Spinal Cord and PNS Flashcards
Gross Spinal Cord Anatomy
The nerves which brand off the spinal cord will innervate our limbs
Spinal Cord Diagram
Butterfly shape - grey matter making up the butterfly and white on the outside (opposite of cerebrum)
Axons in the white and grey has all the somas
Grey matter
Dorsal Horn - neurons involved with sensation
Ventral Horn - motor functions synapse with neurons here within the VH and those neurons send their axons out in our peripheral nerves to innervate our muscles (from brain to our muscles)
Lateral Horn -autonomic neurons that are part of the sympathetic nervous system, sweat, changes blood flow, only seen in (thoracic spinal cord region and first two levels of the spinal cord)
Central canal - CSF flows ependymal cells line the central canal and ensure the movement of CSF
Ventral root - infomation coming out axons moving motor and autonomic information that leaves the spinal cord to innervate structures (EFFerent) heading out of the spinal cord
Dorsal root -sensory information coming into the spinal cord (AFFerent)
Spinal nerve - two way road (info going into both directions)
Within a nerve, will consists of lots axons and within the nerve some efferent carry out info, coming in afferent and some carrying them going out, both sensory, motor, autonamic.
An Individual axon part of a neuron will only carry one type of one type of information.
Dorsal root ganglion - grouping of neurons cell bodies of sensory neurons will be located. The location of the somas of pseudounipolar neurons, our sensory neurons.
What is this space within the middle of the vertebra?
Ventral foramen what lives in there are the spinal cord
Dura mater isn’t connected to our vertebra Spinal column has space filled with adipose tissue.
Intervertebral foramen where the spinal cords come out
How does sensory information get to the brain?
LEFT side of the body end up on the RIGHT somatosenory cortex so this is where lower extremities would be located in our homunculus
The information has crossed over
If you damaged your left somatosenosry cortex you’ll lose information on the right side
How does motor information get to our muscles?
RIGHT motor cortex information comes down through the brain stem (pedicles and pyramids) and crosses at the medulla to innervate our muscles on the LEFT side
Axons traveling to the white matter and second neuron that it’s synapsing with is in the Ventral horn and will ultimately innervate our muscles
Spinal cord
The spinal cord is shorter than the spinal column but the spinal nerve that are coming off of the spinal cord there are going to travel down and exit at the appropriate intervertebral foramen
Spinal Cord Diagram
Cervical region VH - neurons in cevical region within the VH will control our upper extremities
The most white matter in the cervical region
Neurons in Lumbar region within our VH - control muscles in our legs
Smaller VH in thoracic and Sacral bc there’s fewer muscles that innervate there
Very little white matter in sacral matter
Sensory information little information that feeds into the white matter in the spinal cord and as we head up to the brain as we move up we have more sensory information heading in. At the cervical region we have the most sensory information heading up and most motor information heading out.
Spinal Nerves
Part of PNS - Leave the spinal cord that’s PNS
Those axons are myelinated by Swchan cells bc it’s part of the PNS
Supply all regions of the body except head and neck bc (carnial nerves) do that
Mixed (sensory and motor) nerves 31 pairs (left and right) exit from spinal cord
Named according to where they exit from the vertebral column
Clinical Correlate: Herinated Disc
- Most herniations occur in the lumbar and cervical regions
- They are often caused by an activity where the front of the disc is compressed
- Herniations may press on spinal nerves
Annulus - fibrocartilage part resist compression (mixture of hyaline and dense regular connective tissue)
Center of disc (nucleus)
Jelly donut
Lumbar and cervical regions - due to different forces we’re putting on the discs
Lumbar - due to poor posture, obesity
See pain, loss of sensation (like leg falls asleep bc you’re compressing a nerve),serve causes will cause motor problems, no cognitive or visual senses
And doesn’t effect entire region only restricts the spinal nerve impacted.
Spinal tap in the lumbar region
Test CSF and look for infection and take it from the lumbar spinal column and have to be really good and not hit a spinal nerve. If you take it from the Cauda Equina and less likely it will impale one of the spinal nerves
End of Spinal Cord
Conus Medullaris - end of the spinal cord at L2-l1 vertebral level
Remember Neurons that give rise to spinal nerves travel down and will exit through the sacral level
Dural sac surrounds the Cauda equina
Filum Terminale - extension of the pia mater that conus from the conus medullaris and attaches down to coccyx or end of sacrum to provide longitudinal stability so the spinal cord is attached to both ends superior end to the brainstem and inferior end to the coccyx.
Sympathetic Nervous System
Sympathetic and Parasympathetic Nervous System (falls into our autonomic nervous system which controls involuntary actions in our body
Sympathetic Fight or Flight (or freeze) Response
- Increased heart Rate
- Increased Respiratory Rate and Depth
- Dilated Pupils
- Constricted Sphincters (circular muscles and limit movement things through our urniary or digestive tract)
- Sweating
- Altered Vasoconstriction/Vasodilation (blood vessels will dilate)
Sympathetic Nervous System
Cell bodies in our sympathetic nervous system are located in within the Lateral Horn grey matter of the spinal cord only see it between T1- L2 spinal cord levels. send their axons out their through Ventral Root and head to the spinal nerve and head to Sympathetic Chain Ganglion (bundled or neurons) and one of 3 things middle axon (Synapse on the neurons here and Post ganglionic axon and sends it axons right back out to the spinal nerve
Why? Reason there can be multiple axons that synapse on the same neuron here and that neuron here will integrate the input it receives. It receives the message to activate the sweat glands but doesn’t receive the message from 3 of the neurons. (intergrating focus and communicate it back to the spinal nerve and into the body)
Another thing, these axons can entered to the sympathetic chain and head up to another ganglion or head down to a lower ganglion and sends it’s axon to spinal nerve (network and cross talk between neurons from different levels and the way they do it is by their axons traveling up and down the sympathetic chain)
Part where the axons are entering the sympathetic chains are called White Ramus (myelinated) (afferent into the sympathetic chain)
Axons coming out are Grey ramus (unmyelinated) efferent out of the sympathetic chain
Communication is slower if axons are not myelinated
Peripheral Nerves
Plexus are networks of spinal nerves that combine to form peripheral nerves
4 major plexuses (network of spinal nerves from multiple differnet levels are combining to create peripheral nerve that head out in our body) : cervical, brachial, lumbar, lumbosacral
Cervical
Phrenic nerve - comes from the cervical plexus and innervates our diaphragm (c3, 4 and 5 keep the diaphragm alive)
The Peripheral Nervous System
Three layers of connective tissue
Each nerve consist of 1000’s axon
Some axons are efferent and some are afferent
Epineurium - surrounds the nerve extension of dura mater
Fascicles - bundle of axons
Each fascicles will be will be surrounded by a Perineurium (around) which is an extension of our arachnoid mater
Within each fascicles going to have 1000’s axons which are wrapped with Endoneurium (inside) extension of Pia Mater
Individual axon can only carry one type of information
Blood vessels send a lot of electric information outside of the nerve in among the fascicles axons uses a lot of ATP with mitochondria and need oxygen
Coiled structure which allows our nerves to stretch for example raise arm and not tear it to pieces
