G5_Spinal_Cord_Somatic_NS_EXAM1 Flashcards
Neuronal cell bodies organized into nuclei or columns
Gray matter
Axons organized into tracts
White Matter
What are the 3 types of GANGLIA in the PNS?
- Cranial nerve ganglia (afferent)
- Posterior root ganglia (afferent)
- Autonomic ganglia (efferent)
What are the 2 Types of Peripheral Nerves?
Cranial Nerves (12 Pair) Spinal Nerves (31 Pair)
What are the two somatic sensory receptors of the nervous system?
- Exteroceptors (mechano,thermo,noci)
2. Propioceptors (muscle spindles, golgi tendon organs)
Sensory Receptors of NS:
What two Categories? what types in each?
- Somatic (Exteroceptors & Propioceptors)
- Exteroceptors-Mechano, Thermo, Nociceptors
- Proprioceptors- muscle spindles, golgi tendon organs - Visceral (Interoceptors)
- Chemo, Baro, Mechano, Nociceptors
Somatic Pain vs Visceral Pain
Somatic pain- Very acute/Well known/
Visceral pain- broad/not well identified/generalized internal
What is a MOTOR UNIT?
BOTH: LMN + MUSCLE
- LMN (neuron directly innervates skeletal muscle)
- Muscle fiber it innervates
Effector Organs
Somatic- Skeletal muscle
Visceral- Cardiac/Smooth/Glandular epithelium
Where does the spinal cord start and end? What is that called?
Where does it end in Fetus? Neonate?
STARTS: Foramen Magnum (medulla)
ENDS: L1/L2 IVD in ADULTS at CONUS MEDULLARIS
Fetus: Sacrum
Neonate: L3/L4
What 2 places do the spinal cord change size? why? What called?
Enlarges due to extremities:
- Cervical enlargement (brachial plexus)
- Lumbosacral enlargement (lumbar/sacral plexus)
What is the anterior/posterior parts of the spinal cord called?
Anterior median fissure (Wider groove)
Posterior median sulcus (thin crack)
anterior vs posterior Rootlets/roots
Anterior rootlets/roots: MOTOR ONLY
Posterior rootlets/roots: SENSORY ONLY
Describe the formation of Spinal Nerves. Describe the Anterior ramus vs Posterior ramus.
- Anterior roots merge with posterior roots to form a mixed spinal nerve (short/motor & sensory)
- MSN branches to Anterior & Posterior Ramus
Ant Ramus- LARGE- (Efferent hypaxial- afferent: skin)
Post Ramus- SMALL- (Efferent Epaxial- afferent: skin)
What innervates Efferent Hypaxial muscles of the body wall and limb? What is Afferent function?
What innervates Efferent Epaxial deep back muscles?
What is its Afferent innervation?
Anterior Ramus- Hypaxial- wall/limbs- Large
- Motor Efferent- muscles wall/limb - Sensory Afferent- skin over limbs/wall
Posterior Ramus- Epaxial- Deep back muscles
- motor- deep back muscles - sensory- skin over middle of back
What happens to the relative locations of spinal nerves and the corresponding roots on the spinal cord where the spinal nerves are derived from?
Spinal cord segment and spinal nerve location gets further away from each other as you move inferiorly because the spinal cord ends at L1/L2 IVD, but spinal nerves continue down to the sacral level
How many CERVICAL spinal nerves are there? Why? What is significant about C1 spinal nerve?
8 cervical spinal nerves b/c of the space between the skull and C1.
C1 spinal nerve lacks Afferent component and its posterior roots are absent in 50% of individuals.
How many THORACIC spinal nerves? What do thoracic spinal nerves form?
What special about the last thoracic spinal nerve?
T1 to T12 (start between rib 1 and 2)
-Anterior rami of thoracic spinal nerves form intercostal nerves
T12- “Subcostal nerve” - Under last 12th rib
How many spinal nerves in lumbar, sacral, and coccyx?
Which pass through the sacral hiatus?
Lumbar L1-L5
Sacral S1-S5
Coccygeal Co1
S5 and Co1 pass through SACRAL HIATUS
What does the Cauda equina consist of?
Anterior and posterior roots arising from conus medullaris and coursing within the lumbar cistern (filled w/ CSF)
Dermatome Vs Myotome
Dermatome: Area of skin innervated by all the sensory nerve fibers of a single spinal nerve
Myotome- Muscles innervated by all the motor nerve fibers of a single spinal nerve
What dermatome located at the Nipple and Umbilicus?
Caution: What is the generalization?
T4 Dermatome at the Nipples
T10 Dermatome at the Umbilicus
Dermatome maps are idealized b/c of OVERLAP of adjacent dermatomes
What offers reliable locations to test sensory abnormalities of spinal nerve/root lesions?
“Autonomous Sensory Zones”
What do most spinal nerves do/go? What spinal nerves are the exception? what are these types of spinal nerves called?
