Tubular bundle of nervous tissue and support cells. Component of CNS. Runs from cervical vertebra to level of L2, ends in conus medullarus. Spinal nerves continue to descend.
Sugar cone shaped lower end of the spinal cord (L2). Present in this area: filum terminale (composed of pia mater), cauda equina,
Latin for horse's tail. As spinal cord tapers out at the conus medullaris, the spinal nerves branch out of the conus medullaris forming the cauda equina. Located in the lumbar cistern (subarachnoid space). Dorsal and ventral rootlets are directed towards the intervertebral foramina in order to exit the spinal column.
Composed of pia mater, delicate strand of fibrous tissue proceeding downward from conus medullaris. Provides longitudinal support to the spinal cord.
Spinal Cord Gray Matter
Collection of Cell Bodies (neurons) and unmyelinated axons and dendrites (processes of neurons) within the CNS in order to send/receive messages to/from other neurons.
Spinal Cord White Matter
Contain myelinated dendrites and axon. No cell bodies. These are the tracts used to transmit messages over long distances.
Receive information from brain to transmit to upper limbs. Extends from C3 to T2, largest at C6.
Receive information from brain to transmit to lower limbs. Extends L1-S3.
Vasculature of the Spinal Cord
Three arteries supply the spinal cord: anterior spinal artery, right posterior spinal and left posterior spinal artery. All are branches of the vertebral arteries, and travel in subarachnoid space, send branches into spinal cord. All are rather small, posteriors even smaller than anterior. Anterior spinal artery travels anteriomedially down the entire length of the spinal cord. Posterior spinal arteries descend the cord and are resupplied by various other arteries along the way, including posterior intercostal arteries, lumbar arteries, and lateral sacral arteries.
Layers of the spinal meninges
Dura mater, arachnoid mater, pia mater
Tough mother, outside layer, thick, durable
Intermediate layer, thin, glossy (like spider web)
Inner layer, very delicate, unlike brain comes off laterally in a saw tooth manner. Serves as an anchor. (Filum terminales is pia mater)
Attachments of the pia mater to the other layers of the meninges and to the spinal cord. One on each side of the spinal cord. Named for their tooth-like apperance. Provide stability for the spinal cord against motion within the vertebral column.
Space outside/above the dura mater. Epi=on/upon. Space is used for administration of anesthetic (blocking transmission of signals through nerve fibers in spinal cord). Epidural hematoma is a type of TBI where a buildup of blood occurs in the space between dura mater and skull (epidural space). Can be deadly because of build up of pressure.
Only normally fluid filled space in the brain. Typically has CSF present in it.
Enlargement of the subarachnoid space between the conus medullaris (L2) and the inferior end of the inferior end of subarachnoid space (S2). Houses the cauda equina and filum terminale, and is filled with CSF (as is all subarachnoid space). Site for lumbar puncture/spinal tap.
Collection of neuronal (cell) processes, dendrites (sensory) and axons (motor), surrounded by connective tissue coverings. 31 pairs: 8 cervical, 12 thoracic,5 lumbar, 5 sacral, 1 coccygeal. Distributed peripherally into zones
Area of skin supplied by a single spinal nerve
Group of muscles supplied by a single nerve root
Basic functional unit of the Nervous System
Functional communication between a series of neurons
Neuron which sends impulses towards the CNS. Sensory. Goes to the posterior part of CNS.
Neuron which sends impulses away from the CNS. Motor. Starts in ventral part of CNS.
Pertaining to the body, typically the body wall
AKA Sphlanchnic Pertaining to the gut, viscera
Collection of cell bodies (nuclei of neurons) outside of the CNS
How are spinal nerves roots numbered?
For most vertebra, the spinal nerve is numbered for the vertebra above it. Cervical spinal nerves: for vertebra BELOW them (unlike others, because there is one more spinal nerve than vertebra. EX the spinal nerve exiting between C1 and C2 is spinal nerve 2 whereas the spinal nerve exiting between T1 and T2 would be T2).
Spinal Cord Rootlets
Found within subarachnoid space directed toward intervertebral foramina so they can exit. Dorsal = sensory, ventral = motor. Combine to form roots.
Ventral horn of spinal cord Sends information OUT of spinal cord. MOTOR INFORMATION
Dorsal horn of spinal cord. Sends information INTO spinal cord. Sensory information
Ventral rootlets come off of anterior aspect of spinal cord and combine to form ventral root. Only motor information at this point. Surrounded in connective tissue
Dorsal rootlets come off of posterior aspect of spinal cord and combine to form dorsal root. Only sensory information at this point. Surrounded in connective tissue
Dorsal Root Ganglion
collection of cell bodies located in intervertebral foramen of vertebral column. Receives/propogates mostly sensory signals
Dorsal and ventral roots combine into spinal nerve. Both motor and sensory information combined in connective tissue sheath. 31 pairs.
