What do these innervate?
Innervate the bone, skin, muscles, and joints
Visceral - AKA Autonomic
What does it innervate?
Involuntary; autonomic Internal. Innervates the visceral tissues, smooth muscle, cardiac muscle, and glands.
Motor Supplies skeletal
Sensory Sensation from the skin, bone, joint
detecting temp, pain, burn
Visceral efferent - Autonomic Efferent
Motor Sympathetic or Parasympathetic Smooth muscle cardiac muscle and glands
Visceral Afferent - Autonommic Afferent
localized within organs and sending sensory information to the CNS
Cell body Where are they normally found?
Soma Usually found in collections (ganglia, nuclei, gray matter)
Dendrite What type of signal do they carry?
Multiple Carry Afferent impulses
Axon What Type of signals do they carry?
single Carries Efferent impulses
Point of communication between neurons or between neurons and effector cells (skin, muscle, gland)
Myelin...what does it do?
Insulates axons electrically Boosts nerve conduction
What are the cells that form the myelin sheath in the CNS?
What makes oligo dendrocytes unique to the CNS?
One oligo cell reaches out and mylinates many axons
Ehat are the cells that form the myelin sheath in the PNS?
What makes Scwann cells unique for the PNS?
One schwann cell mylinates a single axon
What is a collection of axons called?
What is the order and name of the connective tissue sheaths surrounding peripheral nerves?
1. Endoneurium (surrounds axon)
2. Perineurium (around fascicles)
3. Epineurium (around whole nerves)
Gray matter consists of
Nerve cell bodies
Dendrites and short Axon segments
White Matter Consists of
Axons. These primarily form the tracts
Where is white and gray matter on the spinal cord?
White = peripheral
Gray = central
Where is white and gray matter located in the cerebral cortex?
White = central
Gray = peripheral
What are the three membranes that surround the spinal cord and roots?
From Outermost to innermost
AKA Spinal Meninges
1. Dura Mater
2. Arachnoid mater
3 Pia mater
Dense Connective Tissue
Forms Dural Root Sleeve
Blends with Epineurium (the outer connective tissue covering of the spinal nerves).
Encloses CSF-filled subarachnoid space
Held against the dura by CSF pressure
Arachnoid trabeculae connect the arachnoid and the pia mater.
Adherent (like shrinkwrap) to brain, spinal cord, and nerve roots
Forms Denticulate ligament
Helps limit lateral movement of spinal cord
What are denticulate ligaments?
Lateral extension of pia mater
attach pia to arachnoid and dura
provides support for the spinal cord
What are the 3 main divisions of the gray matter in the spinal cord?
1. Dorsal horn
2. Lateral Horn - Intermediolateral column
3. Ventral horn
Originate from one spinal cord segment and merge to form larger root
Dorsal Root Ganglion
Swelling of the Dorsal root where the primary sensory neurons are locate
Area where ventral and dorsal root merge
Branching of the spinal nerve into dorsal and ventral rami
Dorsal Rami innervate
synovial joints of vertebral column, intrinsic back muscles and overlying skin
Ventral Rami innervate
anterior and lateral regions of the trunk and upper and lower limbs
What is the order of structures from the spinal cord that make a spinal nerve
dorsal and ventral rootlets -> merge to form dorsal and ventral roots -> form spinal nerve
Spinal roots have how many funstional fibers?
What are the two types of roots?
One single functional fiber type
A. Dorsal Root - afferent (sensory) -reception
B. Ventral Root - efferent (motor)- distribution
Spinal Nerves and Rami have how many functional fiber types?
Afferent (sensory) -reception
Efferent (motor) - distribution
Spinal Somatic reflex arc
What is the pathway?
Reaction to stimulus that does not involve the brain it's immediate.
Sensory input -> travels dorsal afferent signal -. dorsal horn -> Ventral horn -> signal transferred via efferent signal to muscle receptors.