Most spinal nerves merge with adjacent spinal nerves to form a PLEXUS
- Except for thoracic (intercostal) spinal nerves
What is a lesion to a spinal nerve/root called?
What is a lesion to a peripheral nerve called?
Spinal root/nerve lesion- RADICULOPATHY
Peripheral nerve lesion- NEUROPATHY
What is one of the most common radiculopathies? What it caused by? What is the general rule about its compression?
Herniated disc
-causes shooting pains down course of nerve
- usually compresses the nerve root that is inferior to the actual herniation
Ie- L4/L5 IVD will compress the L5 nerve root
Describe the arterial supply to the spinal cord and nerve roots. What reinforcement does it have?
1 Anterior, 2 Posterior spinal arteries
-reinforced by anastomoses w/ cervical, intercostal, & sacral arteries
Where does the Anterior spinal artery run?
Where does the two Posterior spinal arteries run?
Anterior Artery- runs within the Anterior median fissure of the spinal cord
Posterior Spinal artery- Near origin of posterior rootlets
What arteries anastomose with anterior and posterior arteries of the spinal cord?
Where do they originate? Where do they enter?
Segmental medullary arteries
- multiple origins (vertebral, posterior, intercostal, lumbar etc).
-enter through intervertebral foramen
What arteries supply spinal nerve roots and rootlets?
Radicular arteries
- do not anastomose with ant/post spinal arteries
- origin similar to segmental medullary arteries
- supply nerve roots and rootlets
What is the difference between Radicular arteries and Segmental medullary arteries?
Radicular arteries supply nerve roots/rootlets but DONT anastomose w/ ant/post spinal arteries
Segmental medullary arteries anastomose with ant/post arteries
Describe the venous drainage of spinal cord and spinal nerve roots. How many? Where? What drained by? Communication? Concern?
Anterior and Posterior Spinal Veins
- 3 on each side
- parallel spinal arteries in subarachnoid space
- drained by segmental medullary and radicular veins
- communicate w/ internal/external vertebral venous plexuses (Route concern for metastasis)
What type of CT makes up pia mater?What does Pia cover?How does it stabilize the spinal cord?What lines the dural sac?
-Loose Areolar CT-spinal blood vessels & spinal nerve roots & Spinal cord-forms Denticulate ligaments attaching to dural sac-arachnoid lined dural sac
What is the FILUM TERMINALE?What is it called when inside the dural sac?Function?
Thin strand of PIA MATER-extends from tip of conus medullaris (L1/L2)-Penetrates dural sac @S2 attaches to coccyx-filum terminale internum (WHITE-inside dura)-Anchors the inferior end of the spinal cord
What are the two parts of Arachnoid mater?Where at? whats inside space?
- Arachnoid barrier cells- membrane by dura2. Arachnoid trabeculae- web of CT attach to piabetween pia and duraCSF
What type of CT makes up the dura mater? What does it cover?What range/continuous with?
DiRCT-extends to proximal part of spinal nerve before blending with their epineurium- continuous w/ cranial dura-Ranges from Foramen Magnum to end of dural sac @ S2
Where does the dural sac end?
S2
What happens to the filum terminale when it penetrates the dural sac?What is it called when outside the dural sac?Where does it attach? What does it stabilize?
-Filum Terminale Externum-exits dural sac at S2-gains a layer of arachnoid and dura mater-attaches to coccyx to anchor spinal cord and meninges
What is the LUMBAR CISTERN?What is a myelogram?
L1/L2 IVD (end of spinal cord) to S2 (end of dural sac)- safe area to draw CSF “Spinal Tap”-can inject anesthesia into subarachnoid space-contrast injected to subarachnoid space (old procedure)
Where is the EPIDURAL SPACE? What is it and why? What can be done here?
Inferior to L1/L2 IVD-Potential space between spinal dura and Periosteum/ligaments of the vertebral canal-potential space b/c no fluid in there (filled w/ fat/vertebral venous plexuses, spinal nerve roots)-bathe spinal nerve roots in anesthesia-SAFE b/c only cauda equina exists at this level
What landmark used for epidural and lumbar puncture? what vertebral level does it identify ?WHERE is Safe puncture areas?WHERE IS CRITICAL TO BE BELOW?
Iliac crests= SPINOUS PROCESS OF L4Safe to insert between L3/L4 or L4/L5-CRITICAL TO BE BELOW L1/L2 IVD (Conus medullaris- end of spinal cord)
What layers do you penetrate for Lumbar puncture? What layers for Epidural injection?Pop= “release of resistance”
LP- Penetrates Dura Mater-Skin/Fat/Thoracolumbar fascia/Muscle/Ligamentum Flavum “POP”/ Dura Mater “POP”- in lumbar cisternEpidural- outside Dura Mater-Skin/Fat/Thoracolumbar fascia/Muscle/Ligamentum Flavum
