Axons Flashcards
The component axons of the dorsal root
All roots transmit GSA and GVA
*note: C1 has very few afferent and a very small DRG
The component axons of the sympathetic chain
The sympathetic chain transmits preganglionic sympathetic axons from the white rami of T1-L2/3 to all levels of the chain; the chain ganglion itself consists of postganglionic sympathetic cell bodies, thus the axons will be present as well. Also, from the thoracic and abdominopelvic viscera, GVAs will return to the dorsal root via the sympathetic chain. Therefore: pre- and postganglionic sympathetic axons and GVA axons are transmitted by the sympathetic chain.
The component axons of the gray ramus
The gray rami transmit postganglionic GVE sympathetic axons to all spinal nerve levels. Therefore, there are gray rami for all spinal nerves. No other axons are transmitted by these nerves.
The component axons of the T5 ventral root
The ventral roots from T1-L2/3 will transmit both GSE axons and preganglionic GVE sympathetic axons because the preganglionic axons arise from those segments
Ventral root
All roots transmit GSE; T1-L2/3 also transmit Preganglionic GVE Somatic; S2-4 also transmit Preganglionic GVE Parasympathetic
The white Rami
Only exist between T1-L2/3
Transmits Preganglionic GVE Somatic and GVA (only high threshold)
The gray rami
Exists for all levels
Transmits postganglionic GVE Somatic ONLY. Moreover these axons are bound for the body wall and limbs only.
What is in the sympathetic chain?
The sympathetic chain ganglia exhibit the following axons: GVA, pre-and post ganglionic GVE somatic; the house the cell bodies of the postganglionic GVE somatic
What is in CNX?
(Vagus nerve)
Transmits GVA (low threshold) axons and Preganglionic GVE parasympathetic axons.
What is in the ventral primary rami?
Transmits: GVA, GSA, GSE, and postganglionic GVE sympathetic.
The ventral ramus projects to the lateral and anterior body walls and skin as well as the entire upper and lower extremity. The GVAs in these nerve branches are both HT and LT
What is in the dorsal primary rami?
Transmits: GVA, GSA, GSE, and postganglionic GVE sympathetic.
The dorsal ramus projects to the posterior body wall and skin of the intrinsic back muscles
What is in the prevertebral ganglia?
The prevertebral ganglia house the postganglionic GVE sympathetic cell bodies for the abdominopelvic viscera. They transmit the GVA, pre-and post ganglionic sympathetic axons as well as the preganglionic GVE parasympathetic. (both the high and low threshold GVAs are present)
What is in the splanchnic nerve?
The splanchnic nerves transmit preganglionic sympathetic axons and high threshold GVA axons.
What is in the cardiopulmonary nerves?
The seven cardiopulmonary nerves transmit postganglionic sympathetic axons and high threshold GVA axons.
What is in the cardiopulmonary ganglia?
The cardiopulmonary ganglion is a parasympathetic ganglion housing postganglionic parasympathetic cell bodies, pre-and post ganglionic parasympathetic axons, Post ganglionic sympathetic axons, and both high threshold and low threshold GVA axons.
What generally enters the lateral division of the dorsal root?
The A-delta and C-fibers enter the lateral division of dorsal root
Generally, what fibers enter the medial division of the dorsal root?
The larger Ia, Ib, and A-bets divers enter the medial division of the dorsal root
What two spinal nerves represent exceptions to the general schema of spinal nerves?
The first cervical and first coccygeal spinal nerve.
C1 nerve transmits almost no sensory component
The coccygeal nerve usually does not exhibit any somatic motor component, it is mainly a sensory nerve supplying the perineum
Is the ventral root composed of primarily myelinated or unmyelinated axons?
Ventral root is composed of primarily myelinated axons. Any unmyelinated axons May be sensory axons that enter and “turn around” returning to the dorsal root.
Where do most of the myelinated axons arise from?
Large anterior horn cells (GSE) in Rexed Laminae IX. These axons are also known as Alpha motor neurons or final common pathway axons.
Where do the sympathetic Preganglionics exit the spinal chord?
Through the ventral root, and then become part of the white communicating ramus
White rami
Myelinated, sympathetic Preganglionic fibers (GVE- Preganglionic) and visceral Afferent axons, returning information from the organ systems and internal cavity vessels to the CNS
Only associated with spinal nerves T1-L2/3
Gray rami
Contain only unmyelinated postganglionic fibers (GVE- postganglionics) arising from the sympathetic chain and destined for the body wall and limbs. These postganglionics will innervates only 3 different types of structure: sweat glands, vascular smooth muscle and erector pili muscles. Gray rami are branches of all spinal nerves.
Dermatome
The sensory innervation of a dorsal root
Spinal nerves
31 pairs of spinal nerves
8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal
They each transmit GSA and GSE axons as well as GVA and GVE sympathetic components
