous terminal branches with small swelling associated with bundles of collagen fibers in tendon, located in tendon near muscle
Withdrawal Reflex
reflex function to remove a body limb from a painful stimulus, have reciprocal innervation and crossed extensor reflex
Reciprocal Innervation
causes relaxation of extensor muscle when flexor muscle contracts in withdrawal reflex, also involved in stretch reflex
Crossed Extensor Reflex
when a withdrawal reflex is initiated in one lower limb, the crossed extensor reflex causes extension of opposite lower limb
Spinal Nerve Structure
consist of axon bundles, schwann cells and connective tissue, have endoneurium, perineurium and epineurium layers
surrounds individual axons and their Shcwann cell sheath
surrounds groups of axons (fascicles)
surrounds the entire nerve
Dorsal Ramus
branches of nerves that innervate deep muscles of the trunk responsible for movements of the vertebral column and the CT and skin near the midline of the back
Ventral Ramus
branches of nerve, what they innervate depends on what part of the spinal cord is considered
Thoracic Region
part of ventral ramus, form intercostal nerves that innervate the intercostal muscles and the skin over the thorax
organization produced by the intermingling of the nerve, five in the body
Cervical Plexus
C1-C4 innervate superficial neck, structures, skin of neck, posterior portion of head, have ansa cervicalis, and phrenic nerve
Ansa Cervicalis
in cervical plexus, loop between C1 and C3
Phrenic Nerve
in cervical plexus, C3-C5, part of both cervical and brachial plexus, innervates diaphragm
Brachial Plexus
C4, C5-T1, five ventral rami form three trunks, separate into six divisions of cords giving rise to beaches/nerves; axillary, radial, musculocutabeous, ulnar, median, and small nerves that innervate muscles action on scapula and arm
Lumbar and Sacral Plexus
ventral rami of L1-L4 and L4-S4, considered together because of close relationship, major nerves;obturator, femoral, tibial, common fibular