Spinal nerves with pathways Flashcards
Where does the spinal cord begin and end?
Begins at foramen magnum, ends at L1 or L2
Where is the conus medularis located?
L1 or L2
What remnant of the spinal cord extends down to the coccyx
Filum terminate internum
Where is the cervical enlargement found?
Upper limbs
Where is the lumbosacral enlargement found?
Lower limbs
What are the main functions of the spinal cord? (2)
- Main reflex center of the body
2. Interconnects the periphery to the brain
What type of tissue is the outer portion of the spinal cord made of?
Peripheral tissue made of white matter
What does the peripheral tissue contain?
tracts of ascending and descending axons
What type of matter makes up the inside portion of the spinal cord?
gray
What does the grey matter contain in the spinal cord?
synapses (dorsal horns, ventral horns, lateral horns
Describe the central canal of the spinal cord
Continuous with the ventricles of the brain, filled with CSF
Name the meninges of the spinal cord
Dura mater, arachnoid mater, pia mater
Describe the dura mater
tough leathery wrapping for the spinal cord
Describe the epidural space
Surrounds the bone and is filled with fat, found outside the dura mater
What is inside the subarachnoid space?
CSF
Which meninge gives the spinal cord its shiny appearance?
pia mater
What are denticulate ligaments?
folds of the pia mater that allow it to attach to the dura mater
Where in the vertebrae do spinal nerves emerge?
intervertebral foramina
How many pairs of spinal nerves are there?
31 pairs: C1-C8; T1-T12; L1-L5; S1-S5, Co1 (not paired)
Which spinal nerve is not paired?
Co1
About how long are spinal nerves?
1 cm, they immediately branch into other nerves
What types of fibers are found in dorsal roots?
sensory
What types of fibers are found in ventral roots?
motor
What do dorsal roots branch into and where do they synapse?
Branch into dorsal rootlets that synapse into the dorsal horn of the spinal cord
What is a dorsal root ganglion?
cluster of cell bodies of sensory neurons
Where do ventral rootlets converge?
ventral root
Where do somatic motor neurons come from?
Ventral horn
Where do autonomic motor neurons come from?
Lateral horn
Where are the sympathetic and parasympathetic neurons located respectively?
T1-L2 = sympathetic S2-S4 = parasympathetic
What area of the body do the dorsal rami innervate?
central back
What area of the body do ventral rami innervate?
The whole body except for the central back and the head
What are the 4 pairs of ventral rami plexuses
Cervical, brachial, lumbar, sacral
Describe the cauda equina
spinal cord roots found after L2 that hang down from the spinal cord and exit the vertebral canal from their corresponding vertebrae
What region is the cauda equina found and what else is present there?
Lumbar cistern, CSF
Describe the short circuit neural pathway
Spinal reflexes, no tracts to or from the brain
Describe the full circuit neural pathway
Involves the brain
True or false: C1 involves only motor neurons
True: no DRG in C1
Describe the pathway for both somatic and visceral sensory input
Peripheral nerves –> spinal nerve rami –> spinal nerve –> dorsal root –> dorsal rootlets –> dorsal horn of spinal cord
Describe the pathway for somatic motor input
Ventral horn of spinal cord –> ventral rootlets –> ventral root –> spinal nerve –> spinal nerve rami –> peripheral nerves
Describe the first option pathway for sympathetic input
Lateral horn (T1-L2) –> Ventral rootlets –> ventral root –> spinal nerve –> ventral ramus –> white ramus communicantes –> paravertebral ganglion –> synapse onto post-synaptic neuron within the ganglion
Describe the second option pathway for sympathetic input
Lateral horn (T1-L2) –> Ventral rootlets –> ventral root –> spinal nerve –> ventral ramus –> white ramus communicantes –> paravertebral gnalgion –> pass through ganglion –> travel up through sympathetic chain –> synapse onto post-synaptic neuron within higher paravertebral ganglion
Describe the third option pathway for sympathetic input
Lateral horn (T1-L2) –> Ventral rootlets –> ventral root –> spinal nerve –> ventral ramus –> white ramus communicantes –> paravertebral ganglion –> pass through ganlgion –> travel down through sympathetic chain –> synpase onto post synaptic neuron within lower paravertebral ganglion
Describe the fourth option pathway for sympathetic input
Lateral horn (T1-L2) –> Ventral rootlets –> ventral root –> spinal nerve –> ventral ramus –> white ramus communicantes –> paravertebral ganglio –> pass through ganglion –> travel through sympathetic chain –> exit without synapsing –> enter splancnic nerve –> enter prevertebral ganglion –> synapse onto post ganglionic neurons innervating viscera
What 4 places do sympathetic nerves travel to?
- neck, body wall, limbs 2. head 3. thoracic viscera 4. abdominal viscera
Describe the pathway of the sympathetics to the neck, body walls and limbs
Post-synaptic cell bodies within paravertebral ganglion –> fibers exit gray ramus communicanted –> enter spinal nerve rami of all 31 spinal nerves
What actions are the sympathetics to the head, body wall and limbs responsible for?
vasomotion, pilomotion, sudomotion
Describe the pathway of the sympathetics to the head
Post-synaptic cell bodies within superior cervical ganglion –> fibers exit cephalic arterial rami (carotis nerves) –> bind to carotid arteries –> branch and follow various arteries to specific areas in the head
What actions are the sympathetics to the head responsible for?
vasomotion, pilomotion, sudomotion, pupillary dilation via the pupillary dilator muscle, xerostomia (salivary gland inhibition)
Describe the pathway of the sympathetics to thoracic viscera
post-synaptic cell bodies within superior, middle and inferior (stellate) cervical ganglion and to the thoracic paravertebral ganglia from T1-T5 –> fibers enter cardiopulmonary splancnic nerve (superior, middle, inferior)
What do the superior and middle splacnic nerves innervate?
heart
What do the inferior splancnic nerves innervate
lungs and other pulmonary structures
What actions are the sympathetics to the thoracic viscera responsible for?
increase HR and strength of contraction, vasodilation of coronary arteries, bronchodilation
Describe the pathway of the sympathetics to the abdominal viscera
pre-synaptic fibers exit thoracic paravertebral ganglia from T5-L2 –> enter into abdominopelvic splancnic nerve (greater, lesser, least, lumbar) –> synapse onto post-synaptic cell bodies within prevertebral ganglia (celiac, superior mesenteric, aorticorenal, inferior mesenteric) –> fibers exit prevertebral ganglia within small nerve –> abdominal viscera
What is the exception to the symapthetic pathway to abdominal viscera
innervation of adrenal medulla: pre-synaptic fibers pass through aorticorenal ganglion and synapse onto cells within adrenal medulla (for epinephrine secretion)
What types of fibers are found in cardiopulmonary splancnic nerves
postsynaptic fibers
What types of fibers are found in abdominopelvic splancnic nerves
presynaptic fibers
Describe the pathway of parasympathetic nerve fibers
Lateral horn (S2-S4) –> ventral rootlets –> ventral root –> exit via pelvic splancnic nerves –> to pelvic organs and leat half of large intestine
Where do pelvic splancnic nerves branch from?
ventral rami from ventral rami of S2-S4
Where are peripheral ganglia located in regards to target organ?
adjacent to them