Dorsal Primary Ramus
Smaller than ventral primary ramus. Despite name (dorsal), has mix of motor and sensory information. Goes to the back of the body. Carry visceral/somatic motor and sensory information to and from the skin and deep muscles of the back, and are responsible for the joints of the vertebral column. THAT IS IT; EVERYTHING ELSE IS VENTRAL PRIMARY RAMUS.
Ventral Primary Ramus
Larger than dorsal priamry ramus. Mix of motor and sensory information. Goes to front of body. Carries visceral/somatic motor and sensory information to: remaining areas of trunk, upper, and lower limbs. Branches arranged into nerve plexi: Cervical, Brachial, Intercostal, Lumbar, Sacral, Coccygeal.
Plexi of the Ventral Primary Ramus
Cervical (C1-C5), Brachial (C5-T2), Intercostal (T2-T11), Lumbar (T12-L4), Sacral (L4-S5), Coccygeal (Co)
General Sensory (General Somatic Afferent)
Component of typical spinal nerve. Transmits pain, temp. touch, pressure and proprioception to the spinal cord
Somatic Motor (General Somatic Efferent)
Transmits impulses from spinal cord to skeletal muscle
Visceral Sensory (General Visceral Afferent)
Transmits reflex pain from viscera, glands, mucous membranes and blood vessels to spinal cord
Visceral Motor (General Visceral Efferent)
Transmits impulses from CNS to smooth muscle and glandular tissue (ANS)
Posterior Cutaneous Branch
From dorsal ramus, provide innervation of back skin
Anterior Cutaneous Branch
from ventral ramus for skin innervation
Medial Cutaneous Branch
from ventral ramus for skin innervation
Presynaptic neuron (ANS)
Initial signal. Does not touch organ/muscle being innervated. Leaves spinal cord/brain and connects with sympathetic chain to postsynaptic neuron.
Post synaptic neuron (ANS)
Located in the periphery. Receives signal from the presynpatic neuron and transmits it to the target organ/muscle.
Thoracolumbar Division of Visceral Motor System
T1-L2, location of lateral horn (presynaptic ANS cell bodies). Energy Expending System. (Fight/Fright/Flight). Nt: Norepinephrine.
Involved in activity of sympathetic division of the autonomic motor system. Present at T1-L2.
Sympathetic chain of ganglion.
Hangs off the spinal nerve. Part of the autonomic nervous system. Uses the spinal nerves to distribute ANS sympathetic information to the body. Connects via ramus communicans. Begins at C1 and ends as ganglion impar before coccyx starts
Nerve connecting spinal nerve to sympathetic chain/trunk. Can be either more myelinated (white) or less myelinated (gray)
White Ramus Communicans
Contain preganglionic nerve fibers of the sympathetic nervous system. Need to fire faster because they are the initial transmission.
Gray Ramus Communicans
Contain postganglionic nerve fibers of the sympathetic nervous system.
End of the sympathetic chain
Course of presynaptic fibers of thoracolumbar
Enter spinal nerve via ventral root, enter sympathetic chain via white ramus, may synapse immediately or choose to ascend/descend to relevant level, can chose to pass through the sympathetic trunk without synapsing (sphlanic nerves to prevertebral ganglion)
Course of postsynaptic sympathetic fibers
Run through the gray ramus entering the spinal nerve. If from head: follow branches of carotid. If sphlanchnic: follow branches of the abdominal aorta. Visceral Afferent (Sensory) Neurons run with the Sympathetic Division of the ANS in a Dermatomal pattern
Energy conserving. Feed/assimilate. Sites of presynaptic cell bodies are physically separated: CN III, VII, IX, X & S2,3,4. Sites of postsynaptic cell bodies are within the organ/muscle they innervate. LONG PRESYNAPTIC, SHORT POSTSYNAPTIC. Frequently called the cranialsacral division. Nt: Acetylcholine.
In the peripheral nervous system, nerve fibers are each wrapped in a protective sheath known as the endoneurium. These are bundled together into groups known as fascicles, each surrounded by a protective sheath known as the perineurium. Several fascicles may be in turn bundled together with a blood supply and fatty tissue within yet another sheath, the epineurium.