Mediated by receptors inside the muscle
Ex: biceps, triceps, patellar, achilles tendon, and deep tendon reflexes
Mediated by receptors outside muscle
**Golgi tendon has a dysnaptic pathway
Ex: sensory receptors in the skin --touching a hot object
How many pairs of spinal nerves are there?
How many are cervical?
How many thoracic?
How many Lumbar?
How many Sacral?
How many coccygeal?
How many cervical spinal nerves are there?
How many cervical vertebrae are there?
One nerve exits above C1
C8 exits between C7 and T1
All other nerves exit just below the vertebrae with the same number
Where does a spinal nerve exit the spinal column?
Where are the intervertebral discs located in proximity to the IV foramen
The intervertebral (IV) foramen
Adjacent to the lower half of the IV foramen
Where would a herniated disc have its impact?
L4/L5 herniation affects what spinal nerve?
C5/C6 herniation affects which spinal nerve?
Affects the spinal nerve directly below it.
What about the cervical region C5/C6 and C6/C7 disks are most commonly herniated?
The presence of the extra cervical spianl nerve C8 results in cervical nerves contacting the disk of the next higher number.
Where on the spinal cord are there enlargements?
C4-T1 because need more ventral rami to form the brachial plexus that supplies the upper limb
T11-S1 more ventral rami are need to form the lumbrosacral plexus that supplies the lower limb
Which spinal cord level is found at the L2 vertebral level?
What area can this spinal cord actually occur in real patients?
high as T12 or as low as L3
Spinal nerve roots form lumbosacral (lumbar) enlargement
Anchors inferior end of spinal cord (Tip of the conus medullaris) to the coccyx
What are the two parts of the Filum Terminale?
1. Filum terminale internum (pia mater)
2. Filum terminale externum (dura mater)
What is the Lumbar Cistern?
Where is it located?
What does it contain?
Enlargement of the subarachnoid space
Inferior end of spinal cord (conus medullaris at L2)
Inferior end of dura mater and subarachnoid space at S2
Cauda Equina, Filum Terminale, CSF
why does spinal cord end higher than the vertebral (spinal) canal?
What is a practical application of this?
During development, the vertebral column grows more than the spinal cord.
Spinal cords in children end at lower vertebral level than in adults. This is important when performing a lumbar puncture.
Where is the tip of the spinal typically found in an adult?
Where is the tip found in a newborn
L1/L2 IV disc
What creates and is occupied by the cauda equina?
Which way are lumbar and sacral spinal nerve roots in the cauda equina?
What is a lumbar puncture
What anatomical features allows this procedure to be performed safely?
Extraction of CSF from the lumbar cistern
The lumbar cistern is filled with fluid with the spinal nerves directed inferiorly in CSF. When you puncture a fluid filled space it gives greater chance that the nerve will be pushed out of the way instead of being punctured by the needle
Which space contains CSF?
what are the two spaces lumbar anesthesia is typically placed?
1. epidural space - area before the dura mater (no spinal cord puncture)
2. Subarachnoid space - more risky because you are puncturing the spinal cord
What do most ventral rami form?
A peripheral nerve plexus
Cervical plexus is made up of which ventral rami?
The Brachial Plexus?
The lumbar plexus?
The Sacral plexus?
Why is there no thoracic plexus?
Thoracic ventral rami form individual parallel intercostal nerves (next to ribs)
Where does the brachial plexus begin?
What ventral rami form it?
What is it?
Where does the plexus extend into?
What is it's purpose?
Branching network of intersecting nerves
Into the Axilla (armpit)
It's branches supply the upper limb
What are the 3 Regions of the brachial plexus?
2. Posterior to clavicle
Mnuemonic to remember parts of the brachial plexus
Rugby Team Drinks Cold Beer
What are the 5 terminal branches?
All spinal nerves transmit sensory information from where? What is the single exception?
C1 nerve does not
What is a Dermatome?
Dermatomes on the trunk, neck, and posterior head form what?
Skin of the face and scalp are suppplied by what nerve?
A region of skin innervated by a single spinal nerve.
The trigeminal nerve (CN V)
What is a Myotome?
Portion of skeletal muscle innervated by a single spinal nerve